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There are four key points to natural selection:

• first, that individuals in all species show variation
• second, that this variation is genetic and therefore heritable
• third, t...

The mutation alters the base sequence which therefore changes the sequence of Amino Acids coded for (the primary structure). Now the sequence of Amino Acids has been changed when bonds form and folding oc...

1. Arteries have a much narrower lumen (the middle bit of space) and a much thicker wall. This is due to the fact that arterial walls contain more muscle and elastic fibres, than those of veins. Reason...

Water moves from the roots to the leaves through tissue called the xylem, in a process called transpiration. As water evaporates out of the leaf, more water is 'pulled upwards' to replace what has been lo...

Sarcomeres are formed of myosin and actin filaments which are interleaved. If myosin cannot bind to each other then thick filaments cannot be formed. Thus, there is nothing to anchor myosin so actin canno...