ZIMSEC O-Level Biology (4025)

Ecology, Environment and Health: notes

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Producer: a green plant that makes food. Consumers eat other organisms. Decomposers break down dead matter.
Energy flow: energy comes from the Sun and falls at each step of a food chain; about 10% passes on.
Carbon cycle: photosynthesis takes carbon dioxide in; respiration and burning put it back.
Pollution: fertiliser run-off causes eutrophication; carbon dioxide adds to global warming.
Conservation: protecting habitats and species, such as national parks, and replanting trees against deforestation and soil erosion.
Malaria: spread by the female Anopheles mosquito. Cholera: spread by dirty water. Bilharzia: a parasite from snails in water.
Vaccination: a harmless form of a germ makes the body produce antibodies and memory cells.
Drugs: antibiotics kill bacteria but not viruses.