EVERYDAY SCIENCE - ECOSYSTEMS
Question 1

Churros collected a sample of green microorganisms from a lake. He observed them under a microscope and found out that they are a type of bacteria called cyanobacteria. Cyanobacteria have chlorophyll to carry out photosynthesis.

There is a large farm beside the lake. After a period of heavy rainfall, there was a sudden increase in the population of cyanobacteria and they covered the surface of the lake.

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Answer 1

Fill in the blanks with the keywords provided below.
[rainwater] • [respiration] • [fertiliser] • [dissolved oxygen] • [fully submerged] • [block] • [population] • [decompose]

a) Explain why there was an increase in cyanobacteria after the heavy rainfall.

Answer:

The used in the farm was washed by into the lake. The increase in nutrients in the water caused the bacteria to multiply rapidly.


b) After the cyanobacteria grew rapidly, they covered the water surface. Explain how this can affect the population of fully submerged plants.

Answer:

When they cover up the water surface, the cyanobacteria will some sunlight from passing through. The plants will receive less sunlight for photosynthesis.
They cannot grow well. Some will die and their will decrease.


c) After a while, the large number of cyanobacteria in the lake will die. Explain why this will cause many fish in the lake to die.

Answer:

When the cyanobacteria die, other types of bacteria will feed on them and them.
The decomposers will take in from the water in order to carry out to release energy for life processes. The rapid growth of decomposers will deplete the dissolved oxygen in the water and cause many fish to die.




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“Plants are not the only organisms that provide us with oxygen. Cyanobacteria contribute to approximately 20 to 30 percent of all photosynthesis that occurs on earth.”