Because this is for sexual reproduction, it is hard to distinguish in organisms that reproduce asexually, as well as being the case for bacterial conjugation. and for a strange example see this answer on Yahoo #3: http://answers.yahoo.com/question/index?qid=20100218214618AA0aUCQ
1. asexually-reproducing organisms such as bacteria viruses, and
2. difficult to apply in practice
there is variation within the species the changes are not due to any other factor
If animals can breed and produce a viable (fertile) offspring they are termed a "species". Often two closely related species can inter-breed and produce an offspring that will be a non-viable (sterile) hybrid. An example of the later would be the cross-breeding of a horse with a donkey.This cross produces a "Mule", which is sterile & unable to reproduce.
>The structural and well-organised gradual process of change means 'biological evolution'. >Variation and heridity are two basic factors of evolution. >In long term.evolution leads to existence of new species which have different characteristics than their ancestors.
the competitive exclusion principle
Biological has two definitions. Biological is an adjective meaning "of or relating to biology or living organisms" Biological is also a noun meaning "a therapeutic substance derived from biological sources."
According to the biological species concept, two organisms are of different species if they do not do which of these
Organisms are the same species if the have the potential, or actually interbreed one with another. Does not apply to all organisms. Bacteria being an example of this. Is not as strong a concept as once it was as it did not adequately address hybridization.
There are two main problems that can be identified in the biological species concept. This concept emphiasizes interfertility between organisms. However, reproductive barriers between sexual reproducing species are not always effective. Sometimes, individuals of different species interbreed and produce offspring call hybrids. Also this concept fails to describe species that are predominantly asexual in their reproduction, including all bacteria as well as some protists, fungi, plants, and even a few animals.
Paradoxes:* Two organisms "supposed to be"of the same species, and both masculine, cannot breed together, so they can't be of the same species. * If an organism "A" can breed with two other organisms "B" and "C", it means that "A", "B" and "C" all (appear to) belong to a single species, but not necessarily "B" and "C" must be capable of breed together, meaning that "B" and "C" belong to different species.
The hypothesis supported is that the two species share a common ancestor and have evolved from a common gene pool. This similarity in DNA suggests that they are closely related evolutionarily.
A symbiotic relationship is a close and often long-term interaction between different biological species.
Chemical (lipophilicity, size) and biological (species, genetics).
there is variation within the species the changes are not due to any other factor
When they have reproductive isolation. This happens when either physical or biological barriers prevent reproduction between the two populations. At that point, their mix of genes will be significantly different that they will be considered two new species.
Endosymbiosis enabled the formation of true living cells. This concept explains the origin of two biological structures, the mitochondria and the chloroplasts.
Speciation is the process by which new biological species arise. It is part of the evolutionary process; how two or more populations of one species, when separated geographically, can gradually change over time in different ways, to become separate species.
Mutualism is a biological interaction between individuals of two different species, where both individuals derive a fitness benefit, for example increased survivorship. Similar interactions within a species are known as co-operation.