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What is the difference between allopatric and sympatric speciation?

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 ther...
TM
Answered by Tom M. • Biology tutor
65481 Views

What is the structure and function of DNA?

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 ar...
SD
Answered by Sylvia D. • Biology tutor
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Why is the pancreas both an endocrine and exocrine gland?

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 alpha ...
RC
Answered by Rym C. • Biology tutor
41403 Views

"why has the amount of antibiotics in animal feeds gone down in recent times"

. 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/ red...
WT
Answered by William T. • Biology tutor
2913 Views

What is natural selection, and how is it related to changes in allele frequency?

Natural selection describes the selective pressure favouring those species with certain phenotypes (characteristics) which make them better suited to the environment than other species. Those with favourable...
VU
Answered by Vishal U. • Biology tutor
3551 Views