BIO

Jean2979

Animal_Diversity_8e_Ch_01.pptx

Home >Biology homework help >BIO

Chapter 1

Science of Zoology and Evolution of animal diversity

A Legacy of Change

Evolutionary diversification of Hawaiian honeycreepers

Science of Zoology (1)

Zoology:

The scientific study of animals

Phylogeny or phylogenetic tree:

A diagram depicting the history of animal life

Branches represent evolutionary lineages

Each branching event represents the historical splitting of an ancestral species to form new ones

Science of Zoology (2)

One major goal of studying animal diversity is to locate the origins of certain key developments such as multicellularity, a coelom, spiral cleavage, vertebrae, and homeothermy

Another goal is to understand historical processes that generate and maintain diverse species and adaptations

Essential Characteristics of Science

Science is guided by natural law

Science must be explanatory by reference to natural law

The conjectures of science are testable against the observable world

The conclusions of science are tentative and therefore not necessarily the final word

Science is falsifiable

Scientific Method

Hypothetic-deductive Method:

Scientific process of making a conjecture and then seeking empirical tests that potentially lead to its rejection

One begins this process by generating hypotheses, or potential explanations of a phenomenon of nature

Hypotheses

Potential answers to questions being asked

Derived from prior observations of nature or from theories derived on such observations

Often constitute general statements about nature that may explain a large number of diverse observations

A scientist must say “If my hypothesis correctly explains past observations, then future observations must match specific expectations.”

Steps of the Scientific Method

Observation

Question

Hypothesis Formation

Empirical Test

Controlled experiment including at least 2 groups

Test Group and Control Group

Conclusions

Accept or reject your hypothesis

Publication

Founders of Theory of Evolution by Natural Selection

Charles Robert Darwin and Alfred Russel Wallace were the first to establish evolution as a powerful scientific theory. Darwin and Wallace independently developed the same theory. A letter and essay from Wallace written to Darwin in 1858 spurred Darwin into writing On the Origin of Species, published in 1859.

Source: Thomas Herbert Maguire/National Library of Medicine

©New York Public Library/Science Source

Pre-Darwinian Evolutionary Ideas

Early Greek philosophers Xenophanes, Empedocles, and Aristotle

Recorded idea that life has a long history of evolutionary change

Recognized fossils as evidence of former life

However, they failed to establish an evolutionary concept that could guide a meaningful study of life’s history

Lamarckism

Jean Baptiste de Lamarck (1744 to 1829)

Authored 1st complete hypothesis of evolution in 1809

Made convincing case that fossils were remains of extinct animals

Proposed an evolutionary mechanism, inheritance of acquired characteristics

Lamarck’s concept of evolution was transformational

We now reject transformational theories because genetic studies show that traits acquired during an organism’s lifetime are not transmitted to offspring

Transformational versus Variational

Darwin’s evolutionary theory

Differs from Lamarck's in being a variational not a transformational theory

According to Darwin, evolutionary change is based in differences that occur among organisms within a population

Evolution occurs at the level of the population, with the frequency of favorable traits increasing over generations

Uniformitarianism

Charles Lyell (1797 to 1875) – Geologist

Principle of Uniformitarianism

Guides scientific study of the history of nature

Laws of physics and chemistry have not changed throughout earth’s history

Past geological events occurred by natural processes similar to those observed today

Lyell’s studies led him to conclude that the earth’s age must be measured in millions of years

Claims left important marks on Darwin’s evolutionary theory

Darwin’s Great Voyage of Discovery

Darwin made extensive collections and observations on a 5 year voyage (1831 to 1836) on the H.M.S Beagle

1-‹#›

Galapagos Islands

The Galapagos Islands viewed from the rim of a volcano, with a giant tortoise in the foreground.

©Cleveland P. Hickman, Jr.

Down House

Darwin’s study at Down House in Kent, England is preserved today much as it was when Darwin wrote On the Origin of Species.

©Cleveland P. Hickman, Jr.

