CH24

Question 1

Define

Speciation

Answer 1

Process by which one species splits into two or more species. It is responsible for the tremendous biodiversity observable and links microevolution to macroevolution

Question 2

Define

Macroevolution

Answer 2

Broad pattern of evolution above the species level

Question 3

Define

Biological species concept

Answer 3

Species are differentiated by their ability to interbreed and produce fertile, viable offspring

Question 4

Define

Morphological species concept

Answer 4

Species differentiated by body shape and features (subjective but works for asexual species)

Question 5

Define

Ecological species concept

Answer 5

Species differentiated by how species interact with their environment

Question 6

Define

Phylogenetic species concept

Answer 6

Species defined by the smallest group of individuals that share a common ancestor

Question 7

Define

Reproductive isolation

Answer 7

Biological factors that prevents members of 2 different species from interbreeding and producing fertile + viable offspring

Question 8

What are the prezygotic barriers?

Answer 8

1. Habitat isolation
2. Temporal isolation
3. Behavioural isolation
4. Mechanical isolation
5. Gametic isolation

Question 9

What are the postzygotic barriers?

Answer 9

1. Reduced Hybrid Viability
2. Reduced Hybrid Fertility
3. Hybrid breakdown (above problems occur for hybrid-hybrid offspring)

Question 10

Define

Allopatric speciation

Answer 10

Interruption of gene flow by geographical isolation. Groups are separated and gene pools may diverge, which leads to reproductive barriers

Question 11

Define

Sympatric speciation

Answer 11

Interruption of gene flow despite lack of physical separation

Question 12

What are some ways by which sympatric speciation occurs?

Answer 12

• Polyploidy (mutation-driven speciation)
• Habitat differentiation (subset of population exploits a habitat or diurnal/nocturnal cyclles)
• Non-random mating (ex: mosquitofish choosing mates with similar body shape)

Question 13

What are the forms of polyploidy?

Answer 13

• Autopolyploidy: species just doubles its number of chromosomes, either autopollinate or mate with others 2ns
• Allopolyploidy: Infertile hybrid offspring that can propagate asexually (ex: 2n=6 and 2n=4) come together, create a 5 chromosome infertile offspring)

Question 14

Define

Hybrid zone

Answer 14

Region in which members of different species meet and mate, producing some offspring of mixed ancestry (intermediate mediocre phenotype)

Question 15

What are the possibilities for a hybrid zone (what can become of it)?

Answer 15

• Reinforcement: hybrids are less fit than parents, natural selections strengthens prezygotic barriers
• Fusion: reproductive barriers weaken/vanish, fusion of species
• Stability: continuous production of hybrids, happens in narrow hybrid zones

Question 16

What are the ways in which species fall and rise?

Answer 16

• Plate Tectonics
• Mass Extinctions
• Adaptive Radiations

Question 17

Define

Plate tectonics

Answer 17

• Continents float on mantle in a movement called continental drift
• Their collision causes the creation of mountains, islands (promotes geographical separation)

Question 18

What were the biggest events of mass extinction?

Answer 18

Permian Extinction and Cretaceous Extinction

Question 19

Describe

Permian Extinction

Answer 19

Permian Extinction: 250 mya for 500k years. Extreme volcanic activity, acid oceans, anoxia, global warming and formation of Pangea. Loss of 95% marine life and 70% terrestrial.

Question 20

Describe

Cretaceous Extinction

Answer 20

Cretaceous Extinction: 65 mya, few k years. Asteroid collides with earth, volcanic activity, huge cloud of debris. Loss of dinosaurs and 50% marine life.

Question 21

Describe

Adaptive radiations

Answer 21

• Rapid speciation and diversification
• Organisms will out vacant areas/niches otherwise occupied by other species
• Regional: face little competition after migrating to a new location
  ex: Mammals adaptively radiated after Cretaceous Extinction