Biodiversity and Evolution

Chapter 4

4-1 What Is Biodiversity and WhyIs It Important?

Concept 4-1 The biodiversity found in genes,species, ecosystems, and ecosystem processesis vital to sustaining life on earth.

Biodiversity Is a Crucial Part of theEarth’s Natural Capital

Vital renewable resource

Species diversity

Ecosystem diversity

Functional diversity

Natural Capital: Major Components ofthe Earth’s Biodiversity

4-2 Where Do Species Come From?

Concept 4-2A The scientific theory of evolutionexplains how life on earth changes over timethrough changes in the genes of populations.

Concept 4-2B Populations evolve when genesmutate and give some individuals genetic traitsthat enhance their abilities to survive and toproduce offspring with these traits (naturalselection).

Biological Evolution by Natural SelectionExplains How Life Changes over Time

Biological evolution

Natural selection• Charles Darwin• Alfred Russel Wallace

Tree of Life

Six Major Kingdoms of Species asa Result of Natural Selection

Fig. 4-3, p. 81

CenozoicMesozoic

Paleozoic

Precambrian

Mill

ions

of y

ears

ago

First humansExtinction of dinosaursPlantscolonize land

Origin ofmulticellularorganisms

Oldesteukaryotic fossils

Accumulation ofO2 in atmospherefrom photosyntheticcyanobacterium

Prokaryotes Eukaryotes

Origin of Earth

Earth cool enoughfor crust to solidify

Oldest prokaryoticfossils

AnimalsFungiPlantsProtistsArchaebacteriaEubacteria

0

500

4,500

4,000

3,500

3,000

2,500

2,000

1,500

1,000

The Fossil Record Tells Much of theStory of Evolution

Fossils• Physical evidence of ancient organisms• Reveal what their internal structures looked

like

Fossil record is incomplete: why?

Fossilized Skeleton of an Herbivore thatLived during the Cenozoic Era

The Genetic Makeup of a PopulationCan Change

Populations evolve by becoming geneticallydifferent

Genetic variations• First step in biological evolution• Occurs through mutations in reproductive cells

Individuals in Populations with BeneficialGenetic Traits Can Leave More Offspring

Natural selection: acts on individuals• Second step in biological evolution• Adaptation may lead to differential reproduction• Genetic resistance

When environmental conditions change,populations• Adapt• Migrate• Become extinct

Fig. 4-5, p. 83

A group of bacteria,including geneticallyresistant ones, areexposed to anantibiotic

Most of the normalbacteria die

The geneticallyresistant bacteriastart multiplying

Eventually theresistant strainreplaces the strainaffected bythe antibiotic

Normalbacterium

Resistantbacterium

Evolution by Natural Selection

Case Study: How Did Humans BecomeSuch a Powerful Species?

Three human adaptations• Strong opposable thumbs• Walk upright• Complex brain

Adaptation through Natural SelectionHas Limits

Genetic change must precede change in theenvironmental conditions• Traits must already be present

Reproductive capacity• Fast vs slow

Three Common Myths about Evolutionthrough Natural Selection

“Survival of the fittest” is not “survival of thestrongest”

Organisms do not develop traits out of need orwant

No grand plan of nature for perfect adaptation

4-3 How Do Geological Processes andClimate Change Affect Evolution?

Concept 4-3 Tectonic plate movements,volcanic eruptions, earthquakes, and climatechange have shifted wildlife habitats, wiped outlarge numbers of species, and createdopportunities for the evolution of new species.

Geologic Processes Affect NaturalSelection

Tectonic plates affect evolution and the locationof life on earth• Location of continents and oceans• Species physically move, or adapt, or form new

species through natural selection

Earthquakes• Species isolation

Volcanic eruptions• Habitat destruction

Animation: Continental drift

Fig. 4-6, p. 85

225 million years ago 135 million years ago

65 million years ago Present

Climate Change and Catastrophes AffectNatural Selection

Ice ages followed by warming temperatures

Collisions between the earth and large asteroids• New species• Extinction

Fig. 4-7, p. 85

18,000years beforepresent

Modern day(August)

Northern HemisphereIce coverage

LegendContinental ice

Sea iceLand above sea level

Changes in Ice Cover in the Northern HemisphereDuring the last 18,000 years

Science Focus: Earth Is Just Rightfor Life to Thrive

Certain temperature range

Dependence on water

Rotation on its axis

Revolution around the sun

Enough gravitational mass

4-4 How Do Speciation, Extinction, andHuman Activities Affect Biodiversity?

Concept 4-4A As environmental conditionschange, the balance between formation of newspecies and extinction of existing speciesdetermines the earth’s biodiversity.

