Species Diversity

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Species Diversity
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Greater Diversity Healthier, More Stable
Environment
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• Genetic diversity
• Variability genetic makeup among individuals in a
  populations
• Species diversity
• of species in an area
• Ecological diversity
• Variety of communities interacting with
  environment

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Species Diversity

• Tropical rain forest/coral reefs HIGH
  diversity
• Low of
• individual
  species

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Species Diversity

• Deserts and mountain tops LOW diversity
• High
  of
• individual
  species

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Ecotone

• Transitional zone where 2 or more communities
  meet
• Intertidal zones

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Edge Effect

• Highest diversity if there are two overlapping
  undisturbed areas
• Organisms from both ecosystems present
• Meadow
  
• 
  Forest

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Concern with edge effects

• Edge effects can be problematic when a natural
  habitat converges with the urban environment.
• Habitats can be fragmented or exotics can enter
  into natural ecosystem from urban area - can
  reduce biodiversity.
• Species that can adapt really well to the edge
  can sometimes out-compete other species.

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Factors That Determine Species Diversity

• Habitat stress
• Available niches
• Dominant species
• Geological history

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EVOLUTION
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Convergent Evolution

• Two unrelated species tend to look more similar
  or have analogous structures over time because of
  the similarity in the niches that they occupy.
• An example is the different sorts of anteaters,
  found in Australia, Africa, and America. Though
  not closely related, they all evolved the "tools"
  necessary to subsist on an ant diet a long,
  sticky tongue, few teeth, a rugged stomach, and
  large salivary glands. In each case, evolutionary
  adaptations allow them to exploit a food niche of
  ants and termites, but the developments occurred
  independently.

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Convergent Evolution
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Divergent Evolution

• This occurs when two species have structures that
  once carried out the same function, but have
  changed or diverged over time.
• These structures are called homologous
  structures because they have a common genetic
  origin.

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Darwins Finches
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Evolution Via Natural Selection

• Describes how populations change over time.
• Four assumptions must be made
• Over-production
• Variation
• Limits on population growth
• Survival of the fittest

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• 1. Overproduction

• More organisms are produced each generation than
  can survive

Why is this important for evolution?
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• 2. Genetic Variation

• Chance mutation within the chromsomes

How do mutations facilitate evolution?
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Genetic Mutations Lead to Visible Changes in
Phenotypes
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• 3. Limits on Population Growth

• Limiting factors such as food

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4. Survival of the Fittest
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Survival of the Fittest

• Natural Selection
• Individuals that are best-suited to the
  environment produce more
  offspring

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Populations Change Over Time
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• What is a Species?
• Considered separate species if they cannot
  successfully interbreed (or are reproductively
  isolated)

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Isolating Mechanisms

• Geographic
• Mountains, islands they never meet
• Temporal
• Breed in different seasons, time of day
• Behavioral
• Courtship differs not attractive
• Anatomical
• Parts dont match any more
• Gametic
• Zygotes die or infertile offspring

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• Male Horse Female Donkey

Ligers and tigons are also sterile and are
therefore NOT separate species.
Sterile Mule
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• Microevolution

• Small genetic changes in a population
• Change in frequency of a single allele due to
  selection
• What is
• an allele??

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Macroevolution

• Large-scale changes in organisms
• Involves new genera

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Evolution of the Horse
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Types of Natural Selection

• Directional
• Stabilizing
• Diversifying

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Stabilizing Selection

• Center are the only ones to reproduce
• Individuals look more similar over time
• Range narrows

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Disruptive Selection

• Ends are the only ones to reproduce
• Produces 2 separate phenotypes
• Range increases

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Directional Selection

• Just one side reproduce
• Population looks different over time
• Mean changes

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ADAPTIVE RADIATION

• Massive explosions of new species
• Usually
  follows
  mass
  extinctions

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SUCCESSION
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How Communities Change Over Time

• Succession a process of community development
  that involves a changing sequence of species

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Primary Succession

• Occurs when there is a major event that wipes
  everything out of an ecosystem, usually even
  soil. A volcanic eruption, for example, causes
  this.
• Usually the first plant species to colonize are
  mosses, lichens, algae, and fungus.

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Primary Succession
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Pioneer Community
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Secondary Succession
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SUCCESSIONAL PATTERNS
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Fire Succession

• Needed for
• Reproduction
• Clearing out competitors

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As Ecosystems Mature

• Increase in biomass
• Decrease in net productivity
• Greater capacity to hold nutrients

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As Ecosystems Mature

• Increase in diversity population numbers
• Increased system stability

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Is There Really Such a Thing as a Climax
Community?
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Successional Disturbance

• Catastrophic interuption of successional stages
• Natural or human

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Why is Disturbance Important?

• Sometimes Species Richness is highest
  midsuccessional stage (Chaparral)
• Dominance of one species reduced richness
• Early, mid and late successional species can
  survive via disturbance
• Habitat heterogeneity over time