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Campbell Essential Biology, Seventh Edition, and Campbell Essential Biology with Physiology, Sixth Edition

Chapter 17

The Evolution of Animals

PowerPoint® Lectures created by Edward J. Zalisko, Eric J. Simon, Jean L. Dickey, and Jane B. Reece

Are You 100% Homo Sapiens? According to Recent DNA Analysis, Many of Us Have a Bit of Neanderthal in Our Genes

Biology and Society: Evolving Adaptability (1 of 2)

What makes humans such successful animals?

Much of our success is due to brain power.

The ratio of brain volume to body mass in humans is roughly 2.5 times the brain volume to body mass ratio in chimpanzees, our closest primate relatives.

The part of our brain that deals with problem solving, language, logic, and understanding other people is particularly well developed.

Although body size has remained roughly the same for about the last 1.5 million years of human evolution, brain size has increased by about 40%.

Biology and Society: Evolving Adaptability (2 of 2)

Other species can fly, breathe underwater, or produce millions of offspring in their lifetimes, but none can match our ability to learn and change our behavior.

Humans are just one of the 1.3 million species of animals named and described by biologists.

This amazing diversity arose through hundreds of millions of years of evolution as natural selection shaped animal adaptations to Earth’s many environments.

Comparison of Human and Chimpanzee Skulls, Showing a Large Difference in Brain Size

The Origins of Animal Diversity: What is an Animal?

Animal life began in Precambrian seas with the evolution of multicellular creatures that ate other organisms.

Animals are eukaryotic, multicellular, heterotrophic organisms that obtain nutrients by eating, and are able to digest the food within their bodies.

Animal cells lack the cell walls that provide strong support in the bodies of plants and fungi.

Most animals have muscle cells for movement and nerve cells that control the muscles.

Student Misconceptions and Concerns

1. Students struggle to think through the requirements of invertebrates and to consider them as animals with basic needs. It is intellectually challenging to see the similarities between an earthworm and a bird or a tick and a cat. The common features of animals addressed at the start of Chapter 17 can be expanded to include the needs for oxygen, nourishing food, a tolerable environment, and a suitable habitat to reproduce, applied to animals representing all of the major phyla. Illustrating these common demands can help to build the intellectual foundations that can be so difficult to fully comprehend.

Teaching Tips

1. Depending on what chapters you have included to this point in your course, you might consider carefully examining the defining traits common to all animals. Consider challenging your students to identify at least one characteristic of each of the other kingdoms in the domain Eukarya that is distinctly different from animals.

2. You might wish to share the now somewhat famous quote of Lewis Wolpert, who in 1986 said, “It is not birth, marriage, or death, but gastrulation, which is truly the most important time in your life.” The development and arrangement of the basic embryonic layers (ectoderm forming skin and nervous system, mesoderm forming muscle and bone, and endoderm forming the digestive tract) establish the basic body plan.

3. Your students might enjoy discussing whether or not they are larvae and if they can be said to go through metamorphosis. (No, to both questions.)

4. The website of the University of California Museum of Paleontology is an excellent resource in support of evolution and the history of life. The following portion of that website specifically addresses the Cambrian period: www.ucmp.berkeley.edu/cambrian/camb.html.

Active Lecture Tips

1. When considering animals in general, students are typically biased toward vertebrate examples. As a thought exercise, consider starting your first lecture on animal diversity by asking students to write down the name of the very first type of animal that comes to their minds, without giving it any extra thought. Depending upon your class size, either tabulate their responses quickly or have students raise their hands to indicate the type of animal they chose. In general, fewer than 5% (often fewer than 1%) of my students have thought of an invertebrate. This exercise makes the point that what we tend to think of, when we think of animals, is vertebrates. Many of us have had a dog, cat, or other vertebrate for a pet. Yet more than 95% of all known species of animals are invertebrates. The content in Chapter 17 should help expand students’ understanding of what it means to be an animal.

2. Before addressing the subject of animal symmetry, ask your students to work in pairs and try to list the adaptive advantages of radial versus bilateral symmetry found in animals. This sort of comparison raises an opportunity to make some larger points about biology. There is no one best animal. Each form, each adaptation, and each body plan has advantages and disadvantages. The value of adaptations is relative to the organism’s environment. Most adaptations represent a compromise.

Nutrition by Ingestion, the Animal Way of Life

What is an Animal?

Most animals

are diploid,

reproduce sexually, and

proceed through basic stages found in most animal life cycles.

In a sea star life cycle, the larva undergoes a major change of body form, called metamorphosis, in becoming an adult capable of reproducing sexually.

Student Misconceptions and Concerns

Teaching Tips

3. Your students might enjoy discussing whether or not they are larvae and if they can be said to go through metamorphosis. (No, to both questions.)

Active Lecture Tips

The Life Cycle of a Sea Star as an Example of Animal Development

Early Animals and the Cambrian Explosion (1 of 3)

Scientists hypothesize that animals evolved from a colonial flagellated protist.

Although molecular data point to a much earlier origin, the oldest animal fossils that have been found are about 560 million years old.

Student Misconceptions and Concerns

Teaching Tips

3. Your students might enjoy discussing whether or not they are larvae and if they can be said to go through metamorphosis. (No, to both questions.)

Active Lecture Tips

Hypothetical Common Ancestor of Animals

Fossils of Precambrian Animals

Early Animals and the Cambrian Explosion (2 of 3)

Animal diversification appears to have accelerated rapidly from 525 to 535 million years ago, during the Cambrian period.

Because so many animal body plans and new phyla appear in the fossils from such an evolutionarily short time span, biologists call this episode the Cambrian explosion.

Student Misconceptions and Concerns

Teaching Tips

3. Your students might enjoy discussing whether or not they are larvae and if they can be said to go through metamorphosis. (No, to both questions.)

Active Lecture Tips

Early Animals and the Cambrian Explosion (3 of 3)

What ignited the Cambrian explosion?

Scientists have proposed several hypotheses, including increasingly complex predator-prey relationships and an increase in atmospheric oxygen.

But whatever the cause of the rapid diversification, it is likely that the set of “master control” genes—the genetic framework of information flow for building complex bodies—was already in place.

Student Misconceptions and Concerns

Teaching Tips

3. Your students might enjoy discussing whether or not they are larvae and if they can be said to go through metamorphosis. (No, to both questions.)

Active Lecture Tips

A Cambrian Seascape

Identifying Major Themes (1 of 3)

It is likely that the set of “master control” genes that allow building complex bodies was in place before rapid diversification.

Which major theme is illustrated by this action?

The relationship of structure to function

Information flow

Pathways that transform energy and matter

Interactions within biological systems

Evolution

Major Themes Answer—Information flow: The information needed to direct the development of diverse body forms is contained in DNA, which is transmitted between generations.

Animal Phylogeny (1 of 2)

Historically, biologists have categorized animals by “body plan,” general features of body structure.

Distinctions between body plans were used to construct phylogenetic trees showing the evolutionary relationships among animal groups.

More recently, a wealth of genetic data has allowed evolutionary biologists to modify and refine groups.

A major branch point in animal evolution distinguishes sponges from all other animals based on structural complexity. Unlike more complex animals, sponges lack tissues, groups of similar cells that perform a function.

Student Misconceptions and Concerns

Teaching Tips

3. Your students might enjoy discussing whether or not they are larvae and if they can be said to go through metamorphosis. (No, to both questions.)

Active Lecture Tips

An Overview of Animal Phylogeny

Checkpoint: In the phylogeny shown to the right, chordates are most closely related to which other animal phylum?

Checkpoint response: Echinoderms

Animal Phylogeny (2 of 2)

A second major evolutionary split is based on body symmetry.

Radial symmetry refers to animals that are identical all around a central axis.

Bilateral symmetry exists where there is only one way to split the animal into equal halves.

The evolution of body cavities also helped lead to more complex animals. A body cavity is a fluid-filled space separating the digestive tract from the outer body wall.

Student Misconceptions and Concerns

Teaching Tips

3. Your students might enjoy discussing whether or not they are larvae and if they can be said to go through metamorphosis. (No, to both questions.)

Active Lecture Tips

Body Symmetry

Body Plans of Bilateral Animals

Major Invertebrate Phyla: Sponges

Invertebrates are animals without backbones and represent 95% of the animal kingdom.

Sponges (phylum Porifera)

are stationary animals,

lack true tissues, and

probably evolved very early from colonial protists.

The body of a sponge resembles a sac perforated with holes. Choanocyte cells move water through the pores into a central cavity and then out of the sponge through a larger opening.

Student Misconceptions and Concerns

1. Students typically expect that an animal will have a head. The subject of a head might have already been introduced when discussing body plans. As you proceed through the animal phyla, have students consider how sponges and cnidarians meet their basic needs without the benefit of a well-defined head.

Teaching Tips

1. Imagine a country cabin with a roaring fire in a fireplace. The windows are partially opened to permit air to rush into the house to feed the fire. This flow of air through the windows, through the home, to the fireplace, and then out the chimney is analogous to the flow of water through a sponge. Many sponges, especially commercial bath sponges, have outer body walls that are highly folded. Simpler vase sponges, with straighter walls, are good examples to show students when discussing this basic water flow pattern.

2. Students may be challenged to fully appreciate why sponges are animals. It might be helpful to return to the distinctions between animals, plants, and fungi when introducing sponges.

3. Just about any glass bottle with a narrow neck makes a good model of the cnidarian body plan. The narrowed neck of the body represents the constricted region of a cnidarian that regulates what enters and leaves the gastrovascular cavity.

