Biotic and Abiotic Factors

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Biotic and Abiotic Factors
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Different Approaches to the Study of Ecology

• Ecology is the study of an organism or organisms
  and their relationship to the environment.
• An organisms environment consists of the
  physical, chemical and biological factors with
  which it interacts.
• The mollusks seen at the right must deal with
  changes in temperature, tides, wave action,
  predators and competition for food. Each plays
  its own role or niche.

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How can we study Environmental Interactions?

• At the most basic level, an ecologist may be
  interested in the interactions of a single
  organism and its environment.
• Population ecologists focus on factors that
  affect populations of organisms that are found in
  a specific area. (i.e. What determines the
  reproductive success of wood storks in South
  Florida.)
• At the community level of study one is interested
  in understanding the interactions between
  populations of different species living in an
  area. For example, what determines composition
  and distribution of trees in a hardwood hammock?

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An Ecosystem Approach

• At a fourth level, studies may examine an
  ecosystem.
• The ecosystem includes all the organisms in an
  area and all of the abiotic factors that affect
  them.
• In South Florida there are many ongoing studies
  of the Everglades ecosystem, as biologists,
  geologists, hydrologists and atmospheric
  scientists work together in efforts to understand
  how all the parts of it relate to each other.
  Without this knowledge we cannot hope to
  preserve, protect or manage the unique natural
  environment that is South Florida .

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Abiotic factors are the non-living Components of
the Environment

• Abiotic factors include
• Sunlight
• Water
• Temperature
• Wind
• Soil/substrate
• Special events such as
• Fires
• Hurricanes
• Floods
• Volcanic eruptions
• Tsunamis

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The atmosphere has a tremendous effect on the
distribution of plants and animals. Global
patterns of circulations affect rainfall patterns
and the prevailing wind directions. Changes in
air circulation over the Pacific Ocean can lead
to events, such as El Nino, which have global
repercussions (i.e. torrential rains in the Andes
and severe drought in Australia)
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Regional climate affects biological communities

• The unequal heating of the earths surface leads
  to the global patterns of rainfall and winds. At
  the equator there is maximum heating of the
  earths surface. This causes hot air to rise,
  and as it rises it cools, forming clouds and
  increasing precipitation. At high altitudes the
  air cools and moves away from the equator. At
  the mid-latitudes this cool air sinks back to the
  surface. This results in both the trade winds
  and relatively dry conditions.

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Prevailing wind patterns, set ocean currents in
motion.

• The patterns of wind flow can be seen in the
  figure at the right. Land masses can interrupt
  these patterns at a local or regional level.
• Ocean currents are created by the flow of winds,
  and cause great patterns of circular flow in the
  oceans. The Gulf Stream is one such current.
  Without the heat in this mass of water, the
  climate of northern Europe would be much cooler.
  This would alter the biological communities found
  there.

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Rain shadows greatly affect the availability of
moisture!

• As previously stated, land masses affect
  atmospheric movements. Rain shadow effects are
  seen when moist oceanic air masses encounter
  mountains. The moist air is forced up, cools,
  and releases its moisture in the form of rain.
  On the back side of the mountains, the cooled air
  decends towards the surface, but is no quite dry.
  This may create arid or semi-arid conditions.

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Other Abiotic Factors

• Temperature also affects the distribution of
  plants and animals.
• As a rule, temperature are lower as you move
  towards the poles or as you climb in elevations.
  For this reason arctic or sub-arctic plant
  communities can be found at high elevations in
  the tropics.
• In the temperate latitudes living organisms must
  be able to tolerate the temperature extremes of
  summer and winter. This could range from 90s in
  the summer to well below freezing in the winter.
• In the tropics there is very little seasonal
  change and many organisms have a narrow range of
  temperature tolerance. Years ago an important
  paper was publish titled Why mountain passes
  are higher in the tropics. What does that
  mean??
• It means that in the tropics differences in
  elevation can be barriers to the distribution of
  species. The temperature at which you can live
  may prevent your population from moving from one
  suitable habitat to another, because of the
  temperature zones through which you would need to
  pass in a vertical migration.

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Other Abiotic Factors

• Here are some abiotic factors that you may not
  have thought about.
• Calcium The lack of availability of calcium
  will restrict the distribution of land snails.
  If there is no calcium a shell cant be secreted.
• Sand the size of the sand grains in the soil
  can impact animal that are burrowers.
• Nitrogen Not just nitrogen, but nitrate (NO3).
  This is the form of nitrogen used by plants.
  When nitrate is not readily available in the
  soil, some plants supplement it with a meat diet.
  (insectivorous plants).

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Biotic Factors

• A living organism is also affected by the living
  components of its environment.
• Competition exists for available food resources.
• Predators feed on members of the population.
• Microbes can bring diseases. (If time travel were
  possible, and you could be transported to the
  Cretaceous Era to look at dinosaurs, dont be
  afraid of fear Tyrannosaurus, fear the microbes.
  You would have no immunity to them!!)
• There may be competition for nesting space.
• Plants may compete for the light needed to
  carryout photosynthesis.
• These are many other biological factors determine
  the success of an individual or species.