The living planet We depend on nature for lots of things, from food to medicines, but most people are unaware of benefits provided by intact ecosystems and only when we begin to lose these benefits, we realize how valuable they are. This Unit deals with ecosystems and biomes. It also explains how food chain works. Answer the following questions. a. What does the word ecosystem mean to you? b. Do you know the difference between an ecosystem and a biome? c. Have you already studied the food chain in your Science lessons? d. What can you say about the food chain? What is an ecosystem? 1 Read the text, then label each paragraph with one of the titles below. Par. 1 a. Size of ecosystems Par. 2 b. Ecological factors Par. 3 c. Definition of ecosystem Par. 4 d. The role of Man Par. 5 e. Kinds of ecosystems Par. 6 f. Relations among species PAR. 1 - A central principle of ecology is that each living organism has a continual relationship with every other element that makes up its environment. The sum total of interacting living organisms (the biocoenosis) and their non-living environment (the biotope) is called an ecosystem. PAR. 2 - Ecosystems can be of any size, for example, a rock and the plant life growing on it might be considered an ecosystem. This rock might be in a plain, with many other rocks, small grass, and grazing animals this, too, is an ecosystem. This plain might be in the tundra, which is also an ecosystem. The surface of the Earth, all the matter which composes it, the air and all living organisms can be considered one huge ecosystem. PAR. 3 - Ecosystems can be roughly divided into: terrestrial ecosystems (forests, plains, mountains and so on) freshwater ecosystems (lakes, ponds and rivers) marine ecosystems (seas and oceans) PAR. 4 - Ecological factors that affect a given environment are usually divided into two groups: abiotic and biotic. Abiotic factors are geological, geographical, hydrological and climatological parameters. A biotope is a region characterized by a particular set of abiotic ecological factors. Specific abiotic factors include: water, which is an essential element to life; air, which provides oxygen, nitrogen, and 1
carbon dioxide to living species and allows the dissemination of pollen and spores; soil, a source of nutriment and physical support; temperature, which should not exceed certain extremes; light, which provides energy to the ecosystem through photosynthesis. PAR. 5 - Biotic factors are considered either intraspecific or interspecific relations. Intraspecific relations are those established between individuals of the same species, forming a population. They are relations of cooperation or competition with division of the territory, and sometimes organization in hierarchical societies. Interspecific relations are the interactions between different species and are usually described according to their beneficial, detrimental, or neutral effect (for example, mutualism or competition). The most significant relation is the relation of predation (eat or be eaten), which leads to the essential concepts in the ecology of food chains (for example, grass is consumed by a herbivore, itself consumed by a carnivore, itself consumed by a larger carnivore). PAR. 6 - Man s survival and well-being depend largely on the food he eats, such as fruit, vegetables and meat. It also depends on his association with other living things. For example, some bacteria help him digest certain food. Man s social and cultural surroundings are an important part of his biotic environment. His highly developed nervous system has made memory, reason and communication possible. Human beings teach their children what they have learnt. By passing on knowledge, man has developed art, music, literature, religion, technology and science. Man s biological and cultural inheritance have enabled him to advance beyond any other animal in controlling the environment. 2 Find the English translation of these words in the text. a. immenso:... b. permette:... c. approssimativamente:... d. nocivo:... e. eredità:... 3 Answer the following questions. a. What is an ecosystem? b. How wide can an ecosystem be? c. What are the factors that affect an ecosystem? d. What are the specific abiotic factors? e. How can the biotic factors be considered? f. What does Man s well-being depend on? Hopetoun Falls, Australia. Example of freshwater ecosystem. 4 Write down the answers and join them into a brief passage about ecosystems. GLOSSARY to affect: influire su. grass: erba. to graze: pascolare. hierarchical: gerarchico. highly: altamente. to make up: formare. pollen: polline. through: attraverso. 2
The food chain A food chain shows how each living thing gets its food. Some animals eat plants and some animals eat other animals. Each link in this chain is food for the next link. A food chain always starts with plant life and ends with an animal. Each species occupies a particular position known as a trophic level. Link 1. Plants are called producers because they are able to use light energy from the sun to produce food (sugar) from carbon dioxide and water through photosynthesis. Link 2. Animals cannot make their own food so they must eat plants and/or other animals. They are called consumers. There are three groups of consumers: a. animals that eat only plants are called herbivores or primary consumers. b. animals that eat other animals are called carnivores and are secondary consumers (carnivores that eat herbivores), or tertiary consumers (carnivores that eat other carnivores) c. animals and people which eat both animals and plants are called omnivores. Link 3. Then there are decomposers bacteria and fungi which feed on decaying matter. The decaying process releases mineral salts back into the food chain for absorption by plants as nutrients. In a food chain, energy is passed from one link to another. When a herbivore eats, only a fraction of the energy that it gets from the plant food becomes new body mass. The rest of the energy is lost as waste or used by the