1. Biotic Factors Science 10

2. 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: 1.Detritus: decomposing animals and plants 2.Disease 3.Predator/prey interactions 4.Competition 5.Symbiotic relationships (symbiosis).

3. 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. 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.

4. 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).

5. 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.

6. 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.

7. 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.

8. 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.

9. 2 Types of Competition 1.Inter-Specific Competition: competition between different species. Example: Lion and hyena or bear and wolf competing for food 2.Intra-Specific Competition: competition between species. Example: Tigers competing for mates or birds competing for nesting space.

10. 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: 1.Mutualism 2.Commensalism 3.Parasitism 4.Parisitoidism 5.Predation.

11. 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.

12.  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.

13.  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).

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

15.  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.

16.  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.

17.  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.

18. 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.

19.  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.

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

21.  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.

22. 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.

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