Topic 6 Ecology

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Topic 6 Ecology

• The study of interactions between organisms and
  their environments.

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I. Parts of an Ecosystem

• A. Biotic factors
• Biotic factors all living organisms in a
  biosphere
• Ex. Plants, bacteria, animals, us
• Biosphere life-supporting layer of Earth
• Biomass the mass of all biotic factors

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B. Abiotic Factors

• Nonliving factors in an environment
• Examples
• Air currents (wind)
• Temperature (climate)
• Water (rain, snow, oxygen content)
• Sunlight (energy)
• Soil (pH)

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C. Organization of Life

• A species specific environment is known as their
  habitat
• Examples fields, forests, oceans, streams
• A habitat is a home

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Organization of Life

• All species that live in the same area or habitat
  make up a population
• Examples ants living in the same anthill, frogs
  in the same pond

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Organization of Life

• Populations combine to form a community
• Example ants, birds, frogs, fish, deer live in
  the Ellison Park community
• Example rabbits, coyotes, snakes, birds, mice
  and cacti live in a desert community

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Organization of Life

• Communities combine to form ecosystems
• All of Earths ecosystems together make up the
  Biosphere
• ? includes the Earths surface, water, and the
  atmosphere

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Organization of Life
Biosphere
Ecosystems
Communities
Populations
Organisms
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Organization of Life
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II. Population LimitsA. Factors that limit
population growth are called limiting factors

• Temperature
• Soil pH too acidic/basic
• Sunlight in a forest
• Space in a nest

• They include
• Food
• Minerals
• Water
• Oxygen

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B. Competition

• The struggle for resources
• Keeps the population in check
• Predator - Prey Relationships
• As predators kill their prey, the prey population
  is limited (decreased)
• If too many prey are killed, predators starve
• Fewer predators allows prey populations to
  repopulate
• Too many of one kind will cause suffering

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Competition

• If there is too much of one kind of animal, the
  rest will suffer. For example
• Since there are so few wolves around, deer have
  multiplied.
• Because there are so many deer, the bark of many
  trees has been stripped off.
• Now, deer are invading peoples yards in search
  of food and eating my bird seed!
• Deer bring Lyme Disease, which sickens people,
  and they cause many car accidents
• More car accidents means higher insurance rates

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C. Carrying Capacity

• The number of organisms an ecosystem can support
  or carry
• Determined by the amount of resources available
  and by organisms interactions
• Ex. An increased mouse population in a field will
  increase the carrying capacity of foxes to a
  certain extent
• Ex. Increased medical advances has increased the
  human population but for how long???

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Human Population Growth
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What will happen if the human population
continues to grow at this same rate?

• Is there a human carrying capacity?
• Yes - what will happen if we reach it?
• Famine, death, disease, war over resources
• More Human Ecology to come in Topic 7

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III. Ecosystem Relationships

• A. Organisms have certain roles in an ecosystem
• Called their ecological niche
• Only one species can occupy a particular niche
• If two species attempt to occupy the same niche
  they will compete for resources

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Ecosystem Relationships

• Deer and moose appear to have the same niche
• They seem to live in the same area and eat the
  same plants, but that isnt the case
• Deer and moose only eat the same plants when food
  is scarce
• When this occurs they must compete

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B. Symbiotic Relationships

• In ecosystems, populations are linked
• They depend on each other in different ways ?
  interdependent
• Sometimes relationships are cooperative,
  sometimes they are competitive
• There are 3 types of relationships

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Symbiotic Relationships

• Commensalism one organisms benefits, the other
  is not affected
• Ex. Barnacles on whales
• Mutualism both organisms benefit
• Ex. Bees and flowers, birds and rhinos
• Parasitism one benefits, one is harmed
• Ex. Tapeworms, lice, ticks, heartworms

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Symbiotic Relationships Chart
(Symbiosis living together)
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C. Feeding (Trophic) Relationships -one of the
most common

• Organisms are identified by how they obtain their
  food
• Autotrophs ? self-feeders or producers
• Heterotrophs ? consumers
• Herbivores eat plants
• Carnivores eat meat
• Omnivores eat both plants and meat
• Scavengers eat dead organisms
• Decomposers ? break down remains of all organisms
  and recycle nutrients

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D. Trophic Pyramids

• Show distribution of biomass in an ecosystem
• Autotrophs (producers) most biomass
• Primary consumers (herbivores)
• Secondary consumers (carnivores)
• Tertiary consumers (carnivores/top predators)
  least biomass
• Some trophic pyramids include energy distribution
  as well

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Trophic Pyramids
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E. Food Chains/Food Webs

• Also show relationships between organisms ?
  predator - prey
• Normally, each organism feeds on more than one
  food source
• Food webs show a more complex feeding
  relationship
• They are more realistic than food chains see
  example

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