Evolution%20and%20Community%20Ecology

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Evolution and Community Ecology
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CHAPTER
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Black and White, and Spread All Over

• Zebra mussels and quagga mussels were
  accidentally introduced into Lake St. Clair in
  the late 1980s.
• They have since spread throughout the Great Lakes
  system and connecting rivers.
• The invasive mussels have a high economic and
  ecological cost.

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Lesson 5.1 Evolution

• Scientists have identified and described over
  1.5 million species. Millions more have yet to
  be discovered.

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Evolution and Natural Selection
Lesson 5.1 Evolution

• Gene A sequence of DNA that codes for a
  particular trait
• Gene pool All the genes present in a population
• Biological evolution The change in a
  populations gene pool over time

A starting population of fish. Genes control the
color and pattern of the fishs scales.
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Mechanisms of Biological Evolution Mutation and
Migration
Lesson 5.1 Evolution

Mutation
Migration (gene flow)
Accidental change in DNA that can give rise to
variation among individuals
Movement of individuals into (immigration) or out
of (emigration) a population
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Mechanisms of Biological Evolution Genetic Drift
and Natural Selection
Lesson 5.1 Evolution
Genetic Drift
Natural Selection
Process by which traits useful for survival and
reproduction are passed on more frequently than
those that are not
Evolution that occurs by chance
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Conditions of Natural Selection

Lesson 5.1 Evolution
(1) Organisms produce more offspring than can
survive.
(2) Individuals vary in characteristics, some of
which are heritable.
(3) Individuals vary in fitness, or reproductive
success.
Did You Know? Darwin privately researched natural
selection for two decades before publishing On
the Origin of Species.
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Artificial Selection

Lesson 5.1 Evolution

• Selection under human direction
• Throughout history, humans have chosen and bred
  animals and plants with beneficial traits.

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Speciation

Lesson 5.1 Evolution

• Process by which new species are generated
• Can occur in a number of different ways the most
  important way is called allopatric speciation
• Has resulted in every form of life on Earth
  today and in the past

Allopatric Speciation
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Extinction

Lesson 5.1 Evolution

• The disappearance of species from Earth
• Generally occurs gradually, one species at a
  time, when environmental conditions change more
  rapidly than the species can adapt
• There are five known mass extinction events, each
  of which wiped out a large proportion of Earths
  species.

Trilobites Marine arthropods that went extinct at
the end of the Permian period.
Did You Know? During the Permo-Triassic
extinction 250 million years ago, 70 of all land
species and 90 of all marine species went
extinct.
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Lesson 5.2 Species Interactions

• The zebra mussel has completely displaced 20
  native mussel species in Lake St. Clair.

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The Niche
Lesson 5.2 Species Interactions

• Describes an organisms use of resources and
  functional role in a community
• Affected by an organisms toleranceits ability
  to survive and reproduce under changing
  environmental conditions
• Often restricted by competition

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Competition
Lesson 5.2 Species Interactions

• Organisms compete when they seek the same limited
  resource.
• In rare cases, one species can entirely exclude
  another from using resources.
• To reduce competition, species often partition
  resources, which can lead to character
  displacement.

Resource Partitioning
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Predation (/)
Lesson 5.2 Species Interactions

• The process by which a predator hunts, kills, and
  consumes prey
• Causes cycles in predatory and prey population
  sizes
• Defensive traits such as camouflage, mimicry, and
  warning coloration have evolved in response to
  predator-prey interactions.
• Some predator-prey relationships are examples of
  coevolution, the process by which two species
  evolve in response to changes in each other.

Rough-Skinned Newt
Did You Know? A single rough-skinned newt
contains enough poison to kill 100 people.
Unfortunately for the newt, its predator, the
common garter snake, has coevolved resistance to
the toxin.
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Parasitism and Herbivory (/)
Lesson 5.2 Species Interactions

• Parasitism One organism (the parasite) relies on
  another (the host) for nourishment or for some
  other benefit
• Herbivory An animal feeding on a plant

Hookworm (a parasite)
Did You Know? One study of Pacific estuaries
suggests that parasites play an important role in
keeping these ecosystems healthy by controlling
host populations.
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Mutualism (/) and Commensalism (/0)
Lesson 5.2 Species Interactions

• Mutualism a relationship in which two or more
  species benefit
• Commensalism a relationship in which one species
  benefits while the other is unaffected

Lichen a symbiotic relationship between a fungus
and a photosynthetic partner, such as an alga
Did You Know? Symbiosis describes a long-lasting
and physically close relationship between species
in which at least one species benefits.
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Lesson 5.3 Ecological Communities

• The sun provides the energy for almost all of the
  ecological communities and species interactions
  on Earth.