Theories of Evolution and Heredity (1)

Ernst Mayr (Harvard University) proposed that Darwinism should be viewed as five major theories:

Perpetual Change

Common Descent

Multiplication of the Species

Gradualism

Natural Selection

Theories of Evolution and Heredity (2)

Perpetual Change

The living world is neither constant nor perpetually cycling, but is always changing

The varying forms of organisms undergo measurable change across generations throughout time

Documented by the fossil record

Theory upon which the remaining 4 are based

Theories of Evolution and Heredity (3)

Common Descent

All forms of life propagated from a common ancestor through a branching of lineages

Life’s history has the structure of a branching evolutionary tree, known as a phylogeny

Serves as the basis for our taxonomic classification of animals

The Tree of Life

An early tree of life drawn in 1874 by the German biologist Ernst Haeckel, who was strongly influenced by Darwin’s theory of common descent. Some hypotheses shown here have been verified, while others have been rejected in favor of other groupings.

Source: Haeckel, Ernst, The Evolution of Man, New York, NY: D. Appleton, 1886.

Theories of Evolution and Heredity (4)

Multiplication of Species

The evolutionary process produces new species by splitting and transforming older ones

When populations of a species become isolated from each other, the isolated populations undergo separate evolutionary change and can diverge from each other

Theories of Evolution and Heredity (5)

Gradualism

Large differences in anatomic traits that characterize disparate species originate through the accumulation of many small incremental changes over very long periods of time

This theory opposes the notion that large anatomical differences arise by sudden genetic changes within a generation

Theories of Evolution and Heredity (6)

Natural Selection

A natural process by which populations accumulate favorable characteristics throughout long periods of evolutionary time

Adaptations are anatomical structures, physiological processes, or behavioral traits that improve an organism’s ability to survive and leave descendants

Theory of Natural Selection

Darwin developed his theory of natural selection as a series of five observations

He made three inferences based on these observations

Evolution by Natural Selection

Observation 1

Organisms have great potential fertility, which permits exponential growth of populations. (Source: Thomas Malthus)

Observation 2

Natural populations normally do not increase exponentially but remain fairly constant in size. (Source: Charles Darwin and many others)

Observation 3

Natural resources are limited. (Source: Thomas Malthus)

Inference 1

A struggle for existence occurs among organisms in a population. (Source: Thomas Malthus)

Observation 4

Variation occurs among organisms within populations. (Source: animal breeding and systematics)

Observation 5

Variation is heritable. (Source: animal breeding)

Inference 2

Varying organisms show differential survival and reproduction, favoring advantageous traits (natural selection). (Source: Charles Darwin)

Inference 3

Natural selection, acting over many generations, gradually produces new adaptations and new species. (Source: Charles Darwin)

Source: E. Mayr, One Long Argument, 1991, Harvard University Press, Cambridge, MA.

A Two-Step Process

Natural selection can be considered a two-step process with a random component and a nonrandom component

Production of variation by mutation is the random part

Differential persistence of adaptations is nonrandom

Evidence for Perpetual Change

Perpetual Change

Evidenced by the fossil record

Fossil: remnant of past life uncovered from the crust of the earth

Many organisms left no fossils

Examples of Fossil Material - Crinoids

This example of fossilized material shows stalked crinoids (sea lilies, class Crinoidea, phylum Echinodermata) from Devonian rocks. The fossil record shows that these echinoderms reached their greatest diversity millions of years earlier and began a slow decline to the present.

©Alan Morgan RF

Examples of Fossil Material – Insect in Amber

This example of fossilized material shows an insect that got stuck in the resin of a tree approximately 25 million years ago, after which the resin hardened into amber.

©McGraw-Hill Education/Carlyn lverson, photographer

Examples of Fossil Material - Fish

This example of fossilized material shows a fish of the perciform genus Priscacara from rocks of the Green River Formation, Wyoming. Such fish swam here during the Eocene epoch approximately 50 million years ago.

©Alan Morgan RF

Interpreting the Fossil Record

The fossil record is biased because preservation is selective

Vertebrate skeletons and invertebrates with shells provide more records

Soft-bodied animals leave fossils only in exceptional conditions

Fossils form in stratified layers

New deposits are on top of older material

Animals of the Cambrian Period

The major body plans of living animals appear rather abruptly in fossils dated approximately 540 million years old, as reconstructed from fossils preserved in the Burgess Shale of British Columbia, Canada.

