1. Define species, habitat, population, community, ecosystem, ecology and trophic level.
Species: a group of organisms which 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 individuals of the same species living in a particular geographic area
Community: consists of all the organisms that inhabit a particular area; an assemblage of populations of different species
Ecosystem: all abiotic factors in addition to the community of species that exists in a certain area
Ecology: the study of relationships between living organisms and between organisms and their environment
Trophic level: the position an organism occupies in a food chain that is determined by the number of energy-transfer steps to that level

2. Distinguish between
a) Autotroph and heterotroph
Autotroph: (producers), organisms that synthesize their organic molecules from simple inorganic substances; net producers of oxygen
Heterotrophs: (consumers), organisms that obtain organic molecule nutrients from other organisms; net producers of carbon dioxide

b) Consumers, detritivores and saprotrophs
Consumers: organisms that ingest other organic matter that is living or recently killed
Detritivore: organisms that feed on the detritus and decomposing organic material of living organisms; ingests non-living organic matter
Saprotrophs: (decomposers), organisms that feed on dead organisms and products of living organisms; absorb decomposed and digested food into their bodies

3. a) Describe what is meant by a food chain, giving three examples each with at least three linkages (four organisms) Use real examples from natural ecosystems, with each chain including a producer and consumers, but not decomposers. Named organisms at either species or genus level should be used and common species names can be used instead of binomial names. Ex: Marine phytoplankton  Zooplankton  Sand eels  Puffins
Ex: Marine phytoplankton  Amphipod crustaceans  Arctic cod  Ringed seals  Polar bears
Ex: Diatoms  Cyclops (small copepod crustaceans)  Minnows  Pike  Carmorants

b) Explain the energy flow in a food chain.
At the beginning of every food chain is the producer which first receives the energy from the sun (light energy) by means of photosynthesis. This energy in the matter then gets passed from the producer to the primary consumer to the secondary consumer and so on. At each trophic level, energy is lost for example as heat through cell respiration or through the organic matter that is not digested. Finally the energy is passed onto detritivores and saprotrophs where energy is already lost through the decomposition of tissue. The final amount of energy is used by the detritivores and saprotrophs by cell