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Charleston Academy Biology National 5 Unit 3: Life on Earth Revision: What you should know (From Torrance (2013) National 5 Biology) Key areas 1-3 Biodiversity and the distribution of life Energy in ecosystems Sampling techniques and measurements Word bank 1. abiotic ammonium animals bacteria base biomass biomes biotic chain climate community consumer decomposers decreases ecosystem energy heat human interspecific intraspecific level light many meters niche nitrification nitrogen numbers pH pitfall predation protein pyramid quadrats rainfall sampling temperature transfer valid Biodiversity in an ecosystem can be affected by BIOTIC and abiotic factors and HUMAN influences that can increase or decrease it. 2. Biotic factors such as grazing and PREDATION are caused by living things; abiotic factors such as pH and TEMPERATURE are non-living. 3. Various large regions of the Earth, distinguished by their CLIMATE and native plants and ANIMALS, are called BIOMES. Their global distribution can be affected by RAINFALL and temperature. 4. An ECOSYSTEM is made up of a community of living organisms and the nonliving factors with which they interact. A NICHE is the role that an organism plays within a COMMUNITY. 2 5. About 90% of ENERGY is lost at each level in a food CHAIN as undigested material or as HEAT or during movement. Some of the energy in waste material is gained by the ecosystem’s DECOMPOSERS. 6. A pyramid of NUMBERS illustrates the numerical relationship between the organisms in a food chain, with the producer (the most numerous) at the BASE and the final CONSUMER (the least numerous) at the top. 7. A pyramid of BIOMASS shows that the producer at the base has the greatest biomass and that this DECREASES, level by level, to the final consumer, which has the smallest biomass. 8. A PYRAMID of energy illustrates the energy content at each LEVEL in a food chain and the TRANSFER of energy from one level to another. 9. NITROGEN is cycled round ecosystems. Nitrate absorbed by plants is made into plant PROTEIN, which becomes converted to animal protein on being consumed. 10. Several different types of BACTERIA play essential roles in the nitrogen cycle by bringing about the processes of NITRIFICATION, nitrogen-fixation and the decomposition of wastes to AMMONIUM compounds. 11. When competition for the same resource(s) occurs between individuals of different species in an ecosystem, it is called INTERSPECIFIC competition and when it occurs between individuals of the same species it is called INTRASPECIFIC competition. 12. Biologists investigate an ecosystem’s community by SAMPLING its plants and animals. To do this, they often use quantitative techniques such as PITFALL traps and QUADRATS. 13. For sampling to give a VALID representation of the community, MANY samples must be taken and mean results calculated. 3 14. An ecosystem is affected by many ABIOTIC factors including LIGHT intensity, temperature, moisture content and pH. These can be measured using appropriate METERS and probes linked to computer software. 4 Key areas 4-5 Adaptation, natural selection and evolution Human impact on environment Word bank adaptation adapted advantage alleles bacteria biological bloom disadvantage enemies fatal fertiliser fittest genetic increase indicator intensive isolation mutagenic mutation non-biodegradable natural offspring oxygen quality radiation random selection speciation toxicity yield 1. A MUTATION is a change in the structure or composition of an organism’s GENETIC material. It may confer an advantage or a DISADVANTAGE on the organism or be neutral and not affect it. 2. Mutations occur spontaneously and at RANDOM but rarely. They are the only source of new ALLELES. 3. Rate of mutation can be increased by MUTAGENIC agents such as RADIATION and certain chemicals. 4. An inherited characteristic that makes an organism well suited to survive in its environment is called an ADAPTATION. 5. The members of a species produce far more OFFSPRING than the environment can support. This leads to a struggle where only the FITTEST survive. 5 6. Those individuals best ADAPTED to a changing environment pass on the genes that confer a selective ADVANTAGE to their offspring. The less well adapted members die. This weeding out process is called NATURAL selection. 7. SPECIATION occurs when a population becomes isolated for a very long time and natural SELECTION takes a new direction. Gradually the group becomes adapted to environmental conditions that differ from those that affected it before ISOLATION. 8. The human population continues to INCREASE rapidly and this needs to be matched by an increase in food YIELD. 9. When FERTILISER from farmland leached into watercourses or lochs it may over-enrich the water and cause formation of an algal BLOOM. When the algae die, the decomposer BACTERIA that act on them undergo a population explosion and use up the water’s dissolved OXYGEN supply during respiration. 10. Molecules of pesticides that are NON-BIODEGRADABLE can accumulate in the bodies of organisms. This leads to an increase of TOXICITY along food chains, which may be FATAL to the final consumers. 11. A species that by its presence indicates the QUALITY of the environment is called an INDICATOR species. 12. Attempts are made to balance the adverse effects of INTENSIVE farming by using GM crops and employing BIOLOGICAL control as alternatives to the use of pesticides. Biological control is the reduction of a pest population by the introduction of one of its natural ENEMIES. 6