5.2 natural selection

Question 1

what are the 3 causes of variation

Answer 1

mutation,
meiosis,
sexual reproduction and random fertilisation

Question 2

how does mutation lead to genetic variation

Answer 2

any change to the DNA sequence of an organism, in base substitution, deletion, insertion or translocation, may form new alleles

mutation types: missense, nonsense, silent

Question 3

how does meiosis affect genetic variation

Answer 3

in crossing over of prophase 1:
non-sister chromatids touch or cross over each other, and genes can be exchanged resulting in new combo of genes on chromosome

in independent assortment of chromosomes of metaphase 1:
homologous chromosomes randomly line up leading to new combinations of genes in gametes

Question 4

how does sexual repro and random fertilisation lead to genetic variation

Answer 4

random combination of gametes, resulting in a zygote with genes from both parents

Question 5

what does producing more offspring result in (2)

Answer 5

higher chance some survive
+
ensures power struggle within population, indirectly ensuring individuals best adapted to the environment will survive

Question 6

explain the steps of natural selection / evolution

Answer 6

overproduction of offspring with genetic differences (useful and harmful variations)

eradication of poorly adapted individuals

thriving of well adapted individuals

surviving organisms that reach reproductive age pass their favourable genetic characteristics to next generation

change in gene pool as there is an accumulation of changes in the heritable characteristics of a population –> evolution

Question 7

reasons for development of antibiotic resistance in bacteria

Answer 7

bacteria generation times are short

widespread use of antibiotics

often coded for by a gene or genes located on plasmids, easily exchanged between bacteria

hospitals are breeding grounds for antibiotic resistance