©Kevin Schafer/Alamy Stock Photo

Index Fossils

“Index” or “guide” fossils are “indicators” of specific geological periods

Layers often tilt and crack, and can erode or be covered with new deposits

Under heat and pressure, rock becomes metamorphic and fossils are destroyed

A Fossil Skeleton

Shown here is a fossil skeleton from Dinosaur Provincial Park, Alberta, Canada.

©Cleveland P. Hickman, Jr.

Inferred Evolutionary Relationships

Geological Time

Geologists divided Earth’s history into a table of succeeding events based on ordered layers of sedimentary rock

The Law of Stratigraphy

Produces sequence of dates with the oldest layers at the bottom

Radiometric Dating (late 1940s)

Method for determining the absolute age of rocks

Radioactive decay of naturally occurring elements is independent of heat and pressure

Potassium-Argon Dating

Potassium-40 decays to argon-40 and calcium-40

Half-life of potassium-40 is 1.3 billion years

Half of a sample will be gone at end of 1.3 billion years

Half of the remaining potassium-40 will be gone at end of next 1.3 billion years

Calculating the ratio of remaining potassium-40 to amount originally there provides mathematically close estimate of age of deposit

Uranium-Lead Dating

One of the most useful radioactive clocks depends on decay of uranium into lead

Can date age of earth

Error is less than 1% over 2 billion years

Evolutionary Trends

Trends are directional changes in features and diversity of organisms

Fossil record allows observation of evolutionary change over broad periods of time.

Animals species arise and become repeatedly extinct.

Animal species typically survive 1 to 10 million years

Trends in Horse Evolution

Horse evolution shows clear trend

Change occurred in both features of horses and numbers of species

Trends in fossil diversity are due to different rates of species formation and extinction

Stratigraphy of Genera of Horses

Diversity Profile of Animal Groups

Evidence for Common Descent

Darwin proposed that all plants and animals descended from a common ancestor

Life’s history forms a branching tree called a phylogeny

All forms of life, including extinct branches, connect to this tree

Phylogenetic research is successful at reconstructing the history of life

Homology

Darwin saw homology as major evidence for common descent

Richard Owen described homology as “the same organ in different organisms under every variety of form and function”

Vertebrate limbs show the same basic structures modified for different functions

Darwin’s central idea that apes and humans have a common ancestor was explained by anatomical homologies

Homologous Forelimbs

Public Perception of Common Descent

This 1873 advertisement for Merchant’s Gargling Oil ridicules Darwin’s theory of the common descent of humans and apes, which was widely doubted by the general public during Darwin’s lifetime. Darwin devoted an entire book, The Descent of Man and Selection in Relation to Sex, largely to the idea that humans share common descent with apes and other animals. Darwin built his case mostly on homologies between humans and apes.

Source: Library of Congress Prints and Photographs Division, [LC-USZ62-48534]

Reconstruction of Phylogeny

The sharing of homologies among species provides evidence for common descent

We can use homologies to reconstruct a branching evolutionary history of life

We illustrate such evidence using a phylogenetic tree

Different groups of species located at the tips of branches contain different combinations of homologies

Branching points show common ancestry

Phylogeny of Flightless Birds

The tree on the left shows the pattern specified by 15 homologous structures in the skeletons of a group of flightless birds

On the right, the molecular data suggest a different pattern of relationships

Jump to Phylogeny of Flightless Birds Long Description

Ontogeny

Ontogeny is the development of an organism through its entire life

From its origin as a fertilized egg or bud through adulthood to death

Homologous genes may guide developmental differentiation

For example, homeotic genes provide an evolutionary “tool kit” that can be used to construct new body parts by relocating patterns of gene expression to different parts of a developing embryo

Mutations in such genes in fruit flies can cause developmental changes such as legs in place of antennae or an extra pair of wings

