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Allopatric speciation occurs when populations of a species are separated by a physical barrier - this could be a river for animals that cannot swim, for example. Separation of the populations means that t...

DNA (deoxyribonucleic acid) is a double helix composed of units called nucleotides. Each nucleotide is composed of a single deoxyribose sugar, a phosphate group and one of four nitrogen bases. The 4 bases...

Endocrine organs release their products (usually hormones) directly into the blood. The pancreas contains islets of Langerhans which are made up of alpha and beta cells. Beta cells secrete insulin and alp...

. increase in the number of cases of antibiotic resistance . increase in risk of horizontal gene transfer of resistance . resistant bacteria causes harm/ ineffective medical treatments . reduces risk of/ ...

Vaccines are made of dead or inactive pathogens. White blood cells in the body come into contact with the pathogen and produce antibodies which destroy the pathogen. The body produces memory cells which m...