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Biology
A Level

How may allopatric and sympatric speciation be distinguished? (4 marks)

First it is important to establish what a species is. A species is a population of similar organisms that can interbreed to produce fertile offspring; meaning they are reproductively isolated from other s...

GL
Answered by Gabrielle L. Biology tutor
5030 Views

Describe the process of DNA replication

In DNA replication, first the hydrogen bonds between the nitrogenous bases are broken catalysed by the enzyme helicase, causing the DNA double helix to unwind and unzip, leaving the nitrogenous bases expo...

HN
Answered by Helena N. Biology tutor
11168 Views

Describe the process of phagocytosis and how antigen presentation leads to antibody production (9 marks)

White cell (macrophage/neutrophil) detects bacteria antigen by binding to cell surface receptorsWhite cell engulfs bacteria (this is endocytosis), bacteria is held in a phagosome Lysosomes enter phagosome...

CR
Answered by Caine R. Biology tutor
2585 Views

Describe how the body adapts the solute pressure of the blood (thorough its use of ADH) after a person has drank a large volume of water.

Located at the base of the hypothalamus is the pituitary gland which contains osmoreceptor cells that sense the solute potential of the blood and release ADH in response to changes of the solute potential...

DD
Answered by Daniel D. Biology tutor
2286 Views

Describe and explain how the small intestine is adapted for its function?

The small intestine contains microvilli which increase the surface area of the membrane. It also has a rich blood supply, this maintains the concentration gradient. The small intestine has a membrane whic...

UI
Answered by Uma I. Biology tutor
24380 Views

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