19. Organism and Their Environment

• State that the Sun is the principal source of energy input to biological systems

• Describe the flow of energy through living organisms including light energy from the Sun and chemical energy in organisms and its eventual transfer to the environment

• Define a food chain as showing the transfer of energy from one organism to the next, beginning with a producer

• State that energy is transferred between organisms in a food chain by ingestion

• Construct simple food chains

• Define a food web as a network of interconnected food chains

• Define producer as an organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis

• Define consumer as an organism that gets its energy by feeding on other organisms

• Explain why there is a greater efficiency in supplying plants as human food, and that there is a relative inefficiency in feeding crop plants to livestock that will be used as food

• State that consumers may be classed as primary, secondary and tertiary according to their position in a food chain

• Define herbivore as an animal that gets its energy by eating plants

• Define carnivore as an animal that gets its energy by eating other animals

• Define decomposer as an organism that gets its energy from dead or waste organic material

• Interpret food chains and food webs in terms of identifying producers and consumers

• Use food chains and food webs to describe the impacts humans have through over-harvesting of food species and through introducing foreign species to a habitat

• Draw, describe and interpret pyramids of numbers

• Identify producers, primary consumers, secondary consumers, tertiary consumers and quaternary consumers as the trophic levels in food webs, food chains, pyramids of numbers and pyramids of biomass

• Draw, describe and interpret pyramids of biomass

• Discuss the advantages of using a pyramid of biomass rather than a pyramid of numbers to represent a food chain

• Describe the carbon cycle, limited to photosynthesis, respiration, feeding, decomposition, fossilisation and combustion

• Discuss the effects of the combustion of fossil fuels and the cutting down of forests on the carbon dioxide concentrations in the atmosphere

• Describe the water cycle, limited to evaporation, transpiration, condensation and precipitation

• Describe the nitrogen cycle in terms of: – decomposition of plant and animal protein to

ammonium ions – nitrification – nitrogen fixation by lightning and bacteria – absorption of nitrate ions by plants – production of amino acids and proteins – feeding and digestion of proteins – deamination – denitrification

• State the roles of microorganisms in the nitrogen cycle, limited to decomposition, nitrification, nitrogen fixation and denitrification (generic names of individual bacteria, e.g. Rhizobium, are not required)

• Define population as a group of organisms of one species, living in the same area, at the same time

• Identify and state the factors affecting the rate of population growth for a population of an organism, limited to food supply, predation and disease

• Discuss the increase in human population size over the past 250 years and its social and environmental implications

• Interpret graphs and diagrams of human population growth

• Define community as all of the populations of different species in an ecosystem

• Define ecosystem as a unit containing the community of organisms and their environment, interacting together, e.g. a decomposing log, or a lake

• Identify the lag, exponential (log), stationary and death phases in the sigmoid population growth curve for a population growing in an environment with limited resources

• Explain the factors that lead to each phase in the sigmoid curve of population growth, making reference, where appropriate, to the role of limiting factors