Ecology And Evolution

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species

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an organism who can interbreed and produce fertile offspring

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Population

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a group of the same species living in the same place and the same time

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Community

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Populations of different species living in the same area and interacting

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Ecosystems

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A community and its abiotic environment

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Ecology

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The study of the relationship between different organisms and between those organisms and their environment

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Autotroph

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Producer. An organism that synthesizes organic molecules from simple inorganic molecules

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Heterotroph

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Consumer. An organism that obtains organic molecules from other organisms

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Consumers

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an organism that ingests organic matter that is living or recently dead

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Detritivores

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an organism that ingests non-living organic matter

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Saprotroph

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Organism that lives on or in non-living organic matter, secreting digestive enzymes into it and absorbing products of digestion

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Describe what is meant by a food chain, giving three examples, each with at least three linkages

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A food chain shows the direction in which energy flows from one species to another. For example: Carrotplant → carrotfly → flycatcher → sparrow hawk

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food web

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A food web is a diagram that shows how food chains are linked together into more complex feeding relationships. The advantages of a food web is that it shows how some animals have different trophic levels and how more than one producer supports a community.

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trophic level

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The trophic level of an organism defines the feeding relationship of that organism to other organisms in a food web

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Explain the energy flow in a food chain

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Producers receive their energy from light energy (sun) through photosynthesis. Then, the energy in organic matter flows from producer to primary consumer and so on. However, between these trophic levels energy is always lost because all trophic levels lose energy as heat through cell respiration. Also, not all is digested so energy is lost in secretion, tissue loss and death. This energy passes to detritivores and saprotrophs, this also loses energy in form of heat through cell respiration

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Explain reasons for the shape of pyramids of energy

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The reason for the shape of the pyramids of energy is the loss of energy between each trophic level
Loss of energy from solar radiation
The volume of one layer is 10% of the previous layer
Loss of energy makes food chains short. Consumers at the top have less energy and that’s why their numbers are relatively few in most communities.

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Explain the relationship between rises in concentrations of atmospheric carbon dioxide, methane and oxides of nitrogen and the enhanced greenhouse effect

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1. The incoming radiation from the sun is short wave ultraviolet and visible radiation.
2. Some of this radiation is absorbed by the earth’s atmosphere.
3. Some of the radiation is reflected back into space by the earth’s surface.
4. The radiation, which is reflected back into space is infrared radiation and has a longer wavelength.
5. The greenhouse gases in the atmosphere absorb some of this infrared radiation and re-reflect it back towards the earth.
6. This causes the green house effect and results in an increase in average mean temperatures on earth.
7. A rise in greenhouse gases results in an increase of the green house effect, which can be disastrous for the planet.

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precautionary principle

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Precautionary principle; When an activity raises threats of harm, measures should be taken, even if a cause-and-effect relationship has not been established scientifically

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Outline the consequences of a global temperature rise on arctic ecosystems

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• The arctic ice cap may disappear as glaciers start to melt and break up into icebergs.
• Permafrost will melt during the summer season, which will increase the rate of decomposition of trapped organic matter, including peat and detritus. This in turn will increase the release of carbon dioxide, which will increase the green house effect even further.
• Species adapted to temperature conditions will migrate north which will alter food chains and have consequences on the animals in the higher trophic levels.
• Marine species in the arctic water may become extinct, as these are very sensitive to temperature changes within the seawater.
• Polar bears may face extinction as they loose their ice habitat and therefore can no longer feed or breed as they normally would.
• Pests and diseases may become quite common with rises in temperature.
• As the ice melts, sea levels will rise and flood low-lying areas of land.
• Extreme weather events such as storms might become common and have disastrous effects

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Lag phase

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Little or no cell multiplication. A period of adaptation to conditions

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Exponential growth or log phase

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Population increases exponentially, a period of no constraints on growth.

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Linear grow phase

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Natality rate has started to fall but still exceeds rising mortality rate so the population rises, but at a linear rate with time.

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Plateau phase

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Natality and mortality rates are equal due to the exhaustion of natural resource

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List three factors that set limits to population increase

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• Shortage of resources (food, shelter, water)
• Increase in predators
• Increase in disease and parasites