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PowerPoint® Lecture Presentations for Biology

Eighth Edition

Neil Campbell and Jane Reece

Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp

Conditions on Early Earth

Chemical and physical processes on early Earth seem to have produced simple unicellular life. This was not spontaneous but over time through a sequence of stages:

1. Abiotic synthesis of small organic molecules

2. Joining of these into macromolecules

3. Packaging of molecules into membranes

4. Emergence of self-replicating molecules

(a) Simple reproduction by

liposomes

(b) Simple metabolism

Phosphate

Maltose

Phosphatase

Maltose

Amylase

Starch

Glucose-phosphate

20 µm

Figure 25.3 Laboratory versions of protobionts

See the following summary of how biology is a special subset of chemistry. Animations of the chemical reactions are particularly illustrative.

https://www.youtube.com/watch?v=fgQLyqWaCbA

The Fossil Record

The fossil record reveals changes in the history of life on earth

Few individuals have fossilized, and even fewer have been discovered; the fossil record is incomplete and biased in favor of species:

That existed for a long time

Were abundant and widespread

Had hard parts capable of mineralizing

Dating rocks and fossils

Recall that sedimentary strata reveal the relative ages of fossils

The absolute ages of fossils can be determined by radiometric dating

A “parent” isotope decays to a “daughter” isotope at a constant rate

Each isotope has a known half-life, the time required for half the parent isotope to decay

Time (half-lives)

Accumulating

“daughter”

isotope

Remaining

“parent”

isotope

Fraction of parent isotope remaining

1/2

1/4

1/8

1/16

Fig. 25-5

Figure 25.5 Radiometric dating

Radiocarbon dating can be used to date fossils up to 75,000 years old

For older fossils, some isotopes can be used to date sedimentary rock layers above and below the fossil

Reversals of the magnetic poles have left their signature on rocks throughout the world, also providing dating information

The geologic record is divided into the Archaean, the Proterozoic, and the Phanerozoic eons

The Phanerozoic encompasses multicellular eukaryotic life and is divided into 3 eras: the Paleozoic, Mesozoic, and Cenozoic (current)

Major boundaries correspond to extinction events in the fossil record

Focus on relative age and order. You need not memorize any numbers (or next 2 slides).

The History of Life

Table 25-1b

Table 25.1

Table 25-1a

Table 25.1

Fig 25-UN2

Prokaryotes

Billions of

years ago

The first single-celled organisms

The oldest known evidence of life are fossilized stromatolites, rock-like layers of bacteria and sediment

Stromatolites date back 3.5 billion years ago

Prokaryotes were the sole inhabitants of Earth until about 2.1 BYA

Stromatolites

Fig. 25-4i

Fig. 25-4j

Fossilized stromatolite

Figure 25.4 Documenting the history of life

Fig 25-UN3

Atmospheric

oxygen

Billions of

years ago

The oxygen revolution

Most atmospheric oxygen is of biological origin, a byproduct of photosynthesis

By about 2.7 billion years ago, O2 began accumulating in the atmosphere and rusting iron-rich terrestrial rocks

The source was likely bacteria similar to modern cyanobacteria

Fig. 25-8

Banded iron formations = evidence of oxygenic photosynthesis

Fig 25-UN4

Single-

celled

eukaryotes

Billions of

years ago

The first eukaryotes

The oldest fossils of eukaryotic cells date back 2.1 billion years

The theory of endosymbiosis explains that mitochondria and plastids (e.g., chloroplasts) were originally prokaryotes living within larger host cells

Ancestors of these organelles may have entered hosts as undigested prey or internal parasites

In the process of becoming more interdependent, they eventually became a single organism

Fig. 25-9-4

Ancestral photosynthetic

eukaryote

Photosynthetic

prokaryote

Mitochondrion

Plastid

Nucleus

Cytoplasm

DNA

Plasma membrane

Endoplasmic reticulum

Nuclear envelope

Ancestral

prokaryote

Aerobic

heterotrophic

prokaryote

Mitochondrion

Ancestral

heterotrophic

eukaryote

Figure 25.9 A model of the origin of eukaryotes through serial endosymbiosis

Fig 25-UN5

Multicellular

eukaryotes

Billions of

years ago

The origin of multicellularity

The evolution of eukaryotic cells allowed for a greater range of unicellular forms, leading to emergence of colonial forms…

A second wave of diversification occurred when true multicellularity evolved, giving rise to algae, plants, fungi, and animals

The oldest known multicellular fossils are small algae from about 1.2 BYA

Fig 25-UN7

Colonization of land

Billions of

years ago

The colonization of land

Multicellular organisms began to colonize land about 500 MYA

Plants and fungi likely colonized land together by 420 MYA

Arthropods and tetrapods then became the most widespread and diverse land animals

Would it even be possible for animals to establish themselves on land before plants and fungi? Our ecology section should provide insights on this.

