Ecology A Review

Habitat The place in which an organism lives. Some organisms can share the same habitat but they will have different microhabitats. Organisms usually cannot survive in other habitats where conditions can be quite different. However some organisms can tolerate a range of conditions and live in a variety of habitats

Niche Simply put, this is the organism’s role in the community – its job. Generally it is related to how the species obtains food eg as a predator, producer etc. It is a description of the opportunities provided by the habitat and the adaptations of the organism that enable it to take advantage of the opportunities

Each of the organisms in this ecosystem has a particular way of fitting into the oak tree environment - they each occupy a niche within the ecosystem. For example the blue tits and the squirrels, though they both inhabit the same tree, do not directly compete for food: the squirrels feed on acorns, while the tits feed on moth larvae. The two species occupy different niches within the oak ecosystem. /gcsebitesize/biology/livingthing senvironment/0habitatsandpops rev5.shtml

Gause’s Principle No two species can occupy the same ecological niche in the same habitat for an indefinite period.

Environmental Factors There are 2 types of environmental factorsenvironmental factors Biotic – living factors, including other organisms such as food, predators, parasites, competitors Abiotic – physical, non-living factors, including temperature, light intensity, salinity

Tolerance and Limiting Factors The environmental factors that can effect an organism do not remain constant. For a species to be able to survive in its habitat it needs to be able to tolerate variation in these factors. The range in which it thrives is called an organisms optimum range. Outside the optimum range are tolerance limits. If an organism exceeds this, it can suffer stress and, if too severe, die. Acclimation is the adjusting of tolerance limits, eg getting a tan, growing thicker fur in winter

Adaptations All organisms inherit characteristics that increase their chances of survival. These are commonly divided into three categories: Behavioural – how the organism behaves Structural – the shape and size of an organism Physiological – the working of an organisms body

Camels are well adapted for survival in the desert. They have: the ability to store a lot of water, and to lose very little via urination and sweating the ability to tolerate body temperatures up to 42 degrees C a large surface area / volume ratio - maximising heat loss a hump which can store scarce food as fat without insulating the body thick fur on the top of the body to provide shade, and thin fur on the rest of the body to allow easy heat loss, and large, flat feet well-suited for walking on sand ze/biology/livingthingsenvironment/0hab itatsandpopsrev6.shtml

Cacti are well adapted for survival in the desert. They have: spines instead of leaves, which minimise surface area and therefore evaporation, and also... protect them from animals which might eat them stems which can store water, and widespread root systems, which can collect water from a large area

Community Patterns Communities are often complex and their composition and structure is ever changing This can be caused by physical factors (eg tidal wave) or biotic factors (eg forest shading) 3 Patterns of change in a community are: Succession Stratification Zonation

Relationships Relationships exist between all organisms in an ecosystem. Co-operative or competitive relationships Co-operative or competitive These can be: Beneficial (+) Harmful (-) Neutral (0) Summary of Relationships

Revision Activity Try these links to complete revision activities: ogy/quizengine?quiz=habitatsandpops&templateStyle =biology ogy/quizengine?quiz=habitatsandpops&templateStyle =biology

Relationships Type of InteractionSpecies ASpecies B Mutualism Both species benefit from the association ++ Commensalism The presence of one species has a beneficial effect on the other, but is not itself affected by the association 0+ Amensalism The presence of one species has a harmful effect on the other, but is not itself affected by the association 0- Exploitation One species benefits at the expense of the other. May include Predation, Herbivory, Parasitism -+ Antibiosis One species benefits the other by producing a compound which inhibits the growth of another organism +- Competition Species or individuals, compete for the same resources, with both parties suffering, especially when resources are limited --

Stratification Vertical layering of organisms

Zonation Horizontal bands forming in relation to a gradient