4. If students have been stung by a jellyfish, it was a toxin produced by the cnidocytes that caused a reaction. (Nematocysts are the firing part of a cnidocyte cell. The toxin is delivered by the firing of the nematocysts. A new cnidocyte must take the place of one that has fired its nematocyst, since cnidocytes cannot “reload.”)

5. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, they may also include portions of the intestines.

6. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the shell.

7. When discussing cephalopods, the subject of animal intelligence may be noted. Defining and identifying animal intelligence is not a simple task. Consider discussing the correlation of intelligence and predation. Why might these two traits be linked? What other characteristics correlate with intelligence (perhaps sophistication of communication)?

8. The undercooking of meat contributes to the spread of parasitic diseases. If you addressed the denaturation of proteins in Chapter 3, here is a chance to reinforce the points about the effects of heat. Proteins denature and discolor when heated (pink meat turns brown). This same process denatures proteins in parasites and can kill them (although some parasites can survive relatively high temperatures). If any portion of a steak is still pink, the meat has not been cooked enough to denature the meat or parasitic proteins.

9. Annelids and nematodes have the advantage of a digestive tract with openings at both ends. This permits the efficiency and specialization of the digestive tract for one-way flow of ingested materials. Assembly lines enjoy this same advantage, but in the reverse process of construction. Annelids and nematodes use a sort of “disassembly line,” breaking down food as it moves through the digestive tract.

10. Leeches remain an important tool in modern medicine. Consider presenting to your class some examples of the latest use of leeches in medicine or ask your students to research and discuss them. Such short asides can liven up your class.

11. Conceptually, and very generally speaking, the exoskeleton of an arthropod is like the hard outside of an M&M candy. The exoskeleton prevents physical damage to the internal anatomy and prevents desiccation. The outside of an M&M prevents damage to the chocolate and keeps the chocolate from melting or drying out.

12. Many students assume that all insects possess six legs and two pairs of wings. As common examples of variation on this theme, challenge students with images of beetles (in which the outer wings, called elytra, are hardened) and flies (in which one pair of wings is reduced to a pair of structures called halteres).

13. Beetles have a long history in human culture, used in textiles, ornamentation, and jewelry. A quick image search of the Internet will reveal many examples. In particular, note the significance of scarab beetles in ancient Egypt.

14. The life history of dung beetles is a fun and amusing insect story for lecture, revealing the important role of these animals in recycling animal waste. Details of their interesting life cycle can be obtained from many resources, including those resulting from an Internet search for “dung beetle life history.”

15. The bodies of adult echinoderms reveal degrees of radial symmetry, which may cause students to wonder why echinoderms are not grouped with cnidarians. As discussed in the text, the bilateral symmetry of embryonic echinoderms demonstrates the acquisition of radial symmetry from a bilaterally symmetrical ancestor. Thus, echinoderms are more closely associated with other bilaterally symmetrical organisms.

Active Lecture Tips

1. As students survey the major animal phyla, they might perceive the diversity of animals as spread somewhat evenly across the nine major phyla of invertebrates. Yet two-thirds of all known species of life (and at least 80% of all described animal species) are arthropods. Although sources disagree on the number of living species that have been described, there is widespread agreement that the number of undescribed species is many times more than the number of described species. By examining the number of described species, some amazing proportions emerge. You might consider this exercise to make the point. Determine how many students represent 1% of the class. Then have the entire class stand. Tell the students that, collectively, they represent all of the animal species known to exist today. Have 5% of the class sit, representing the proportion of known animal species that are vertebrates. Next, have 15% of the class sit, representing all of the remaining types of animals except arthropods. At this point, everyone standing (80% of the class) represents the proportion of known animal species that are arthropods (a conservative fraction). Finally, have 60% of the arthropod group sit (48% of the entire class), leaving 32% of the entire class standing. Have the class guess what group of animals is represented now (clearly some subgroup of arthropods). This final 32% represents the known number of species of beetles! (The numbers used are rounded. Even higher percentages for beetles and invertebrates may be more accurate. The point of this exercise is the relative proportions rather than precise percentages.)

2. The gastrovascular cavity of cnidarians and flatworms is the functional equivalent of two systems in our bodies. Ask students to work in pairs to explain how nutrients consumed at a meal nourish the cells in our toes. Nutrients absorbed by our gut are transported throughout our body by the circulatory system. Extensions of the gastrovascular cavity permit nutrient distribution in these cnidarians and flatworms.

3. Challenge your students to work in pairs or small groups to identify the advantages of radial and bilateral symmetry. Radial symmetry, such as that seen in many adult echinoderms, enables organisms to respond well to resources and threats in any direction. You cannot sneak up behind their “backs”. This ability is especially adaptive in sedentary or relatively sedentary organisms, such as sea urchins, sea stars, and cnidarians. Ask your students if these same advantages also occur in radially symmetrical plants.

4. See the Activity What Animal Subgroup Do I Belong To? A Twenty Questions Game on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.

Anatomy of a Sponge

Checkpoint: In what fundamental way does the structure of a sponge differ from that of all other animals?

Checkpoint response: A sponge has no tissues.

Cnidarians (1 of 2)

Cnidarians (phylum Cnidaria) are characterized by

the presence of body tissues,

radial symmetry, and

tentacles with stinging cells.

The basic body plan of a cnidarian is a sac with a central digestive compartment, the gastrovascular cavity.

The body plan has two variations:

the stationary polyp and

the floating medusa.

Student Misconceptions and Concerns

Teaching Tips

2. Students may be challenged to fully appreciate why sponges are animals. It might be helpful to return to the distinctions between animals, plants, and fungi when introducing sponges.

5. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, they may also include portions of the intestines.

6. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the shell.

Active Lecture Tips

Polyp and Medusa Forms of Cnidarians

Checkpoint: In what fundamental way does the body plan of a cnidarian differ from that of other animals?

Checkpoint response: The body of a cnidarian is radially symmetric.

Cnidarians (2 of 2)

Cnidarians (phylum Cnidaria) are carnivores that use tentacles, arranged in a ring around the mouth, to capture prey and push the food into the gastrovascular cavity, where digestion begins.

The tentacles are armed with cnidocytes (“stinging cells”) that function in

defense and

prey capture.

Student Misconceptions and Concerns

Teaching Tips

2. Students may be challenged to fully appreciate why sponges are animals. It might be helpful to return to the distinctions between animals, plants, and fungi when introducing sponges.

5. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, they may also include portions of the intestines.

6. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the shell.

Active Lecture Tips

Cnidocyte Action

Video: Hydra Eating Daphnia (time lapse)

https://mediaplayer.pearsoncmg.com/assets/secs-hydra-eating-daphnia

Video: Jelly Swimming

https://mediaplayer.pearsoncmg.com/assets/secs-jelly-swimming

Video: Thimble Jellies

https://mediaplayer.pearsoncmg.com/assets/secs-thimble-jellies

Molluscs (1 of 3)

Molluscs (phylum Mollusca) are

soft-bodied animals and

usually protected by a hard shell.

Many molluscs feed by extending a file-like organ called a radula to scrape up food.

There are 100,000 known species of molluscs, with most being marine animals.

Student Misconceptions and Concerns

Teaching Tips

2. Students may be challenged to fully appreciate why sponges are animals. It might be helpful to return to the distinctions between animals, plants, and fungi when introducing sponges.

5. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, they may also include portions of the intestines.

6. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the shell.

Active Lecture Tips

Molluscs (2 of 3)

All molluscs have a similar body plan with three main parts:

a muscular foot usually used for movement,

a visceral mass containing most of the internal organs, and

a mantle, a fold of tissue that secretes the shell if present.

Student Misconceptions and Concerns

Teaching Tips

2. Students may be challenged to fully appreciate why sponges are animals. It might be helpful to return to the distinctions between animals, plants, and fungi when introducing sponges.

5. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, they may also include portions of the intestines.

6. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the shell.

Active Lecture Tips

The General Body Plan of a Mollusc

Molluscs (3 of 3)

There are three major groups of molluscs.

Gastropods include snails, which are protected by a single, spiraled shell into which the animal can retreat when threatened, or have no shell at all, as with slugs and sea slugs.

Bivalves include clams, oysters, mussels, and scallops; they have a shell divided into two halves hinged together.

Cephalopods include squids and octopus, are all marine, have fast and agile bodies, have large brains, and include a few species with large, heavy shells, but in most it is small and internal.

Student Misconceptions and Concerns

Teaching Tips

2. Students may be challenged to fully appreciate why sponges are animals. It might be helpful to return to the distinctions between animals, plants, and fungi when introducing sponges.

5. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, they may also include portions of the intestines.

6. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the shell.

Active Lecture Tips

Mollusc Diversity

Video: Nudibranchs

https://mediaplayer.pearsoncmg.com/assets/secs-nudibranchs

Flatworms

Flatworms (phylum Platyhelminthes)

Flatworms are the simplest animals with bilateral symmetry and are ribbonlike, ranging from about 1 mm to about 20 m (about 65 ft) in length.

Most flatworms have a highly branched gastrovascular cavity with a single opening.

There are about 20,000 species of flatworms living in marine, freshwater, and damp terrestrial habitats.

Flatworms include forms that are parasites or free-living in marine, freshwater, or damp habitats. Blood flukes and tapeworms parasitize many vertebrates.

Student Misconceptions and Concerns

Teaching Tips

2. Students may be challenged to fully appreciate why sponges are animals. It might be helpful to return to the distinctions between animals, plants, and fungi when introducing sponges.

5. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, they may also include portions of the intestines.

6. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the shell.

Active Lecture Tips

Flatworm Diversity

Checkpoint: Flatworms are the simplest animals to display a body plan that is ________.

Checkpoint response: bilaterally symmetric

Identifying Major Themes (2 of 3)

The head of a tapeworm is equipped with suckers and hooks that lock the worm to the intestinal lining of the host.

Which major theme is illustrated by this action?

The relationship of structure to function

Information flow

Pathways that transform energy and matter

Interactions within biological systems

Evolution

Major Themes Answer—Relationship of structure to function: The suckers and hooks function as effective tools that allow tapeworms to attach to hosts.

Annelids (1 of 3)

Annelids (phylum Annelida)

Annelids have body segmentation, which is the subdivision of the body along its length into a series of repeated parts called segments.

There are about 16,500 annelid species, ranging in length from less than 1 mm to the giant Australian earthworm, which can grow up to 3 m long.

Annelids live in damp soil, the sea, and most freshwater habitats.

Student Misconceptions and Concerns

Teaching Tips

2. Students may be challenged to fully appreciate why sponges are animals. It might be helpful to return to the distinctions between animals, plants, and fungi when introducing sponges.

5. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, they may also include portions of the intestines.

6. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the shell.

Active Lecture Tips

Annelids (2 of 3)

Annelids exhibit two characteristics shared by all other bilateral animals except flatworms:

a complete digestive tract, which is a digestive tube with two openings—a mouth and an anus—and

a body cavity.

Checkpoint: The body plan of an annelid displays ________, meaning that the body is divided into a series of repeated regions.

Checkpoint response: segmentation

Student Misconceptions and Concerns

Teaching Tips

2. Students may be challenged to fully appreciate why sponges are animals. It might be helpful to return to the distinctions between animals, plants, and fungi when introducing sponges.

5. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, they may also include portions of the intestines.

6. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the shell.

Active Lecture Tips

Segmented Anatomy of an Earthworm

Annelids (3 of 3)

Recent molecular evidence has identified two major groups of annelids.

Errantia—Most errantians are marine and many have active, mobile ways of life. Some errantians, such as a ragworm, crawl or burrow in the sediments; others are free-swimming.

Sedentaria—Sedentarians, which include earthworms, many tube-dwellers, and leeches, tend to be less mobile than errantians. Tube-dwellers build tubes by secreting calcium carbonate or by mixing mucus with bits of sand and broken shells.

Student Misconceptions and Concerns

Teaching Tips

2. Students may be challenged to fully appreciate why sponges are animals. It might be helpful to return to the distinctions between animals, plants, and fungi when introducing sponges.

5. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, they may also include portions of the intestines.

6. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the shell.

Active Lecture Tips

Annelid Diversity

Video: Earthworm Locomotion

https://mediaplayer.pearsoncmg.com/assets/secs-bio-video-earthworm-locomotion

Roundworms

Roundworms (also called nematodes, phylum Nematoda) get their common name from their cylindrical body, which is usually tapered at both ends.

Nematodes are important decomposers and parasites in plants and animals.

Roundworms are among the most numerous and widespread of all animals. About 25,000 species of roundworms are known, and perhaps ten times that number actually exist.

Roundworms range in length from 1 mm to 1 m.

Student Misconceptions and Concerns

Teaching Tips

2. Students may be challenged to fully appreciate why sponges are animals. It might be helpful to return to the distinctions between animals, plants, and fungi when introducing sponges.

5. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, they may also include portions of the intestines.

6. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the shell.

Active Lecture Tips

Roundworm Diversity

Video: Lobster Mouth Parts

https://mediaplayer.pearsoncmg.com/assets/secs-lobster-mouth-parts

Arthropods

Arthropods (phylum Arthropoda) are named for their jointed appendages.

Arthropods include crustaceans (crabs and lobsters), arachnids (spiders and scorpions), and insects. There are over 1 million arthropod species identified, mostly insects.

Arthropods are the most successful animal phylum and are represented in nearly all habitats of the biosphere.

Arthropods are segmented animals with specialized segments and their appendages are adapted for a great variety of functions.

Student Misconceptions and Concerns

Teaching Tips

2. Students may be challenged to fully appreciate why sponges are animals. It might be helpful to return to the distinctions between animals, plants, and fungi when introducing sponges.

5. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, they may also include portions of the intestines.

6. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the shell.

Active Lecture Tips

Arthropod Diversity

General Characteristics of Arthropods

The body of an arthropod is completely covered by an exoskeleton, an external skeleton that provides protection and points of attachment for the muscles that move appendages.

A growing arthropod must occasionally shed its old exoskeleton and secrete a larger one.

This process, called molting, leaves the animal temporarily vulnerable to predators and other dangers.

Student Misconceptions and Concerns

Teaching Tips

2. Students may be challenged to fully appreciate why sponges are animals. It might be helpful to return to the distinctions between animals, plants, and fungi when introducing sponges.

5. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, they may also include portions of the intestines.

6. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the shell.

Active Lecture Tips

Anatomy of a Lobster, a Crustacean

Arachnids

include scorpions, spiders, ticks, and mites,

usually live on land, and

usually have four pairs of walking legs and a specialized pair of feeding appendages.

Student Misconceptions and Concerns

Teaching Tips

2. Students may be challenged to fully appreciate why sponges are animals. It might be helpful to return to the distinctions between animals, plants, and fungi when introducing sponges.

5. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, they may also include portions of the intestines.

6. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the shell.

Active Lecture Tips

Arachnid Characteristics and Diversity

Crustaceans

include crabs, lobsters, crayfish, shrimp, and barnacles, which anchor themselves to rocks, boat hulls, and even whales,

have multiple pairs of specialized appendages, and

are nearly all aquatic.

One group of crustaceans, the isopods, is represented on land by pill bug.

All of these animals exhibit the arthropod characteristic of multiple pairs of specialized appendages.

Student Misconceptions and Concerns

Teaching Tips

2. Students may be challenged to fully appreciate why sponges are animals. It might be helpful to return to the distinctions between animals, plants, and fungi when introducing sponges.

5. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, they may also include portions of the intestines.

6. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the shell.

Active Lecture Tips

Crustacean Characteristics and Diversity

Millipedes and Centipedes (1 of 2)

Millipedes and centipedes are terrestrial arthropods that have similar segments over most of the body.

Millipedes

eat decaying plant matter and

have two pairs of short legs per body segment.

Centipedes

are carnivores, with a pair of poison claws used in defense and to paralyze prey, and

have one pair of legs per body segment.

Student Misconceptions and Concerns

Teaching Tips

2. Students may be challenged to fully appreciate why sponges are animals. It might be helpful to return to the distinctions between animals, plants, and fungi when introducing sponges.

5. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, they may also include portions of the intestines.

6. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the shell.

Active Lecture Tips

Millipedes and Centipedes (2 of 2)

Insect Anatomy and Insect Diversity

Insects typically have a three-part body consisting of a head, a thorax, and an abdomen.

The insect head usually bears a pair of sensory antennae and a pair of eyes.

The mouthparts are adapted for particular kinds of eating.

Flight is one key to the great success of insects.

Insects outnumber all other forms of life combined.

Insects live in almost every terrestrial habitat, fresh water, and the air, but are rare in the seas, where crustaceans are the dominant arthropods.

Student Misconceptions and Concerns

Teaching Tips

2. Students may be challenged to fully appreciate why sponges are animals. It might be helpful to return to the distinctions between animals, plants, and fungi when introducing sponges.

5. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, they may also include portions of the intestines.

6. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the shell.

Active Lecture Tips

Anatomy of a Grasshopper

Insect Diversity (1 of 4)

Animals so numerous, diverse, and widespread as insects affect the lives of all other terrestrial organisms, including people, in many ways.

The bees, flies, and other insects that pollinate our crops and orchards are a beneficial interaction.

Other interactions are harmful to people. For example, insects are carriers of the microbes that cause many human diseases, such as malaria. Insects also eat our field crops.

Thus, insects provide many examples of interactions within biological systems.

Student Misconceptions and Concerns

Teaching Tips

2. Students may be challenged to fully appreciate why sponges are animals. It might be helpful to return to the distinctions between animals, plants, and fungi when introducing sponges.

5. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, they may also include portions of the intestines.

6. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the shell.

Active Lecture Tips

Insect Diversity (2 of 4)

Insect Diversity (3 of 4)

Many insects undergo metamorphosis in their development.

Young resemble adults but are smaller and have different body proportions. The animal goes through a series of molts, each time looking more like an adult, until it reaches full size.

In other cases, insects have distinctive larval stages specialized for eating and growing that look entirely different from the adult stage, which is specialized for dispersal and reproduction. Metamorphosis from the larva to the adult occurs during a pupal stage.

Student Misconceptions and Concerns

Teaching Tips

2. Students may be challenged to fully appreciate why sponges are animals. It might be helpful to return to the distinctions between animals, plants, and fungi when introducing sponges.

5. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, they may also include portions of the intestines.

6. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the shell.

Active Lecture Tips

Metamorphosis of a Monarch Butterfly

Identifying Major Themes (3 of 3)

Bees and flies pollinate our crops and orchards. Other insects are carriers of the microbes that cause many human diseases. Insects also compete with people for food by eating our crops.

Which major theme is illustrated by this action?

The relationship of structure to function

Information flow

Pathways that transform energy and matter

Interactions within biological systems

Evolution

Major Themes Answer—Interactions within biological systems: Insects have multiple types of interactions with people. Some interactions are beneficial to both humans and insects. Others are harmful to humans, insects, or both.

