Biotic Factors

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Biotic Factors

• Science 10

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Biotic factors

• Are factors that affect the living environment
  and include all other organisms that interact
  with the individual (either the same species
  and/or other species).
• There are 5 biotic factors
• Detritus decomposing animals and plants
• Disease
• Predator/prey interactions
• Competition
• Symbiotic relationships (symbiosis).

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1. Detritus

• Refers to non-living organic material such as
  decomposing dead organisms as well as their
  wastes.
• Example
• Sea Foam is caused by decaying organic material
  in the ocean, such as the dissolved waste of
  algal blooms. Organic pollution from run off
  water can also increase foam production. 

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Detritivores or Saprobes

• Obtain nutrients by consuming detritus
  (decomposing organic matter).
• Examples
• millipedes, woodlice, terrestrial worms, burying
  beetles
• Micro-organisms such as bacteria, fungi, and
  protists are important to an ecosystem because
  they recycle materials by breaking them down
  into their elements and returning them to the
  soil (so plants can use these nutrients).

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2. Disease

• is the result of an infection by fungi, bacteria,
  virus, and other pathogens.
• Pathogen
• an infectious agent, or more commonly germ, is
  a biological agent that causes disease or illness
  to its host.
• Disease is an important biotic factor because
  disease tends to reduce the number of organisms
  within the community.

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3. Predator-Prey Interaction (Predation)

• is another important biotic factor which helps to
  limit the size of populations within an
  ecosystem.
• Predation occurs when one animal (the predator)
  eats another living animal (the prey) to utilize
  (or use) the energy and nutrients from the body
  of the prey for its own growth, maintenance, or
  reproduction.

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Example of Predation

• Jaguar and Tapir (Belize)
• When a jaguar kills a tapir for food, the jaguar
  helps to prevent the overpopulation of the tapir.
  
• If the number of tapir declines too much the
  jaguar will starve.
• ? there is a balance between the numbers of
  predator and prey in any ecosystem.

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4. Competition

• Is a struggle for survival that occurs (or
  happens) between organisms either of the same or
  different species.
• Competition tends to limit the size of the
  population keeping it in balance with the
  available resources.

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2 Types of Competition

• Inter-Specific Competition competition between
  different species.
• Example Lion and hyena or bear and wolf
  competing for food
• Intra-Specific Competition competition between
  species.
• Example Tigers competing for mates or birds
  competing for nesting space.

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5. Symbiotic Relationships

• Are biotic relationships in which different
  organisms live in close association with each
  other to the benefit of at least one.
• There are 5 types of symbiotic relationships
  including
• Mutualism
• Commensalism
• Parasitism
• Parisitoidism
• Predation.

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Mutualism

• resulting in mutual benefit to both of the
  organisms in the relationship.
• An example of this would be the relationship
  between the algae and fungus of lichens.
• The fungi penetrate the roots of the plants and
  makes soil nitrogen available to the plant,
  receiving carbohydrates in return. This allows
  them to live in an environment in which neither
  could survive alone.

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• An example is a polyp found in the deep water off
  the coast of Newfoundland
• It attaches itself to the shell of a certain
  species of the hermit crab, and by budding,
  covers the entire shell with a colony that
  dissolves the original shell.

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• Because the colony grows at the same rate as the
  crab, it provides continuous protection, and the
  crab does not shed its shell at periodic
  (varying) intervals as it normally would.
• The polyp in turn benefits by moving around with
  the crab (mobile) thus obtaining a greater food
  supply then it would obtain if attached to a
  stationary object (immobile).

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Commensalism

• relationship in which one organism benefits from
  the relationship but the other organism seems to
  neither be harmed nor benefits.

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• An example of commensalism is the relationship
  between trees and nesting birds.
• The tree provides a nesting space for the bird
  but the bird may neither harm nor benefit the
  tree.

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• On the other hand, if the bird eats insects that
  normally cause harm to the tree or if the bird
  produces wastes that are absorbed by the tree,
  one might argue that the tree and the bird both
  benefit.
• In this case the example would be considered
  mutualism.
• It is often difficult to determine the complete
  nature of any relationship and as a result it is
  often difficult to distinguish between mutualism
  and commensalism.

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• The anemonefish lives among the forest of
  tentacles of an anemone and is protected from
  potential predators not immune to the sting of
  the anemone.
• The anemonefish is protected from the sting of
  the anomone tentacles by a substance contained in
  the mucous on its skin.
• The anemone treats the fish as part of itself and
  does not sting it.

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Parasitism

• is a symbiotic relationship in which one organism
  benefits and the other is harmed.
• The organism that benefits is called the
  parasite, the organism that is harmed is called
  the host.
• Some parasites only cause slight damage to their
  host, while others kill them.

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• An example would be the tapeworm. They live in
  the digestive tracts of various organisms, while
  there they are provided with nutrients and an
  environment in which to grow and reproduce.
• However, the host is harmed by the presence of
  the tapeworm.

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Parisitoidism

• similar to parasitism. One organism benefits but
  the other is eventually killed - a sort of slow
  death.

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• An example is when a female wasp stings a spider
  causing paralysis but not death.
• The wasp then lays a single egg on the spider.
• When the egg hatches into a larva, it slowly eats
  the body of the spider eventually killing it -
  but slowly.

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Predation

• is where the interaction is beneficial to one
  species and detrimental to the other.
• This is not always considered a symbiotic
  relationship, although it is quite similar to
  parasitism, except for the degree of harm to the
  host or prey.
• With predation, the prey is killed.

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• An example of predation is when a lion kills an
  antelope and eats it as its source of food.