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Ask your partner these questions.
• Is biodiversity index in natural communities high or low? Why?
• Is biodiversity index in communities affected by humans high or
low? Why?
• What factors affect biodiversity in communities?
After that answer your partner’s questions.
27. Read the text FOOD WEBS and guess the meanings of the words
in bold.
FOOD WEBS
The living portion of an ecosystem is best described in terms of feeding
levels known as trophic levels. Green plants make up the first trophic level
and are known as primary producers. Plants are able to convert energy from
the sun into food in a process known as photosynthesis. In the second trophic
level, the primary consumers, known as herbivores, are animals and insects
that obtain their energy solely by eating the green plants. The third trophic
level is composed of the secondary consumers, flesh-eating or carnivorous
animals that feed on herbivores. At the fourth level are the tertiary consum-
ers, carnivores that feed on other carnivores. Finally, the fifth trophic level
consists of the decomposers, organisms such as fungi and bacteria that break
down dead or dying matter into nutrients that can be used again.
Some or all of these trophic levels combine to form what is known as a
food web, the ecosystem's mechanism for circulating and recycling energy
and materials.
24. Fill in the table below for an aquatic (marine) ecosystem with the
following participants:
Fungi and bacteria, salmon, water plants (algae) , brown bear, insects
and small fish.
Aquatic (Marine) Ecosystem
primary producers
primary consumers
secondary consumers
tertiary consumers
decomposers
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