Term
| How do biologists define a species? |
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Definition
| A group of populations that evolves independently. |
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Term
| Evolutionary independence is based on reproductive isolation. What is reproductive isolation? |
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Definition
| It is the inability to successfully breed outside the group. |
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Term
| What are isolating mechanisms? |
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Definition
| Morphologial, physiological, behavioral, or ecological differences that prevents members of two species from interbreeding. |
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Term
| What is the benefit of isolating mechanisms? |
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Definition
| The organism will not reproduce or will produce sterile or unfit offspring so the reproductive effort is then not wasted because of isolating mechanisms. |
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Term
| Distinguish between pre and post-mating isolating mechanisms. |
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Definition
| Premating isolating mechanisms prevent mating between species. Post isolating mechanisms prevent the formation of vigorous, fertile hybrids between species. |
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Term
| Describe five different pre-mating isolating mechanisms. |
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Definition
1. Geographic Isolation - The species cannot interbreed b/c a physical barrier separates them.
2. Ecological isolation - The species do not interbreed even if they are in the same area b/c they occupy different habitats.
3. Temporal isolation - The species cannot interbreed b/c they bred at different times.
4. Behavioral isolation - The species do not interbreed b/c they have different courtship and mating rituals.
5. Mechanical incompatability - The species cannot interbreed b/c their reproductive systems are incompatable. |
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Term
| Describe three post-mating isolating mechanisms. |
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Definition
1. Genetic incompatability - sperm from one species cannot fertilize eggs of another species
2. Hybrid invariability - Hybrid offspring fail to survive to maturity.
3. Hybrid infertility - Hybrid offspring are sterile or have low fertility. |
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Term
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Definition
| The process of species formation in which a single species splits into two or more species. |
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Term
| What two factors are necessary for speciation? |
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Definition
1. Isolation of populations
2. Genetic divergence of populations |
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Term
| How does genetic divergence arise? |
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Definition
| It can arise by chance (genetic drift) or through natural selection if the isolated populations experience difference environmental conditions. |
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Term
| Name and describe two categories of speciation. |
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Definition
1. Allopatric speciation - The process by which new species arise following physical separation of parts of a population (geographic isolation).
2. Sympatric Isolation - The process by which new species arise in populations that are not physically divided; the genetic isolation required for sympatric speciation may be due to ecological isolation or chromosomal aberrations (such as polyploidy). |
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Term
| Explain how new species can arise by allopatric speciation. |
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Definition
| Populations are separated, for example by an impassable geographic barrier, causing the population to be divided and therefore evolve differently. When enough mutations make the population different, the two new populations will become 2 different species. |
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Term
| Describe some examples of a population might be separated by an impassable barrier. |
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Definition
| Some members of a population of land-dwelling organisms might colonize an oceanic island, land bound organisms could be carried to another island by a "raft." Fish could be carried to different coral reefs by currents. |
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Term
| Explain how new species can arise by sympatric speciation. |
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Definition
| A geographical area contains 2 distinct types of habitats, and different members of a species may begin to specialize in one habitat or another. Natural selection in the two habitats may lead to evolution of different traits of the groups. If the differences become large enough to prevent interbreeding, then the species will have split into two separate species. |
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Term
| Provide an example of sympatric speciation occurring today. |
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Definition
| Rhagoletis - a parasite - found in apple trees are now appearing in hawthorn trees as well. |
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Term
| What is adaptive radiation? When does it typically occur? |
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Definition
| The rise of many new species in a relatively short time, may occur when a single species invades different habitats, and evolves in response to different environmental conditions in those habitats. It typically occurs when species encounter a wide variety of unoccup9ied habitats. |
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Term
| What does the Y-axis represent on an evolutionary tree? |
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Definition
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Term
| What do the forks represent on an evolutionary tree? |
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Definition
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Term
| What do lines represent on an evolutionary tree? |
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Definition
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Term
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Definition
| The death of all members of a species. |
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Term
| What is usually the immediate cause of any species extinction? |
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Definition
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Term
| Explain how having a localized distribution or being overspecialized can make a species vulnerable to changing environments. |
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Definition
If a population has a localized distribution, it is vulnerable b/c any disturbance of that area could easily result in extinction b/c that is the only place that species is located.
If a species is overspecialized, it is vulnerable b/c the organism is so specific, and if any small detail is out of place, the whole population is at risk. |
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Term
| Describe two interactions with other organisms that may lead to extinction. |
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Definition
1. Competition - organisms compete for limited resources in all environments.
2. Predation - predator, prey relationship - more predators than prey and prey is killed. |
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Term
| What is the leading cause of extinction today? |
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Definition
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