ENVIRONMENTAL SCIENCE 13 e CHAPTER 4 Biodiversity and

ENVIRONMENTAL SCIENCE 13 e CHAPTER 4: Biodiversity and Evolution

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 • A set of individuals that can mate and produce fertile offspring • 8 -100 million species total; likely 1014 million • 2 million species identified • ~50% in endangered tropical rainforests

Biodiversity (2) • Genetic diversity • Ecosystem diversity – Biomes • Distinct climate • Certain species, especially vegetation • Functional diversity

Fig. 4 -2, p. 61

Functional Diversity The biological and chemical processes such as energy flow and matter recycling needed for the survival of species, communities, and ecosystems. Genetic Diversity The variety of genetic material within a species or a population. Ecological Diversity The variety of terrestrial and aquatic ecosystems found in an area or on the earth. Species Diversity The number and abundance of species present in different communities Fig. 4 -2, p. 61

Fig. 4 -3, p. 61

Fig. 4 -4, p. 63

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. ) Denver Baltimore San Francisco St. Louis Las Vegas Coastal mountain ranges Sierra Nevada Great American Desert Coastal chaparral Coniferous and scrub forest Rocky Mountains Desert Great Plains Coniferous forest Mississippi Appalachian River Valley Mountains Prairie grassland Deciduous forest Fig. 4 -4, p. 63

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

4 -2 How Does the Earth’s Life Change over Time? • Concept 4 -2 A The scientific theory of evolution explains how life on earth changes over time through changes in the genes of populations. • Concept 4 -2 B 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 • Fossils – Mineralized and petrified remains – Skeletons, bones, and shells – Leaves and seeds – Impressions in rocks – Fossil record incomplete: ~1% of all species • Charles Darwin, On the Origin of Species, 1859

Population Changes over Time • Populations 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.

Fig. 4 -5, p. 65

(a) (b) (c) (d) A group of bacteria, including genetically resistant ones, are exposed to an antibiotic Most of the normal bacteria die The genetically resistant bacteria start multiplying Eventually the resistant strain replaces all or most of the strain affected by the antibiotic Normal bacterium Resistant bacterium Fig. 4 -5, p. 65

A group of bacteria, including genetically resistant ones, are exposed to an antibiotic Normal bacterium Most of the normal bacteria die The genetically resistant bacteria start multiplying Eventually the resistant strain replaces the strain affected by the antibiotic Resistant bacterium Stepped Art Fig. 4 -5, p. 83

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 – Walk upright – Complex brains • Transmit ideas to others • Develop technologies to alter environment Technology dominates earth’s life support systems and NPP

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

Fig. 4 -6, p. 66

225 million years ago 135 million years ago 65 million years ago Present Fig. 4 -6, p. 66

225 million years ago 65 135 million years ago Present Stepped Art 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

Fig. 4 -7, p. 67

18, 000 years before present Northern Hemisphere Ice coverage Modern day (August) Legend Continental ice Sea ice Land above sea level Fig. 4 -7, p. 67

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

Fig. 4 -8, p. 68

Arctic Fox Northern population Early fox population Spreads northward and southward and separates Adapted to cold through heavier fur, short ears, short legs, and short nose. White fur matches snow for camouflage. Different environmental conditions lead to different selective pressures and evolution into two different species. Gray Fox Southern population Adapted to heat through lightweight fur and long ears, legs, and nose, which give off more heat. Fig. 4 -8, p. 68

Science Focus: Changing Genetic Traits • Artificial selection – Selective breeding: crossbreeding varieties within same species to enhance desired traits – Grains, fruits, vegetables, dogs, other animals • Genetic engineering – Add, delete, or alter DNA segments – Add desirable genes from other species – New drugs, pest-resistant plants – Controversial

Extinction (1) • Biological extinction – Entire species gone • Local extinction – All members of a species in a specific area gone • Endemic species vulnerable to extinction • Background extinction • Speciation generally more rapid than extinction

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

Human Activities and Extinction • 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 • • Species richness Species evenness Varies with geographic location Species richness 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 Specialist species Native species Nonnative species – Spread in new, suitable niches

Fig. 4 -10, p. 72

Herring gull is a tireless scavenger Black skimmer seizes small fish at water surface Flamingo feeds on minute organisms in mud Brown pelican dives for fish, which it locates from the air Avocet sweeps bill through mud and surface water in search of small crustaceans, insects, and seeds Louisiana heron wades into water to seize small fish Scaup and other diving ducks feed on mollusks, crustaceans, and aquatic vegetation Ruddy turnstone searches under shells and pebbles for small invertebrates Dowitcher probes deeply into mud in search of snails, marine worms, and small crustaceans 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 (sandpiper) picks up worms and small crustaceans left by receding tide Fig. 4 -10, p. 72

Science Focus: Cockroaches • Existed for 350 million years – 3, 500 known species • Highly adapted, rapidly producing generalists – Consume almost anything – Endure food shortage – Survive everywhere except polar regions – Avoid predation • Carry human diseases

Fig. 4 -11, p. 72

Indicator Species • • • Early warning system Fish Birds Butterflies Amphibians

Fig. 4 -12, p. 74

Adult frog (3 years) Young frog Tadpole develops into frog Sperm Sexual reproduction Eggs Fertilized egg development Tadpole Egg hatches Organ formation Fig. 4 -12, p. 74

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 • Pollinators • Top predators

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 We Protect 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.