17 Selection and evolution

Question 1

Define continous variation and how its caused

Answer 1

• phenotypes not in grous/categories
• phenotypes are quantative
• normal distribution
• polygenic/controlled by many genes
• diff genes have additive effect
• enviornmental factors contribute to variation

Question 2

Describe selective breeding could produce vraities of rice w fats growing stems

Answer 2

• crossbreed rice plants with fast growing stems
• select/choose + breed offspring with fast growing stems
• repeat crossing and selection over generations
• outbreed to avoid inbreeding depression

Question 3

Describe how SB can produce varities of rice w fast growing stems

Answer 3

• cross breed indivduals w fats growing stems
• select and choose + breed offspring w fast growing stems
• repeat crossing and selection over generations
• outbreed/outcross to avoid inbreeding depression

Question 4

Sympatric speciation

Answer 4

• diff habitats/eco isolation
• prevents interbreeding/no gene flow/ reproduction isolated
• polyploidy/genetically diff
• 1 is adapted to diff conditions than the other
• describe sympatric speciation
  -no geographical barrier / not geographically isolated ;
• behavioural isolation / described ;
  -to reproductive isolation / described

Question 5

Suggets why mtDNA used instead of nuclear DNA when studying closeness of rs between pops

Answer 5

• inherited from mother alone
• crossing over/recombinance doesnt occur
• many copies of mtDNA
• smaller
• not associated with histone proteins
• mtDNA analysis is quicker

Question 6

Explain why specific primers were used for tiger mtDNA sections

Answer 6

• to bind to complimentry base sequences in mtDNA
• amplify specific mtdNA sections

Question 7

define term haploid and diploid

Answer 7

• haploid is one (complete) set of chromosomes ;
• diploid is two (complete) sets of chromosomes ;

Question 8

3 examples of evidence obtained helped to confirm species are the same species

Answer 8

• interbreed to produce fertile offspring / not reproductively isolated
• occupy the same niche ;
• same / similar, morphology / physiology / biochemistry ;
• have, similar / same, genes / DNA sequences / genomes ;
• similar / same, proteins / amino acid sequences

Question 9

2 domains which are good sources of RE

Answer 9

• bacteria and archae

Question 10

suggest and explain what conditions of harvey weinberg principle are likely to be met in populations of rats on islands

Answer 10

• no flow of, alleles / genes, into / out of, the population ;
• population is isolated / described ; e.g. separated by geographical barrier
• random mating is occurring ;
• rats move around island / AW ;
  -large population ;
  -rats have high reproductive rate / no predators ;
• rats are diploid ;

Question 12

genetic drift

Answer 12

• genetic drift / not natural selection ;
• directional selection
  2 as small size in north not, adaptive / beneficial ;
  3 (small) lose heat faster / harder to keep warm ;
  4 smaller fat reserves not good with unstable food supply ;
  5 less food in north reduces, growth / size ;

Question 13

directional vs stabalising selection

Answer 13

• stabilising = when environment is stable/natural selection, no longer longer brings about change because organisms already well adapted
• directional = if environment changes alleles that were advantageous now disadvantages which is bad/genetic drift

Question 14

Disruptive selection

Answer 14

• Occurs when environmental conditions favour, both extremes of a population, but don’t against those who are in the middle
• maintains polymorphism and population and gene split some new species formed

Question 15

Continuous versus discontinuous variation

Answer 15

• Continuous = no distinct categories,quantitative, polygenic/controlled by many genes, influenced by environment
• discontinuous = categorical, qualitative controlled,genetucally detremined, unaffected by environment

Question 16

how do hybrid populations compare to pure subspecies?

Answer 16

• (hybrid populations have) more, genetic variation / alleles ;
• genes / mutations / alleles, from both (sub)species ;
• more potential to adapt / can adapt better (in future) ;
• genes / alleles, for migration may let some find new habitats ;
• have, genes / alleles, for, warm and cold / different temperatures ;