ENVIRONMENTAL SCIENCE 13e

CHAPTER 4:Biodiversity and Evolution

Core Case Study p. 59

• What is the problem with amphibians since 1980?

• ____ % of all known amphibian species are threatened with extinction

• More than ____ % in the Caribbean

• Populations of another ____ % are declining

Core Case Study: Why Are Amphibians Vanishing? (1)

• Habitat loss and fragmentation

• Prolonged drought

• Increased ultraviolet radiation

• Parasites

• Viral and fungal diseases

Core Case Study: Why Are Amphibians Vanishing? (2)

• Pollution

• Climate change

• Overhunting

• Nonnative predators and competitors

• 33% of all amphibian species face extinction

Fig. 4-1, p. 61

4-1 What Is Biodiversity and Why Is It Important?

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

Biodiversity (1)

• Species diversity• Species=a set of individuals that can

mate and produce fertile offspring• 8-100 million species total; likely 10-14

million• 2 million species identified• ~50% in endangered tropical rainforests

Biodiversity (2)

• Genetic diversity- the variety of genetic material within a species or a population

• Ecosystem diversity- the variety of terrestrial aquatic ecosystems found in an area or on the earth

– Biomes: Large regions with distinct climate and certain species especially vegetation

• Functional diversity- the biological and chemical processes such as energy flow and matter recycling needed for the survival of species, communities, and ecosystems

Functional DiversityThe biological and chemical processes such as energyflow and matter recycling needed for the survival of species,communities, and ecosystems.

Genetic DiversityThe variety of genetic materialwithin a species or a population.

Species DiversityThe number and abundance of speciespresent in different communities

Ecological DiversityThe variety of terrestrial andaquatic ecosystems found inan area or on the earth.

Fig. 4-2, p. 61

Coastal mountain

ranges

Deciduous forest

Prairie grassland

Coniferous forest

DesertConiferous forest

Coastal chaparraland scrub

AppalachianMountains

MississippiRiver Valley

GreatPlains

RockyMountains

Great American

Desert

Sierra Nevada

Fig. 4-4, p. 63

San Francisco

Las Vegas

Denver

St. Louis

Baltimore

Average annual precipitation

100-125 cm (40-50 in.)75-100 cm (30-40 in.)50-75 cm (20-30 in.)25-50 cm (10-20 in.)below-25 cm (0-10 in.)

Major biomes found in 39th parallel across the USDifferences reflect changes in climate,Mainly average precipitation and temp

Science Focus: Insects

• Around for ~400 million years

• Bad reputation

• Useful to humans and ecosystems

• Vital roles in sustaining life– Pollinators

– Natural pest control

– Renewing soils

Fig. 4-A, p. 62

Fig. 4-A, p. 62

4-2 How Does the Earth’s Life Change over Time?

• Concept 4-2A The scientific theory of evolution explains how life on earth changes over time through changes in the genes of populations.

• Concept 4-2B 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).

Theory of Evolution

• Most of what we know of the history of life on earth comes from fossils

• Fossils– Mineralized and petrified remains– Skeletons, bones, and shells– Leaves and seeds– Impressions in rocks– Fossil record incomplete: ~1% of all species

• P. 64 Charles Darwin, On the Origin of Species, 1859

Population Changes over Time

• Populations (not individuals) evolve by becoming genetically different over time

• Genetic variability – mutations– Random changes in DNA molecules in

genes

– Can occur spontaneously

– External agents: radiation

– Can create a heritable trait

Natural Selection

• Adaptive traits - genetically favorable traits that increase the probability to survive and reproduce

• Trait – heritable and lead to differential reproduction

• Faced with environmental change– Adapt through evolution– Migrate– Become extinct

Evolution through Natural Selection Summarized

• Genes mutate, individuals are selected, and populations evolve such that they are better adapted to survive and reproduce under existing environmental conditions.

Natural Selection

An example

• In face of snow and cold a few gray wolves in a population that have thicker fur might live longer and produce more offspring. Genes for thicker fur spread throughout the population and individuals with those genes increase in number and pass this helpful trait on to more offspring.

Fig. 4-5, p. 83

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

Evolution by natural selection

Adaptation through Natural Selection Has Limits

• Humans unlikely to evolve and have skin that’s not harmed by UV radiation

1. Desired trait must already be in the gene pool.

2. Must have high reproductive capacity so adaptive traits can be spread rapidly

Three Myths about Evolution through Natural Selection Refuted

1. “Survival of the fittest” does not mean “survival of the strongest”

2. Organisms don’t develop traits just because they would be useful: giraffes and long necks

3. There is no grand plan of nature to create more perfectly adapted species – no trend toward genetic perfection

Science Focus: How Did We Become Such a Powerful Species?• Key adaptations – also enabled us to modify

environment– Opposable thumbs allow us to grip and use tools– Walk upright which freed out hands for many uses– Complex brains

• Transmit ideas to others• Develop technologies to alter environment

We have developed powerful technology and taken over much of the earth’s net primary productivity for our own use

4-3 How Do Geological Processes and Climate Changes Affect Evolution?

• Concept 4-3 Tectonic plate movements, volcanic eruptions, earthquakes, and climate change have shifted wildlife habitats, wiped out large numbers of species, and created opportunities for the evolution of new species.

