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CHAPTER 4:Biodiversity and
Evolution
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Core Case Study: Why Should We Protect
Sharks?• 400 known species• 6 human deaths/year from
shark attacks• 79-97 million sharks killed
every year• Fins – used in Asia for soups and
cure-alls• Organs, meat, hides also valuable• 32% shark species threatened with
extinction• Current news? Not good…
• Keystone species in the ocean • Cancer resistant species!
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Fig. 4-1, p. 80
Threatened Sharks!
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What is Biodiversity?
• Species diversity• Genetic diversity• Ecosystem diversity• Biomes: regions with distinct
climates/species
• Functional diversity – energy flow and nutrient cycling
• Biodiversity is an important part of natural capital
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Fig. 4-2, p. 82
Functional Diversity The biological and chemical processes such as energy flow and matter recycling needed for the survival of species, communities, and ecosystems.
Ecological Diversity The variety of terrestrial and aquatic ecosystems found in an area or on the earth.
Solar energyChemical
nutrients (carbon dioxide, oxygen, nitrogen, minerals)
Heat
Heat Heat
Decomposers (bacteria, fungi)
Producers (plants)
Consumers (plant eaters, meat eaters)Heat Heat
Genetic Diversity The variety of genetic material within a species or a population.
Species Diversity The number and abundance of species present in different communities.
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Biodiversity Is a Crucial Part of the Earth’s Natural
Capital• Species: set of individuals who
can mate and produce fertile offspring
• Estimate: 8 million to 100 million species on earth• 10-14 million is the “best guess” • Insects make up most of the world’s
known species
• 1.9 million identified species• Unidentified are mostly in rain
forests and oceans
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Classifying Homo Sapiens
Supplement 5, Fig. 2, p. S19
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Science Focus: Have You Thanked the Insects Today?
• Bad rep: sting us, bite us, spread disease, eat our food, invade plants
• Pollination: lets flowering plants reproduce sexually
• Free pest control: insects eat other insects
• We need insects more than they need us!
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Major Biomes: large regions with distinct climates and certain species
(especially vegetation)
Fig. 4-5, p. 84
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Individuals Matter: Edward O. Wilson- A Champion of
Biodiversity• Loved bugs as a kid; Specialized in
ants• Widened scope to earth’s
biodiversity • Encyclopedia of Life – Harvard
• Theory of island biogeography• How species diversity on islands is
affected by the size and location of the islands
• First to use “biodiversity” in a scientific paper
• Won two Pulitzers for his nonfiction books
• His website
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Edward O. Wilson
Fig. 4-B, p. 85
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Biological Evolution by Natural Selection Explains How Life
Changes over Time
• Fossils• Physical evidence of ancient
organisms• Reveal what their external
structures looked like
• Fossil record: entire body of fossil evidence• Only have fossils of 1% of all
species that lived on earth
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Fossilized Skeleton of an Herbivore that Lived during the Cenozoic Era
Fig. 4-6, p. 86
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Biological Evolution by Natural Selection Explains How Life
Changes over Time • Biological evolution: how earth’s
life changes over time through changes in the genetic characteristics of populations• Darwin: Origin of Species
• Natural selection: individuals with certain traits are more likely to survive and reproduce under a certain set of environmental conditions
• Huge body of evidence
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Evolution of Life on Earth
Supplement 5, Fig. 2, p. S18
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Evolution by Natural Selection Works through
Mutations and Adaptations• POPULATIONS EVOLVE by
becoming genetically different• INDIVIDUALS DO NOT EVOLVE!!
• Genetic variations• First step in biological evolution• Occurs through mutations in
reproductive cells• Mutations: random changes in DNA
molecules
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Evolution by Natural Selection Works through
Mutations and Adaptations• Natural selection: acts on
individuals• Second step in biological evolution• Adaptation may lead to differential
reproduction, causing a shift in the traits expressed in a population
• Simulation• Genetic resistance: ability of one or
more members of a population to resist a chemical designed to kill it
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Most of the normal bacteria die
The genetically resistant bacteriastart multiplying
Eventually the resistant strainreplaces the strain affected bythe antibiotic
A group of bacteria, including genetically resistant ones, areexposed to an antibiotic
Normal bacterium
Resistant bacterium
Stepped Art
Fig. 4-7, p. 87
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Case Study: How Did Humans Become Such a
Powerful Species?• Strong opposable thumbs
• Walk upright
• Complex brain
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Adaptation through Natural Selection Has
Limits• Adaptive genetic traits must
precede change in the environmental conditions• Individuals cannot adapt their
own genetics when they environment changes!