Video: Butterfly Emerging

https://mediaplayer.pearsoncmg.com/assets/secs-butterfly-emerging

Echinoderms (1 of 2)

Echinoderms (phylum Echinodermata) are named for their spiny surfaces. They

lack body segments,

usually have radial symmetry as adults, but the larval stage is bilaterally symmetrical,

have an endoskeleton (interior skeleton) made of hard plates just beneath the skin, and

are all marine and have a water vascular system, a network of water-filled canals that circulate water throughout the echinoderm’s body, facilitating gas exchange and waste disposal.

Student Misconceptions and Concerns

Teaching Tips

2. Students may be challenged to fully appreciate why sponges are animals. It might be helpful to return to the distinctions between animals, plants, and fungi when introducing sponges.

5. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, they may also include portions of the intestines.

6. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the shell.

Active Lecture Tips

Echinoderm Diversity

Video: Echinoderm Tube Feet

https://mediaplayer.pearsoncmg.com/assets/secs-echinoderm-tube-feet

Echinoderms (2 of 2)

Echinoderms share an evolutionary branch with chordates, the phylum that includes vertebrates.

Analysis of embryonic development can differentiate the echinoderms and chordates from the evolutionary branch that includes molluscs, flatworms, annelids, roundworms, and arthropods.

Checkpoint: Contrast the skeleton of an echinoderm with that of an arthropod.

Checkpoint response: An echinoderm has an endoskeleton; an arthropod has an exoskeleton.

Student Misconceptions and Concerns

Teaching Tips

2. Students may be challenged to fully appreciate why sponges are animals. It might be helpful to return to the distinctions between animals, plants, and fungi when introducing sponges.

5. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, they may also include portions of the intestines.

6. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the shell.

Active Lecture Tips

Vertebrate Evolution and Diversity

Vertebrates are the group that includes humans and our closest relatives.

All vertebrates have endoskeletons, a characteristic shared with most echinoderms.

However, vertebrate endoskeletons are unique in having a skull and a backbone, a series of bones called vertebrae (singular, vertebra), for which the group is named.

Student Misconceptions and Concerns

1. The classification of life has been undergoing some major changes, with the addition of domains and the rearrangement of vertebrate groups. Birds are now commonly classified as reptiles, an association likely not seen previously in older K–12 textbooks. Students may be surprised by this association. Fossil discoveries, new techniques, and the attempt to classify organisms only into monophyletic groups have required these reconsiderations.

2. Students might think of vertebrate groups as sharply defined, lacking appreciation for the transitional organisms that illuminate aspects of the rich evolutionary history of vertebrates. Recent discoveries such as the 375-million-year-old fossil fish Tiktaalik reveal important traits that are intermediate between ancient fishes and modern amphibians. Discussion of this important transitional species, as well as similar species such as Archaeopteryx and modern monotremes, will reveal the blurry boundary lines between our classifications of vertebrate groups.

Teaching Tips

1. If you can obtain a model or image of a 1-month-old human embryo, you can demonstrate our four main chordate characteristics. A figure of a human embryo, comparing human and dog embryos of similar stages, was prepared by Charles Darwin and included in the first chapter of his book The Descent of Man.

2. The movement of lampreys from Lake Ontario to the other Great Lakes was historically limited by Niagara Falls. However, the creation of canals to bypass the falls created a channel for lamprey invasion. Lampreys are just one example of the tremendous problem of invasive (alien) species.

3. Eel-skin wallets and purses are typically made from the skin of hagfish. It is possible that one or more of your students has such an item.

4. The wide, flat bodies of rays provide an obvious exception to the general rule that cartilaginous fishes have streamlined bodies. Their ventral mouths and flattened form are well adapted to a life on the ocean bottom.

5. Unlike bony fishes, sharks lack a swim bladder. To lift off the bottom, they swim using their stiff pectoral fins and tail for uplift (along with some buoyant materials in their body cavity).

6. The menacing perception of sharks may be due in part to their particular method of maneuvering in water. Shark fins do not rotate to brake their forward movements. Cruising sharks that swim near an object of interest are not necessarily out to intimidate their prey (although it may have this effect). They may simply be curious, but unable to remain motionless while they investigate their environment.

7. Of all of the vertebrate clades alive today, ray-finned fishes are the most abundant. As noted in the text, more than 27,000 species of ray-finned fishes have been identified.

8. Our knowledge of the basic development of vertebrates was significantly advanced by the early study of amphibian embryos. With clear outer layers, the detailed anatomy of many developing amphibians may be observed without disturbing the organism. Furthermore, their size permitted the identification of basic systems without requiring magnification.

9. Adult salamanders are the only adult tetrapods that can completely regenerate a lost limb. Although some reptiles can regenerate portions of their tails, no other tetrapod can replace part or all of a limb. Even more amazingly, salamanders that suffer the partial loss of a limb regenerate only the missing sections. Research into the mechanisms of regeneration informs our understanding of limb development and brings hope that medical science may one day be able to achieve the same thing in humans.

10. One of the most widely studied laboratory amphibians over the past 200 years has been the axolotl, a Mexican salamander that retains juvenile characteristics, including gills that persist into the adult state. These animals do not normally undergo metamorphosis, reproducing instead in their strictly aquatic form. Many images of these neotenic/paedomorphic axolotls can be found by performing a simple Internet image search for “axolotl.”

11. Reptiles diversified in the Mesozoic in much the same way that mammals have diversified today. To make this point, choose some well-known dinosaurs and compare their habitats to modern mammals that live in a similar ecological niche. (Triceratops was a grazer, much like a modern bison; a duck-billed hadrosaur shares much the same diet as a hippopotamus today; Tyrannosaurus rex may have been an aggressive hunter like a modern tiger.)

12. In the last few years, the debate about the evolution of birds has been punctuated by exciting new fossil discoveries including many from China. Your students should be able to find images and details about these recent discoveries on the Internet.

13. Feathers perform several functions, typically in the same bird. They insulate, they provide species-specific camouflage and coloration for identification by members of the same species, and they form aerodynamic surfaces. As you list these diverse functions, note that all of these functions may not have arisen simultaneously. Thus, feathers may have first evolved as identifying traits or as an important source of insulation long before their role in flight.

14. The intermediate nature of Archaeopteryx can be demonstrated to your students. Have your students compare an Archaeopteryx fossil to the skeleton of a modern chicken. Good photographs of both organisms can be sufficient. Have them note the shared and unique characteristics of the two organisms.

15. The marsupial distribution on Earth is a fine example of biogeography. The geographic isolation of Australia has allowed these animals to evolve independent of much of the eutherian evolution, resulting in greater diversification of marsupials. As suggested for the dinosaurs, students can be encouraged to make parallels between the lifestyles of Australian marsupials and eutherian mammals, which occupy similar ecological niches elsewhere in the world.

Active Lecture Tips

1. The transition to a life on land required some major changes. Ask your students to work in pairs to create a list of the challenges of a vertebrate moving from an aquatic to terrestrial lifestyle. These include adaptations to breathing air, additional skeletal support to account for the loss of the support and buoyancy provided by water, new sensory adaptations with the loss of a lateral line system, adaptations for hearing in air, and mechanisms to reduce water loss through the skin. Reptiles were the first group to be independent of standing water.

2. Challenge your students to work in pairs to contrast the movements (or lack of movement) of the vertebral columns of an alligator, horse, dolphin, and goose. The way amphibians and reptiles move on land reveals the ancestral derivation of their anatomy. As an alligator swings its body from side to side, moving its legs forward, the lateral undulations of its vertebral column resemble those of a fish. In contrast, the movements of a dolphin in water reveal its more recent terrestrial and mammalian ancestry. A dolphin moves its vertebral column vertically so that its back undulates in the same direction, just like a galloping horse. The vertebral column of birds, between their wings, moves little. The rigid back of birds forms a strong base for flight muscle attachments and helps create a smooth aerodynamic surface. However, the necks of birds, such as geese, are extra-long and flexible to compensate for the rigid back.

3. See the Activity, Vertebrate Phylogeny on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.

A Vertebrate Endoskeleton

Characteristics of Chordates (1 of 2)

Chordates (phylum Chordata) share four key features that appear in the embryo and sometimes in the adult.

a dorsal, hollow nerve cord,

a notochord,

pharyngeal slits, and

a post-anal tail.

Chordates also have body segmentation, apparent in the backbone of vertebrates and segmental muscles of all chordates.

Student Misconceptions and Concerns

Teaching Tips

3. Eel-skin wallets and purses are typically made from the skin of hagfish. It is possible that one or more of your students has such an item.

5. Unlike bony fishes, sharks lack a swim bladder. To lift off the bottom, they swim using their stiff pectoral fins and tail for uplift (along with some buoyant materials in their body cavity).

7. Of all of the vertebrate clades alive today, ray-finned fishes are the most abundant. As noted in the text, more than 27,000 species of ray-finned fishes have been identified.

Active Lecture Tips

3. See the Activity, Vertebrate Phylogeny on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.

Chordate Characteristics

Characteristics of Chordates (2 of 2)

Two groups of chordates, tunicates and lancelets, are invertebrates (Figure 17.29).

All other chordates are vertebrates, which retain the basic chordate characteristics but have additional features that are unique, including the backbone.

Figure 17.30 provides an overview of chordate and vertebrate evolution.

Student Misconceptions and Concerns

Teaching Tips

3. Eel-skin wallets and purses are typically made from the skin of hagfish. It is possible that one or more of your students has such an item.

