Ecology Quizzes.docx

Types of Organisms in an Ecosystem Definitions **Need to know all definitions** Producer (autotroph): An organism which makes its own food. Green plants make their own food by photosynthesis. Chemosynthetic organisms make their food using chemical energy. Consumer (heterotroph): an organism that tak...

Types of Organisms in an Ecosystem Definitions **Need to know all definitions** Producer (autotroph): An organism which makes its own food. Green plants make their own food by photosynthesis. Chemosynthetic organisms make their food using chemical energy. Consumer (heterotroph): an organism that takes in food from another organism. Herbivore: an animal which eats plants only e.g., rabbit, greenfly, honeybee. Carnivore: an animal which eats meat only e.g., fox, hawk, ladybird. Omnivore: an animal which eats both plant and animals e.g., sparrow, crow, blackbird, thrush, badger, field mouse, hedgehog. Decomposer: feeds on dead organic matter e.g., earthworm, many bacteria and fungi. Saprophyte: bacteria and fungi that feed on dead organic matter e.g., Rhizopus Primary consumer: an animal which feeds on producers e.g., herbivores or decomposers. Secondary consumer: an animal that feeds on primary consumers e.g., carnivores and scavengers (who feed on animals killed by other sources) Tertiary consumers: feed on secondary consumers. (1) Food Chain A Food Chain is a feeding relationship between plants, animals, and microorganisms. Energy flow: All organisms need energy to live. Sun is the primary source of energy. Energy flows from one organism to the next by means of a food chain. Food chains are normally only three to four steps long and are rarely more than five because only 10% of the energy is transferred from one link to the next. Grassland Food Chain (2) Aquatic Food Chain (3) Dependence and Interdependence: If a species relies on another species to survive, then it is said to be dependent. For example, the blackcurrant moth caterpillar needs currant bushes for food. However, the blackcurrant does not need the blackcurrant moth caterpillar to survive. If two species need each other to survive, they are said to be interdependent. For example, flowers need to pollinate them, and bees need flowers to supply their food in the form of nectar and pollen. Trophic level is the position of an organism in a food chain. First trophic level – Primary producers (green plants) Second trophic level – Herbivores that eat first trophic level species (primary consumers) Third trophic level – Carnivores that eat the herbivores in the second trophic level (secondary consumers) Fourth trophic level – Carnivores (tertiary consumers) that eat the carnivores in the third trophic level A food web is two or more interconnected food chains. (4) Pyramid of Numbers A pyramid of numbers is a chart showing the number of organisms at each trophic level. The numbers normally decrease as you move up the pyramid due to high energy loss (about 90% in respiration as heat, excretion, and decay) at each trophic level and the fact that organisms usually increase in size as you go up a pyramid and need to feed on a greater number. This limits the length of a food chain (4 or 5 steps). Pyramids of numbers are limited because the size of the organisms can change the standard shape, or it may not be possible to represent large numbers of organisms correctly. (5) The size of organisms is not considered in a pyramid of numbers. e.g., one rose bush can support thousands of greenflies. When organism size is not considered very unusual pyramid shapes are likely to occur, this leads to an inverted food pyramid. (6) Niche **Know Definition and basic explanation** Niche is the functional role of an organism in its habitat. This includes a variety of factors including where it lives, what it eats and in turn, what eats it. Each species is adapted to its own niche. No two species can occupy the same niche for any length of time because competition will result in one species ousting the other, depending on which species is better adapted to the habitat.