• Reproductive capacity• Species that reproduce rapidly
and in large numbers are better able to adapt• Gene mutations and
differential reproduction occur faster
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Three Common Myths about Evolution through Natural
Selection1.“Survival of the fittest” is
not “survival of the strongest”
2.Organisms do not develop traits out of need or want
3.No grand plan of nature for perfect adaptation
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Geologic Processes Affect Natural
Selection• Tectonic plates affect
evolution and the location of life on earth• Locations of continents and
oceans have shifted• Species physically move, or
adapt, or form new species through natural selection
• Earthquakes – can separate and isolate species, can cause speciation• Volcanic eruptions – can
destroy habitats and reduce species populations
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Fig. 4-8, p. 89
225 million years ago
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Fig. 4-8, p. 89
135 million years ago
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Fig. 4-8, p. 89
65 million years ago
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Fig. 4-8, p. 89
Present
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Climate Change and Catastrophes Affect Natural
Selection• Ice ages followed by warming
temperatures
• Collisions between the earth and large asteroids • New species• Extinctions
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Fig. 4-9, p. 89
18,000 years before present
Northern Hemisphere Ice coverage
Modern day (August)
Legend
Land above sea level
Sea ice
Continental ice
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Science Focus: Earth Is Just Right
for Life to Thrive• Temperature range: supports life
• Orbit size: moderate temperatures
• Liquid water: necessary for life
• Rotation speed: sun doesn’t overheat surface
• Size: gravity keeps atmosphere
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How Do New Species Evolve?
• Speciation: one species splits into two or more species
• Geographic isolation: happens first; physical isolation of populations for a long period• animation
• Reproductive isolation: mutations and natural selection in geographically isolated populations lead to inability to produce viable offspring when members of two different populations mate• “rat island”
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Fig. 4-10, p. 91
Arctic Fox
Northern population
Early fox population
Spreads northward and southward and separates
Different environmental conditions lead to different selective pressures and evolution into two different species.
Southern population
Adapted to heat through lightweight fur and long ears, legs, and nose, which give off more heat.
Gray Fox
Geographic Isolation Can Lead to Reproductive
IsolationAdapted to cold through heavier fur, short ears, short legs, and short nose. White fur matches snow for camouflage.
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Extinction is Forever • Extinction• Biological extinction – gone from the
planet• Local extinction - lost of a species
over a large area
• Endemic species • Found only in one area (islands,
rainforests, etc.)• Particularly vulnerable to extinction
• Background extinction: typical low rate of extinction
• Mass extinction: 3-5 over 500 million years
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Golden Toad of Costa Rica, Extinct
Fig. 4-11, p. 92
Used to live in the cloud forest – went extinct in 1989 when the forest dried up
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Science Focus: Changing the Genetic Traits of Populations• Artificial selection• Use selective
breeding/crossbreeding
• Genetic engineering, gene splicing
• Consider• Ethics• Morals• Privacy issues• Harmful effects
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Species Diversity: Variety, Abundance of Species in a
Particular Place• Species diversity: the number
and variety of species
• Species richness: • The number of different species in a
given area
• Species evenness: • Comparative number of individuals
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Variations in Species Richness and Species Evenness
Fig. 4-12, p. 93
High species richnessHigh species evenness
Low species richnessLow species evenness
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Species Diversity: Variety, Abundance of Species in a
Particular Place• Diversity varies with
geographical location
• The most species-rich communities• Tropical rain forests• Coral reefs• Ocean bottom zone• Large tropical lakes
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Global Map of Plant Biodiversity
Supplement 8, Fig. 6, p. S36
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Science Focus: Species Richness on Islands
• Species equilibrium model, theory of island biogeography• Rate of new species
immigrating should balance with the rate of species extinction
• Island size and distance from the mainland need to be considered• Helps to predict needs of
isolated wildlife areas, such as national parks
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Species-Rich Ecosystems Tend to Be Productive
