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What is natural selection, and how is it related to changes in allele frequency?

Natural selection describes the selective pressure favouring those species with certain phenotypes (characteristics) which make them better suited to the environment than other species. Those with favourable...
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Answered by Vishal U. • Biology tutor
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Explain the difference between chromatin, chromatids, chromosomes and homologous pairs.

Genetic information is stored in the nucleus as DNA. Humans have 46 molecules of DNA in each cell; each molecule known as a chromosome. When the cell is in interphase of the cell cycle, the DNA is in the chr...
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Answered by Maggie B. • Biology tutor
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How can vaccination prevent illness?

Vaccination is a way of preparing the body's immune system to fight potential infection. By exposing the body to markers of the virus or bacteria, the white blood cells are able to recognise, memorise and fi...
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Answered by Gareth H. • Biology tutor
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Using Fick's Law, explain how rapid gaseous exchange takes place in a mammal

Gaseous exchange of oxygen and carbon dioxide (diffusion) occurs between the alveoli (tiny air sacs) and capillaries (microscopic blood vessels) inside the lung. Diffusion refers to the passive net movement ...
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Answered by Timothy C. • Biology tutor
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How does an electrical impulse travel the gap between two nerves?

The electrical impulse that travels along a nerve, known in biology as an action potential, gets passed along to an adjacent nerve as a chemical signal. When an action potential reaches the end of a nerve, i...
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Answered by Lucy M. • Biology tutor
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