5. Unlike bony fishes, sharks lack a swim bladder. To lift off the bottom, they swim using their stiff pectoral fins and tail for uplift (along with some buoyant materials in their body cavity).

7. Of all of the vertebrate clades alive today, ray-finned fishes are the most abundant. As noted in the text, more than 27,000 species of ray-finned fishes have been identified.

Active Lecture Tips

3. See the Activity, Vertebrate Phylogeny on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.

Invertebrate Chordates

The Vertebrate Genealogy

Fishes (1 of 3)

The first vertebrates were aquatic and probably evolved during the early Cambrian period, about 542 million years ago.

They lacked jaws and are represented today by hagfishes and lampreys.

Hagfishes scavenge dead or dying animals on the cold, dark seafloor.

Most species of lampreys are parasites that use their jawless mouths as suckers to attach to the sides of large fish.

Student Misconceptions and Concerns

Teaching Tips

3. Eel-skin wallets and purses are typically made from the skin of hagfish. It is possible that one or more of your students has such an item.

5. Unlike bony fishes, sharks lack a swim bladder. To lift off the bottom, they swim using their stiff pectoral fins and tail for uplift (along with some buoyant materials in their body cavity).

7. Of all of the vertebrate clades alive today, ray-finned fishes are the most abundant. As noted in the text, more than 27,000 species of ray-finned fishes have been identified.

Active Lecture Tips

3. See the Activity, Vertebrate Phylogeny on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.

Fishes (2 of 3)

The two major groups of living fishes are the

cartilaginous fishes (sharks and rays), with a flexible skeleton made of cartilage, and

bony fishes, with a skeleton reinforced by hard calcium.

Bony fishes include

ray-finned fishes such as tuna and trout and

lobe-finned fishes such as lungfishes and the coelacanth, a deep-sea dweller once thought to be extinct.

Student Misconceptions and Concerns

Teaching Tips

3. Eel-skin wallets and purses are typically made from the skin of hagfish. It is possible that one or more of your students has such an item.

5. Unlike bony fishes, sharks lack a swim bladder. To lift off the bottom, they swim using their stiff pectoral fins and tail for uplift (along with some buoyant materials in their body cavity).

7. Of all of the vertebrate clades alive today, ray-finned fishes are the most abundant. As noted in the text, more than 27,000 species of ray-finned fishes have been identified.

Active Lecture Tips

3. See the Activity, Vertebrate Phylogeny on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.

Fish Diversity

Fishes (3 of 3)

Cartilaginous and bony fishes have a lateral line system that detects minor vibrations in the water.

Bony fish have

a protective flap called the operculum that covers a chamber housing the gills and

a swim bladder, a gas-filled sac that helps them be buoyant.

Student Misconceptions and Concerns

Teaching Tips

3. Eel-skin wallets and purses are typically made from the skin of hagfish. It is possible that one or more of your students has such an item.

5. Unlike bony fishes, sharks lack a swim bladder. To lift off the bottom, they swim using their stiff pectoral fins and tail for uplift (along with some buoyant materials in their body cavity).

7. Of all of the vertebrate clades alive today, ray-finned fishes are the most abundant. As noted in the text, more than 27,000 species of ray-finned fishes have been identified.

Active Lecture Tips

3. See the Activity, Vertebrate Phylogeny on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.

Video: Manta Ray

https://mediaplayer.pearsoncmg.com/assets/secs-manta-ray

Video: Shark Eating A Seal

https://mediaplayer.pearsoncmg.com/assets/secs-shark-eating-a-seal

Amphibians (1 of 2)

Amphibians

exhibit a mixture of aquatic and terrestrial adaptations,

are tied to water because their eggs, lacking shells, dry out quickly in the air, and

typically undergo metamorphosis from an aquatic larva to a terrestrial adult.

Student Misconceptions and Concerns

Teaching Tips

3. Eel-skin wallets and purses are typically made from the skin of hagfish. It is possible that one or more of your students has such an item.

5. Unlike bony fishes, sharks lack a swim bladder. To lift off the bottom, they swim using their stiff pectoral fins and tail for uplift (along with some buoyant materials in their body cavity).

7. Of all of the vertebrate clades alive today, ray-finned fishes are the most abundant. As noted in the text, more than 27,000 species of ray-finned fishes have been identified.

Active Lecture Tips

3. See the Activity, Vertebrate Phylogeny on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.

Amphibian Diversity

Amphibians (2 of 2)

Amphibians were the first vertebrates to colonize land.

They descended from fishes that had lungs and fins with muscles and skeletal supports strong enough to enable some movement, however clumsy, on land.

Terrestrial vertebrates—amphibians, reptiles, and mammals— are collectively called tetrapods, which means “four feet.”

The fossil record chronicles the evolution of four-limbed amphibians from fishlike ancestors.

Student Misconceptions and Concerns

Teaching Tips

3. Eel-skin wallets and purses are typically made from the skin of hagfish. It is possible that one or more of your students has such an item.

5. Unlike bony fishes, sharks lack a swim bladder. To lift off the bottom, they swim using their stiff pectoral fins and tail for uplift (along with some buoyant materials in their body cavity).

7. Of all of the vertebrate clades alive today, ray-finned fishes are the most abundant. As noted in the text, more than 27,000 species of ray-finned fishes have been identified.

Active Lecture Tips

3. See the Activity, Vertebrate Phylogeny on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.

The Origin of Tetrapods

Reptiles

Reptiles include snakes, lizards, turtles, crocodiles, alligators, and birds and a number of extinct groups, including most of the dinosaurs.

Reptiles display two adaptations to living on land.

Scaled waterproof skin prevents dehydration.

Reptiles (including birds) and mammals are amniotes, which produce amniotic eggs, which are fluid-filled, have waterproof shells, and enclose the developing embryo. The amniotic egg functions as a self-contained “pond” that enables amniotes to complete their life cycle on land.

Student Misconceptions and Concerns

Teaching Tips

3. Eel-skin wallets and purses are typically made from the skin of hagfish. It is possible that one or more of your students has such an item.

5. Unlike bony fishes, sharks lack a swim bladder. To lift off the bottom, they swim using their stiff pectoral fins and tail for uplift (along with some buoyant materials in their body cavity).

7. Of all of the vertebrate clades alive today, ray-finned fishes are the most abundant. As noted in the text, more than 27,000 species of ray-finned fishes have been identified.

Active Lecture Tips

3. See the Activity, Vertebrate Phylogeny on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.

Reptile Diversity

Video: Snake Ritual Wrestling

https://mediaplayer.pearsoncmg.com/assets/secs-bio-video-snake-ritual-wrestling

Nonbird Reptiles (1 of 2)

Nonbird reptiles are often called “cold-blooded” animals because they do not use their metabolism extensively to control body temperature.

Because lizards and other nonbird reptiles absorb external heat rather than generating much of their own, they are said to be ectotherms.

By heating directly with solar energy rather than through the metabolic breakdown of food, a nonbird reptile can survive on less than 10% of the calories required by a mammal of equivalent size.

Student Misconceptions and Concerns

Teaching Tips

3. Eel-skin wallets and purses are typically made from the skin of hagfish. It is possible that one or more of your students has such an item.

5. Unlike bony fishes, sharks lack a swim bladder. To lift off the bottom, they swim using their stiff pectoral fins and tail for uplift (along with some buoyant materials in their body cavity).

7. Of all of the vertebrate clades alive today, ray-finned fishes are the most abundant. As noted in the text, more than 27,000 species of ray-finned fishes have been identified.

Active Lecture Tips

3. See the Activity, Vertebrate Phylogeny on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.

Nonbird Reptiles (2 of 2)

Reptiles were far more widespread, numerous, and diverse during the Mesozoic era.

Dinosaurs were the most diverse reptile group and the largest animals ever to live on land.

The age of reptiles began to fade about 70 million years ago. Around that time, the global climate became cooler and more variable.

This was a period of mass extinctions that claimed all the dinosaurs by about 66 million years ago, except for one lineage, known today as birds.

Student Misconceptions and Concerns

Teaching Tips

3. Eel-skin wallets and purses are typically made from the skin of hagfish. It is possible that one or more of your students has such an item.

5. Unlike bony fishes, sharks lack a swim bladder. To lift off the bottom, they swim using their stiff pectoral fins and tail for uplift (along with some buoyant materials in their body cavity).

7. Of all of the vertebrate clades alive today, ray-finned fishes are the most abundant. As noted in the text, more than 27,000 species of ray-finned fishes have been identified.

Active Lecture Tips

3. See the Activity, Vertebrate Phylogeny on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.

The Geologic Time Scale

Birds (1 of 2)

Genetic and fossil evidence shows that birds are indeed reptiles, having evolved from a lineage of small, two-legged dinosaurs called theropods.

Birds have many adaptations that enhance flight, including honeycombed bones, only one ovary instead of a pair, and lack of teeth.

Unlike other reptiles, birds are endotherms, meaning they use their own metabolic heat to maintain a warm, constant body temperature.

Student Misconceptions and Concerns

Teaching Tips

3. Eel-skin wallets and purses are typically made from the skin of hagfish. It is possible that one or more of your students has such an item.

5. Unlike bony fishes, sharks lack a swim bladder. To lift off the bottom, they swim using their stiff pectoral fins and tail for uplift (along with some buoyant materials in their body cavity).

7. Of all of the vertebrate clades alive today, ray-finned fishes are the most abundant. As noted in the text, more than 27,000 species of ray-finned fishes have been identified.

