Biotic & Abiotic Factors What do species compete for?

edited/chap25/b asp

Abiotic factors are the nonliving factors which affect life in any ecosystem. Space - All organisms require enough space or territory to insure adequate resources to food, water, shelter, and mates. Temperature - Environmental temperature affects biological processes and the ability of most organisms to regulate their temperature. –Ectotherms can maintain their body temperature only within a few degrees of ambient temperature. Endotherms function best in a temperature range for which they are adapted.

Oxygen - Most living organisms need oxygen for cellular respiration. Sunlight - is the ultimate source of energy Water - Water (humidity) is necessary for all life. Nutrients –Inorganic soil nutrients include minerals such as phosphates, nitrates, potassium, magnesium and many others derived from rocks. –Organic nutrients include compounds in humus that promote the growth of bacteria, fungi, and other organisms beneficial to soil. Soil - The physical structure, water holding potential, pH, and nutrient level of soil limit the distribution of plants and in turn the animals that inhabit a terrestrial region. The composition of the substrate in a stream affects the chemistry of the water above and in turn affects plant and animal life living there. The type of substrate also influences what animals can attach to or burrow in (especially in the intertidal zone).

Biotic factors refer to the living environment and include all other organisms that interact with the individual, of the same species and other species. Detritus - decomposing plant and animal materials including their dead bodies as well as their wastes. (Important in recycling.) Disease - result of infection by fungi, bacteria, virus, and other pathogens. Tends to reduce the number of organisms in the community. Predator/prey interaction - helps to limit the size of populations. A predator is an animal that kills and eats another animal for food. The prey is the hunted animal. There is a balance between the number of predators and prey in any ecosystem.

Competition - struggle for survival that occurs between two organisms either of the same or different species. Limits the size of the population keeping it in balance with available resources. Interspecific Competition is between different species. Intraspecific Competition is between members of the same species.

Competitive Exclusion Principle No two species of organisms can have exactly the same niche (requirements). They will compete with each other until only one species remains. Pg. 236

Density Independent Factors. –Abiotic factors that have an impact, no matter how many organisms there are in the population Density Dependent Factors –Supplies of resources, transmission of disease, sufficient space; all of these are things that change depending on how many organisms there are.

Symbiotic relationships: two different organisms live in close association with each other to the benefit of at least one. Mutualism - benefit to both of the organism. Example - the relationship between the algae and fungus of lichens. The fungi provide structure and absorb water and nutrients, and make soil nitrogen available to the alga, receiving carbohydrates in return. Commensalism - one organism benefits from the relationship but the other organism seems to neither be harmed nor benefited. Beaver builds a dam to regulate water. Fish often inhabit the beaver pond. The fish benefit from the beaver, but beaver is neither harmed nor gains benefit from the fish.

Parasitism - 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. Tapeworm lives in the digestive tracts of where they are provided with nutrient and an environment in which to grow and reproduce. The host is harmed by the presence of the tapeworm, having its nutrients “stolen”. Parasitoidism - one organism benefits, the other is eventually killed - a sort of slow death. Ichneumen wasp lays egg inside an insect it has paralyzed. Egg hatches and feeds on insect until it is dead. Predation - the interaction is beneficial to one species and detrimental to the other. Not always considered a mutualistic relationship.