Chapter 5

Chapter 5

Evolution and Biodiversity

Chapter Overview Questions How do scientists account for the

development of life on earth? What is biological evolution by natural

selection, and how can it account for the current diversity of organisms on the earth?

How can geologic processes, climate change and catastrophes affect biological evolution?

What is an ecological niche, and how does it help a population adapt to changing the environmental conditions?

Chapter Overview Questions (cont’d)

How do extinction of species and formation of new species affect biodiversity?

What is the future of evolution, and what role should humans play in this future?

How did we become such a powerful species in a short time?

Updates OnlineThe latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at www.thomsonedu.com to access InfoTrac articles.

InfoTrac: Life After Earth: Imagining Survival Beyond This Terra Firma. Richard Morgan. The New York Times, August 1, 2006 pF2(L).

InfoTrac: Rhinos Clinging to Survival in the Heart of Borneo, Despite Poaching. US Newswire, March 17, 2006.

InfoTrac: Newfound Island Graveyard May Yield Clues to Dodo Life of Long Ago. Carl Zimmer. The New York Times, July 4, 2006 pF3(L).

NASA: Evolvable Systems American Museum of Natural History: Tree of Life PBS: Evolution

Video: Creation Vs. Evolution

This video clip is available in CNN Today Videos for Environmental Science, 2004, Volume VII. Instructors, contact your local sales representative to order this volume, while supplies last.

Core Case StudyEarth: The Just-Right, Adaptable

Planet During the 3.7 billion

years since life arose, the average surface temperature of the earth has remained within the range of 10-20oC.

Figure 4-1

ORIGINS OF LIFE

1 billion years of chemical change to form the first cells, followed by about 3.7 billion years of biological change.

Figure 4-2

Fig. 4-2, p. 84

Variety ofmulticellularorganismsform, firstin the seasand lateron land

Biological Evolution(3.7 billion years)

Chemical Evolution(1 billion years)

Formationof the

earth’searly

crust andatmosphere

Small organic

moleculesform in

the seas

Large organic

molecules(biopolymers)

form in the seas

First protocells form in the

seas

Single-cell prokaryotes

form in the seas

Single-celleukaryotes

form inthe seas

Animation: Stanley Miller’s Experiment

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Biological Evolution

This has led to the variety of species we find on the earth today.

Figure 4-2

Fig. 4-3, p. 84

Modern humans (Homo sapiens sapiens) appear about 2 seconds before midnightRecorded human history begins about 1/4 second before midnight

Origin of life (3.6-3.8 billion years ago)

Age of mammals

Age of reptiles

Insects and amphibians invade the land

First fossil record of animals

Plants begin invading land Evolution and

expansion of life

Animation: Evolutionary Tree of Life

PLAYANIMATION

Video: Creation vs. Evolution

From ABC News, Environmental Science in the Headlines, 2005 DVD.

PLAYVIDEO

How Do We Know Which Organisms Lived in the Past?

Our knowledge about past life comes from fossils, chemical analysis, cores drilled out of buried ice, and DNA analysis.

Figure 4-4

EVOLUTION, NATURAL SELECTION, AND ADAPTATION

Biological evolution by natural selection involves the change in a population’s genetic makeup through successive generations. genetic variability Mutations: random changes in the structure or

number of DNA molecules in a cell that can be inherited by offspring.

Animation: Stabilizing Selection

PLAYANIMATION

Natural Selection and Adaptation: Leaving More Offspring With

Beneficial Traits Three conditions are necessary for biological

evolution: Genetic variability, traits must be heritable, trait

must lead to differential reproduction. An adaptive trait is any heritable trait that

enables an organism to survive through natural selection and reproduce better under prevailing environmental conditions.

Animation: Disruptive Selection

PLAYANIMATION

Animation: Moth Populations

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Animation: Adaptive Trait

PLAYANIMATION

Coevolution: A Biological Arms Race

Interacting species can engage in a back and forth genetic contest in which each gains a temporary genetic advantage over the other. This often happens between predators and prey

species.

Hybridization and Gene Swapping: other Ways to Exchange Genes

New species can arise through hybridization. Occurs when individuals to two distinct species

crossbreed to produce an fertile offspring. Some species (mostly microorganisms) can

exchange genes without sexual reproduction. Horizontal gene transfer

Limits on Adaptation through Natural Selection

A population’s ability to adapt to new environmental conditions through natural selection is limited by its gene pool and how fast it can reproduce. Humans have a relatively slow generation time

(decades) and output (# of young) versus some other species.

Common Myths about Evolution through Natural Selection

Evolution through natural selection is about the most descendants. Organisms do not develop certain traits because

they need them. There is no such thing as genetic perfection.