Active Lecture Tips

3. See the Activity, Vertebrate Phylogeny on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.

Birds (2 of 2)

Bird wings are airfoils that illustrate the same principles of aerodynamics as airplane wings.

They are powered by breast muscles anchored to a keel-like breastbone.

Feathers are made of the same protein that forms the scales of reptiles.

Feathers may have functioned first as insulation, helping birds retain body heat, or for courtship displays.

Only later were they adapted as flight gear.

Student Misconceptions and Concerns

Teaching Tips

3. Eel-skin wallets and purses are typically made from the skin of hagfish. It is possible that one or more of your students has such an item.

5. Unlike bony fishes, sharks lack a swim bladder. To lift off the bottom, they swim using their stiff pectoral fins and tail for uplift (along with some buoyant materials in their body cavity).

7. Of all of the vertebrate clades alive today, ray-finned fishes are the most abundant. As noted in the text, more than 27,000 species of ray-finned fishes have been identified.

Active Lecture Tips

3. See the Activity, Vertebrate Phylogeny on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.

The Aerodynamics of a Bald Eagle in Flight

Video: Flapping Geese

https://mediaplayer.pearsoncmg.com/assets/secs-flapping-geese

Video: Soaring Hawk

https://mediaplayer.pearsoncmg.com/assets/secs-bio-video-soaring-hawk

Video: Swans Taking Flight

https://mediaplayer.pearsoncmg.com/assets/secs-swans-taking-flight

Mammals (1 of 2)

There are two major lineages of amniotes: one that led to the reptiles and one that produced mammals.

The first mammals arose about 200 million years ago and were small, nocturnal insect eaters. Mammals became much more diverse after the downfall of the dinosaurs.

Mammals have two unique characteristics:

mammary glands (which produce milk, a nutrient-rich substance to feed the young) and

hair, which insulates the body.

100

Student Misconceptions and Concerns

Teaching Tips

3. Eel-skin wallets and purses are typically made from the skin of hagfish. It is possible that one or more of your students has such an item.

5. Unlike bony fishes, sharks lack a swim bladder. To lift off the bottom, they swim using their stiff pectoral fins and tail for uplift (along with some buoyant materials in their body cavity).

7. Of all of the vertebrate clades alive today, ray-finned fishes are the most abundant. As noted in the text, more than 27,000 species of ray-finned fishes have been identified.

Active Lecture Tips

3. See the Activity, Vertebrate Phylogeny on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.

Mammals (2 of 2)

There are three major groups of mammals.

Monotremes are egg-laying mammals.

Marsupials are pouched mammals with a placenta. The placenta consists of embryonic and maternal tissues. It joins the embryo to the mother within the uterus. In the placenta, the embryo receives oxygen and nutrients from maternal blood that flows near the embryonic blood system.

Eutherians are also called placental mammals because their placentas provide a more intimate and longer-lasting association between the mother and her developing young.

101

Student Misconceptions and Concerns

Teaching Tips

3. Eel-skin wallets and purses are typically made from the skin of hagfish. It is possible that one or more of your students has such an item.

5. Unlike bony fishes, sharks lack a swim bladder. To lift off the bottom, they swim using their stiff pectoral fins and tail for uplift (along with some buoyant materials in their body cavity).

7. Of all of the vertebrate clades alive today, ray-finned fishes are the most abundant. As noted in the text, more than 27,000 species of ray-finned fishes have been identified.

Active Lecture Tips

3. See the Activity, Vertebrate Phylogeny on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.

Mammalian Diversity

102

The Human Ancestry: The Evolution of Primates

Primates is the mammalian group that includes Homo sapiens and our closest kin.

Primates evolved from insect-eating mammals in the late Cretaceous, about 65 million years ago.

Those early primates were small, arboreal (tree-dwelling) mammals. Thus, primates were first distinguished by characteristics that were shaped, through natural selection, by the demands of living in the trees.

103

Student Misconceptions and Concerns

1. At the start of the chapter section “The Emergence of Humankind,” the authors directly address two common misconceptions about human evolution. One of these is the depiction of human evolution as a “march of progress” image, a series of apes giving way to increasingly modern-looking and upright humans in a linear progression. Such images are common and can be found easily by searching “human evolution” on a Google image search. The human family tree has many branches, with multiple species existing simultaneously for long periods (more than a million years). Furthermore, representing the diversity of hominin evolution as a narrow progression from past to present is misleading. It would be the equivalent of depicting any one student’s family history as a direct lineage of grandparent to parent to student, ignoring all siblings, cousins, aunts, and uncles.

2. Students will need to be reminded that modern apes and humans share ancestry. Humans are not descendants of modern chimpanzees. This basic observation may need to be repeated to remind students that evolution is a branching family tree united by common descent.

3. Students and biologists in general often expect evolutionary intermediates to have characteristics that are an average of ancestors and descendants. They may expect intermediate forms to have intermediate traits. The concept of mosaic evolution, in which intermediates demonstrate a mixture of primitive and derived traits, also depicts part of the history of life. Human ancestors did not walk partially upright with mid-sized brains. Instead, upright posture evolved before larger brains, revealing a “mosaic” of traits.

4. Students may continue to struggle with false Lamarckian concepts of evolution. They should be reminded that organisms do not acquire characteristics because of want or need. Instead, naturally occurring genetic variations are selected for or against depending on a population’s interactions with its environment. Many students need to be reminded about the process of natural selection wherever it applies.

5. Some students raise objections about evolution because they believe it is incompatible with their religious philosophy or teachings. Some students see humans as an exception to biological rules. How you handle these objections depends upon the greater context of your course in the curriculum and the specific political and social circumstances of your institution. Reminding students about the rules and philosophy of science may help to clarify the particular perspective of biology and science.

Teaching Tips

1. You may wish to discuss with your class the human versions of the primate traits addressed at the beginning of this chapter section. For example, do we have a loosely connected shoulder, good dexterity, eyes with overlapping fields of vision, and extensive periods of parental care? (The answer to all of these questions is “yes.”)

2. Students are often unaware of a second type of chimpanzee, the bonobo. An excellent source of information about this underappreciated species can be found at http://bonobo.org/.

3. Your students may enjoy a conversation to identify traits unique to humans. To what degree are tool-marking and symbolic language only human traits? What traits are found only in humans?

4. Figure 17.39 is an excellent way to introduce the history of human evolution. The vertical bars represent the known history of each species based on the discovery of fossils. However, the relationships between the species are not represented, because of uncertainty. The ongoing efforts to work through human ancestral relationships reveal the process of science: forming tentative hypotheses that are refined as more evidence and insight are added.

5. Students may wish to debate whether we are more intelligent than our cave-dwelling ancestors. What is the distinction between knowledge and intelligence? If your course permits it, these could be some interesting discussions.

6. Students may wonder if people living today with larger brains are indeed more intelligent than other smaller-brained people. Although this relationship may generally be true between species, there is no clear evidence that it is valid within a species.

7. There are many excellent Internet sites addressing aspects of human evolution. Here are two:

The Smithsonian Institute at http://humanorigins.si.edu/

http://www.sciencemag.org/topic/human-evolution

Active Lecture Tips

1. See the Activity, What Do My Classmates Think about Evolution? What Do Scientists Believe About Religion? on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.

2. Consider asking your students to work in small groups to speculate on the adaptive advantages of speech, language, and music in early humans. The resulting discussion may help students practice the language of evolution and natural selection.

The Evolution of Primates (1 of 3)

The arboreal primate traits include

limber shoulder joints, which make it possible to swing from branch to branch,

eyes that are close together on the front of the face, creating overlapping fields of vision that enhance depth perception,

excellent eye-hand coordination, and

extensive parental care. Mammals devote more energy to caring for their young than most other vertebrates, and primates are among the most attentive parents of all mammals.

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Student Misconceptions and Concerns

Teaching Tips

2. Students are often unaware of a second type of chimpanzee, the bonobo. An excellent source of information about this underappreciated species can be found at http://bonobo.org/.

3. Your students may enjoy a conversation to identify traits unique to humans. To what degree are tool-marking and symbolic language only human traits? What traits are found only in humans?

7. There are many excellent Internet sites addressing aspects of human evolution. Here are two:

The Smithsonian Institute at http://humanorigins.si.edu/

http://www.sciencemag.org/topic/human-evolution

Active Lecture Tips

The Evolution of Primates (2 of 3)

Taxonomists divide the primates into three main groups.

The first group of primates lives in Madagascar, southern Asia, and Africa and includes lemurs, lorises, and bush babies.

Tarsiers, small nocturnal tree-dwellers found only in Southeast Asia, form the second group of primates.

The third group, anthropoids, includes monkeys and apes. Anthropoids also have a fully opposable thumb; that is, they can touch the tips of all four fingers with their thumb.

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Student Misconceptions and Concerns

Teaching Tips

2. Students are often unaware of a second type of chimpanzee, the bonobo. An excellent source of information about this underappreciated species can be found at http://bonobo.org/.

3. Your students may enjoy a conversation to identify traits unique to humans. To what degree are tool-marking and symbolic language only human traits? What traits are found only in humans?

7. There are many excellent Internet sites addressing aspects of human evolution. Here are two:

The Smithsonian Institute at http://humanorigins.si.edu/

http://www.sciencemag.org/topic/human-evolution

Active Lecture Tips

The Evolution of Primates (3 of 3)

Our closest anthropoid relatives are the nonhuman apes: gibbons, orangutans, gorillas, and chimpanzees, which live only in tropical regions of the Old World.

Although all apes are capable of living in trees, only gibbons and orangutans are primarily arboreal.

Gorillas and chimpanzees are highly social.

