ENVIRONMENTAL SCIENCE 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

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 10-14 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

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

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 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.

Adaptation through Natural Selection Has Limits Humans unlikely to evolve and have skin that’s not harmed by UV radiation Desired trait must already be in the gene pool. Must have high reproductive capacity so adaptive traits can be spread rapidly

Three Myths about Evolution through Natural Selection Refuted “Survival of the fittest” does not mean “survival of the strongest” Organisms don’t develop traits just because they would be useful: giraffes and long necks 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

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

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 Geographic isolation Reproductive isolation One species splits into two or more species that can no longer breed and produce fertile offspring Geographic isolation Reproductive isolation

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 Local 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

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

Indicator Species Early warning system Fish Birds Butterflies Amphibians

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.

Three Big Ideas from This Chapter - #3 Each species plays a specific ecological role in the ecosystem where it is found (ecological niche).