ENVIRONMENTAL SCIENCE

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ENVIRONMENTAL SCIENCE
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CHAPTER 4Biodiversity and Evolution
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Core Case Study Why Are Amphibians Vanishing? (1)

• Habitat loss and fragmentation
• Prolonged drought
• Increased ultraviolet radiation
• Parasites
• Viral and fungal diseases

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Core Case Study Why Are Amphibians Vanishing? (2)

• Pollution
• Climate change
• Overhunting
• Nonnative predators and competitors
• 33 of all amphibian species face extinction

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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.

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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

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Biodiversity (2)

• Genetic diversity
• Ecosystem diversity
• Biomes
• Distinct climate
• Certain species, especially vegetation
• Functional diversity

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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

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4-2 How Does the Earths 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).

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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

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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

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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

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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.

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Adaptation through Natural Selection Has Limits

• Humans unlikely to evolve and have skin thats
  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

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Three Myths about Evolution through Natural
Selection Refuted

1. Survival of the fittest does not mean survival
   of the strongest
2. Organisms dont 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

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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 earths life support systems
  and NPP

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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.

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Plate Tectonics

• Locations of continents and oceans determine
  earths 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

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Earths 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

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Science Focus Earth is Just Right for Life to
Thrive

• Life needs a temperature range that results in
  liquid water
• Earths orbit right distance from sun
• Earths optimal gravity keeps atmosphere
• Favorable temperature range over earth history
  has promoted evolution and biodiversity
• Favorable oxygen level in atmosphere

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

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

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Speciation

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

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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

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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

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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

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Human Activities and Extinction

• Cause premature extinction of species

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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.

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Species Diversity

• Species richness
• Species evenness
• Varies with geographic location
• Species richness declines towards poles

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Richness and Sustainability

• Hypothesis
• Does a community with high species richness have
  greater sustainability and productivity?
• Research suggests yes

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

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

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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

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Ecological Niche (2)

• Generalist species
• Specialist species
• Native species
• Nonnative species
• Spread in new, suitable niches

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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

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Indicator Species

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

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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

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Foundation Species

• Create habitats and ecosystems
• Beavers
• Elephants
• Seed dispersers

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Science Focus American Alligator

• Highly adaptable
• Only natural predator is humans
• 1967 endangered species list
• Successful environmental comeback
• Keystone species

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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

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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).

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Three Big Ideas from This Chapter - 2

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

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Three Big Ideas from This Chapter - 3

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