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Population structure (also called genetic structure and population stratification) is the presence of a systematic difference in allele frequencies between subpopulations.In a randomly mating (or panmictic) population, allele frequencies are expected to be roughly similar between groups.
This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms.It is intended as introductory material for novices; for more specific and technical definitions from sub-disciplines and related fields, see Glossary of cell biology, Glossary of genetics, Glossary of evolutionary biology, Glossary of ecology ...
Stratification (seeds), where seeds are treated to simulate winter conditions so that germination may occur Stratification (clinical trials), partitioning of subjects by a factors other than the intervention
Through the formation of different layers a given habitat is better utilized. Strongly vertically stratified habitats are very stable ecosystems. The opposite is not true, because several less stratified vegetation types, such as reed beds, can be very stable. The layers of a habitat are closely interrelated and at least partly interdependent.
The driving force in stratification is gravity, which sorts adjacent arbitrary volumes of water by local density, operating on them by buoyancy and weight.A volume of water of lower density than the surroundings will have a resultant buoyant force lifting it upwards, and a volume with higher density will be pulled down by the weight which will be greater than the resultant buoyant forces ...
Examples of non-keratinized stratified squamous epithelium include some parts of the lining of oral cavity, pharynx, conjunctiva of eye, upper one-third esophagus, rectum, vulva, and vagina. Even non-keratinized surfaces, consisting as they do of keratinocytes, have a minor superficial keratinized layer of varying thickness, depending on the ...
Stratified layers are a barrier to the mixing of water, which impacts the exchange of heat, carbon, oxygen and other nutrients. [1] The surface mixed layer is the uppermost layer in the ocean and is well mixed by mechanical (wind) and thermal (convection) effects. Climate change is causing the upper ocean stratification to increase.
Any seeds that are indicated as needing a period of warm stratification followed by cold stratification should be subjected to the same measures, but the seeds should additionally be stratified in a warm area first, followed by the cold period in a refrigerator later. Warm stratification requires temperatures of 15–20 °C (59–68 °F).