Continental Drift

At three points, the land masses of Earth have formed a supercontinent

Earth’s continents move slowly over the underlying hot mantle

Oceanic and continental plates can collide, separate, or slide past each other

Interactions between plates cause earthquakes and formation of mountains and islands

Fig. 25-12a

(a) Cutaway view of Earth

Inner

core

Outer

core

Crust

Mantle

Figure 25.12 Earth and its continental plates

Fig. 25-12b

(b) Major continental plates

Pacific

Plate

Nazca

Plate

Juan de Fuca

Plate

Cocos Plate

Caribbean

Plate

Arabian

Plate

African

Plate

Scotia Plate

North

American

Plate

South

American

Plate

Antarctic

Plate

Australian

Plate

Philippine

Plate

Indian

Plate

Eurasian Plate

Figure 25.12 Earth and its continental plates

Fig. 25-13a

South

America

Millions of years ago

65.5

Eurasia

India

Africa

Antarctica

Australia

North America

Madagascar

Cenozoic

Present

Figure 25.13 The history of continental drift during the Phanerozoic eon

Fig. 25-13b

Pangaea

Millions of years ago

135

Mesozoic

251

Paleozoic

Gondwana

Laurasia

Figure 25.13 The history of continental drift during the Phanerozoic eon

Formation of the supercontinent Pangaea about 250 MYA had many effects:

A reduction in shallow water and a colder, drier inland habitat

Changes in climate as continents moved toward and away from the poles

Changes in ocean circulation patterns leading to global cooling

The breakup of Pangaea likely caused widespread speciation (what kind?)

Mass Extinctions

The fossil record shows that most species that have ever lived are now extinct

At times, the rate of extinction has increased dramatically and caused a mass extinction

In each of the “big five” mass extinction events, more than 50% of Earth’s species became extinct

Evidence indicates that a sixth human-caused mass extinction is now occurring

Fig. 25-14

Total extinction rate

(families per million years):

Time (millions of years ago)

Number of families:

Cenozoic

Mesozoic

Paleozoic

542

488

444

416

359

299

251

200

145

Era

Period

65.5

200

100

300

400

500

600

700

800

Figure 25.14 Mass extinction and the diversity of life

Consequences of Mass Extinctions

Mass extinction can alter ecological communities and the niches available to organisms

It can take from 5 to 100 million years for diversity to recover following a mass extinction

Mass extinction can also pave the way for a process that is our next topic

Adaptive Radiation

Rapid speciation as individuals spread to new environments or evolve to carve new niches

Range from global to local, involving one or many ancestors

Largely understood at the microevolutionary level, and hypothesized to occur similarly at the macroevolutionary level

4. Colonization of islands.

5. Colonization of islands.

5. Species evolve different adap-

tations to minimize competition

with other species (character

displacement).

4. Species evolve different

adaptations in allopatry.

3. Populations on

different islands

evolve to become

different species.

2. The ancestral

species spreads

to different

islands.

1. An ancestral

species flies

from mainland

to colonize

one island.

Worldwide Adaptive Radiations

Mammals underwent radiation after the extinction of terrestrial dinosaurs

The Cambrian explosion saw the rapid emergence of most current animal phyla

Other notable radiations include photosynthetic prokaryotes, land plants, insects, and tetrapods

Fig. 25-17

Millions of years ago

Monotremes

(5 species)

250

150

100

200

ANCESTRAL

CYNODONT

Marsupials

(324 species)

Eutherians

(placental

mammals;

5,010 species)

Ancestral

mammal

Figure 25.17 Adaptive radiation of mammals

Regional Adaptive Radiations

Adaptive radiations can occur whenever organisms colonize new environments with little competition

The Hawaiian Islands are one of the world’s great showcases of adaptive radiation

Fig. 25-18

Close North American relative,

the tarweed Carlquistia muirii

Argyroxiphium sandwicense

Dubautia linearis

Dubautia scabra

Dubautia waialealae

Dubautia laxa

HAWAII

0.4

million

years

OAHU

3.7

million

years

KAUAI

5.1

million

years

1.3

million

years

MOLOKAI

MAUI

LANAI

Figure 25.18 Adaptive radiation on the Hawaiian Islands

Evolutionary novelties

Most novel biological structures evolve in many stages from previous structures.

However, natural selection can only act in the context of its current utility. It must always pass the cost/benefit analysis to be favored (cannot build or save up for future generations).

Complex eyes have independently evolved from simple photosensitive cells at least two times: cephalopods and vertebrates.

Fig. 25-24

(a) Patch of pigmented cells

Optic

nerve

Pigmented

layer (retina)

Pigmented cells

(photoreceptors)

Fluid-filled cavity

Epithelium

Optic nerve

Cornea

Retina

Lens

(e) Complex camera-type eye

(d) Eye with primitive lens

Optic nerve

Cornea

Cellular

mass

(lens)

(b) Eyecup

Pigmented

cells

Nerve fibers

Figure 25.24 A range of eye complexity among molluscs

Evolution is not goal oriented

Evolution is like tinkering: a process in which new forms arise by the modification of existing forms and structures.

Apparent trends should always be examined in a broad context, including both extinct and extant lineages.

Extracting a single evolutionary progression from the fossil record can be highly misleading.

E.g., things could have turned out very differently for the lineage leading to modern horses.

Fig. 25-25

Recent

(11,500 ya)

Neohipparion

Pliocene

(5.3 mya)

Pleistocene

(1.8 mya)

Hipparion

Nannippus

Equus

Pliohippus

Hippidion and other genera

Callippus

Merychippus

Archaeohippus

Megahippus

Hypohippus

Parahippus

Anchitherium

Sinohippus

Miocene

(23 mya)

Oligocene

(33.9 mya)

Eocene

(55.8 mya)

Miohippus

Paleotherium

Propalaeotherium

Pachynolophus

Hyracotherium

Orohippus

Mesohippus

Epihippus

Browsers

Grazers

Key

Figure 25.25 The branched evolution of horses

Origin of solar system

and Earth

Paleozoic

Meso-

zoic

Ceno-

zoic

Proterozoic

Archaean

Billions of

years ago

If the history of Earth were rescaled to an hour (minute hand on our “clock” diagram),

humans would have originated less than

0.2 seconds ago!

Check out the following video that uses a football field to map key events in the history of life.

https://www.youtube.com/watch?v=M8V_glRW1hA