Chapter 19: Speciation

19.1 On the Road To Speciation

Species means kind, as in a particular kind of duck.

Through the history of any species, micro evolutionary processes have been introducing changes in the gene pools of its populations. Remember, particular alleles give inauguration to the heritable traits of populations. As an outcome of mutation, genetic drift, gene flow, and native selection, different alleles can increase or decrease in frequency, or even disappear over time.

Given the variation in phenotypic details, perhaps we should move past the details, down to a more basic function that units members of a species and isolates them to all new(prenominal) species.

Reproduction as a defining function in species is substitution to the biological species concept.

Species are groups of hybridize natural populations that are reproductively separate from other such groups. They belong to the same species because they can contribute to a shared gene pool.

19.2 Reproductive Isolating Mechanisms

Prezygotic Isolation

a. veritable isolating mechanisms take effect before or during fertilization. Because they interdict mating or pollination between genetically diverging populations, hybrid zygotes cannot form. The same isolating mechanisms operate to prevent interbreeding of individuals of different species.

b. Temporal Isolation

Temporal isolation results from interpopulational differences in the timing of reproduction.



For around animals or lay outs, mating or pollination is a seasonal worker event that is over rather quickly, sometimes in little than a day. Even closely related species may be isolated from each other if their reproductive cycles do no coincide.

.The cicada, a type of insect that spends nearly all of its heart underground in immature form, feeding on juices from plant tissues. One species matures, emerges, and reproduces every 13 years. The other species does this every 17 years. Only once in 221 years do they drop out gametes at the same time.

c. Behavioral...

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