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How is a nerve impulse transmitted across a synapse?

Synapses are a gap or a junction between two neurones. When a nerve impulse is travelling along the axon of the first neurone and the impulse reaches the axon terminal (the end of the axon), a chemical calle...
SK
Answered by Smita K. • Biology tutor
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Explain the differences between diffusion, osmosis and active transport.

Diffusion is the movement of particles (gases and liquids) from an area of high concentration to an area of low concentration. No energy is required (it is a passive process).Osmosis is the movement of water...
RM
Answered by Rikesh M. • Biology tutor
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How is heart rate controlled?

The heart muscle is myogenic , meaning that it is able to initiate its own contraction. The wall of the right atria has a region of specialised fibres known as the sinoatrial node (SAN). This node acts as th...
BM
Answered by Beth M. • Biology tutor
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What is a pathogen and what role do they have in causing disease?

A pathogen is a harmful organism that causes infectious diseases. There are many types of pathogens: bacteria, fungi, viruses, protoctists, worms and insects. They allow diseases to be transmitted from perso...
MT
Answered by Molly T. • Biology tutor
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Describe how the ancestors of modern lemurs may have evolved into the species shown in Figure 14. (June 2018, 5 marks)

The ancestors of modern Lemurs arrived in Madagascar and spread across the island. At some point after this, the once contiguous population became fragmented into three separate populations. Each of these po...
JB
Answered by Joseph B. • Biology tutor
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