Speciation

Question 1

Reproductive isolation

Answer 1

Populations cannot interbreed successfully to produce viable, fertile offspring.

Question 2

What is the result of reproductive isolation?

Answer 2

• Genetic isolation –> this is when a lack of gene flow between populations due to reproductive barriers mean that they cannot interbreed successfully.
• This prevents the exchange of genes between populations and facilitates speciation.

Question 3

Prezygotic reproductive barriers:

Answer 3

• Prevent fertilisation and formation of a zygote and act before the fertilisation of the egg cell
• Include habitat isolation, variations in mating rituals

Question 4

Postzygotic reproductive barriers:

Answer 4

• Result of hybridisation between different species.
• Produce an infertile / non-viable hybrid offspring, reducing reproductive potential

Question 5

What are the two main types of speciation?

Answer 5

• Allopatric speciation
• Sympatric speciation

Question 6

Steps in allopatric speciation?

Answer 6

1. Some members of population geographically separated from the rest by a physical barrier
2. Geographical separation exposes distinct parts of population to different environmental pressures.
3. These prezygotic reproductive barriers lead to reproductive isolation.
4. Reproductive isolation prevents gene flow and the physical separation leads to genetic divergence
5. This causes the populations to evolve separately and form different species

Question 7

Steps in Sympatric speciation?

Answer 7

1. Speciation takes place within the same geographical location
2. Ecological or behavioural separation mechanisms like different habitat preference, mate selection or chromosomal changes lead to the groups becoming reproductively isolated
3. Reproductive isolation prevents gene flow and leads to genetic divergence
4. This causes populations to evolve separately and form separate species

Question 8

Which type of speciation is more frequent in plants?

Answer 8

• Sympatric speciation

Question 9

Which type of speciation is more common overall?

Answer 9

Allopatric speciation

Question 10

What is speciation?

Answer 10

The process by which new species form due to evolution.

Question 11

Speciation typically occurs due to:

Answer 11

1. Reproductive isolation of populations, which is the inability of two groups of organisms to breed with one another.
2. Genetic divergence, which is driven by natural selection and genetic drift.

Question 12

Adaptive radiation:

Answer 12

• Organisms diversify rapidly from an ancestral species into a wide ray of new forms, each adapted to a specific ecological niche.
• More likely to occur when a change in the environment makes new resources available.
• This diversification is a pivotal mechanism behind speciation

Question 13

Why can organisms in different species no longer interbreed to produce fertile offspring?

Answer 13

• Isolated
• Alleles continue to undergo random mutations, so different characteristics selected for and against
• Changes in phenotype

Question 14

adaptive radiation

Answer 14

an evolutionary event in which a lineage rapidly diversifies to form multiple lineages, each differing in some adaptive feature.

Question 14

Example of allosteric speciation?

Answer 14

• Galapagos Islands and the finches (also example of adaptive radiation)