Natrual Selection

Question 1

Natrual selection

Answer 1

Main mechanism which drives evolution

Question 2

V M A S S R P A

Answer 2

Variation present due to mutation
Produce advantageous alleles
Selected for
Increases survival
Increases reproductive success
Alleles passed on
Allele frequency increases

Question 3

What are the 3 selection pressures

Answer 3

Predatation, disease, competition

Question 4

Stabalising selection

Answer 4

• occurs in an unchanging enviroment
• mean value for a characteristic is selected for
• extremes are selected against

Question 5

Example of stabalising selection

Answer 5

• birth weight
• large babies are selected against due to difficulties being born due to movement theough the cervix
• small babies are selected against due to SsA:V ratio being too large so they loose heat too quickly

Question 6

Directional selection

Answer 6

• occus in a changing environment
• one of the extrememe vaules for a cahracteristic is selcted for
  -the mean is selected against

Question 7

Example of directional selection

Answer 7

-antibiotic resistance in bacteria
-allele for resistance is selcted for in an environment where antibiotics are being used
-in this environment this is an advantageous allele so is passed on and allele frequency increases very quickly