Plate Tectonics

• Locations of continents and oceans determine earth’s climate

• Movement of continents allow species to move and adapt

• Earthquakes and volcanoes affect biological evolution by separating populations of a species and allowing new species to develop

Present65 million years ago

135 million years ago225 million years ago

Fig. 4-6, p. 66

Earth’s Long-Term Climate Changes

• Cooling and warming periods – affect evolution and extinction of species– Change ocean levels and area– Glaciers expanding and contracting– Climate changes

• Opportunities for the evolution of new species

• Many species go extinct

18,000years beforepresent

Modern day(August)

Northern HemisphereIce coverage

Fig. 4-7, p. 67

LegendContinental ice

Sea ice

Land above sea level

Science Focus: Earth is Just Right for Life to Thrive

• Life needs a temperature range that results in liquid water

• Earth’s orbit: right distance from sun• Earth’s optimal gravity: keeps atmosphere• Favorable temperature range over earth

history has promoted evolution and biodiversity

• Favorable oxygen level in atmosphere

4-4 How Do Speciation, Extinction, and Human Activities Affect Biodiversity?

• Concept 4-4 Human activities decrease the earth’s biodiversity by causing the premature extinction of species and by destroying or degrading habitats needed for the development of new species.

Speciation

• Speciation– One species splits into two or more

species that can no longer breed and produce fertile offspring

• Geographic isolation

• Reproductive isolation

• Geographic isolation-occurs when different groups of the same population of a species become physically isolated from one another for a long period of time

• Reproductive isolation- the inability of a species to breed successfully due to geographical, behavioral, physiological, or genetic barriers or differences

Spreads northwardand southwardand separates

Arctic Fox

Gray Fox

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

Adapted to coldthrough heavier fur, short ears, short legs, and short nose. White fur matches snow for camouflage.

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

Northernpopulation

Southernpopulation

Early foxpopulation

Fig. 4-8, p. 68

Extinction (1)

• Biological extinction: entire species gone• Local extinction: All members of a species in a

specific area gone

• Endemic species (species found only in one area) vulnerable to extinction

• Background extinction- normal low rate of species disappearance

• Speciation generally more rapid than extinction• Extinction is normal process but humans have

become major source of premature extinction of growing number of species (Ch 8)

Extinction (2)

• Mass extinction– Earth took millions of years to recover

from previous mass extinctions

• Balance between speciation and extinction determines biodiversity of earth

• Humans cause premature extinction of species

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

• Concept 4-5 Species diversity is a major component of biodiversity and tends to increase the sustainability of some ecosystems.

Species Diversity: number of different species combined with the relative abundance of individuals within each of those species

• Species richness-the number of different species contained in a community

• Species evenness-relative abundance of individuals within each of the species in a community

• Fig 4-9 Coral Reef: high species richness, low evenness. Grove of Aspen trees low richness, high evenness.

• Varies with geographic location• Species richness highest in the tropics, declines towards

poles

Richness and Sustainability

• Hypothesis– Does a community with high species

richness have greater sustainability and productivity?

• Research suggests “yes”

4-6 What Roles Do Species Play in an Ecosystem?

• Concept 4-6 Each species plays a specific ecological role called its niche.

Ecological Niche (1)

• Species occupy unique niches and play specific roles in an ecosystem

• Includes everything required for survival and reproduction– Water– Sunlight– Space– Temperatures– Food requirements

Ecological Niche (2)

• Generalist species-broad niches, can live in many different places, eat a variety of different foods, can tolerate a wide variety of different environmental conditions

• Specialist species- narrow niches, may be able to live only in one type of habitat, use one or a few types of food, or tolerate a narrow range of climatic or environmental conditions

• Native species

• Nonnative species– Spread in new, suitable niches

Fig. 4-10, p. 72

Specialized feeding niches of various bird species in a coastal wetland.

What benefit does specialization provide?

Case Study: CockroachesGeneralists or Specialists?

• Existed for 350 million years – 3,500 known species

• Highly adapted, rapidly producing– Consume almost anything– Endure food shortage– Survive everywhere except polar regions– Avoid predation

• Carry human diseases

Fig. 4-11, p. 72

Niches

• Niches can be occupied by native and nonnative species– Native species: those species that normally

thrive in a particular ecosystem– Nonnative species: invasive, alien, exotic

• Migrate into or are deliberately or accidently introduced into an ecosystem

Indicator Species

• Species that provide early warning of damage to a community or ecosystem

• Ex. presence or absence of trout species is indicator of water quality because trout need clean water with high levels of dissolved oxygen

• Birds• Butterflies • Amphibians

Fig. 4-12, p. 74

Keystone

• Keystone is a wedge shaped stone placed at the top of a stone archway. Remove this stone and the arch collapses.

• In some communities and ecosystems, ecologists hypothesize that certain species play a similar role

Keystone Species

• Significant role in their food web: large affect on types and abundances of other species in an ecosystem

• Elimination may alter structure and/or function of ecosystem ex. American alligator

• Pollinators ex. Bees, butterflies, hummingbirds, bats

• Top predators ex. Alligator, wolf, leopard, lion, shark

Foundation Species

• Create habitats and ecosystems

• Beavers

• Elephants

• Seed dispersers

Science Focus: American Alligator

• Highly adaptable

• Only natural predator is humans

• 1967 – endangered species list

• Successful environmental comeback

• Keystone species

Case Study: Why Should WeProtect Sharks?

• Remove injured, sick animals

• Many are gentle giants

• Provide potential insight into cures for human diseases such as cancer

• Keystone species

• Hunted and killed by humans

Three Big Ideas from This Chapter - #1

• 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).

Three Big Ideas from This Chapter - #2

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

Three Big Ideas from This Chapter - #3

• Each species plays a specific ecological role in the ecosystem where it is found (ecological niche).

Core Case Study p. 59

• What is the problem with amphibians since 1980? Hundreds of species vanishing

• __33__ % of all known amphibian species are threatened with extinction

• More than __80__ % in the Caribbean

• Populations of another _43___ % are declining