and Sustainable• Species richness seems to• increase productivity (primary
producers), and • increase stability or
sustainability, and • provide insurance against
catastrophe
• How much species richness is needed is debatable
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Each Species Plays a Unique Role
in Its Ecosystem• Ecological niche, niche• Pattern of living: everything that
affects survival and reproduction• Water, space, sunlight, food,
temperatures
• Generalist species• Broad niche: wide range of tolerance
• Specialist species • Narrow niche: narrow range of
tolerance
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Specialist Species and Generalist Species Niches
Fig. 4-13, p. 95
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Fig. 4-14, p. 96
Brown pelican dives for fish, which it locates from the air
Herring gull is a tireless scavenger
Ruddy turnstone searches
under shells and pebbles
for small invertebrates
Ruddy turnstone searches
under shells and pebbles
for small invertebrates
Black skimmer seizes small fish at water surface
Black skimmer seizes small fish at water surface
Avocet sweeps bill through mud and surface water in search of small crustaceans, insects, and seeds
Avocet sweeps bill through mud and surface water in search of small crustaceans, insects, and seeds
Dowitcher probes deeply into mud in search of snails, marine worms, and small crustaceans
Dowitcher probes deeply into mud in search of snails, marine worms, and small crustaceans
Flamingo feeds on minute organisms in mud
Scaup and other diving ducks feed on mollusks, crustaceans, and aquatic vegetation
Louisiana heron wades into water to seize small fish
Oystercatcher feeds on clams, mussels, and other shellfish into which it pries its narrow beak
Knot (sandpiper) picks up worms and small crustaceans left by receding tide
Piping plover feeds on insects and tiny crustaceans on sandy beaches
Specialized Feeding Niches of Various Bird Species in a Coastal Wetland
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Case Study: Cockroaches: Nature’s
Ultimate Survivors• 3500 species , been around for
350 million years• Generalists• Eat almost anything• Live in almost any climate
• High reproductive rates• 1 Asian cockroach leads to 10
million new cockroaches
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Species Can Play Five Major Roles within
Ecosystems• Native species: normally live and
thrive in a specific ecosystem• Nonnative species: aka
invasive/alien/exotic species• Can be deliberately or accidentally
introduced• Food crops, flowers, livestock – all
beneficial nonnatives• Some compete with and reduce a
community’s native species (killer bees)• Can spread rapidly if there are no
predators/diseases to keep their population in check
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• Indicator species• Provide early warning of damage to an
ecosystem because they respond quickly to environmental changes
• Example: fish, birds , butterflies, & amphibians
• Keystone species• Species whose roles have large effect on
the types and abundance of other species in a ecosystem
• Usually exist in small numbers and are susceptible to extinction
• Examples: pollinators and predators
Species Can Play Five Major Roles within
Ecosystems
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• Foundation species• Species that play a major role in shaping
their communities by creating and enhancing their habitats in way that benefit other species
• Elephants – push over trees• Beavers – build dams• Some bats and birds – spread fruit plants
with droppings• Difference between this and keystone?• Foundation species create habitats• Keystone can do this plus maintain the ecosystem
Species Can Play Five Major Roles within
Ecosystems
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Case Study: Why Are Amphibians Vanishing? • Habitat loss and fragmentation
• Prolonged drought
• Pollution
• Increase in UV radiation
• Parasites
• Viral and fungal diseases
• Climate change
• Overhunting
• Nonnative predators and competitors
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Case Study: Why Are Amphibians Vanishing? • Importance of amphibians• Sensitive biological indicators of
environmental changes• Adult amphibians• Important ecological roles in biological communities
• Genetic storehouse of pharmaceutical products waiting to be discovered
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Case Study: Why Should We Care about the American Alligator?
• Largest reptile in North America
• 1930s: Hunters and poachers
• Importance of gator holes and nesting mounds: a keystone species
• 1967: endangered species
• 1977: comeback, threatened species
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Three Big Ideas1. 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).
2. Human activities are decreasing the earth’s vital biodiversity by causing the extinction of species and by disrupting habitats needed for the development of new species.
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Three Big Ideas3. Each species plays a specific
ecological role (ecological niche) in the ecosystem where it is found.