1. ENVIRONMENTAL SCIENCE
CHAPTER 4: Biodiversity and Evolution

2. Core Case Study: Why Are Amphibians Vanishing? (1)
Habitat loss and fragmentation
Prolonged drought
Increased ultraviolet radiation
Parasites
Viral and fungal diseases

3. Core Case Study: Why Are Amphibians Vanishing? (2)
Pollution
Climate change
Overhunting
Nonnative predators and competitors
33% of all amphibian species face extinction

4. 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.

5. Biodiversity (1) Species diversity
A set of individuals that can mate and produce fertile offspring
8-100 million species total; likely million
2 million species identified
~50% in endangered tropical rainforests

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

7. 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

8. 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).

9. 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

10. 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

11. 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

12. 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.

13. 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

14. 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

15. 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

16. 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.

17. 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

18. 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

19. 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

20. 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.

21. 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

22. 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

23. 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

24. 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

25. Human Activities and Extinction
Cause premature extinction of species

26. 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.

27. Species Diversity Species richness Species evenness
Varies with geographic location
Species richness declines towards poles

28. Richness and Sustainability
Hypothesis
Does a community with high species richness have greater sustainability and productivity?
Research suggests “yes”

29. 4-6 What Roles Do Species Play in an Ecosystem?
Concept 4-6 Each species plays a specific ecological role called its niche.

30. 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

31. Ecological Niche (2) Generalist species Specialist species
Native species
Nonnative species
Spread in new, suitable niches

32. 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

33. Indicator Species Early warning system Fish Birds Butterflies
Amphibians

34. 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

35. Foundation Species Create habitats and ecosystems Beavers Elephants
Seed dispersers

36. Science Focus: American Alligator
Highly adaptable
Only natural predator is humans
1967 – endangered species list
Successful environmental comeback
Keystone species

37. 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

38. 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).

39. 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.

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