Evolution 1.7

Question 1

What is Evolution?

Answer 1

Evolution is the process of gradual changes in the inherited characteristics of organisms over generations as a result of genetic variations

Question 2

What is Vertical Transfer?

Answer 2

Genes transferred from parents to offspring either as a result of sexual or aesexual reproduction

Question 3

What is sexual reproduction?

Answer 3

It involves two genetically different parents - the offspring inherit different combinations of genes from each parent.

Question 4

What is Asexual reproduction?

Answer 4

Reproduction from the same parent - offspring are genetically identical and show no variation

Question 5

What is Horizontal Transfer?

Answer 5

When genes are transferred between members of the same generation.

Question 6

What can experience horizontal transfer and how?

Answer 6

Prokaryotes - can exchange in many ways; transformation, transduction and conjunction (bacterial)
Gives potential for faster evolutionary change.

Question 7

What is Rapid Evolutionary Change?

Answer 7

Obtaining a gene from a neighbor is much faster than waiting for one to evolve - allowing a rapid evolution of prokaryotes.
Can be risky because there’s no guarantee that the transferred genes will be advantageous.

Question 8

Prokaryotes and antibiotic resistance

Answer 8

Resistance to antibiotics has occurred through the transfer of plasmids carrying antibiotic resistant genes from bacteria to bacteria

Question 9

What is Selection in a species?

Answer 9

Where the frequency of alleles in a population increases or decreases in a non-random way, meaning there is selection for or against a particular characteristic.

Question 10

Natural Selection Summarised?

Answer 10

1. More offspring than environment can support
2. All show variation from each other
3. Many offspring die from selection pressures eg disease, overcrowding
4. Survival of the fittest pass advantageous adaptations to offspring. Less favourable characteristics aren’t passed on.
5. Repeated till the naturally selected predominate the population and allele frequency is altered.

Question 11

Natural Selection Defined?

Answer 11

A non-random process that results in the increase of frequency of the DNA sequences that confer a selective advantage, these increase survival. It is also the non-random reduction in deleterious sequences which confer a selective disadvantage.

Question 12

Quantitative Traits?

Answer 12

Phenotypic traits that can be measured and controlled by many genes e.g height

Question 13

What is Stabilizing Selection?

Answer 13

When selection is against extreme variants and favours the average stereotypes. Leads to a reduction in genetic diversity

Question 14

What is Directional Selection?

Answer 14

(Common during a period of environmental change) Selection that favours one extreme of the phenotype which is initially less common. Causes a shift in the mean.

Question 15

What is Disruptive Selection?

Answer 15

Selection pressure selects extreme versions of a phenotype at the expense of the averages. The population splits into two (or more) distinct groups (This is the driving force of sympatric speciation).

Question 16

What is Speciation?

Answer 16

The production of two or more separate species. It is brought by isolation, mutation and selection.

Question 17

Species defined?

Answer 17

A species is a group of organisms which can interbreed to produce fertile off spring and which does not normally breed with other groups.

Question 18

What is Allopatric Speciation?

Answer 18

Occurs when the isolation barrier preventing gene flow between two (or more) populations is a geographical barrier

Question 19

Allopatric speciation summary..

Answer 19

1. Large interbreeding population
2. Split into two isolated sub-populations by geographical barrier - prevents interbreeding and gene exchange.
3. Mutations occur at random. Different in each population. New variation in each group.
4. Natural selection. This increases frequency of new alleles causing tow gene pools to become so altered they become genetically distinct and isolated
5. If barrier is removed and they can no longer interbreed to produce fertile offspring speciation has occurred.

Question 20

What is Sympatric Speciation?

Answer 20

Two (or more) populations living in close proximity to one another in the same environment, the gene flow between them is prevented by the presence of a behavioural or ecological barrier.

Question 21

Sympatric speciation summary..

Answer 21

1. Large interbreeding population sharing same ecological or behavioural niche
2. Alternative niche becomes available so some members start two exploit new niche
3. Now exploit different niches and no longer interbreed
4. Mutations produce new variation in each group - the mutants are better adapted to exploit alternative niche
5. Natural selection
6. Two genetically distinct species formed that are no longer able to produce fertile offspring.