CHAPTER 4:Biodiversity and

Evolution

Core Case Study: Why Should We Protect

Sharks?• 400 known species• 6 human deaths/year from

shark attacks• 79-97 million sharks killed

every year• Fins – used in Asia for soups and

cure-alls• Organs, meat, hides also valuable• 32% shark species threatened with

extinction• Current news? Not good…

• Keystone species in the ocean • Cancer resistant species!

Fig. 4-1, p. 80

Threatened Sharks!

What is Biodiversity?

• Species diversity• Genetic diversity• Ecosystem diversity• Biomes: regions with distinct

climates/species

• Functional diversity – energy flow and nutrient cycling

• Biodiversity is an important part of natural capital

Fig. 4-2, p. 82

Functional Diversity The biological and chemical processes such as energy flow and matter recycling needed for the survival of species, communities, and ecosystems.

Ecological Diversity The variety of terrestrial and aquatic ecosystems found in an area or on the earth.

Solar energyChemical

nutrients (carbon dioxide, oxygen, nitrogen, minerals)

Heat

Heat Heat

Decomposers (bacteria, fungi)

Producers (plants)

Consumers (plant eaters, meat eaters)Heat Heat

Genetic Diversity The variety of genetic material within a species or a population.

Species Diversity The number and abundance of species present in different communities.

Biodiversity Is a Crucial Part of the Earth’s Natural

Capital• Species: set of individuals who

can mate and produce fertile offspring

• Estimate: 8 million to 100 million species on earth• 10-14 million is the “best guess” • Insects make up most of the world’s

known species

• 1.9 million identified species• Unidentified are mostly in rain

forests and oceans

Classifying Homo Sapiens

Supplement 5, Fig. 2, p. S19

Science Focus: Have You Thanked the Insects Today?

• Bad rep: sting us, bite us, spread disease, eat our food, invade plants

• Pollination: lets flowering plants reproduce sexually

• Free pest control: insects eat other insects

• We need insects more than they need us!

Major Biomes: large regions with distinct climates and certain species

(especially vegetation)

Fig. 4-5, p. 84

Individuals Matter: Edward O. Wilson- A Champion of

Biodiversity• Loved bugs as a kid; Specialized in

ants• Widened scope to earth’s

biodiversity • Encyclopedia of Life – Harvard

• Theory of island biogeography• How species diversity on islands is

affected by the size and location of the islands

• First to use “biodiversity” in a scientific paper

• Won two Pulitzers for his nonfiction books

• His website

Edward O. Wilson

Fig. 4-B, p. 85

Biological Evolution by Natural Selection Explains How Life

Changes over Time

• Fossils• Physical evidence of ancient

organisms• Reveal what their external

structures looked like

• Fossil record: entire body of fossil evidence• Only have fossils of 1% of all

species that lived on earth

Fossilized Skeleton of an Herbivore that Lived during the Cenozoic Era

Fig. 4-6, p. 86

Biological Evolution by Natural Selection Explains How Life

Changes over Time • Biological evolution: how earth’s

life changes over time through changes in the genetic characteristics of populations• Darwin: Origin of Species

• Natural selection: individuals with certain traits are more likely to survive and reproduce under a certain set of environmental conditions

• Huge body of evidence

Evolution of Life on Earth

Supplement 5, Fig. 2, p. S18

Evolution by Natural Selection Works through

Mutations and Adaptations• POPULATIONS EVOLVE by

becoming genetically different• INDIVIDUALS DO NOT EVOLVE!!

