tailieunhanh - Ebook Biology at a glance (4th edition): Part 2

(BQ) Part 2 book "Biology at a glance" presents the following contents: Human effects on the environment, microbes, the human body, nutrition and circulation, gas exchange and respiration, homeostasis, reproduction, coordination, plants, words to remember. | HUMAN EFFECTS ON THE ENVIRONMENT IMPORTANCE OF TROPICAL RAIN FORESTS These are found in hot and wet areas . South America Western Africa Indonesia Australia and South-East Asia. Many trees are being cut down to provide land for farming and housing. The large scale permanent removal of forests is called deforestation. Provide a unique habitat for many plant and animal species. Many would face extinction without them. Provide a homeland for human Canopy layer communities. prevents leaching. Clouds form Water vapour Carbon dioxide taken in by trees in photosynthesis reduces carbon dioxide in air reducing the greenhouse effect. Wide variety of plants are a valuable source of medicines. Water vapour released in transpiration causes rain in areas far from the sea. Oxygen is added to the air in photosynthesis. Trees anchor the soil so fertile soil is not washed away. Leaching If heavy rain hits the soil soluble minerals such as nitrates are washed out of the leached out. top soil. They are CO2 in air The world s forests remove a great deal of carbon dioxide. Photosynthesis Trees provide dead material for decomposers to change into nitrates. This keeps the soil fertile. Endangered species are animals and plants whose numbers have dropped so low that they are close to extinction. They can be protected in several ways Protect sites in the wild - on-site conservation . tropical forests. Rare breeds parks wild life parks and zoos. Breeding is encouraged and predators removed. Seed banks - prevent the loss of genes in plants. Legal protection of certain species. Educate the public. Effect of deforestation cutting down tropical rainforests Soil is no longer anchored down. Fertile top soil is washed away. Without the canopy leaching occurs and soluble nutrients in the soil are washed away out of the top soil. Land becomes infertile nothing grows. Burning the cut trees adds more carbon dioxide to the air -increasing the greenhouse effect. Less transpiration reduces rainfall