Cape Biology Notes

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An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving or abiotic, physical components of the environment with which the organisms interact, such as air, soil, water and sunlight. In a typical ecosystem, plants and other photosynthetic organisms are the producers that provide the food. (Leibold) Ecosystems can be permanent or temporary and they usually form a number of food webs. Examples of ecosystem include:

Marine Ecosystems: oceans, coral reefs, intertidal zones, estuaries (harbour, lagoons) Terrestrial Ecosystems: deserts, forest, grasslands, tropical rain forests, tundra, taiga Freshwater Ecosystems: streams, rivers, pond, lake, swamps and marshes A habitat is a place or area in which organisms or a community of organisms live, including all the living and non-living conditions or factors of the surrounding the environment. The habitat must supply the needs of the organism including water, sunlight and oxygen, therefore a habitat is specific to a population (a group of similar organisms living and interacting in the same place at the same time). Examples of habitats include:

Under a stone, the forest floor,
A rotten log- insects and fungi
The intestine- E.coli bacteria
Forest- deer, rabbit. Fox
Tropical grasslands: zebra, giraffe, Lion, Ostrich
Tundra: Snow birds, Polar bear
An ecological niche refers to the role of a population in its ecosystem, or in its living and non-living environment. This usually means its feeding role in the food chain, so a particular population niche could be a producer, a predator, a parasite or a herbivore. ( Mader) A niche includes many different aspects such as its food, its habitat, its reproduction methods etc. The different niches help us to identify the interaction between populations. Members of the same population always have the same niche, and will be adapted to that niche. For example nectar feeding birds have long thin beaks. It describes how organisms fit into its habitat by making use of available resources, withstanding abiotic and biotic factors, using the help of adaptations. Examples of ecological niches include:

seaweed is an inter-tidal autotroph,
fungi are soil-living saprophytes
Lion as a grassland carnivore
Humans are terrestrial omnivores

Energy is the ability to do work, when work is done, energy is used, or converted from one form to another. Living things get their energy from the food it consumes and this is called chemical energy. Energy flow in an ecosystem is in the form of carbon-carbon bonds. The transformations of energy in an ecosystem begin first with the input of energy from the sun. Energy from the sun is captured by the process of photosynthesis. During photosynthesis carbon dioxide is combined with hydrogen (derived from the splitting of water molecules or photolysis) to produce carbohydrates (CHO). The energy from the sun becomes interlocked in organic molecules in the form of chemical bonds. During respiration energy in glucose is released from the oxidation of glucose and this energy is stored in the high energy bonds of adenosine triphosphate, or ATP. Respiration releases the energy, which is either used by the organism or the energy may be lost as heat. Energy flows through the ecosystem in one direction, typically from the sun, through photosynthetic organisms including green plants and algae, to herbivores to carnivores and decomposers. Almost everything you eat can be traced back through food chains to the sun. A food chain consists of a series of organisms in which the first organism is eaten by a second and the second is eaten by a third. During this process, nutrients and energy in the eaten organism are transferred to the organism that eats it. The food chain begins with producers, organisms such as green plants that can make their own food. Through photosynthesis, producers convert solar energy to chemical energy, energy in the...
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