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According to Darwin's theory, genetic variation within the population means that some elephants are born with longer noses. Longer noses are better suited to the environment, so longer-nosed elephants are...

Mutation, meiosis and sexual reproduction causes variation amoung members of the same species. Species tend to produce more offspring than the environment can support leading to competition for food or pr...

The haemoglobin in red blood cells carries oxygen. - Red Blood cells are flattened biconcave disc shapes which means they have a large surface area to carry oxygen. - They are small cells so can fit into ...

Mutations are a random change in the nucleotide sequence in a genome. Genes code for proteins, such as enzymes, and are found in the genome. When a change in the nucleotide sequence within a gene happens,...

Receptor triggers a sensory neuron to fire an electrical impulse. Synapses with relay neuron which fires an electrical impulse. Synapses with motor neuron which fires an electrical impulse. The motor neur...