Humans And Their Effects On The Environment
Resumen
There are more of us than there have ever been, and each of us now uses more energy, more packaging, more water and more manufactured food than our grandparents did. Every one of those choices leaves something behind. The waste has to go somewhere, and biology is the study of what happens once it gets there: which organisms tolerate it, which ones disappear, and how a single substance released in one field can empty a river three kilometres downstream.
This lesson takes you through the four routes by which human activity reaches living systems: what we release into water, into the air and onto land, what happens when tropical forest is cleared, and what rising carbon dioxide and methane are doing to climate. You will learn to write the eutrophication sequence as a chain of causes rather than a list of words, and you will practise the skill this section really tests: reading an unfamiliar set of environmental measurements and deciding how much they are actually worth as evidence.
Objetivos
- Rapid growth in the human population and an increase in the standard of living mean that increasingly more waste is produced. Unless waste and chemical materials are properly handled, more pollution will be caused.
- Waste may pollute: water, with sewage, fertiliser or toxic chemicals; air, with smoke and gases such as sulfur dioxide, which contributes to acid rain; land, with toxic chemicals such as pesticides and herbicides, which may be washed from land into water; sewage and fertilisers may cause eutrophication: an increase in the concentration of mineral ions in the water stimulates the growth of algae and/or plants; eventually the growth of the algae and/or plants results in some of these being unable to receive sufficient light for photosynthesis and these organisms die; there is a large increase in the population of microorganisms that feed on these dead organisms; the respiration of the microorganisms depletes the oxygen concentration in the water, leading to the death of aerobic organisms.
- Large-scale deforestation in tropical areas has led to reduction in biodiversity. Students should be able to describe the effects of deforestation.
- Levels of carbon dioxide and methane in the atmosphere are increasing, and contribute to ‘global warming’. An increase in the Earth’s temperature of only a few degrees Celsius may: cause big changes in the Earth’s climate; cause a rise in sea level; cause changes in migration patterns, eg in birds; result in changes in the distribution of species. Throughout this section, students should be able, when provided with appropriate information: to analyse and interpret scientific data concerning environmental issues; to evaluate methods used to collect environmental data and consider their validity and reliability as evidence for environmental change.
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- Which gas released by burning fuels that contain sulfur is the main cause of acid rain? A. Carbon dioxide B. Methane C. Sulfur dioxide D. Nitrogen Answer: C
- In eutrophication, what directly causes the death of the fish? A. The fertiliser poisons them B. The algae poison them C. The dissolved oxygen concentration falls too low D. The water becomes too acidic Answer: C
- Why do the algae and plants below the surface layer die during eutrophication? A. They are eaten by microorganisms B. They cannot receive enough light for photosynthesis C. They run out of mineral ions D. The water becomes too warm Answer: B
- Which of these is NOT a direct effect of large-scale deforestation? A. Reduced biodiversity B. Increased soil erosion C. More frequent flooding D. A fall in atmospheric carbon dioxide Answer: D
- The dissolved oxygen concentration of a river falls from 10.0 mg/dm3 to 4.0 mg/dm3. What is the percentage decrease? A. 40% B. 60% C. 150% D. 250% Answer: B
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