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Primary Producers (Autotrophs)
Lesson 5.3 Ecological Communities

• Capture energy from the sun or from chemicals and
  store it in the bonds of sugars, making it
  available to the rest of the community
• Energy from the sun is captured by plants, algae,
  or bacteria through photosynthesis.
• Energy from chemicals is captured by some
  bacteria through chemosynthesis.

Did You Know? Deep-sea vents, far from sunlight,
support entire communities of fish, clams, and
other sea animals, which depend on energy
converted through chemosynthesis.
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Consumers (Heterotrophs)
Lesson 5.3 Ecological Communities

• Rely on other organisms for energy and nutrients
• Herbivores plant-eaters
• Carnivores meat-eaters
• Omnivores combination-eaters
• Detritivores and decomposers recycle nutrients
  within the ecosystem by breaking down nonliving
  organic matter
• Use oxygen to break bonds in sugar and release
  its energy through cellular respiration (primary
  producers do this, too)

California Condor
Did You Know? Scavengers, such as vultures and
condors, are just large detritivores.
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Energy in Communities
Lesson 5.3 Ecological Communities

• An organisms rank in a feeding hierarchy is its
  trophic level.
• Primary producers always occupy the first trophic
  level of any community.
• In general, only about10 of the energy
  available at any trophic level is passed to the
  next most of the rest is lost to the environment
  as heat.

Pyramid of Energy
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Numbers and Biomass in Communities
Lesson 5.3 Ecological Communities

• A trophic levels biomass is the mass of living
  tissue it contains.
• In general, there are more organisms and greater
  biomass at lower trophic levels than at higher
  ones.

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Food Chains and Webs
Lesson 5.3 Ecological Communities

• Food chain Linear series of feeding
  relationships
• Food web Shows the overlapping and
  interconnected food chains present in a community

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Keystone Species
Lesson 5.3 Ecological Communities

• Species that have strong and/or wide-reaching
  effects on a community
• Removal of a keystone species can significantly
  alter the structure of a community.

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Lesson 5.4 Community Stability

• A 2010 report on invasive species suggests that
  they cost the U.S. 120 billion a year in
  environmental losses and damages.

Invasive kudzu
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Ecological Disturbances
Lesson 5.4 Community Stability

• A community in equilibrium is generally stable
  and balanced, with most populations at or around
  carrying capacity.
• Disturbances or changes in the environment can
  throw a community into disequilibrium.
• Severe disturbances can cause permanent changes
  to a community and initiate a predictable series
  of changes called succession.

Forest fire
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Primary Succession
Lesson 5.4 Community Stability

• Occurs when there are no traces of the original
  community remaining, including vegetation and
  soil
• Pioneer species, such as lichens, are the first
  to colonize.
• The environment changes as new species move in,
  adding nutrients and generating habitat.

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Secondary Succession
Lesson 5.4 Community Stability

• Occurs when a disturbance dramatically alters a
  community but does not completely destroy it
• Common after disturbances such as fire, logging,
  or farming
• Occurs significantly faster than primary
  succession

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Succession in Water
Lesson 5.4 Community Stability

• Primary aquatic succession occurs when an area
  fills with water for the first time.
• Disturbances such as floods or excess nutrient
  runoff can lead to secondary aquatic succession.

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Climax Communities
Lesson 5.4 Community Stability

• Ecologists once thought succession leads to
  stable climax communities.
• Today, ecologists see communities as temporary,
  ever-changing associations of species.
• Communities are influenced by many factors and
  constant disturbances.

Beech-maple forest, a classic climax community
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Invasive Species
Lesson 5.4 Community Stability

• Nonnative organisms that spread widely in a
  community
• A lack of limiting factors such as predators,
  parasites, or competitors enables their
  population to grow unchecked.
• Not all invasive species are harmful.

Did You Know? Although the European honeybee is
invasive to North America, it is beneficial
because it pollinates our agricultural crops.