BIO II EXAM 1 rev - Review for Exam 1 Below are concepts...

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Review for Exam 1 Below are concepts you should be familiar with as you prepare for the exam. While we have tried to be thorough, items may occur on the exam which are not listed here. Module 1 describe the species concept One way of defining what constitutes a species is often referred to as the biological species concept. According to this definition, a species is a group of organisms that are able to interbreed and produce fertile offspring. If two organisms can not interbreed or produce sterile offspring when they do interbreed, these organisms are considered to belong to separate species. The limitation in this approach to defining a species is that many organisms are not observed to sexually reproduce with another in nature so we would have no basis for grouping them into species. One solution to this problem is to use a practical definition for the species concept. Here we might define a species as a group of organisms that share a number of characteristics and that can be distinguished from other groups of organisms by these characteristics. The emphasis is on morphological and or behavioral similarities, not on their ability to breed with one another. However, this definition also has it problems. For example, how similar do organisms within the same species need to be? What level of dissimilarity justifies placing organisms into different species? When we look at fossil specimens even more questions arise. When we have a lineage of fossil specimens, different from but leading to a living species, do we consider all of those fossil organisms to belong to the same species despite their morphological differences or do we make a cut off at some point saying that organisms from one particular time frame belong to one species while those from another belong to a different species? A third way to try and define what constitutes a species is called the evolutionary species concept. Here the emphasis is on the lineage of the organisms. By this definition, a species is a single lineage of organisms that maintains a distinct identity from another lineage. While this definition could be applied to all organisms regardless of their form of reproduction, it does not help us with the question of classifying extinct organisms or with deciding how closely related organisms must be to constitute a lineage. understand why a species is difficult to define Clearly it is easy to say that a dog and a cat are separate species. They look different, they behave differently and they don't breed together. But when we start to look at organisms less like ourselves, or those we commonly see around us, the concept of a species becomes more difficult to define.
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appreciate the number of species living on earth To date, biologists have described about 1.5 million living species on earth. Everyone agrees that there are more living species than this, the question is how many. A number of researchers have made estimates of how many species might be out there. Most of
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This note was uploaded on 12/14/2009 for the course BIO 1020 taught by Professor Hirt during the Fall '09 term at Pellissippi.

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BIO II EXAM 1 rev - Review for Exam 1 Below are concepts...

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