Evolution and speciation
Introduced| English | Meaning |
|---|---|
| species/ˈspiːsiːz/ | A group of organisms whose members can usually interbreed to produce fertile offspring. |
| evolution/ɪvəˈluːʃn/ | The slow formation of new species from earlier ones. |
| gene pool/dʒiːn puːl/ | All the alleles present in a population at a particular time. |
| common ancestor/ˈkɒmən ˈænsestə/ | An ancestral organism or population from which two or more evolutionary lineages descended. |
| speciation/ˌspiːʃɪˈeɪʃn/ | The formation of new species when populations diverge until they can no longer interbreed. |
| allopatric speciation/ˌæləˈpætrɪk ˌspiːʃɪˈeɪʃn/ | Populations kept apart by a geographical barrier (a sea, a mountain range). |
| sympatric speciation/ˈsɪmpətrɪk ˌspiːʃɪˈeɪʃn/ | Populations in the same area, separated by differences in behaviour or way of life. |
How new species 物种 arise
- Evolution 进化 is the slow formation of new species from earlier ones.
- It happens as the gene pool 基因库 (all the alleles in a population) changes over generations.
- New species form when populations become genetically isolated.
Evolution is best described as:
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Evolution is the change in a population's gene pool over time, which can lead to new species.
Speciation is the formation of a new species, when two populations can no longer interbreed.
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It can be allopatric (geographical barrier) or sympatric (same area).
Evidence from DNA
- DNA sequence data shows how closely two species are related.
- The more similar their DNA, the more recently they shared a common ancestor 共同祖先.
Two species with very similar DNA sequences:
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The more similar the DNA, the more recently the species shared a common ancestor.
Speciation 物种形成
- Speciation happens when two populations become genetically separated, so they can no longer breed together. Two ways:
- allopatric speciation 异域物种形成 — populations kept apart by a geographical barrier (a sea, a mountain range).
- sympatric speciation 同域物种形成 — populations in the same area, separated by differences in behaviour or way of life.
Allopatric speciation
Step through it. A barrier splits one population; the two halves diverge until they can no longer interbreed.
Allopatric speciation requires:
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Allopatric speciation needs a physical barrier (sea, mountains); sympatric happens in the same area via behaviour.
Speciation is the formation of a new ______.
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It happens when two populations become so genetically different they can no longer interbreed.
Put allopatric speciation in order.
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Isolate → diverge → reproductive isolation. The barrier is geographical in allopatric speciation.
Match each term to its meaning.
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Allopatric = geographically separated; sympatric = isolated while together; both end in reproductive isolation.
Types of speciation
- Allopatric speciation: a population is split by a geographic barrier and the groups diverge.
- Sympatric speciation: new species arise without physical separation, in the same area.
Allopatric (a geographical barrier) and sympatric (same area) speciation
You've got it
- evolution = the gene pool changing over generations → new species
- DNA similarity shows relatedness (more similar → more recent common ancestor)
- speciation = genetic isolation so they can't interbreed
- allopatric (geographical barrier) vs sympatric (same area, behaviour)