CHAPTER 7: THE ORIGIN OF SPECIES

Question 1

Taxonomic Species Concept

Answer 1

• Organisms are decided to be species based on whether or not they look like each other
• species are classified based on similarities in their appearances
• phenetic, genetics, ecological and phylogenetic

Question 2

Problems with the taxonomic species

Answer 2

• sexual dimorphism
• if humans have blue eyes, brown eyes, and green eyes, they are obviously different, why are they considered the same species?

Question 3

Cryptic species

Answer 3

• groups of species that look very similar to each other or even almost exactly alike

Question 4

Why are cryptic species considered to be separate species from each other?

Answer 4

• They are reproductively isolated from one another

- They cannot mate adequately and thus their offspring will be unfit and infertile

Question 5

Mayr and the biological species concept

Answer 5

Species are groups of interbreeding individuals that are reproductively isolated from other such groups

Question 6

Pre-mating reproductive isolating mechanisms

Answer 6

• prevents zygote formation
• geographical, ecological - cannot reach other to mate
• temporal, behaviours ; have different mating mechanisms and behaviours
• mechanical; prevents the gametes from fusing and furthermore the zygote from forming
• flies in apple and hawthorn trees
• VERL and lysin proteins coevolving in different directions

Question 7

Postmating Reproductive Isolation mechanisms

Answer 7

• inviability, sterility and abnormal development of zygote

- gene combinations between the two individuals are unfavourable and thus produce unfit and undesirable offspring

Question 8

Fruit Flies in America

Answer 8

• This is an example of where pre-mating and post-mating isolation mechanisms come into play
• Essentially what we see is that these flies live in Africa but on separate sides of the mountains ; thus they are unable to meet each other
• When they do meet however, they have different mating mannerisms and thus it is rare that they do
• if they do, though, the interactions of the gametes of the males and the females causes a sterile and thus infertile offspring

Question 9

What about extinct organisms?

Answer 9

Organisms that have gone extinct cannot be studied for reproductive isolation however we can investigate the extent of their isolation and origin through looking at the fossil record
- The biological species concept also does not apply to species that reproduce asexually (bacteria and hermaphroditic plants)

Question 10

Sister species

Answer 10

Species that are each other’s closest biological relatives but have been separated by geographical barriers

Question 11

Divergent selection

Answer 11

Selection that is imposed on two groups of individuals coevolving in different evolutionary directions

Question 12

The sterility and inviability of hybrids is due to

Answer 12

Genes that are incompatible in hybrids and thus offspring

Question 13

Geographic speciation

Answer 13

The idea that speciation arises when two groups from the same original population are separated from each other geographically and thus begin to diverge and diversify

Question 14

First Evidence of Geographic Speciation

Answer 14

Speciation in organisms other than bacteria happens really slow
- If speciation arises from geographical isolation, there must be a lot of opportunities for this to happen

Question 15

Second Evidence of Geographic Speciation

Answer 15

If populations are reproductively isolated from each other due to geographic speciation, we should be able to see newly formed species from common ancestors in nearby areas
- Archipelagos is a really good place to observe this phenomenon

Question 16

Third Evidence of Geographic Speciation

Answer 16

If geographic separation is the cause of speciation we should be able to see it happening in nature at the moment
- Speciation happens too slowly for us to observe in our own lifetime however,

Question 17

Third Evidence of Geographic Speciation

Answer 17

If geographic separation is the cause of speciation we should be able to see it happening in nature at the moment
- Speciation happens too slowly for us to observe in our own lifetime however, we should be able to see groups of individuals separating and we should be able to see them beginning to develop reproductive barriers

Question 18

Final Evidence of Geographic Speciation

Answer 18

Reproductive isolation must happen very slowly as speciation also happens really slowly

• Types of mating barriers:
  1. Mating discrimination between the pairs
  2. Sterility of Hybrids
  3. Inviability of Hybrids

Question 19

How can we be sure that different species arose in the same geographic area?

Answer 19

• Habitat islands; if the region that these separate species are found in is extremely remote and the probability of finding geographic isolation is almost impossible

Question 20

Allopolyploidy speciation

Answer 20

• Instead of beginning with isolated populations of the same species, it starts with the hybridization of two different species that live in the same area
• It usually requires that these individuals have an abnormal number of chromosomes in their cells
• If haploid gametes of two different species merge, they will be sterile due to genetic incompatibility
• If there was a way that they could double their chromosomes, then this would increase their fertility
• it would also be a new species due to the fact that it is reproductively isolated from their parent species

Question 21

Polyploid speciation doesn’t always require hybridization

Answer 21

a polyploid species can arise by simply doubling all of the chromosomes of an asexually reproducing organisms - seen a lot in plants

Question 22

Polyploidy speciation happens faster than

Answer 22

Normal

Question 23

Jacqueline Weir and Ruth Ingram

Answer 23

synthesized polyploid species by making various crosses between parental species

Question 24

Evidence for Speciation

Answer 24

1. We see lineages splitting in the fossil record
2. We see closely related species separated by geographical barriers
3. We see new populations arising as populations begin to evolve reproductive barriers