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Range of the snail Elona quimperiana, an example of a disjunct distribution. In biology, a taxon with a disjunct distribution is one that has two or more groups that are related but considerably separated from each other geographically. The causes are varied and might demonstrate either the expansion or contraction of a species' range.
Stoma in a tomato leaf shown via colorized scanning electron microscope image A stoma in horizontal cross section The underside of a leaf. In this species (Tradescantia zebrina) the guard cells of the stomata are green because they contain chlorophyll while the epidermal cells are chlorophyll-free and contain red pigments.
The best-known example is the so-called "paradox of the plankton". [6] All plankton species live on a very limited number of resources, primarily solar energy and minerals dissolved in the water. According to the competitive exclusion principle, only a small number of plankton species should be able to coexist on these resources.
For example, an individual plant might receive either more or less water during its growth cycle, or the average temperature the plants are exposed to might vary across a range. A simplification of the norm of reaction might state that seed line A is good for "high water conditions" while a seed line B is good for "low water conditions".
In the late twentieth century the field concept of ontogenesis was "rediscovered" as a useful part of developmental biology. It was found, for example, that different mutations could cause the same malformations, suggesting that the mutations were affecting a complex of structures as a unit, a unit that might correspond to the field of early ...
Here is an example of an A-overhang: 5'-ATCTGACTA-3' 3'-TAGACTGA-5' Longer overhangs are called cohesive ends or sticky ends. [3] They are most often created by restriction endonucleases when they cut DNA. Very often they cut the two DNA strands four base pairs from each other, creating a four-base 3' overhang in one molecule and a ...
Hamas has approved a list of 34 Israeli hostages to be exchanged in a possible ceasefire deal, Reuters reported, citing a Hamas official. The Israeli government denied receiving a list of hostages ...
Passive diffusion across a cell membrane.. Passive transport is a type of membrane transport that does not require energy to move substances across cell membranes. [1] [2] Instead of using cellular energy, like active transport, [3] passive transport relies on the second law of thermodynamics to drive the movement of substances across cell membranes.