Species+Relationships

- interspecific competition
 * __Competition Between Species__**

Competition exists when demand for a resource exceeds supply. The competition can be intraspecific (between members of the same species) or interspecific (between members of different species).

Many animals seem to have similar lives but they are using different resources. //Examples://
 * The New Zealand spotted shag feeds a long way off the coast while the pied shag feeds on the coast.
 * Amoung the grazing animals of the Serengeti plains of East Africa there are differences in diet. The dominant ones are zebras, Thompson's gazelles and wildebeeste. These all migrate across the plains during the dry season. Zebras feed on grass stems but they cannot process food as quickly as the other two species. For this reason, they eat twice as much. Wildebeeste and Thompson's gazelles feed mainly on grass leaves but they do not compete with each other as they migrate at different times. In between the migrations of the two species, the grass has time to recover and therefore provides food for both species.

Strong evidence for interspecific competition is character displacement. This occurs when differences in a character which is common to different species is exaggerated where the species habitats overlap.

__Niches Change__

An animal's diet may change depending on its stage of development. This is especially true of animals which undergo a metamorphosis from a larva to an adult (eg. insects and amphibians). Even within the adult stage, an organism's niche is not necessarily fixed and it may change with the seasons.

Individuals of the same species resemble each other more closely than those of different species. This means that intraspecific competition could be expected to be more intense than interspecific competition.
 * __Intraspecific Competition__**

__Competition for mates__ The aim of all organisms is to pass on their genes to the next generation. This is achieved through mating. Different gametes are produced by males and female individuals which fuse to form new life at fertilisation. Both sexes invest a lot of energy in reproduction, however they do so in different ways. Males produce large amounts of sperm while the female produces a small number of eggs which are larger than sperm. More energy is required to produce and egg than a sperm and therefore an egg represents a bigger investment. Describe the inter-species interactions of: Describe the intra-species interactions of: competition for resources, cooperative strategies, reproductive behaviours. Give examples and adaptive advantage for the inter-specific and intra-speciific interactions. Analyse and interpret information to explain examples of inter-specific and intra-specific interactions in animals and plants
 * **Grazing -**
 * ** Parasitism - **the feeding of an organism (the parasite): on another (the host):, in which the host is harmed but not usually killed.
 * ** Mutualism - **relationship between two organisms in which both benefit.
 * C** ommensalism - **relationship between two organisms in which one benefits but the other is not harmed.
 * **Amensalism:** relationship between two organisms where one is unaffected and the other is harmed or killed.
 * C** ompetition for resources - **
 * ** S **** uccession **
 * ** Z **** onation **
 * ** Stratification **

Therefore, male and female reproductive strategies typically differ in two ways:
 * Females try to ensure that the sperm which fertilises their eggs are of the highest quality. Females therefore tend to be more selective about the male with whom they mate. This results in competition amoung the males of a species for the females. In many species, the female continues to invest energy in caring for the eggs after they are fertilised. In some groups of animals the females feed their young (eg. mammals).
 * Sperm are individually very cheap to produce in terms of energy. Therefore, males try to ensure that their sperm fertilises as many eggs as possible (they mate with many females).

Competition between males for females takes two forms - fighting and display. In both cases, it results in strong selection pressures and the stronger, more genetically fit males tend to win and are able to pass on their genes.

Videos to demonstrate: a) Difference between home range and territory