Chapter 4 Evolution Biodiversity

Chapter 4 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 Online The 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. 

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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 Study Earth: 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

Chemical Evolution (1 billion years)

Formation of the earth’s early crust and atmosphere

Small organic molecules form in the seas

Large organic molecules (biopolymers) form in the seas

Biological Evolution (3.7 billion years)

First protocells form in the seas

Single-cell prokaryotes form in the seas

Single-cell eukaryotes form in the seas

Variety of multicellular organisms form, first in the seas and later on land

Fig. 4-2, p. 84

Biological Evolution  This has led to

the variety of species we find on the earth today.

Figure 4-2

Modern humans (Homo sapiens sapiens) appear about 2 seconds before midnight Age of mammals

Age of reptiles Insects and amphibians invade the land

Recorded human history begins about 1/4 second before midnight Origin of life (3.6-3.8 billion years ago)

First fossil record of animals Plants begin invading land Evolution and expansion of life

Fig. 4-3, p. 84

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.

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.

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

225 million years ago

65 million years ago

135 million years ago

Present Fig. 4-5, p. 88

Climate Change and Natural Selection  Changes in climate throughout the

earth’s history have shifted where plants and animals can live.

Figure 4-6

18,000 years before present

Northern Hemisphere Ice coverage

Legend Continental ice Sea ice

Modern day (August)

Note: Modern sea ice coverage represents summer months

Land above sea level

Fig. 4-6, p. 89

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

Number of individuals

Specialist species with a narrow niche Niche separation

Generalist species with a broad niche

Niche breadth Region of niche overlap Resource use

Fig. 4-7, p. 91

SPOTLIGHT Cockroaches: 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

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

Ruddy turnstone Herring gull is a searches tireless scavenger under shells and pebbles Dowitcher probes deeply for small into mud in search of invertebrates snails, marine worms, and small crustaceans

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

Black skimmer seizes small fish at water surface

Louisiana heron wades into water to seize small fish Flamingo feeds on minute organisms in mud

Scaup and other diving ducks feed on mollusks, crustaceans,and aquatic vegetation

(Birds not drawn to scale)

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

Piping plover feeds on insects and tiny crustaceans on sandy beaches

Knot (a sandpiper) picks up worms and small crustaceans left by receding tide

Fig. 4-8, pp. 90-9

Evolutionary Divergence

 Each species has a

beak specialized to take advantage of certain types of food resource.

Figure 4-9

Fruit and seed eaters

Insect and nectar eaters

Greater Koa-finch Kuai Akialaoa Amakihi Kona Grosbeak

Akiapolaau

Crested Honeycreeper

Maui Parrotbill

Unknown finch ancestor

Apapane

Fig. 4-9, p. 91

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.

Geographic Isolation

 …can lead to reproductive isolation,

divergence of gene pools and speciation. Figure 4-10

Adapted to cold through heavier fur,short ears, short legs,short nose. White fur matches snow for camouflage. Arctic Fox Northern population Early fox Population

Spreads northward and southward and separates

Southern Population

Different environmental conditions lead to different selective pressures and evolution into two different species. Adapted to heat through lightweight fur and long Gray Fox ears, legs, and nose, which give off more heat. Fig. 4-10, p. 92

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

Cenozoic

Era

Period Quaternary

Today

Tertiary 65 Cretaceous

Mesozoic

Species and families experiencing mass extinction Extinction Current extinction crisis caused by human activities. Many species are expected to become extinct Extinction within the next 50–100 years. Cretaceous: up to 80% of ruling reptiles (dinosaurs); many marine species including many foraminiferans and mollusks. Extinction Triassic: 35% of animal families, including many reptiles and marine mollusks.

Millions of Bar width represents relative years ago number of living species

Jurassic 180 Triassic 250

Extinction

345

Extinction

Permian

Paleozoic

Carboniferous

Devonian

Permian: 90% of animal families, including over 95% of marine species; many trees, amphibians, most bryozoans and brachiopods, all trilobites. Devonian: 30% of animal families, including agnathan and placoderm fishes and many trilobites.

Silurian Ordovician Cambrian

500

Extinction

Ordovician: 50% of animal families, including many trilobites. Fig. 4-12, p. 93

Effects of Humans on Biodiversity

 The scientific consensus is that human

activities are decreasing the earth’s biodiversity. Figure 4-13

Quaternary

Tertiary

Cretaceous

Devonian

Jurassic

Permian

Carboniferous

Devonian

Silurian

Ordovician

Cambrian

Pre-cambrian

Number of families

Terrestrial organisms

Marine organisms

Millions of years ago

Fig. 4-13, p. 94

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

Phase 1 Make Modified Gene

E. coli

Cell Extract DNA Gene of interest

DNA

Identify and Identify and remove portion extract gene of DNA with with desired trait desired trait

Extract Plasmid

Genetically modified plasmid

Insert modified plasmid into E. coli

Plasmid Remove Insert extracted plasmid (step 2) into plasmid from DNA of (step 3) E. coli

Grow in tissue culture to make copies

Fig. 4-14, p. 95

Phase 2 Make Transgenic Cell E. Coli A. tumefaciens (agrobacterium)

Foreign DNA Plant cell

Host DNA

Nucleus Transfer plasmid copies to a carrier agrobacterium

Transfer plasmid to surface of microscopic metal particle

Agrobacterium inserts foreign DNA into plant cell to yield transgenic cell

Use gene gun to inject DNA into plant cell

Fig. 4-14, p. 95

Phase 3 Grow Genetically Engineered Plant Transgenic cell from Phase 2

Cell division of transgenic cells

Culture cells to form plantlets Transfer to soil Transgenic plants with new traits

Fig. 4-14, p. 95

Phase 3 Grow Genetically Engineered Plant

Transgenic cell from Phase 2

Cell division of transgenic cells

Culture cells to form plantlets Transfer to soil

Transgenic plants with new traits

Stepped Art Fig. 4-14, p. 95

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.

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).