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Biology AQA Past Paper (2015) - Unit 03 (Higher). Describe how the brain monitors body temperature.

The hypothalamus is the processing centre in the brain that controls body temperature (constant temperature of 37ºC approx.). It triggers changes to effectors, such as sweat glands and muscles controlling bo...
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Answered by Diego M. • Biology tutor
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How does a syanpse work?

An electrical impulse (action potential) travels along the axon of the pre-synaptic neuron. This causes the neuron to release chemical neurotransmitters which diffuse through the synaptic cleft and bind to t...
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Answered by Pavleen D. • Biology tutor
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Explain how atherosclerosis develops and how it leads to coronary heart disease (8)

-Atherosclerosis: hardening of blood vessels (specifically those that withstand high blood pressure, ie arteries.) Blood vessels are composed of three layers: the tunica intima, tunica media and tunica adven...
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Answered by Iliana M. • Biology tutor
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Explain Darwins theory of evolution by natural selection (5 marks)

A mutation will randomly occur in individuals within a species, providing a larger variation in genes. This mutated gene may produce characteristics which are beneficial for the individual in their environme...
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Answered by Elisha R. • Biology tutor
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What is mitosis?

Mitosis is the process of division of a single cell to create two identical daughter cells. It involves four distinct phases: prophase, metaphase, anaphase and telophase, followed by cytokinesis. Each of the...
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Answered by Kerry R. • Biology tutor
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