GEOLOGIC PROCESSES, CLIMATE CHANGE, CATASTROPHES, AND

EVOLUTION

The movement of solid (tectonic) plates making up the earth’s surface, volcanic eruptions, and earthquakes can wipe out existing species and help form new ones. The locations of continents and oceanic basins

influence climate. The movement of continents have allowed

species to move.

225 million years ago

Fig. 4-5, p. 88


Present65 million years ago


Video: Continental Drift

PLAYVIDEO

Climate Change and Natural Selection

Changes in climate throughout the earth’s history have shifted where plants and animals can live.

Figure 4-6

Fig. 4-6, p. 89

Land above sea level

18,000years before present

Northern HemisphereIce coverage

Modern day(August)

Note:Modern sea ice

coveragerepresents

summer months

LegendContinental ice

Sea ice

Video: Dinosaur Discovery


PLAYVIDEO

Catastrophes and Natural Selection

Asteroids and meteorites hitting the earth and upheavals of the earth from geologic processes have wiped out large numbers of species and created evolutionary opportunities by natural selection of new species.

ECOLOGICAL NICHES AND ADAPTATION

Each species in an ecosystem has a specific role or way of life. Fundamental niche: the full potential range of

physical, chemical, and biological conditions and resources a species could theoretically use.

Realized niche: to survive and avoid competition, a species usually occupies only part of its fundamental niche.

Generalist and Specialist Species: Broad and Narrow Niches

Generalist species tolerate a wide range of conditions.

Specialist species can only tolerate a narrow range of conditions.

Figure 4-7

Fig. 4-7, p. 91

Generalist specieswith a broad niche

Num

ber o

f ind

ivid

uals

Resource use

Specialist specieswith a narrow niche

Nicheseparation

Nichebreadth

Region of niche overlap

SPOTLIGHTCockroaches: Nature’s Ultimate

Survivors 350 million years old 3,500 different species Ultimate generalist

Can eat almost anything. Can live and breed almost

anywhere. Can withstand massive

radiation.

Figure 4-A

Specialized Feeding Niches

Resource partitioning reduces competition and allows sharing of limited resources.

Figure 4-8

Fig. 4-8, pp. 90-91

Piping plover feedson insects and tinycrustaceans on sandy beaches

(Birds not drawn to scale)

Black skimmerseizes small fishat water surface

Flamingofeeds on minuteorganismsin mud

Scaup and otherdiving ducks feed on mollusks, crustaceans,and aquatic vegetation

Brown pelican dives for fish,which it locates from the air

Avocet sweeps bill throughmud and surface water in search of small crustaceans,insects, and seeds

Louisiana heron wades intowater to seize small fish

Oystercatcher feeds onclams, mussels, and other shellfish into which it pries its narrow beak

Dowitcher probes deeplyinto mud in search ofsnails, marine worms,and small crustaceans

Knot (a sandpiper)picks up worms andsmall crustaceans leftby receding tide

Herring gull is atireless scavenger

Ruddy turnstone searches

under shells and pebbles

for small invertebrates

Video: Frogs Galore


PLAYVIDEO

Evolutionary Divergence

Each species has a beak specialized to take advantage of certain types of food resource.

Figure 4-9

Fig. 4-9, p. 91

Maui Parrotbill

Fruit and seed eaters Insect and nectar eaters

Kuai AkialaoaAmakihi

Crested Honeycreeper

Apapane

Akiapolaau

Unknown finch ancestor

Greater Koa-finch

Kona Grosbeak

SPECIATION, EXTINCTION, AND BIODIVERSITY

Speciation: A new species can arise when member of a population become isolated for a long period of time. Genetic makeup changes, preventing them from

producing fertile offspring with the original population if reunited.

Animation: Speciation on an Archipelago

PLAYANIMATION

Animation: Evolutionary Tree Diagrams

PLAYANIMATION

Geographic Isolation

…can lead to reproductive isolation, divergence of gene pools and speciation.

Figure 4-10

Fig. 4-10, p. 92

Different environmentalconditions lead to different selective pressures and evolution into two different species.

SouthernPopulation

Northernpopulation

Adapted to heat through lightweightfur and long ears, legs, and nose, which give off more heat.

Adapted to cold through heavier fur,short ears, short legs,short nose. White furmatches snow for camouflage.

Gray Fox

Arctic Fox

Spreadsnorthward

and southwardand separates

Early foxPopulation

Extinction: Lights Out

Extinction occurs when the population cannot adapt to changing environmental conditions.

The golden toad of Costa Rica’s Monteverde cloud forest has become extinct because of changes in climate.

