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Topic 6 Ecology. The study of interactions between organisms and their environments. 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

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topic 6 ecology

Topic 6 Ecology

The study of interactions between organisms and their environments.

i parts of an ecosystem
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
b abiotic factors
B. Abiotic Factors
  • Nonliving factors in an environment
  • Examples:
    • Air currents (wind)
    • Temperature (climate)
    • Water (rain, snow, oxygen content)
    • Sunlight (energy)
    • Soil (pH)
c organization of life
C. Organization of Life
  • A species’ specific environment is known as their habitat
  • Examples: fields, forests, oceans, streams
  • A habitat is a “home”
organization of life
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
organization of life6
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
organization of life7
Organization of Life
  • Communities combine to form ecosystems
  • All of Earth’s ecosystem’s together make up the Biosphere

 includes the Earth’s surface, water, and the atmosphere

organization of life8
Organization of Life






ii population limits a factors that limit population growth are called limiting factors
They include:






Soil pH – too acidic/basic

Sunlight – in a forest

Space – in a nest

II. Population LimitsA. Factors that limit population growth are called limiting factors
b competition
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…
  • 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 people’s 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…
c carrying capacity
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???
what will happen if the human population continues to grow at this same rate
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
iii ecosystem relationships
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
ecosystem relationships
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 isn’t the case
  • Deer and moose only eat the same plants when food is scarce
  • When this occurs they must compete
b symbiotic relationships
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:
symbiotic relationships
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

c feeding trophic relationships one of the most common
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
d trophic pyramids
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…

e food chains food webs
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…