Lecture 21: Species, speciation and Hybridization

Question 1

What are sympatric?

Answer 1

Same species living in the same region.

Question 2

Why is allopatric?

Answer 2

Different species living in different regions

Question 3

What are the two main species concept?

Answer 3

Taxonomic (or morphological): based on distinct measurable differences

Biological: Based on interfertility among individuals

Question 4

What is the biological species concept?

Answer 4

It says species are groups of interbreeding natural populations that are reproductively isolated from other such groups.

Question 5

How do you differentiate between the same species and a different one using the biological species concept?

Answer 5

If two organisms can interbreed then, they are referred to as same species, otherwise they are considered as different species.

Question 6

What does the biological species concept highlight?

Answer 6

1. It focuses on the PROCESS
2. Geographic isolation alone is NOT SUFFICIENT to say organisms are different species, because they can interbreed if the geographic barrier can be removed.

.3. Isolation does NOT have to be absolute

4. Organisms must interbreed together in the wild to be considered as SAME SPECIES

Question 7

What sort of speciation is more common?

Answer 7

Allopatric: It allows for more evolution in isolation, as it has a geographic barrier, which allows for minimal gene flow.

Question 8

What are pre-zygotic reproductive isolation barrier?

Answer 8

Barrier in finding mate, or a successful fertilization

Question 9

What are the post-zygotic reproductive isolation barrier?

Answer 9

Barrier in the development and growth of a zygote ( differential survival of zygote ) or in the adulthood or reproduction of that zygote.

Question 10

What are the reasons behind pre-zygotic barriers?

Answer 10

Geographical, Ecological,

Temporal, Behavioral (mate recognition),

Mechanical (genital structure compatibility),

Cellular (sperm-egg compatibility)

Question 11

What were the results from the study of apple-maggot bees?

Answer 11

The bees on the cultivated apple trees reproduced much faster than the bees on the maggot trees, and this lead to a pre-zygotic reproduction isolation as the bees couldn’t find mates.

Gene flow reduced by 94%

Question 12

What are the examples of post-zygotic barriers?

Answer 12

1. Intrinsic: Zygote is not sterile,
   Inviable, or an abnormally developed hybrid
2. Extrinsic: Ecological mismatch or hybrid or phenotype to environment.

Question 13

Do you always need local adaption for speciation and reproductive isolation?

Answer 13

No genetic drift alone can result in isolation and later speciation, but adaptive evolution speeds up the process.

Question 14

what is ecological isolation?

Answer 14

Local adaptation can lead to isolation and might speed things up, when they try to come back together, the barriers won’t let them. This is termed ecological isolation.

Question 15

What causes adaptations?

Answer 15

1. Ecological opportunities (Abundant resources, Few competitors)
2. Origin of Key innovation
3. High rates of speciation. (b/c without reproduction isolation, speciation cannot occur)

Question 16

What can reverse speciation to merge two groups into one?

Answer 16

Exchange of genes between the two groups (Hybridization)

Hybridization can result in complex variation in patterns.

Question 17

What is polyploidy?

Answer 17

An organism ends up with two sets of chromosomes from both the species or from the same species.

Question 18

What is allopolyploid?

Answer 18

Arises from duplicate karyotypes following hybridization between species.

Question 19

What is autopolyploid?

Answer 19

Arises from duplicated karyotype within a species ( non-disjunction)

Question 20

What is the significance of polyploidy?

Answer 20

1. They are reproductively isolated from their diploid relatives
2. They have new phenotype
3. High Vigor: Often show very high fitness

4.