Figure 4-11

Fig. 4-12, p. 93

Tertiary

Bar width represents relative number of living speciesEra Period

Species and families experiencing

mass extinctionMillions ofyears ago

Ordovician: 50% of animal families, including many trilobites.

Devonian: 30% of animal families, including agnathan and placoderm fishes and many trilobites.

500

345

Cambrian

Ordovician

Silurian

Devonian

Extinction

Extinction

Pale

ozoi

cM

esoz

oic

Cen

ozoi

c

Triassic: 35% of animal families, including many reptiles and marine mollusks.

Permian: 90% of animal families, including over 95% of marine species; many trees, amphibians, most bryozoans and brachiopods, all trilobites.Carboniferous

Permian

Current extinction crisis causedby human activities. Many speciesare expected to become extinctwithin the next 50–100 years.Cretaceous: up to 80% of ruling reptiles (dinosaurs); many marine species including manyforaminiferans and mollusks.

Extinction

Extinction

Triassic

Jurassic

Cretaceous

250

180

65Extinction

ExtinctionQuaternary Today

Effects of Humans on Biodiversity

The scientific consensus is that human activities are decreasing the earth’s biodiversity.

Figure 4-13

Fig. 4-13, p. 94

Marineorganisms

Terrestrialorganisms

Num

ber o

f fam

ilies

Millions of years ago

Qua

tern

ary

Tert

iary

Pre-

cam

bria

n

Cam

bria

n

Ord

ovic

ian

Silu

rian

Dev

onia

n

Car

boni

fero

us

Jura

ssic

Dev

onia

n

Perm

ian

Cre

tace

ous

GENETIC ENGINEERING AND THE FUTURE OF EVOLUTION

We have used artificial selection to change the genetic characteristics of populations with similar genes through selective breeding.

We have used genetic engineering to transfer genes from one species to another.

Figure 4-15

Genetic Engineering: Genetically Modified Organisms (GMO)

GMOs use recombinant DNA genes or portions

of genes from different organisms.

Figure 4-14

Fig. 4-14, p. 95

Insert modifiedplasmid into E. coli

Phase 1Make Modified Gene

CellExtract DNA

E. coli

Gene ofinterest

DNA

Identify and extract gene with desired trait

Geneticallymodifiedplasmid

Identify and remove portion of DNA withdesired trait

Remove plasmidfrom DNA of E. coli

Plasmid

ExtractPlasmid

Grow in tissueculture to

make copies

Insert extracted(step 2) into plasmid

(step 3)

Fig. 4-14, p. 95

Plant cell

Phase 2Make Transgenic Cell

Transfer plasmid to surface of microscopic metal particle

Use gene gun to injectDNA into plant cell

Agrobacterium inserts foreign DNA into plant cell to yield transgenic cell

Transfer plasmid copies to a carrier agrobacterium

Nucleus

E. Coli A. tumefaciens(agrobacterium)

Foreign DNAHost DNA

Fig. 4-14, p. 95

Cell division oftransgenic cells

Phase 3Grow Genetically Engineered Plant

Transfer to soil

Transgenic plantswith new traits

Transgenic cell from Phase 2

Culture cells to form plantlets

Fig. 4-14, p. 95

Phase 3Grow Genetically Engineered Plant

Transgenic cell from Phase 2

Cell division oftransgenic cells

Culture cells to form plantlets

Transgenic plantswith new traits

Transfer to soil

Stepped Art

Animation: Transgenic Plants

From ABC News, Biology in the Headlines, 2005 DVD.

PLAYANIMATION

How Would You Vote?

To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living In the Environment.

Should we legalize the production of human clones if a reasonably safe technology for doing so becomes available? a. No. Human cloning will lead to widespread

human rights abuses and further overpopulation. b. Yes. People would benefit with longer and

healthier lives.

THE FUTURE OF EVOLUTION

Biologists are learning to rebuild organisms from their cell components and to clone organisms. Cloning has lead to high miscarriage rates, rapid

aging, organ defects. Genetic engineering can help improve human

condition, but results are not always predictable. Do not know where the new gene will be located

in the DNA molecule’s structure and how that will affect the organism.

Video: Cloned Pooch

From ABC News, Biology in the Headlines, 2005 DVD.

PLAYVIDEO

Controversy Over Genetic Engineering

There are a number of privacy, ethical, legal and environmental issues.

Should genetic engineering and development be regulated?

What are the long-term environmental consequences?

Case Study:How Did We Become Such a Powerful

Species so Quickly? We lack:

strength, speed, agility. weapons (claws, fangs), protection (shell). poor hearing and vision.

We have thrived as a species because of our: opposable thumbs, ability to walk upright,

complex brains (problem solving).

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Chapter 5