Topic 5

Question 1

What is speciation?

Answer 1

• The process by which new species arise - forms biodiversity.
• Combines ecology, evolution, and genetics.
• Links micro and macroevolutionary processes.

Question 2

What is population divergence driven by?

Answer 2

Natural selection or drift between environments.

Question 3

What causes initial divergence of a population?

Answer 3

Usually a physical barrier such as a mountain range or river.

Question 4

How does reproductive isolation evolve?

Answer 4

Through the accumulation of genetic differences between both groups over time.

Question 5

What is hybridization?

Answer 5

When the two newly formed species mate, creating a hybrid (with less fitness) which could be a new species.

Question 6

When is the process of speciation complete?

Answer 6

The two new populations become reproductively isolated, gene flow stops if they are brought back together. If they mate, the offspring could be unviable.

Question 7

What is allopatric speciation?

Answer 7

• Occurs in different places (geographically).
• Physical barrier divides geographic range (ex. river).
• Gene flow stops and the separate populations evolve independently.
• Over time, different alleles become fixed because of mutation, drift, or selection.

Question 8

What occurs if allopatric speciation is successful?

Answer 8

• Lots of time has elapsed for a significant difference to be noticed between the populations.
• If the physical barrier is removed and the populations come into contact, they will remain extinct.
• Interbreeding prevented by pre zygotic and/or post zygotic mechanisms.

Question 9

What is sympatric speciation?

Answer 9

• There is no physical barrier.
• Differences in behaviour or timing separates populations.
• Ex. palm trees flowering at different times due to the soil they grow on - makes them multiple separate species.

Question 10

What is polyploidization?

Answer 10

• When meiosis fails and the organism produces diploid 2n gametes, rather than haploid n gametes.
• If this 2n is fertilized with another 2n, it creates a new species (4n).
• Causes instant, sudden speciation.
• Very common in ferns.

Question 11

What is autopolyploid?

Answer 11

• When a 2n gamete is fertilized with another 2n gamete.
• Autopolyploid’s can only mate with each other (reproductive isolation).

Question 12

What does reproductive isolation do?

Answer 12

Prevents the mixing of gene pools.

Question 13

What is a prezygotic isolating mechanism?

Answer 13

Type of reproductive isolation that occurs before fertilization. Prevents mating.

Question 14

What is a postzygotic isolating mechanism?

Answer 14

Type of reproductive isolation that occurs after fertilization and gamete formation. Prevents zygote development or reproduction.

Question 15

What are the different types of prezygotic barriers?

Answer 15

• Habitat isolation
• Behavioural isolation
• Temporal isolation
• Mechanical isolation
• Gametic isolation

Question 16

What is habitat isolation?

Answer 16

• Species live in different habitats so they rarely encounter each other.
• Usually organisms will mate with individuals that prefer the same habitat (same host plant for example).

Question 17

What is behavioural isolation?

Answer 17

• Females will respond only to certain behaviours of the male of the same species.
• Ex. Frogs have distinct mating calls, which are species specific even if they look the same.

Question 18

What is temporal isolation?

Answer 18

• When reproductive timing does not overlap, maintaining separation between species (they will not fertilize each other).
• Ex. plants releasing seeds in the same geographical location, but during different seasons.

Question 19

What is mechanical isolation?

Answer 19

• When genitalia don’t match, resulting in no mating.
• Ex. two species of the same flower have different structures to attract different pollinators (bees and hummingbirds).

Question 20

What are the possible outcomes of hybridization?

Answer 20

• Reduced hybrid visibility (lower survival, zygote doesn’t develop fully).
• Reduced hybrid fertility (sterile, offspring cannot physically reproduce).
• Hybrid breakdown (offspring has reduced fitness)

Question 21

What is reduced hybrid visibility?

Answer 21

• When the hybrid embryo dies early in development, fails to reach maturity.
• No viable adult hybrids are produced, which keeps the two species separate.

Question 22

What is reduced hybrid fitness?

Answer 22

• Hybrids are fertile, but will have low fitness.
• Ex. grizzly and polar bear hybrid has low fitness in sea-ice, they can survive better in grizzly habitats.

Question 23

What is a species?

Answer 23

• The concept is based on perception.
• Can be based on:
  
  • Morphological
  • Reproductive
  • Phylogenetic or evolutionary

Question 24

What is the morphological species concept based on?

Answer 24

Species are discrete organisms based on unique morphological characters.

Question 25

What are the advantages and disadvantages of using the morphological species concept?

Answer 25

Advantages: - practical and simple to use Disadvantages: - no clear genetic or evolutionary justification - choice of characteristics can be undefined - some species are cryptic, meaning that they look very similar and cannot be diagnosed by morphology

Question 26

What is the biological species concept?

Answer 26

Species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other groups.

Question 27

What are the advantages and disadvantages of the biological species concept?

Answer 27

Advantages: - clear criteria - clear evolutionary justification Disadvantages: - may be difficult to observe who is actually interbreeding - does not apply to asexual organisms (like bacteria) - less viable today because of genomics

Question 28

What is the phylogenetic species concept?

Answer 28

Based on the reconstruction of the evolutionary tree of an organism (using morphological and genetic data).

Question 29

What is a phylogenetic species?

Answer 29

A cluster of populations that emerge from the same small branch on a phylogenetic tree.

Question 30

What are the advantages and disadvantages of the phylogenetic species concept?

Answer 30

Advantages: - applies better to asexual species - can apply it to any group of organisms - does not require any knowledge about interbreeding in the field Disadvantages: - detailed evolutionary histories have not been discovered for many organisms - species could be split into very small groups based on tiny differences

Question 31

What is a subspecies?

Answer 31

- When geographically separated populations of a species exhibit dramatic phenotypic variation. - Local variants of species. - Interbreed but have different selective pressures/genetic drift. - Ex. brown bear and grizzly could be considered subspecies of each other.

Question 31

What is a ring species?

Answer 31

- When a species has a ring-shaped distribution around terrain that is inheritable. - Can exchange gene flow between neighbouring populations to farther populations. - Ex. lizards in california.

Question 32

What is clinal variation?

Answer 32

- When there is a pattern of variation across a geographical gradient. - Results from gene flow between adjacent populations experiencing different conditions. - Ex. zebras getting more black and white all the way to brown based on their geographical location.