2.1 Structure
2.1.1 - Distinguish between biotic and abiotic (physical) components of an ecosystem.
Biotic: The living components in an ecosystem, the organisms themselves, their wastes and their interactions. Such interactions include;
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2.2.2 - Define the term trophic level.
Trophic level is the position of an organism in food chain, it shows where an organism receives the energy from another organism or where other organisms get the energy from it.
2.2.3 - Identify and explain trophic levels in food chains and food webs selected from the local environment.
Producer is very first trophic level, in the first trophic level usually there are plants, trees little insects or sunlight.
The organisms in trophic level two are also called as Herbivores, the organisms which get the energy from eating the plants. E.g. Mice Trophic level three usually represents the bigger organisms which usually receive the energy by predation Mostly there are only three trophic levels, because energy gets lost while it's been sending from the 1st to 3rd trophic level, but very seldom there is also the trophic level four where we may have eagles. |
2.2.4 - Explain the principles of pyramids of numbers, pyramids of biomass, and pyramids of productivity, and construct such pyramids from given data.
Ecological Pyramids: These are graphical models of the quantitative differences between the amounts of living material stored at each trophic level os a food chain. In accordance with the second law of thermodynamics, there is a tendency for numbers and quantities of biomass and energy to decrease along food chains; therefore the pyramids become narrower as one ascends.
Pyramids of numbers: show relative numbers of individual organisms at each trophic level. Its shows the population size of each species in a food chain.
Pyramid of productivity: show the flow of energy through the trophic levels. Lower trophic levels always have more energy. Pyramids of productivity refer to the flow of energy through a trophic level and invariably show a decrease along the food chain.
Advantages: Show the flow of energy over time (joules per square metre per year), so good to show average or seasonal variation, always a pyramid shape,
Pyramids of numbers: show relative numbers of individual organisms at each trophic level. Its shows the population size of each species in a food chain.
- Advantages: easy method of giving an overview, good for comparing changes over different times (seasons)
- Disadvantages: All organisms included regardless of size, this can lead to an inverted pyramid in the case of single large producer such an Oak tree (see figure below), does not allow for juveniles, number can be too great to represent accurately, difficult to place omnivores (different trophic zones), only a single snapshot in time.
- Advantages: generally more likely to be a true pyramid than a pyramid of numbers, takes into account the mass of the individuals not just simple numbers, also good for comparing changes over different time
- Disadvantages: Can still be inverted in some cases (see Oceanic ecosystem below), only uses samples of biomass so calculating exact biomass is impossible, samples must be killed to measure biomass, different organisms might produce biomass over different times, and in different percentages. Also just a snapshot in time.
Pyramid of productivity: show the flow of energy through the trophic levels. Lower trophic levels always have more energy. Pyramids of productivity refer to the flow of energy through a trophic level and invariably show a decrease along the food chain.
Advantages: Show the flow of energy over time (joules per square metre per year), so good to show average or seasonal variation, always a pyramid shape,
2.2.5 - Discuss how the pyramid structure affects the functioning of an ecosystem.
Pyramid structures reflect state of an ecosystem. We see balances and misbalances. By construction a Pyramid we understand bases of huge food chains and connections between trophic levels. Having data only is not enough, graphical representation is always better.
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2.2.6 - Define the terms species, population, habitat, niche, community and ecosystem with reference to local examples.
Population is number of all the organisms that both belong to the same group or species and live in the same geographical area. Population of Georgia would be the number of people that live inside the country.
Species is a group of organisms, or a class of objects that have the same attributes. Tiger is one type of species.
Habitat is a home or environment of an animal, plant, or other organism. Home of ant (underground lair) is its habitat.
Niche is the role or function of an organism or species in an ecosystem. For example niche of decomposer is to break down dead matter and return energy to the environment.
Community is where two or more organisms live in the same area. It is not necessary to have competition between these organisms.
Ecosystem is a community of interacting organisms and their physical environment. Rainforest is an example of an ecosystem. Every ecosystem has different characteristics.
Species is a group of organisms, or a class of objects that have the same attributes. Tiger is one type of species.
Habitat is a home or environment of an animal, plant, or other organism. Home of ant (underground lair) is its habitat.
Niche is the role or function of an organism or species in an ecosystem. For example niche of decomposer is to break down dead matter and return energy to the environment.
Community is where two or more organisms live in the same area. It is not necessary to have competition between these organisms.
Ecosystem is a community of interacting organisms and their physical environment. Rainforest is an example of an ecosystem. Every ecosystem has different characteristics.
2.2.7 - Describe and explain population interactions using examples of named species.
Population interaction is a common name for food chain and food web. Everything in an ecosystem is somehow related to each other. Here are some examples:
Competition: Interspecific (between species) and intraspecific (within species) FOR RESOURCES: Space, Water, Food, Sunlight, Mates
Predation: Ex) Lynx and Snowshoe have (negative feedback mechanisms. Carnivores of any level eating organism of other species.
Symbiosis: Where two organisms live together.
Parasitism: Ectoparasites... Ex) Ticks, Fleas, Leaches. Endoparasites.... Ex) Tapeworms
Mutualism: Live together, both benefit.... Ex) clown fish and sea anemone
Commensalism: Where one animal benefits but nothing happens to the other.
Competition: Interspecific (between species) and intraspecific (within species) FOR RESOURCES: Space, Water, Food, Sunlight, Mates
Predation: Ex) Lynx and Snowshoe have (negative feedback mechanisms. Carnivores of any level eating organism of other species.
Symbiosis: Where two organisms live together.
Parasitism: Ectoparasites... Ex) Ticks, Fleas, Leaches. Endoparasites.... Ex) Tapeworms
Mutualism: Live together, both benefit.... Ex) clown fish and sea anemone
Commensalism: Where one animal benefits but nothing happens to the other.