Recapitulation

The false notion of recapitulation, also called the biogenetic law, was proposed by the German zoologist Ernst Haeckel

It stated that each successive stage in an organism’s development represented an adult form present in the evolutionary history

Embryologist K.E. von Baer gave an alternative explanation that early developmental features were simply more widely shared among different animal groups than were later ones

Comparison of Vertebrate Embryos

Heterochrony

Evolutionary change in timing of development

Characteristics can be added late in development and features are then moved to an earlier stage

Ontogeny can be shortened or lengthened in evolution

Leads to mosaic of different kinds of developmental evolutionary change in a single lineage

Therefore, cases in which an entire ontogeny recapitulates phylogeny are rare

Multiplication of Species

A branch point in the evolutionary tree occurs where an ancestral species splits into two different species

Total number of species increases in time

Most species eventually become extinct

Definition of “Species”

No consensus exists regarding the definition of species

Most biologists would agree on three important criteria for recognizing a species

Members descend from a common ancestral population

Interbreeding occurs within a species but not among different species

Genotype and phenotype within a species is similar

Reproductive Barriers

Central to forming new species

If diverging populations reunite, before they are isolated, interbreeding maintains one species

Evolution of diverging populations requires they be kept physically separate for a long time

Geographical isolation with gradual divergence provides chance for reproductive barriers to form

Geographic Isolation

Formation of the Isthmus of Panama separated an ancestral population of the sea urchin Eucidaris into two geographically isolated populations. This lead to evolution of separate Caribbean (E. tribuloides) and Pacific (E. thouarsi) species.

(Bottom) ©Sami Sarkis (5)/Alamy Stock Photo (Top) ©Roberto Nistri/Alamy Stock Photo

Allopatric Speciation

Allopatric populations occupy separate geographical areas

Cannot interbreed because they are separated, but could do so if barriers were removed

Separated populations evolve independently and adapt to different environments

Eventually they become distinct enough they cannot interbreed when reunited

Sympatric Speciation

Hypothesis that individuals can speciate while living in different components of the environment

Individuals within a species become specialized for occupying different components of the environment

Parapatric Speciation

Geographically intermediate between allopatric and sympatric speciation

Two species are parapatric if their geographic ranges are primarily allopatric but make contact along a borderline that neither species successfully crosses

Adaptive Radiation

Evolution of several ecologically diverse species from a common ancestral species

Galapagos finches clearly illustrate adaptive radiation on an oceanic archipelago

Speciation in Progress

Populations of Ensatina eschscholtzii form a geographic ring around the Central Valley of California

Adjacent differentiated populations throughout the ring can exchange genes except at the bottom of the ring, where the subspecies E. e. eschscholtzii and E. e. klauberi overlap without interbreeding.

Tentative Model for Evolution of Darwin’s Finches

This model postulates three steps: (1) immigrant finches from South America reach the Galapagos and colonize an island; (2) after a population becomes established, finches disperse to other islands where they adapt to new conditions and change genetically; (3) after a period of isolation, secondary contact is established between different populations. Different populations would be recognized as different species if they cannot interbreed successfully.

Adaptive Radiation of Darwin’s Finches

This figure shows the differences in beaks and feeding habitats of 10 contrasting forms of finches from Santa Cruz, one of the Galapagos Islands. All apparently descended from a single common ancestral finch from South America.

Jump to Adaptive Radiation of Darwin’s Finches Long Description

Gradualism

Darwin’s theory of gradualism

Based on accumulation of small changes over time

Agreed with Lyell that past changes do not depend on catastrophic events not seen today

Evidence for Gradualism

In natural populations

Usually observe small, continuous changes in phenotypes

Under such conditions, major differences among species would require thousands to millions of years

Accumulation of quantitative changes leads to qualitative change

Punctuated Equilibrium

Phyletic Gradualism

If the rule, we would expect to find in the fossil record a long series of intermediate forms bridging phenotypes of ancestral and descendant populations

Instead, we find discontinuous evolutionary changes observed through geological time

Punctuated Equilibrium

Niles Eldridge and Stephen Jay Gould proposed as an explanation for this discontinuity

Theory that phenotypic evolution is concentrated in brief events of speciation followed by long intervals of morphological evolutionary stasis

A Gradualist Model

Changes in morphology on this tree are shown as proceeding more or less steadily through geological time (over millions of years). Bifurcations followed by gradual divergence led to speciation.

