9.3 Genetic Diversity and adaptation

Question 1

what leads to genetic diversity

Answer 1

differences in DNA

Question 2

what is a gene

Answer 2

• a section of DNA that codes for one polypeptide
• all members of the same species have the same genes

Question 3

what is genetic diversity

Answer 3

• the total number of different alleles in a population

Question 4

what is a population

Answer 4

a group of individuals of the same species that live in the same place and can interbreed

Question 5

what is a species

Answer 5

• one or more populations
• the greater the number of different alleles all members of the species possess the greater the genetic diversity of that species

Question 6

advantage of genetic diversity

Answer 6

• the greater the genetic diversity the more likely that some individual in a population will survive an environmental change
• a wider range of alleles and wider range of characteristics
• gives a greater probability that some individuals will possess a characteristic that suits it to the new environmental condition

Question 7

reproductive success and allele frequency

Answer 7

1. within any population there will be a gene pool containing a wide variety of alleles
2. random mutations of alleles within this gene pool may result in a new allele of a gene which may be advantageous
3. these individuals will be better adapted and therefore more likely to survive as they are more likely to obtain the available resources so grow rapidly and live longer
4. better chance of breeding successfully and producing more offsprings
5. pass on their advantageous alleles unto their offsprings
6. over time the frequency of the advantageous alleles in the population increases whilst those of the non advantageous ones decreases

Question 8

what is selection

Answer 8

• the process by which organisms that are better adapted to their environment tend to survive and breed whilst those that are less well adapted tend not to

Question 9

what is directional selection

Answer 9

• selection that favours individuals that vary in one direction form the mean of the population
• changes the characteristics of the population

Question 10

what is stabilising selection

Answer 10

• selection that favours the averages
• preserves the characteristics of a population

Question 11

how does directional selection work

Answer 11

• if the environmental conditions change the phenotypes that are best utired to the new condition are most likely to survive
• some individuals will possess a phenotype more suited to the new conditions which will be more likely to survive and breed
• they will contribute more offspring to the next generation than other individuals

Question 12

direction selection in resistance to penicillin

Answer 12

1. a spontaneous mutation occurred in the allele of a gene in a bacteria than enabled it to make a new protein which was an enzyme (penicillinase) that broke down penicillin before it could kill the bacteria
2. the bacteria happened by chance to be in a situation where penicillin was being used to treat an individual, the mutation gave the bacteria an advantage in being able to use penicillin to break down the antibiotic and survive whilst the other bacteria dies
3. the surviving bacteria divided by binary fission to build up a population of penicillin resistant bacteria
4. these members were more able to survive and multiply and population increased
5. frequency of the allele that enables the production of penicillinase increased in the population
6. the population’s normal distribution curve shifted in the direction of a population having greater resistance to penicillin

Question 13

stabilizing selection in human birth weights

Answer 13

• infant birth rate is between 2.5 and 4 kg
• infant mortality increases when the baby’s weight falls outside this range

Question 14

what are natural selection adaptations

Answer 14

1. anatomical - fur for winter
2. physiological - oxidising fats for additional water
3. behavioural - migration