Lecture 4 - Genetic drift, speciation

Question 1

Phenotype:
Genotype:
Alleles:

Answer 1

Phenotype: Observable traits expressed by organism

Genotype: underlying genetic makeup

Alleles: variants of a gene

Question 2

Reproductive isolation:

Answer 2

Mechanisms that prevent gene flow between members of different species.
-They can be pre-zygotic or post zygotic

Question 3

zygote, pre zygote isolation;

Answer 3

Cell formed by the joining of two gametes (egg + sperm)

preventing interactions, mating or actual union of gametes

Question 4

habitat isolation, temporal isolation, behavioural isolation, mechanical isolation, Gametic isolation

Answer 4

habitat: live in differe, , nt environments therefore, never meet

Temporal: related frogs species have different breeding times

Behavioural: Different mating activities (chicken not attracted to pheasant)

Mechanical: flowers cannot mate because their pollinators cannot feed at the other flower

Gametic: Gametes cannot unite, dog and cat cannot unite to form a zygote.

Question 5

Post zygotic isolation

Answer 5

Post zygotic mechanisms occur after the formation of a zygote

Question 6

hybrid inviability, Hybrid infertility

Answer 6

inviability: gametes unite but viable offspring cannot form (goat and sheep can mate, but zygote will not survive)

infertility: viable hybrid offspring cannot reproduce (zebra and donkey = zonkeys cannot make offspring)

Question 7

why are there more pre zygotic than post zygotic mechanisms?

Answer 7

-mating is costly:
finding+ attracting takes time

-Individuals who mate outside their species will produce less offspring

Question 8

What is allopatric speciation?

Answer 8

-physical isolation (on an island)

Question 9

Explain the beak gape example:

Answer 9

-closed beak is lower pitch
-open beak is higher pitch
= influences frequency of song

-beak size can influence beak movement
=bids with large beaks evolve with simpler songs, less rapid beak movements

Question 10

Why are songs used for species identification and pre-zygotic isolation?

Answer 10

-song is used to identify birds from own species and prevent mating with other species
-females have preferences for song (sexual selection)
-increase species diffences