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

reproductive cells• Mutations: random changes in DNA

molecules

Evolution by Natural Selection Works through

Mutations and Adaptations• Natural selection: acts on

individuals• Second step in biological evolution• Adaptation may lead to differential

reproduction, causing a shift in the traits expressed in a population

• Simulation• Genetic resistance: ability of one or

more members of a population to resist a chemical designed to kill it

Most of the normal bacteria die

The genetically resistant bacteriastart multiplying

Eventually the resistant strainreplaces the strain affected bythe antibiotic

A group of bacteria, including genetically resistant ones, areexposed to an antibiotic

Normal bacterium

Resistant bacterium

Stepped Art

Fig. 4-7, p. 87

Case Study: How Did Humans Become Such a

Powerful Species?• Strong opposable thumbs

• Walk upright

• Complex brain

Adaptation through Natural Selection Has

Limits• Adaptive genetic traits must

precede change in the environmental conditions• Individuals cannot adapt their

own genetics when they environment changes!

• Reproductive capacity• Species that reproduce rapidly

and in large numbers are better able to adapt• Gene mutations and

differential reproduction occur faster

Three Common Myths about Evolution through Natural

Selection1.“Survival of the fittest” is

not “survival of the strongest”

2.Organisms do not develop traits out of need or want

3.No grand plan of nature for perfect adaptation

Geologic Processes Affect Natural

Selection• Tectonic plates affect

evolution and the location of life on earth• Locations of continents and

oceans have shifted• Species physically move, or

adapt, or form new species through natural selection

• Earthquakes – can separate and isolate species, can cause speciation• Volcanic eruptions – can

destroy habitats and reduce species populations

Fig. 4-8, p. 89

225 million years ago

Fig. 4-8, p. 89

135 million years ago

Fig. 4-8, p. 89

65 million years ago

Fig. 4-8, p. 89

Present

Climate Change and Catastrophes Affect Natural

Selection• Ice ages followed by warming

temperatures

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

Fig. 4-9, p. 89

18,000 years before present

Northern Hemisphere Ice coverage

Modern day (August)

Legend

Land above sea level

Sea ice

Continental ice

Science Focus: Earth Is Just Right

for Life to Thrive• Temperature range: supports life

• Orbit size: moderate temperatures

• Liquid water: necessary for life

• Rotation speed: sun doesn’t overheat surface

• Size: gravity keeps atmosphere

How Do New Species Evolve?

• Speciation: one species splits into two or more species

• Geographic isolation: happens first; physical isolation of populations for a long period• animation

• Reproductive isolation: mutations and natural selection in geographically isolated populations lead to inability to produce viable offspring when members of two different populations mate• “rat island”

Fig. 4-10, p. 91

Arctic Fox

Northern population

Early fox population

Spreads northward and southward and separates

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

Southern population

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

Gray Fox

Geographic Isolation Can Lead to Reproductive

IsolationAdapted to cold through heavier fur, short ears, short legs, and short nose. White fur matches snow for camouflage.

Extinction is Forever • Extinction• Biological extinction – gone from the

planet• Local extinction - lost of a species

over a large area

• Endemic species • Found only in one area (islands,

rainforests, etc.)• Particularly vulnerable to extinction

• Background extinction: typical low rate of extinction

• Mass extinction: 3-5 over 500 million years

Golden Toad of Costa Rica, Extinct

Fig. 4-11, p. 92

Used to live in the cloud forest – went extinct in 1989 when the forest dried up

Science Focus: Changing the Genetic Traits of Populations• Artificial selection• Use selective

breeding/crossbreeding

• Genetic engineering, gene splicing

• Consider• Ethics• Morals• Privacy issues• Harmful effects

Species Diversity: Variety, Abundance of Species in a

Particular Place• Species diversity: the number

and variety of species

• Species richness: • The number of different species in a

given area

• Species evenness: • Comparative number of individuals

Variations in Species Richness and Species Evenness

Fig. 4-12, p. 93

High species richnessHigh species evenness

Low species richnessLow species evenness

Species Diversity: Variety, Abundance of Species in a

Particular Place• Diversity varies with

geographical location

• The most species-rich communities• Tropical rain forests• Coral reefs• Ocean bottom zone• Large tropical lakes

