Week 7- Evolution and Speciation Flashcards
The inability of a species to breed successfully with related species due to multiple differences.
Reproductive Isolation
2 types of isolation mechanisms:
*Prezygotic isolation mechanisms
*Postzygotic isolation mechanisms
Once new species arise from the parental species due to the effect of variation and natural selection, ____________________ through reproduction.
Reproductive barriers prevent the two species from exchanging genes
Thus two related species _________ and _________.
cannot mate with each other, remain distinct.
It is the means of two individuals are prevented from successful reproduction and kept genetically distinct from each other.
Role of Reproductive Isolation
The two individuals are unable to mate as they live in geographically different areas.
Ecological Isolation
Also called habitat or geographic.
Ecological Isolation
Mating is prevented because the reproductive organs mature at different times.
Seasonal Isolation
Also called temporal.
Seasonal Isolation
The songs in birds of two species or the coloration isolation of two fishes are so different that one female individual is able to recognize only the male of its species.
Ethological/Behavioral Isolation
The male and female organs for mating differ in different species and prevent their union.
Mechanical Isolation
The sperms of one species are not able to survive in the female tract of another species.
Physiological Isolation
If a zygote formed from different species is formed, it will die after some time. if not, it will die in its development.
Zygotic and Developmental
Also called hybrid inviability.
Zygotic and Developmental
A hybrid or a zygote formed from different species may lead to a normal life but cannot reproduce.
Hybrid Sterility
In rare cases, all the above mechanisms fail and a hybrid is fertile, it can produce only one generation.
F2 breakdown
Also called hybrid breakdown.
F2 breakdown
It is the formation of a new and distinct species in the course of evolution.
Speciation
It involves the splitting of a single evolutionary lineage into two or more genetically independent lineages.
Speciation
It is the evolution of new species from an parent species.
Speciation
3 Modes of Speciation
- Allopatric/geographic speciation
- Sympatric speciation
- Parapatric speciation
Occurs when some members of a population become geographically separated from the other members thereby preventing gene flow.
Allopatric/geographic speciation
Allo means _____, patric - _______.
other, place
Examples of geographic barriers
bodies of water and mountain ranges.
Occurs when members of a population that initially occupy the same habitat within the same range diverge into two or more different species.
Sympatric speciation
It involves abrupt genetic changes that quickly lead to the reproductive isolation of a group of individuals.
Sympatric speciation
change in chromosome number
polyploidization
Sympatric means ___________
same place
Occurs when the groups that evolved to be separate species are geographic neighbors. Gene flow occurs but with great distances is reduced.
Parapatric speciation
There is also abrupt change in the environment over a geographic border and strong disruptive selection must also happen.
Parapatric speciation
Parapatric means?
beside each other
Parapatric means?
beside each other