Apes have larger brains proportionate to body size than monkeys, and more adaptable behavior.

Apes include humans.

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Student Misconceptions and Concerns

Teaching Tips

2. Students are often unaware of a second type of chimpanzee, the bonobo. An excellent source of information about this underappreciated species can be found at http://bonobo.org/.

3. Your students may enjoy a conversation to identify traits unique to humans. To what degree are tool-marking and symbolic language only human traits? What traits are found only in humans?

7. There are many excellent Internet sites addressing aspects of human evolution. Here are two:

The Smithsonian Institute at http://humanorigins.si.edu/

http://www.sciencemag.org/topic/human-evolution

Active Lecture Tips

Primate Phylogeny

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Video: Gibbons Brachiating

https://mediaplayer.pearsoncmg.com/assets/secs-gibbons-brachiating

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Video: Chimp Cracking Nut

https://mediaplayer.pearsoncmg.com/assets/secs-bio-video-chimp-cracking-nut

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Primate Diversity

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The Emergence of Humankind: Some Common Misconceptions

The fossil record and molecular systematics indicate that humans and chimpanzees have shared a common African ancestry for all but the last 6–7 million years.

Misconceptions about human evolution persist. One of these myths is the question “If chimpanzees were our ancestors, then why do they still exist?”

Scientists do not think that humans evolved from chimpanzees. Present-day humans and chimpanzees diverged from a common ancestor several million years ago.

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Student Misconceptions and Concerns

Teaching Tips

2. Students are often unaware of a second type of chimpanzee, the bonobo. An excellent source of information about this underappreciated species can be found at http://bonobo.org/.

3. Your students may enjoy a conversation to identify traits unique to humans. To what degree are tool-marking and symbolic language only human traits? What traits are found only in humans?

7. There are many excellent Internet sites addressing aspects of human evolution. Here are two:

The Smithsonian Institute at http://humanorigins.si.edu/

http://www.sciencemag.org/topic/human-evolution

Active Lecture Tips

Some Common Misconceptions

Another myth envisions human evolution as a ladder with a series of steps leading directly from an ancestral anthropoid to Homo sapiens, often illustrated as a parade of fossil hominins (members of the human family) becoming progressively more modern.

As Figure 17.39 shows, there were times in hominin history when several human species coexisted.

Instead, human evolution is more like a multibranched bush than a ladder.

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Student Misconceptions and Concerns

Teaching Tips

2. Students are often unaware of a second type of chimpanzee, the bonobo. An excellent source of information about this underappreciated species can be found at http://bonobo.org/.

3. Your students may enjoy a conversation to identify traits unique to humans. To what degree are tool-marking and symbolic language only human traits? What traits are found only in humans?

7. There are many excellent Internet sites addressing aspects of human evolution. Here are two:

The Smithsonian Institute at http://humanorigins.si.edu/

http://www.sciencemag.org/topic/human-evolution

Active Lecture Tips

A Timeline of Human Evolution

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Australopithecus and the Antiquity of Bipedalism (1 of 2)

Present-day humans and chimpanzees clearly differ in two major physical features: Humans are bipedal (walk upright) and have much larger brains. When did these features emerge?

In the early 1900s, scientists hypothesized that increased brain size was the initial change that separated hominins from other apes.

That hypothesis was overturned when a team of researchers in Ethiopia unearthed a stunning 3.24-million-year-old female hominin that had a small brain and walked on two legs.

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Student Misconceptions and Concerns

Teaching Tips

2. Students are often unaware of a second type of chimpanzee, the bonobo. An excellent source of information about this underappreciated species can be found at http://bonobo.org/.

3. Your students may enjoy a conversation to identify traits unique to humans. To what degree are tool-marking and symbolic language only human traits? What traits are found only in humans?

7. There are many excellent Internet sites addressing aspects of human evolution. Here are two:

The Smithsonian Institute at http://humanorigins.si.edu/

http://www.sciencemag.org/topic/human-evolution

Active Lecture Tips

Australopithecus and the Antiquity of Bipedalism (2 of 2)

Officially named Australopithecus afarensis, but nicknamed Lucy by her discoverers, the 3.24-million-year-old individual was only about 3 feet tall with a head about the size of a softball.

Corroborating evidence of early bipedalism was found soon after—the footprints of two upright-walking hominins preserved in a 3.6-million-year-old layer of volcanic ash

Since these initial discoveries, many more Australopithecus afarensis fossils have been found, including most of the skeleton of a 3-year-old member of the species and other species of Australopithecus.

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Student Misconceptions and Concerns

Teaching Tips

2. Students are often unaware of a second type of chimpanzee, the bonobo. An excellent source of information about this underappreciated species can be found at http://bonobo.org/.

3. Your students may enjoy a conversation to identify traits unique to humans. To what degree are tool-marking and symbolic language only human traits? What traits are found only in humans?

7. There are many excellent Internet sites addressing aspects of human evolution. Here are two:

The Smithsonian Institute at http://humanorigins.si.edu/

http://www.sciencemag.org/topic/human-evolution

Active Lecture Tips

The Antiquity of Upright Posture

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Homo habilis and the Evolution of Inventive Minds

Enlargement of the human brain is first evident in fossils from East Africa dating to about 2.4 million years ago. Thus, the fundamental human trait of an enlarged brain evolved a few million years after bipedalism.

Anthropologists have found skulls with brain capacities intermediate in size between those of the latest Australopithecus species and those of Homo sapiens.

Simple handmade stone tools are sometimes found with the larger-brained fossils, which have been dubbed Homo habilis (“handy man”).

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Student Misconceptions and Concerns

Teaching Tips

2. Students are often unaware of a second type of chimpanzee, the bonobo. An excellent source of information about this underappreciated species can be found at http://bonobo.org/.

3. Your students may enjoy a conversation to identify traits unique to humans. To what degree are tool-marking and symbolic language only human traits? What traits are found only in humans?

7. There are many excellent Internet sites addressing aspects of human evolution. Here are two:

The Smithsonian Institute at http://humanorigins.si.edu/

http://www.sciencemag.org/topic/human-evolution

Active Lecture Tips

Homo erectus and the Global Dispersal of Humanity

Homo erectus

was the first species to extend humanity’s range from Africa to other continents, beginning about 1.8 million years ago,

was taller and had a larger brain capacity than H. habilis, and

migrated to populate many regions of Asia and Europe, moving as far as Indonesia.

Intelligence enabled this species to continue succeeding in Africa and also to survive in the colder climates of the north.

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Student Misconceptions and Concerns

Teaching Tips

2. Students are often unaware of a second type of chimpanzee, the bonobo. An excellent source of information about this underappreciated species can be found at http://bonobo.org/.

3. Your students may enjoy a conversation to identify traits unique to humans. To what degree are tool-marking and symbolic language only human traits? What traits are found only in humans?

7. There are many excellent Internet sites addressing aspects of human evolution. Here are two:

The Smithsonian Institute at http://humanorigins.si.edu/

http://www.sciencemag.org/topic/human-evolution

Active Lecture Tips

Homo neanderthalensis (1 of 2)

Homo neanderthalensis, commonly called Neanderthals, had a large brain, hunted big game with tools made from stone and wood, and lived in Europe as much as 350,000 years ago. They spread to the Near East, central Asia, and southern Siberia, but by 28,000 years ago were extinct.

Analysis of DNA extracted from Neanderthal fossils showed that humans are not the descendants of Neanderthals but indicated that humans and Neanderthals shared a common ancestor, with their lineages diverging about 400,000 years ago.

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Student Misconceptions and Concerns

Teaching Tips

2. Students are often unaware of a second type of chimpanzee, the bonobo. An excellent source of information about this underappreciated species can be found at http://bonobo.org/.

3. Your students may enjoy a conversation to identify traits unique to humans. To what degree are tool-marking and symbolic language only human traits? What traits are found only in humans?

7. There are many excellent Internet sites addressing aspects of human evolution. Here are two:

The Smithsonian Institute at http://humanorigins.si.edu/

http://www.sciencemag.org/topic/human-evolution

Active Lecture Tips

Homo neanderthalensis (2 of 2)

Sequencing of Neanderthal genomes suggests that interbreeding between Neanderthals and some populations of Homo sapiens left a genetic legacy in our species.

Roughly 2% of the genomes of most present-day humans came from Neanderthals.

Africans are the exception, as their DNA carries no detectable trace of Neanderthal ancestry.

Scientists also learned that at least some Neanderthals had pale skin and red hair.

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Student Misconceptions and Concerns

Teaching Tips

2. Students are often unaware of a second type of chimpanzee, the bonobo. An excellent source of information about this underappreciated species can be found at http://bonobo.org/.

3. Your students may enjoy a conversation to identify traits unique to humans. To what degree are tool-marking and symbolic language only human traits? What traits are found only in humans?

7. There are many excellent Internet sites addressing aspects of human evolution. Here are two:

The Smithsonian Institute at http://humanorigins.si.edu/

http://www.sciencemag.org/topic/human-evolution

Active Lecture Tips

The Origin and Dispersal of Homo sapiens (1 of 4)

The oldest known fossils of our own species, Homo sapiens,

were discovered in Ethiopia and

date from 160,000 to 195,000 years ago.

DNA studies strongly suggest that all living humans can trace their ancestry back to a single African Homo sapiens lineage that began 160,000 to 200,000 years ago.

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Student Misconceptions and Concerns

Teaching Tips

2. Students are often unaware of a second type of chimpanzee, the bonobo. An excellent source of information about this underappreciated species can be found at http://bonobo.org/.