A Punctuated Equilibrium Model

This tree shows evolutionary change concentrated in relatively rapid bursts of branching speciation (lateral lines) followed by prolonged periods of little change throughout geological time (millions of years).

Speciation is Episodic

Punctuated equilibrium predicts that speciation is an episodic event occurring over a period of 10,000 to 100,000 years

Species survive for 5 to 10 million years

Thus a speciation event occurs in a “geological instant”, since speciation may account for less than 1% of species life span

Natural Selection (1)

Natural selection provides a natural explanation for origins of adaptation

Rapid evolution by natural selection of industrial melanism in the peppered moths of England

Neo-Darwinism

Darwin did not know the mechanism of inheritance

Saw inheritance as a blending of parental traits

Believed an organism could alter its heredity through use and disuse of parts

August Weismann’s experiments showed an organism could not modify its heredity

Modifications known as neo-Darwinism

Genetic basis of neo-Darwinism eventually became what is now called the chromosomal theory of inheritance

Modern Darwinism

In the 1930s geneticists reevaluated Darwin’s theory mathematically

Population geneticists: scientists who studied variation in natural populations using statistical methods

A new comprehensive theory emerged that brought together population genetics, paleontology, biogeography, embryology, systematics, and animal behavior

Population Genetics

Population Genetics studies evolution as change in gene frequencies in populations

Microevolution

Evolutionary changes in frequencies of different allelic forms of genes

Macroevolution

Origins of new structures and designs, trends, mass extinctions, etc.

The synthesis theory combines micro- and macroevolution and expands Darwinian theory

Microevolution

Genetic variation and change within species

Gene pool

All alleles of all genes that exist in a population

Polymorphism

Different allelic forms of a gene

Allelic frequency

Frequency of a particular allelic form in a population

Since each person carries two alleles, the total numbers of alleles is twice the population size

Frequencies of Blood-Type B Allele

The blood-type B allele () is more common in eastern Europe than in the west. The allele may have arisen in eastern Europe and gradually diffused westward through genetically continuous populations. This allele has no known selective advantage, and its changing frequency probably represents random genetic drift.

Genetic Equilibrium

Whether a gene is dominant or recessive does not affect its frequency

Dominant genes do not supplant recessive genes

Hardy-Weinberg equilibrium

In large two-parent populations, genotypic ratios remain in balance unless disturbed

Accounts for the persistence of rare traits caused by recessive alleles

Recessive conditions in humans include albinism and cystic fibrosis

Genotype Frequency

Genotype frequency can be calculated by expanding the binomial where p and q are allele frequencies

For example, an albino is homozygous recessive

Trait is represented by in the formula:

Albinos occur in one in 20,000 individuals

and

Non-albino, p, is

Carriers would be 2pq

, so one person in 70 is a carrier

Eliminating Recessive Alleles

Eliminating a “bad” recessive allele is nearly impossible

Selection can only act when it is expressed

Recessive allele will persist through heterozygous carriers

Nonrandom Mating

If mating is nonrandom, genotypic frequencies deviate from Hardy-Weinberg expectations.

Positive assortative mating

Individuals mate preferentially with others of the same genotype

Matings among homozygous parents generate offspring that are homozygous like themselves

Increases homozygous genotypes, but does not change allelic frequencies

Inbreeding

Preferential mating among close relatives

Like positive assortative mating, inbreeding increases homozygosity

However, positive assortative mating usually affects one or a few traits

The traits used to select mates

Inbreeding simultaneously affects all variable traits

Greatly increases the chances that rare recessive alleles become homozygous and thereby expressed

Forces of Evolutionary Change

Population geneticists measure evolutionary change as a change in the frequency of an allele in the gene pool

Force of evolutionary change capable of altering allelic frequencies include:

