Especiacao

Question 1

Speciation

Answer 1

is the evolutionary process by which populations evolve to become distinct species.

Question 2

Biological species concept

Answer 2

a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring—but do not produce viable, fertile offspring with members of other such groups. Thus, the members of a biological species are united by being reproductively compatible, at least potentially.

Question 3

Reproductive isolation

Answer 3

the existence of biological factors (barriers) that impede members of two species from interbreeding and producing viable, fertile offspring. Such
barriers block gene flow between the species and limit the formation of hybrids, offspring that result from an interspecific mating. Although a single barrier may not prevent all gene flow, a combination of several barriers can effectively isolate a species’ gene pool.

Question 4

Pre and Postzygotic mecanisms

Answer 4

Prezygotic barriers (“before the zygote”) block fertilization from occurring. Such barriers typically act in one of three ways: by impeding members of different species from attempting to mate, by preventing an attempted mating from being completed successfully, or by hindering fertilization if mating is completed successfully. If a sperm cell from one species overcomes prezygotic barriers and fertilizes an ovum from another species, a variety of postzygotic barriers (“after the zygote”) may contribute to reproductive isolation after the hybrid zygote is formed. Developmental errors may reduce
survival among hybrid embryos. Or problems after birth
may cause hybrids to be infertile or decrease their chance of
surviving long enough to reproduce.

Question 5

Pre zigoticos

Answer 5

isolamento de habitat/ ambiental/ ecológico (ambientes diferentes), isolamento sazonal/ temporal (Ex: período reprodutivo diferente), isolamento etológico/ comportamental (diferentes tipos de cortejos), isolamento mecânico/ anatômico (mudança na anatomia dos órgãos sexuais) e isolamento gamético (reconhecimento bioquímico de gametas de espécies diferentes).

Question 6

Pos zigoticos

Answer 6

espécies diferentes conseguem acasalar, porém, híbridos gerados a partir do cruzamento de duas espécies não são viáveis e morrem ainda na fase embrionária ou poucos dias após o nascimento. Mesmo se os híbridos nascerem, serão estéreis e produzem gametas inviáveis ou não funcionais.

Question 7

Allopatric speciation

Answer 7

In allopatric speciation, gene flow is interrupted when a population is divided into geographically isolated subpopulations. For example, the water level in a lake may subside, resulting in two or more smaller lakes that are now home to separated populations. Or a river may change course and divide a population of animals that cannot cross it. Allopatric speciation can also occur without geologic remodeling, such as when individuals colonize a remote area and their descendants become geographically isolated from the parent population.

Question 8

Sympatric speciation

Answer 8

their members remain in contact with each other? Although
such contact (and the ongoing gene flow that results) makes
sympatric speciation less common than allopatric speciation, sympatric speciation can occur if gene flow is reduced
by such factors as polyploidy, sexual selection, and habitat
differentiation.