Biological Diversity

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Biological Diversity

• Chapter 5

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Evolution

• Change in inherited characteristics of a
  population from generation to generation.
• One Way Processes
• Fast for some species, but on average very slow

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Evolution Occurs by

• 1. Mutation
• Genes in chromosomes hold DNA.
• DNA is reproduced each time cell divides.
• Changes occur when there is an error in
  reproduction of the DNA
• Affected by external agents (mutagens)
• Radiation (UV, X-rays, Gamma rays)
• Organic chemicals
• Effects
• Inability to survive
• Variation within a species
• Creation of new species (not necessarily better)!

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Not all Mutation is Good!
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2. Natural Selection

• Pressures in the environment select for traits
  best suited in that environment
• More likely to reproduce
• Directional changing env. conditions cause gene
  frequency to shift so individuals with traits at
  one end of the normal range become more common.
• It pays to be different.
• Ex peppered moth, resistance to antibiotics,
  pesticides

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Graphs p.115
Peccaries prefer cacti w/few spines
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• Stabilizing Individuals at both ends of the
  range are eliminated. It pays to be average.
  Good when env. doesnt change much and species is
  well-adapted.

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Peccary eat low-spine cacti insects like very
spiny ones
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• Diversifying Env. conditions favor the extremes
  of the genetic spectrum and the middle is
  eliminated.

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Tourists prefer cacti with some spines
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3. Migration

• Movement of a species into a habitat, possibly
  already occupied by that same species. Can lead
  to changes in gene frequency.
• Ex Seeds of flowers with red genotype dropped
  into area with white genotype flowers. Can mix
  genes red flowers can have new more favorable
  habitat
• Ex movement of Canada goose to NJ

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• Genetic Drift
• Small population gets segmented away from the
  rest.
• Causes limited number of genes to appear,
  reproduce and pass on.
• Can be beneficial, but not usually. Esp.
  problematic in endangered species
• Traits that are less suited to the env. may
  dominate
• Genetic variability is reduced reduces
  adaptability

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4. Species Diversity

• Species Richness Total number of species in an
  ecosystem.
• Species Evenness How many of each type of
  species is there?
• Species Dominance Which species are the most
  abundant.

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• How many species are there? Anywhere from 5-30
  million!
• Probably around 10 million 2 million named
• 5 Kingdoms
• Plants, animals, fungi, protist, bacteria
• 3 Domains
• Eukaryotes, Bacteria and Archaea

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Factors Affecting Diversity

• Increasing Diversity
• Physically diverse habitat
• Moderate disturbances
• Some variation in env. conditions
• High diversity at one trophic level affects next
• Env. highly modified by life
• Middle states of succession
• Evolution

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• Decreasing Diversity
• Env. Stress
• Extreme Env. Conditions
• Severe limitation on essential resources
• Extreme disturbances
• Introduction of exotic species
• Geographical Isolation

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Evolution Diversity

• Convergent Evolution
• Over time, species in similar areas develop
  similar characteristics.
• Ex desert biomes favor needle-shaped leaves on
  plants

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Hummingbird
Hummingbird Moth
http//home.honolulu.hawaii.edu
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• Divergent Evolution
• A population that has been separated
  geographically slowly changes to fit the new
  environment

Rhea S. America
Emu Australia
Ostrich Africa
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• Adaptive Radiation
• Many related species in one area adapted and
  specialized to a particular niche in the
  ecosystem
• Common ancestor
• Darwins finches on the Galapagos

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Pbs.org
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Pop Density Distribution

• Density individuals/area
• Larger animals, lower density
• Higher density
• Use of resources
• Spread of disease
• Distribution Spatial arrangements of individuals

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p. 127
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Random even distribution of resources Ex
rabbits grazing on a lawn
Uniform territorial due to minimal resources Ex
Cacti
Clumped Most common. Grouped around resource,
or for protection Ex Pride of lions, schools of
fish, clover
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Density Factors affecting Population

• Density Dependent Results depends on number of
  individuals present
• Spread of Disease
• Mating
• Resource Availability
• Habitat Availability
• Risk of Predation
• Density Independent Affects species no matter
  how many there are
• Natural Disasters
• Climate extremes

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Survivorship curves

• Type I most likely to survive into adulthood
• Type II equal rates of death at any age
• Type III most likely to die young survival more
  likely when older

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Reproductive Strategies

• r-selected quantity of young, not quality
• r- rate of reproduction
• Great population flux
• live fast, die young
• Dandelions, frogs, fish

Frogs eggs
Dandelion seed
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Reproductive Strategies (cont.)

• K-selected produce and protect relatively few
  young
• K-carrying capacity, often reached
• live long and prosper
• Whales, elephants, humans

Table 5.4, p132