IB Bio Topic 5

Communities and EcosystemsIB Bio Topic 5TopicsDefine species, habit, population, community, ecosystem and ecology.Distinguish between autotroph and heterotroph.Distinguish between consumers, detritivores and saprotrophs.Describe what is meant by a food chain, giving three examples, each with at least three linkages (four organisms).Describe what is meant by a food web.Define trophic level.

Topics contdDeduce the trophic level of organisms in a food chain and a food web.Construct a food web containing up to 10 organisms, using appropriate information.State that light is the initial energy source for almost all communities.Explain the energy flow in a food chain.State that energy transformations are never 100% efficient.Explain reasons for the shape of pyramids of energy.

More topicsExplain that energy enters and leaves ecosystems, but nutrients must be recycled.State that sapotrophic bacteria and fungi (decomposers) recycle nutrients.Species: a group of organisms that can interbreed and produce fertile offspring.Habitat: the environment in which a species normally lives or the location of a living organism.Population: a group of organisms of the same species who live in the same area at the same time.Community: a group of populations living and interacting with each other in an area.Ecosystem: a community and its abiotic environment.Ecology: the study of relationships between living organisms and between organisms and their environment.

Autotrophs are organisms that synthesize their organic molecules from simple inorganic substances whereas heterotrophs are organisms that obtain organic molecules from other organisms.

Think of autotrophs as producers and heterotrophs as consumers. Theyre the same thing!Consumer: an organism that ingests other organic matter that is living or recently killed.Detritivore: an organism that ingests non-living organic matter.Saprotroph: an organism that lives on or in non-living organic matter, secreting digestive enzymes into it and absorbing the products of digestion.

A food chain shows the direction of energy flow from one species to another. For example, an arrow from A to B means that A is being eaten by B and therefore indicates the direction of the energy flow.Example of a food chain

A food web is a diagram that shows all the feeding relationships in a community with arrows which show the direction of the energy flow.Trophic level: the trophic level of an organism is its position in the food chain. Producers, primary consumers, secondary consumers and tertiary consumers are examples of trophic levels.Plants or any other photosynthetic organisms are the producers. Primary consumers are the species that eat the producers. Secondary consumers are the species that eat the primary consumers and tertiary consumers in turn eat the secondary consumers.

Energy transformations are never 100% efficient.Light is the initial energy source for almost all communities.Energy flows from producers to primary consumers, to secondary consumers, to tertiary consumers...Energy is lost between trophic levels in the form of heat through cell respiration, faeces, tissue loss and death.Some of this lost energy is used by detritivores and saprotrophs. These in turn also lose energy in the form of heat through cell respiration.

Only 10% of the energy can move from one trophic level to the next

Saprotrophic bacteria and fungi (decomposers) recycle nutrients.

Questions/Review1. Which of the following descriptions about the organization of an ecosystem is correct?A. Communities make up species, which make up populations.B. Populations make up species, which make up communities.C. Species make up communities, which make up populations.D. Species make up populations, which make up communities.

2. Only 10 percent of the energy stored in an organism can be passed on to the next trophic level. Of the remaining energy, some is used for the organisms life processes, and the rest is

A. Used in reproductionB. Stored as body tissueC. Stored as fatD. Eliminated as heat