Concept 4-4B Human activities can decreasebiodiversity by causing the premature extinctionof species and by destroying or degradinghabitats needed for the development of newspecies.

How Do New Species Evolve?

Geographic isolation• When different groups of the same population

become physically isolated (physical barriers)

Reproductive isolation• Occurs after geographic isolation, mutation and

genetic drift may lead to new species (usuallyover thousands to millions of years)

Fig. 4-8, p. 87

Southernpopulation

Early foxpopulation

Spreads northand southand separates

Northernpopulation

Adapted to heatthrough lightweightfur and long ears,legs, and nose,which give off moreheat.

Different environmentalconditions lead to differentselective pressures and evolutioninto two different species.

Arctic Fox Adapted to coldthrough heavier fur,short ears, short legs,and short nose. Whitefur matches snow forcamouflage.

Gray Fox

Geographic Isolation Can Lead to Reproductive Isolation

Animation: Speciation on an archipelago

Extinction is Forever

Extinction• An entire species ceases to exist

Endemic species (found in only one area)• Particularly vulnerable because they are

generally highly spcialized

Extinction Can Affect One Species orMany Species at a Time

Mass extinction• How numbered is debated: 3–5 (5 is the generally

accepted number)

4-5 What Is Species Diversity and WhyIs It Important?

Concept 4-5 Species diversity is a majorcomponent of biodiversity and tends to increasethe sustainability of ecosystems.

Species Diversity: Variety, Abundance ofSpecies in a Particular Place

Species diversity• Species richness – number of species• Species evenness – relative abundance of each

Diversity varies with geographical location• Most species-rich communities

• Tropical rain forests• Coral reefs• Ocean bottom zone• Large tropical lakes

Variations in Species Richness andSpecies Evenness

Species-Rich Ecosystems Tend to BeProductive and Sustainable

Species richness seems to increase productivityand stability or sustainability

4-6 What Roles Do Species Play inEcosystems?

Concept 4-6A Each species plays a specificecological role called its niche.

Concept 4-6B Any given species may play oneor more of five important roles—native,nonnative, indicator, keystone, or foundationroles—in a particular ecosystem.

Each Species Plays a Unique Rolein Its Ecosystem

Ecological niche – species role• Pattern of living, “a species way of life”

Generalist species• Broad niche (e.g., racoon, Fig. 4-11)

Specialist species• Narrow niche (e.g., panda, Fig. 4-11)

Fig. 4-11, p. 91

Num

ber o

f ind

ivid

uals

Specialist specieswith a narrow niche

Resource use

Region ofniche overlap

Nichebreadth

Nicheseparation

Generalist specieswith a broad niche

Case Study: Cockroaches: Nature’sUltimate Survivors

Cockroaches• Generalists• High reproductive rates

Giant panda and tiger salamanders• Specialists• Low reproductive rates

Cockroach

Fig. 4-13, p. 93

Black skimmerseizes small fishat water surfaceBlack skimmerseizes small fishat water surface

Brown pelican divesfor fish, which itlocates from the air Avocet sweeps bill

through mud andsurface water in searchof small crustaceans,insects, and seeds

Dowitcher probesdeeply into mud insearch of snails,marine worms, andsmall crustaceans Herring gull

is a tirelessscavenger

Ruddy turnstonesearches undershells and pebblesfor smallinvertebrates

Flamingo feedson minuteorganisms inmud

Scaup and otherdiving ducks feedon mollusks,crustaceans, andaquatic vegetation

Louisianaheron wadesinto water toseize smallfish

Oystercatcher feedson clams, mussels,and other shellfishinto which it priesits narrow beak

Knot(sandpiper)picks up wormsand smallcrustaceansleft by recedingtide

Piping ploverfeeds oninsects andtinycrustaceanson sandybeaches

Specialized Feeding Niches of Various Bird Speciesin a Coastal Wetland (e.g., “resource partitioning”)

Niches Can Be Occupied by Native andNonnative Species

Native species

Nonnative species; invasive, alien, or exoticspecies• May spread rapidly• Not all are villains

Indicator Species Serve as BiologicalSmoke Alarms

Indicator species• Can monitor environmental quality

• Trout• Birds• Butterflies• Frogs

Keystone, Foundation Species DetermineStructure, Function of Their Ecosystems

Keystone species• Pollinators• Top predator

Foundation species• Create or enhance their habitats, which benefit

others• Elephants• Beavers

Case Study: Why Should WeProtect Sharks?

Keystone species• Eat dead and dying fish in the ocean• Strong immune systems

• Wounds do not get infected• Almost never get cancer• Could help humans if we understood their immune

system