Global Map of Plant Biodiversity

Supplement 8, Fig. 6, p. S36

Science Focus: Species Richness on Islands

• Species equilibrium model, theory of island biogeography• Rate of new species

immigrating should balance with the rate of species extinction

• Island size and distance from the mainland need to be considered• Helps to predict needs of

isolated wildlife areas, such as national parks

Species-Rich Ecosystems Tend to Be Productive

and Sustainable• Species richness seems to• increase productivity (primary

producers), and • increase stability or

sustainability, and • provide insurance against

catastrophe

• How much species richness is needed is debatable

Each Species Plays a Unique Role

in Its Ecosystem• Ecological niche, niche• Pattern of living: everything that

affects survival and reproduction• Water, space, sunlight, food,

temperatures

• Generalist species• Broad niche: wide range of tolerance

• Specialist species • Narrow niche: narrow range of

tolerance

Specialist Species and Generalist Species Niches

Fig. 4-13, p. 95

Fig. 4-14, p. 96

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

Herring gull is a tireless scavenger

Ruddy turnstone searches

under shells and pebbles

for small invertebrates

Ruddy turnstone searches

under shells and pebbles

for small invertebrates

Black skimmer seizes small fish at water surface

Black skimmer seizes small fish at water surface

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

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

Dowitcher probes deeply into mud in search of snails, marine worms, and small crustaceans

Dowitcher probes deeply into mud in search of snails, marine worms, and small crustaceans

Flamingo feeds on minute organisms in mud

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

Louisiana heron wades into water to seize small fish

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

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

Piping plover feeds on insects and tiny crustaceans on sandy beaches

Specialized Feeding Niches of Various Bird Species in a Coastal Wetland

Case Study: Cockroaches: Nature’s

Ultimate Survivors• 3500 species , been around for

350 million years• Generalists• Eat almost anything• Live in almost any climate

• High reproductive rates• 1 Asian cockroach leads to 10

million new cockroaches

Species Can Play Five Major Roles within

Ecosystems• Native species: normally live and

thrive in a specific ecosystem• Nonnative species: aka

invasive/alien/exotic species• Can be deliberately or accidentally

introduced• Food crops, flowers, livestock – all

beneficial nonnatives• Some compete with and reduce a

community’s native species (killer bees)• Can spread rapidly if there are no

predators/diseases to keep their population in check

• Indicator species• Provide early warning of damage to an

ecosystem because they respond quickly to environmental changes

• Example: fish, birds , butterflies, & amphibians

• Keystone species• Species whose roles have large effect on

the types and abundance of other species in a ecosystem

• Usually exist in small numbers and are susceptible to extinction

• Examples: pollinators and predators

Species Can Play Five Major Roles within

Ecosystems

• Foundation species• Species that play a major role in shaping

their communities by creating and enhancing their habitats in way that benefit other species

• Elephants – push over trees• Beavers – build dams• Some bats and birds – spread fruit plants

with droppings• Difference between this and keystone?• Foundation species create habitats• Keystone can do this plus maintain the ecosystem

Species Can Play Five Major Roles within

Ecosystems

Case Study: Why Are Amphibians Vanishing? • Habitat loss and fragmentation

• Prolonged drought

• Pollution

• Increase in UV radiation

• Parasites

• Viral and fungal diseases

• Climate change

• Overhunting

• Nonnative predators and competitors

Case Study: Why Are Amphibians Vanishing? • Importance of amphibians• Sensitive biological indicators of

environmental changes• Adult amphibians• Important ecological roles in biological communities

• Genetic storehouse of pharmaceutical products waiting to be discovered

Case Study: Why Should We Care about the American Alligator?

• Largest reptile in North America

• 1930s: Hunters and poachers

• Importance of gator holes and nesting mounds: a keystone species

• 1967: endangered species

• 1977: comeback, threatened species

Three Big Ideas1. Populations evolve when genes

mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with these traits (natural selection).

2. Human activities are decreasing the earth’s vital biodiversity by causing the extinction of species and by disrupting habitats needed for the development of new species.

Three Big Ideas3. Each species plays a specific

ecological role (ecological niche) in the ecosystem where it is found.