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Can you explain the different valves of the heart and why they are important?

The heart consists of 4 chamber; left and right atria, plus left and right ventricles. The right atria recieves deoxygenated blood from the superior and inferior vena cava, delivering blood from the head and...
RD
Answered by Radi D. • Biology tutor
3322 Views

Outline the "Sliding Filament Theory" of muscle contraction.

In the resting state, the myosin heads have a partially hydrolysed ATP molecule (ADP + Pi) giving them potential energy. When there is an influx of calcium ions as a result of sarcolemma depolarisation, the ...
SM
Answered by Sohail M. • Biology tutor
7386 Views

How are genetics linked to natural selection?

A population will always have some level of genetic variation for a specific character, giving different variants of the same character. Some characters are essential for fitness and influence survival, thes...
RB
Answered by Rafaelle B. • Biology tutor
2417 Views

How do alveoli create a surface for efficient gas exchange?

This kind of question is extremely common in A level biology, they want you to explain a system and apply your knowledge of biological principals to it. To understand alveoli we need to understand the concep...
MC
Answered by Matthew C. • Biology tutor
8361 Views

Explain how the human eye has both high sensitivity and high acuity.

The human eye has high sensitivity because many rods connect to a singular neurone, so many weak generator potentials combine to reach the threshold and trigger an action potential. The human eye has a high ...
AM
Answered by Anna M. • Biology tutor
4612 Views