1.7 evolution

Question 1

What is evolution?

Answer 1

the changes in organisms over generations as a result of genomic variations.

Question 2

What is the processor evolution/natural selection?

Answer 2

• organisms produce more offspring than the environment can support
• all members of a species show variation from each other
• a struggle for existence occurs and many offspring die before they can reproduce
• only those who are better adapted to their environment (the fittest) will survive and breed and pass those adaptations to their offspring
• this process is repeated generation after generation causing gradual change in the characteristics of a species

Question 3

What is natural selection?

Answer 3

-the non-random increase in frequency of DNA sequences that increase survival and the non-random reduction in the frequency of deleterious sequences.

Question 4

what is polygenic inheritance?

Answer 4

a continuous variable that is controlled by many genes

Question 5

What is stabilising selection?

Answer 5

• an average phenotype is selected for and extremes of the phenotype range are selected against.
• it leads to a reduction in genetic diversity.

Question 6

What is directional selection?

Answer 6

• one extreme of the phenotype range is selected for.

- causing a progressive shift in the mean value.

Question 7

What is disruptive selection?

Answer 7

two or more phenotypes are selected for. Can result in the population being split into distinct groups. This is the driving force behind sympatric speciation.

Question 8

What are the two ways that genetic material can be inherited by?

Answer 8

• vertical transfer

- horizontal transfer

Question 9

What is vertical transfer of genetic material?

Answer 9

genes are transferred from parents down to their offspring as a result of sexual reproduction or asexual reproduction.

Question 10

What is sexual reproduction?

Answer 10

• involves two parents who differ from each other genetically
• offspring inherit different combinations of genes from each parent

Question 11

What is asexual reproduction?

Answer 11

• reproduction from a single parent

- produces offspring that are genetically identical to the parent

Question 12

What is horizontal gene transfer?

Answer 12

where genes are transferred across from an individual to others in the same generation. This doesn’t occur due to reproduction

Question 13

give two examples of horizontal gene transfer

Answer 13

• rapid evolutionary change
  
  • early evolution of prokaryotes there was a lot of horizontal gene transfer
• getting a gene from a neighbour is much faster than waiting for one to evolve .
• There are no guarantees that the transferred genetic material will give an advantage
• spread of antibiotic resistance
  
  • occurred through the transfer of plasmids carrying antibiotic resistance goes from bacteria to bacteria

Question 14

What is speciation?

Answer 14

Speciation is the generation of new biological species by evolution as a result of isolation, mutation and selection.

Question 15

What are the two types of speciation?

Answer 15

• allopatrick speciation

- sympatrick speciation

Question 16

What is a species?

Answer 16

a group of organisms capable of interbreeding to produce fertile offspring and which does not normally breed with other groups.

Question 17

What is allopatric speciation?

Answer 17

-This occurs when gene flow between two or more populations is prevented by a geographical barrier.

Question 18

What is the process of allopatric speciation?

Answer 18

• large interbreeding population is separated by a geographical barrier.
• now two or more populations
• separate populations mutate randomly
• natural selection favours the advantageous mutants
• over a long period of time natural selection increases the frequency of advantageous mutants
• speciation has occurred as even if the barrier was to be removed the different populations cannot interbreed and produce fertile offspring

Question 19

What is sympatric speciation?

Answer 19

-this occurs when gene flow between two or more populations is prevented by a behavioural or ecological barrier.

Question 20

What is the process of sympatric speciation?

Answer 20

• large interbreeding population sharing the same ecological niche
• alternative ecological niche appears
• some members of the population start to exploit to new niche
• the two populations now exploit different resources and no longer interbreed.
• Behaviour has become an isolation barrier
• mutants better adapted to exploit the new resources appear and successfully breed
• natural selection favours the new mutants and eventually over a period of time two genetically distinct species are formed which can no longer interbreed and produce fertile offspring.

Question 21

What is an ecological barrier?

Answer 21

• different habitats, breeding areas, pH and salinity

- groups are not geographically separated but are prevented from mating with each other

Question 22

What is a behavioural barrier?

Answer 22

• a population may carry out complex mating rituals that may create a barrier to reproduction.
• Different timings, locations or mating rituals may result in members of a population who are not geographically separated not being able to mate with each other.