Speciation and Hybridisation

Question 1

What is speciation

Answer 1

the evolutionary process by which new species arise through reproductive isolation

causes one lineage to split into more two or more lineages

Question 2

How to know when speciation occurs?

Answer 2

The process starts with one species, and many populations.

When the populations start accumulating differences to each other, this is the beginning of speciation

During the process, you cannot conclude whether there is one or more than one species

When the two new species are formed, they will not be able to breed to create viable offspring if they underwent speciaton, this is the basis of the biological species concept

Question 3

what is the biological species concept

Answer 3

when a species has undergone speciation, the two new species would not be able to breed to create viable offspring if they underwent speciation, this is the foundation of the biological species concept

groups of actually or potentially interbreeding natural populations that produce fertile offspring

Question 4

Allopatric Speciation

Answer 4

Reproductive isolation from physical barriers, e.g. islands

It prevents reproduction and gene flow, allowing for natural selection and mutations to change the genetic variation in a population to the point where they can no longer interbreed and produce viable offspring

Question 5

Sympatric Speciation

Answer 5

Without physical or geographical barriers
e.g. driven by behaviours of other species or time

for example, if a certain animal is only attracted to the pink variation of a plant, then it will only pollinate the pink variations with one another, causing a reproductive barrier and allowing for speciation

different alleles could make the flowers flower at slightly different times, resulting in them experiencing reproductive isolation

Question 6

Genetically how does speciation occur?

Answer 6

When new alleles become fixed, or when all individuals in that population or species are homozygous for that specific allele

and the new alleles are no longer compatible with one another, but they are compatible with their ancestral gene

they are then reproductively incompatible, and therefore different species

Question 7

What is a species

Answer 7

a group of organisms that interbreed and produce fertile offspring

highly similar genomes

Question 8

How are species kept seperate?

Answer 8

Various mechanisms keep species discrete (seperate)

these include:

prezygotic mechanisms
- prevent reproductive behaviour and fertilization

post-zygotic mechanisms
- prevent the production of fertile offspring after mating has occured

Question 9

What are hybrids?

Answer 9

The inviable and likely infertile offspring produced when two different species interbreed.

The fact that they are infertile is a post-zygotic barrier

some hybrids are fertile, however, does this mean they are actually the same species? up for debate

Question 10

What is hybridisation?

Answer 10

Bredding of two genetically simimlar species can produce viable offspring, but they are often sterile (this is a post zygotic mechanism)

Question 11

Adaptive introgression

Answer 11

inheritance of beneficial variation from a related species that accelerates adaptation to, and survival in new environments (this is used to help prevent extinction)

therefore beneficial traits can be exchanged via hybridisation

Question 12

incomplete lineage hypothesis

Answer 12

Alleles predates the speciation of neanderthals and humans, and by change those alleles were lost in Africans and kept in non-africans

seems less likely

Question 13

What are hybrid zones?

Answer 13

areas where two closely related species cohabit and interbreed

Question 14

How can hybridisatioon impact the involved species?

Answer 14

1. reinforcement
   strengthens reproductive varriers, reducing hybrids
   (birds are attracted to certain coloured plumage, therefore hybrids have undesireable colours, therefore reducing interbreeding and the combination of the two species)
2. fusion
   weakenign of reproductive barriers until the two species become one (murky water made it difficult for females to differentiate species based on colour, resulting in interbreeding, and then they become one species)
3. Stability
   hybrids continue to survive and reproduce
   hybrids form another species because there isnt engout fitness to form one species but there isnt so little fitness that the hybrids die out altogether

Question 15

Fitness and hybrid zones

Answer 15

most fit= fusion (2 species into 1)
medium fitness= stability, hybrid forms a new species (2 species into 3)
not fit= reinforcement, 2 species stay seperate and the hybrid dies

Question 16

Balancing selection

Answer 16

Maintains multiple alleles within a population with two main mechanisms:

1. negative frequency dependent selection
2. heterozygote advantage

it maintains genetic diversity in a population by keeping alleles at frequencies higher than expected by chance

Question 17

negative frequency dependent selection

Answer 17

rare phenotypes have higher selective advantage
kind of like rock paper scissors
when one is common, another takes over, and this cycles throguh
system becomes cyclic and allele combinations fail to remain stable

Question 18

heterozygote advantage

Answer 18

heterozygotes may have advantage over homozygous and will therefore be more likely to survive and reproduce