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: The variety of genetic material within a species or population.
1. The more genetic diversity, the greater will be a species adaptability & survival.
Ecosystem diversity: the variety of terrestrial and aquatic ecosystems found in an area, or on the earth.
Biomes
Distinct climate
Certain species, especially vegetation

7. Biodiversity (3)
Functional diversity: The biological and chemical processes such as energy flow and matter recycling needed for the survival of species, communities & ecosystems.

8. 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

9. 4-2 How Does the Earth’s Life Change over Time?
Concept 4-2: Populations evolve when genes mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with these traits.

10. Population Changes over Time
Populations can micro-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 – inheritable, and lead to individual differences during reproduction.
Faced with environmental change, species will:
Adapt through micro-evolution
Migrate
Become extinct

12. 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.

13. 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

14. Extinction (1) Biological extinction Local extinction
Entire species gone
Local extinction
All members of a species in a specific area gone
Endemic species: found only in one area
1. vulnerable to extinction
Background extinction: disappearance of species at a slow rate.

15. Extinction (2) Mass extinction:
Earth took many of years to recover from previous mass extinctions
Humans cause premature extinction of species

16. 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.

17. Species Diversity Species richness: the number of different species
Species evenness: the relative abundance of each species
Varies with geographic location
Species richness declines towards poles

18. Richness and Sustainability
Hypothesis:
Does a community with high species richness have greater sustainability and productivity?
Research suggests “yes”
The most species-rich environments:
1. tropical rainforests
2. coral reefs
3. ocean (bottom zone)
4. tropical lakes (large ones)

19. 4-6 What Roles Do Species Play in an Ecosystem?
Concept 4-6 Each species plays a specific ecological role called its niche.

20. 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

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

22. 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

23. Indicator Species
Indicator species: species that provide early warning signs of damage to the environment:
1. Fish
2. Birds
3. Butterflies
4. Amphibians

24. Keystone Species
Those species that play a 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
1. Pollinators
2. Top predators

25. Foundation Species
Create habitats and ecosystems for themselves and other species:
1. Beavers
2. Elephants
3. Seed dispersers (like birds)

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

27. 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