3. Your students may enjoy a conversation to identify traits unique to humans. To what degree are tool-marking and symbolic language only human traits? What traits are found only in humans?

7. There are many excellent Internet sites addressing aspects of human evolution. Here are two:

The Smithsonian Institute at http://humanorigins.si.edu/

http://www.sciencemag.org/topic/human-evolution

Active Lecture Tips

The Origin and Dispersal of Homo sapiens (2 of 4)

The oldest known fossils of Homo sapiens were discovered in Ethiopia and date from 160,000 to 195,000 years ago

Evidence suggests that our species emerged from Africa in one or more waves, spreading first into Asia and then to Europe, Southeast Asia, Australia, and finally to the New World (North and South America).

The date of the first arrival of humans in the New World is uncertain, although generally accepted evidence suggests a minimum of 15,000 years ago.

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Student Misconceptions and Concerns

Teaching Tips

2. Students are often unaware of a second type of chimpanzee, the bonobo. An excellent source of information about this underappreciated species can be found at http://bonobo.org/.

3. Your students may enjoy a conversation to identify traits unique to humans. To what degree are tool-marking and symbolic language only human traits? What traits are found only in humans?

7. There are many excellent Internet sites addressing aspects of human evolution. Here are two:

The Smithsonian Institute at http://humanorigins.si.edu/

http://www.sciencemag.org/topic/human-evolution

Active Lecture Tips

The Spread of Homo Sapiens (Dates Given as Years Before Present, BP)

Checkpoint: When would a Homo sapiens individual have had an opportunity to meet a Neanderthal?

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Checkpoint response: between the time Homo sapiens reached the regions inhabited by Neanderthals (no sooner than 115,000 years ago) and the time when the Neanderthals died out (28,000 years ago)

The Origin and Dispersal of Homo sapiens (3 of 4)

Certain uniquely human traits have allowed for the development of human societies.

The primate brain continues to grow after birth.

The period of growth is longest for humans, lengthening the time for parents to care for their offspring and pass along culture, the social transmission of accumulated knowledge, customs, beliefs, and art over generations. The major means of this transmission is language, spoken and written.

Humans have evolved culturally as well as biologically.

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Student Misconceptions and Concerns

Teaching Tips

2. Students are often unaware of a second type of chimpanzee, the bonobo. An excellent source of information about this underappreciated species can be found at http://bonobo.org/.

3. Your students may enjoy a conversation to identify traits unique to humans. To what degree are tool-marking and symbolic language only human traits? What traits are found only in humans?

7. There are many excellent Internet sites addressing aspects of human evolution. Here are two:

The Smithsonian Institute at http://humanorigins.si.edu/

http://www.sciencemag.org/topic/human-evolution

Active Lecture Tips

The Origin and Dispersal of Homo sapiens (4 of 4)

Nothing has had a greater impact on life on Earth than Homo sapiens.

Cultural evolution made modern Homo sapiens a new force in the history of life—a species that could defy its physical limitations.

We do not have to wait to adapt to an environment through natural selection; we simply change the environment to meet our needs.

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Student Misconceptions and Concerns

Teaching Tips

2. Students are often unaware of a second type of chimpanzee, the bonobo. An excellent source of information about this underappreciated species can be found at http://bonobo.org/.

3. Your students may enjoy a conversation to identify traits unique to humans. To what degree are tool-marking and symbolic language only human traits? What traits are found only in humans?

7. There are many excellent Internet sites addressing aspects of human evolution. Here are two:

The Smithsonian Institute at http://humanorigins.si.edu/

http://www.sciencemag.org/topic/human-evolution

Active Lecture Tips

The Process of Science: What Can Lice Tell Us about Ancient Humans?” (1 of 3)

Background: When did humans first start wearing clothes? Archeological evidence provides a very rough time frame.

To find a narrower time range for the origin of clothing, researchers turned to lice, tiny blood-sucking parasites. Our distant ancestors, which were fur-covered like present-day primates, were parasitized by one species of louse.

By about 1.2 million years ago, hominins had lost most of their body hair, stranding lice on our scalps.

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Student Misconceptions and Concerns

Teaching Tips

2. Students are often unaware of a second type of chimpanzee, the bonobo. An excellent source of information about this underappreciated species can be found at http://bonobo.org/.

3. Your students may enjoy a conversation to identify traits unique to humans. To what degree are tool-marking and symbolic language only human traits? What traits are found only in humans?

7. There are many excellent Internet sites addressing aspects of human evolution. Here are two:

The Smithsonian Institute at http://humanorigins.si.edu/

http://www.sciencemag.org/topic/human-evolution

Active Lecture Tips

The Process of Science: What Can Lice Tell Us about Ancient Humans?” (2 of 3)

Researchers hypothesized that analyzing the evolutionary divergence of lice into two distinct types would allow them to estimate when our ancestors first wore clothes.

Method: The number of genetic differences between populations can be used to estimate how long the populations have been separated, a method known as a molecular clock. To construct a molecular clock for the divergence of head lice and clothing lice, researchers compared four DNA sequences for which the mutation rate—the average number of changes—was known.

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Student Misconceptions and Concerns

Teaching Tips

2. Students are often unaware of a second type of chimpanzee, the bonobo. An excellent source of information about this underappreciated species can be found at http://bonobo.org/.

3. Your students may enjoy a conversation to identify traits unique to humans. To what degree are tool-marking and symbolic language only human traits? What traits are found only in humans?

7. There are many excellent Internet sites addressing aspects of human evolution. Here are two:

The Smithsonian Institute at http://humanorigins.si.edu/

http://www.sciencemag.org/topic/human-evolution

Active Lecture Tips

The Process of Science: What Can Lice Tell Us about Ancient Humans?” (3 of 3)

Results: The molecular clock shows that clothing offered a new habitat for the lice between 83,000 and 170,000 years ago, when populations of head lice and clothing lice began to diverge.

Thus, modern humans originated the use of clothing, probably in Africa.

Humans spreading north would have encountered the exceptionally cold climate that resulted from a series of ice ages, making clothing particularly useful.

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Student Misconceptions and Concerns

Teaching Tips

2. Students are often unaware of a second type of chimpanzee, the bonobo. An excellent source of information about this underappreciated species can be found at http://bonobo.org/.

3. Your students may enjoy a conversation to identify traits unique to humans. To what degree are tool-marking and symbolic language only human traits? What traits are found only in humans?

7. There are many excellent Internet sites addressing aspects of human evolution. Here are two:

The Smithsonian Institute at http://humanorigins.si.edu/

http://www.sciencemag.org/topic/human-evolution

Active Lecture Tips

Using Lice to Date the Origin of Clothing

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Evolution Connection: Are We Still Evolving? (1 of 3)

The human body has not changed much in the past 100,000 years.

But as humans wandered far from their site of origin and settled in diverse environments, populations encountered different selective forces.

The high frequency of sickle hemoglobin in certain populations is an adaptation that protects against the deadly disease malaria.

Populations that kept dairy herds evolved the ability to digest lactose as adults.

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Student Misconceptions and Concerns

Teaching Tips

2. Students are often unaware of a second type of chimpanzee, the bonobo. An excellent source of information about this underappreciated species can be found at http://bonobo.org/.

3. Your students may enjoy a conversation to identify traits unique to humans. To what degree are tool-marking and symbolic language only human traits? What traits are found only in humans?

7. There are many excellent Internet sites addressing aspects of human evolution. Here are two:

The Smithsonian Institute at http://humanorigins.si.edu/

http://www.sciencemag.org/topic/human-evolution

Active Lecture Tips

Evolution Connection: Are We Still Evolving? (2 of 3)

One of the most striking differences among people is skin color.

The loss of skin pigmentation in humans who migrated north from Africa is thought to be an adaptation to low levels of ultraviolet (UV) radiation in northern latitudes.

Dark pigment blocks the UV radiation necessary for synthesizing vitamin D, essential for proper bone development, in the skin.

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Student Misconceptions and Concerns

Teaching Tips

2. Students are often unaware of a second type of chimpanzee, the bonobo. An excellent source of information about this underappreciated species can be found at http://bonobo.org/.

3. Your students may enjoy a conversation to identify traits unique to humans. To what degree are tool-marking and symbolic language only human traits? What traits are found only in humans?

7. There are many excellent Internet sites addressing aspects of human evolution. Here are two:

The Smithsonian Institute at http://humanorigins.si.edu/

http://www.sciencemag.org/topic/human-evolution

Active Lecture Tips

People with Different Adaptations to UV Radiation

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Evolution Connection: Are We Still Evolving? (3 of 3)

Recent research has turned up numerous other examples of adaptations that enabled us to colonize Earth’s varied environments.

For instance, indigenous people in the Andes Mountains in South America live at altitudes up to 12,000 feet (2.3 miles), where the air has 40% less oxygen than at sea level.

Researchers have identified genes that have undergone evolutionary changes in response to this challenging environment.

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Student Misconceptions and Concerns

Teaching Tips

2. Students are often unaware of a second type of chimpanzee, the bonobo. An excellent source of information about this underappreciated species can be found at http://bonobo.org/.

3. Your students may enjoy a conversation to identify traits unique to humans. To what degree are tool-marking and symbolic language only human traits? What traits are found only in humans?

7. There are many excellent Internet sites addressing aspects of human evolution. Here are two:

The Smithsonian Institute at http://humanorigins.si.edu/

http://www.sciencemag.org/topic/human-evolution

Active Lecture Tips

Quechuans, Indigenous People Adapted to Living at High Altitude

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