Recurring mutation

Genetic drift

Migration

Natural Selection

Interactions among these factors

Recurring Mutation

Ultimate source of variability in all population

Usually requires interaction with one or more of the other factors to cause noteworthy change in allelic frequencies

The total change in allelic frequencies caused by a single mutation in one individual is vanishingly small

Genetic Drift

Each individual in a population contains at most 2 different alleles at a single locus

Mating pair may have 4 alleles

By chance alone, some of the alleles may not be passed on

Genetic Drift

Chance fluctuation from generation to generation, including loss of alleles

The smaller the population, the greater the effect of drift

Response to change is restricted.

Population Bottlenecks

A large reduction in the size of the population can lead to a loss of genetic variation

Genetic drift takes on increased prominence in the small population

The loss of variation is proportional to the number of generations that population size remains small before the population expands

A bottleneck associated with the formation of a new geographic population is called a founder effect

May lead to speciation

Genetic Drift in Small Populations

Cheetahs are an example of a species whose genetic variability has been depleted to very low levels because of small population size in the past.

Migration

Migration is the movement of individuals from one population to another one prior to mating

Prevents different populations from diverging

If a large species is divided into many small populations genetic drift and selection acting separately in the different populations can produce evolutionary divergence among them

Small amount of migration each generation prevents the different populations from becoming too distinct genetically

Natural Selection (2)

Changes both allelic frequencies and genotypic frequencies

An organism that possesses a superior combination of traits is favored

Sexual selection

Selection for traits that obtain a mate but not for survival

Environmental change alters selective value of traits

Makes fitness a complex problem

Types of Natural Selection

Selection acting on quantitative traits produces 3 evolutionary responses

Stabilizing selection selects against extreme phenotypes

Directional selection phenotypic character shifts in one direction

Disruptive selection selects against average phenotypes

Examples of Types of Selection

Jump to Examples of Types of Selection Long Description

Interactions of Factors

Subdivision of a species into small populations that exchange migrants promotes rapid evolution

Genetic drift and Selection allow many combinations of many genes to be tested

Migration allows favorable new combinations to spread

Interactions of all factors produce change different from what would result from one alone

Major Evolutionary Events

Speciation and Extinction Through Geological Time

A species has two possible fates

Become extinct or

Give rise to new species

Speciation and extinction rates vary among species

Lineages with high speciation and low extinction

Produce the greatest diversity

Species Selection

Differential survival and multiplication of species based on variation among lineages

Species-level properties include mating rituals, social structuring, migration patterns, geographic distribution, etc.

Mass Extinctions

Periodic events where huge numbers of taxa go extinct

Catastrophic species selection may follow these events

Mass extinctions appear to occur at intervals of 26 million years.

The Permian Extinction (225 million years ago)

Half of the families of shallow water invertebrates and 90% of marine invertebrates disappeared

The Cretaceous Extinction (65 million years ago)

Marked the end of the dinosaurs and many other taxa

Mammals were able to use resources due to dinosaur extinction, resulting in adaptive radiation

Five Major Mass Extinctions

Appendix of Image Long Description

Phylogeny of Flightless Birds Long Description

A phylogenetic analysis of molecular data suggests skeletal structures were lost or arose independently. Multiple origins and losses complicate phylogenetic analysis.

Jump back to Phylogeny of Flightless Birds

Adaptive Radiation of Darwin’s Finches Long Description

Tree finches that eat fruit or insects have grasping bills, certain insect eaters and cactus eaters have probing bills, including the warbler finch that has a very slender bill. The ground finches are seed eaters and have stronger crushing bills.

Jump back to Adaptive Radiation of Darwin’s Finches

Examples of Types of Selection Long Description

An ancestral snail population is shown with a normal distribution in coloration. An example of stabilizing selection would favor medium coloration, with more snails in the center of the distribution and both very light and very dark coloration disappearing from the population. An example of directional selection would be a favoring of very dark snails at the detriment of light coloration. An example of disruptive selection would be increases in both very light and very dark snails, but a decrease in medium colored snails.

Jump back to Examples of Types of Selection