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Mutualism is an interaction between individuals of different species that results in positive (beneficial) effects on per capita reproduction and/or survival of the interacting populations. One well-understood example of mutualism is the interaction between protozoa and methanogenic archaea in the digestive tracts of animals that digest ...
It is postulated that this symbiotic partnership progressed via the cellular fusion of the partners to generate a chimeric or hybrid cell with a membrane bound internal structure that was the forerunner of the nucleus. The next stage in this scheme was transfer of both partner genomes into the nucleus and their fusion with one another.
[25] In other words, we expect selfish genes ("selfish" meaning that it promotes its own survival without necessarily promoting the survival of the organism, group or even species). This theory implies that adaptations are the phenotypic effects of genes to maximize their representation in future generations.
Given the right circumstances, and enough time, evolution leads to the emergence of new species. Scientists have struggled to find a precise and all-inclusive definition of species. Ernst Mayr defined a species as a population or group of populations whose members have the potential to interbreed naturally with one another to produce viable ...
Eukaryotes are organisms whose cells have a nucleus enclosed within membranes, whereas prokaryotes are the organisms that do not have a nucleus enclosed within a membrane. [ 1 ] [ 2 ] [ 3 ] The three-domain system of classifying life adds another division: the prokaryotes are divided into two domains of life, the microscopic bacteria and the ...
Every aspect of an organism that has a function has a history. Now, an adaptation must have a functional history: therefore we expect it must have undergone selection caused by relative survival in its habitat. It would be quite wrong to use the word adaptation about a trait which arose as a by-product. [16] [17] [verification needed]
Adaptation affects all aspects of the life of an organism. [24] The following definitions are given by the evolutionary biologist Theodosius Dobzhansky: 1. Adaptation is the evolutionary process whereby an organism becomes better able to live in its habitat or habitats. [25] [26] [27] 2.
Morphological adaptations observed at the cellular level include atrophy, hypertrophy, hyperplasia, and metaplasia. [1] In the medical context, outside of specialized branches of biomedicine, morphological adaptations are not always referenced to the fundamental cellular level, but are observed and assessed at the level of tissues and organs.