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What happens during eutrophication?

The addition of nutrients such as nitrate means that nutrients no longer limit plant growth.Algae begins to bloom which blocks out sunlight. As a result, plants cannot photosynthesise (or photosynthesis is r...
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Answered by Emily C. • Biology tutor
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Why does as an excess of nutrients such as nitrates lead to animal death in bodies of freshwater?

This is an unexpected result as usually nutrients are considered beneficial to organisms. Some organisms do benefit enourmously from the nutrients, but this leads to the deaths of other. The high concentrati...
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Answered by Daniel A. • Biology tutor
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How is immunity developed after a primary infection by bacteria?

Phagocytosis - A phagocyte detects the bacteria has foreign antigens and so envelops it with its cytoplasm, packaging it into a phagosome via endocytosis. Lysosomes then fuse with the phagosome releasing hyd...
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Answered by Daniel V. • Biology tutor
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In some parts of Africa, where malaria commonly occurs, there are higher frequencies of the allele that causes sickle-cell anaemia.

Individuals with the recessive sickle-cell anaemia allele have a lower chance of developing severe malaria. Therefore, they are more likely to survive and reproduce than those without the allele. The allele ...
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Answered by Laura N. • Biology tutor
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Describe the differences between active transport and facilitated diffusion.

Facilitated diffusion is a passive process that occurs down a concentration gradient. Active transport requires energy (from ATP) to allow movement of substances against a concentration gradient.
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Answered by Laura N. • Biology tutor
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