herbivore to carry out its life processes, such as movement, digestion, reproduction and so on. Therefore, when a herbivore is eaten by a carnivore, it passes only a small amount of the total energy that it has received to the carnivore. The carnivore then has to eat many herbivores to get enough energy to grow. In a food chain, at each link the amount of energy decreases more and more. Because of the loss of energy at each link, ecosystems develop what are called ecological pyramids. For example, a simple ecological pyramid links the trees and shrubs, the giraffes that eat them, and the lions that eat the giraffes. A change in the size of one population in a food chain will affect the other populations. For example, if there are too many giraffes, there will be insufficient trees and shrubs to eat, so many giraffes will die. Fewer giraffes also means less food for the lions, which could starve to death. But if there are fewer lions, the giraffe population will increase. Most animals are part of more than one food chain and eat more than one kind of food in order to get energy. These form a food web. An example of ecological pyramid. 3
5 Match each word with its definition. a. link 1. microscopic organisms b. chain 2. network c. waste 3. animals that feed on plants d. herbivores 4. connection e. decaying 5. decomposing f. bacteria 6. series of connected things g. web 7. material to be thrown away 6 Put the words into the correct order to make questions. a. food/a/does/show/what/chain...? b. and/food/a/where/chain/end/does/start...? c. producers/are/called/plants/why...? d. difference/is/herbivores/between/and/what/the/carnivores...? e. are/carnivores/what...? f. do/decomposers/on//what/feed...? g. pyramid/an/is/what/ecological...? h. chain/a/is/than/smaller/food/a/web/food...? 7 Write down the answers to the previous questions. a.... b.... c.... d.... e.... f.... g.... h.... 8 Use the words to complete a marine food chain and draw the ecological pyramid. a. krill b. killer whale c. squid d. seal e. plankton f. fish...... 9 Now think about a food chain or a food web on your own. Draw it in your exercise-book, then explain it to your schoolmates and your teacher. GLOSSARY both and: sia che. carbon dioxide: anidride carbonica. to carry out: compiere. enough: abbastanza. own: proprio. shrubs: arbusti. 4
From ecosystems to biomes Ecosystems are not isolated from each other, but interrelated. For example, water may flow between ecosystems by means of a river or an ocean current. Some species of animals, such as salmon, move between marine systems and freshwater systems. The relationships between the ecosystems lead to the concept of biome. A biome is a geographically defined area of ecologically similar conditions such as communities of plants, animals, and soil organisms. Biomes are defined by factors such as plant structures (trees, shrubs, and grasses), leaf types (broadleaf and needleleaf, and so on), plant spacing (forest, woodland, savanna), and climate. An ecosystem has many biotopes and a biome can have many ecosystems. Biomes, like ecosystems, can be classified as: 1. terrestrial (land) biomes 2. freshwater biomes 3. marine biomes. Biomes are often known by local names. For example, a temperate grassland or shrubland biome is commonly known as steppe in central Asia, prairie in North America, and pampas in South America. Tropical grasslands are known as veldt in Australia, whereas in Southern Africa they are known as savanna. Climate is a major factor determining the distribution of terrestrial biomes. Among the important climatic factors are: latitude: arctic, boreal, temperate, subtropical, tropical climates. humidity: humid, semi-humid, semi-arid, and arid. elevation: increasing elevation causes a distribution of habitat types similar to that of increasing latitude. The most widely used systems of classifying biomes correspond to latitude and humidity. Biodiversity generally increases from the poles towards the equator and increases with humidity. The map of terrestrial biomes 1. Ice sheet & polar desert 2. Tundra 3. Taiga 4. Temperate broadleaf forest 5. Temperate steppe 6. Subtropical rainforest 7. Mediterranean vegetation 8. Monsoon forest 9. Arid desert 10. Xeric shrubland 11. Dry steppe 12. Semiarid desert 13. Grass savanna 14. Tree savanna 15. Subtropical dry forest 16. Tropical rainforest 17. Alpine tundra 18. Montane forest 5
10 Decide if the following statements are true (T) or false (F) and correct the false ones. T F a. Ecosystems and biomes are the same thing. b. The kind of trees is essential to classify a biome. c. Biomes can be classified in the same way as ecosystems. d. Biomes take their names from local languages. e. Climate isn t an important factor. f. Seasonal variations in rainfalls must be taken into consideration. g. Latitude is the only system to classify biomes. 11 Match the following words with their definitions. a. plant 1. Not salty water. b. freshwater 2. To a large extent or degree. c. humidity 3. The two points at the top and bottom of the Earth. d. seasonal 4. Living organism usually with roots and leaves. e. rainfall 5. Happening during a particular season. f. widely 6. Degree of moisture. g. poles 7. Total amount of rain falling in an area in a given time. 12 Listen to the definition of climate and choose T if the statement is true or F if the statement is false. Correct the false ones in your exercise book. T F a. The word climate derives from ancient Greek. b. Climate is the weather in a place usually during 40 years. c. A popular phrase says that the climate is what you get and the weather is what you expect. d. Lots of variables determine the climate. e. Alteration in the quantity of greenhouse gases can lead to global cooling. f. Climatologists are not interested in climate changes. 13 DICTATION. Listen to the CD again (or your teacher reading) and write down the text about CLIMATE. GLOSSARY to flow: scorrere. to increase: aumentare. plant spacing: distanza tra le piante. widely: ampiamente. 6