<span>D.) increased number of small crabs because fishing nets catch mostly large crabs
This situation is caused indirectly.</span>
Their difference is that Eukaryotes posses nucleus & nuclear bound organelles whereas prokaryotes doesn't!
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Answer:
If a whole specie of organisms has to survive, they should must possess the ability to reproduce and adopt to environmental conditions in better way.
For example: If a disaster occurs or a condition of unfavorable weather occurs, the specie will survive even if only few members remain alive. Because those members will reproduce and regrow the community.
The reason is this that reproduction is not important for the survival of one organism, like organism will still survive even if he do not reproduce, but if a whole specie has to survive and continue, reproduction is most important trait.
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Answer:
Species separated by a physical barrier for a long time, suffer allopatric speciation, so they can not interbreed anymore.
Explanation:
Allopatric speciation consists of the geographic separation of a continuous genetic background giving place to two or more new geographically isolated populations. These separations might be due to migration, extinction of geographically intermediate populations, or geological events. In this speciation, some barriers impede genetic interchange, or genetic flow, as the two new populations that are separated can not get together and mate anymore. These barriers might be geographical or ecological.
Vicariance is the geographical separation of an original population into two or more new groups. Discontinuities in the physical environment like rivers, mountains, water, etc., are physical barriers that impede genetic flow between the separated groups.
The process of allopatric speciation involves different steps:
- The emergence of the barrier.
- Interruption in the genetic interchange
- The occurrence of new mutations and their accumulation in time in each population. Slow and gradual differentiation.
- Genetic divergence by natural selection and reproductive isolation makes it impossible for the two groups to mate even if the barrier disappears.
- Prezigotic isolation mechanisms favored by selection once occurs a secondary contact between the new species in formation.
