LO topic 6b

Question 1

Define evolution, and describe how the existence of fossil organisms supports the idea that organisms have slowly evolved over large time scales

Answer 1

Evolution - change in heritable characteristics of biological populations over successive generations.
Fossils like, nesting, faeces, bones, footprints and skin impression are all made overtime, the sedimentary layer of holds the fossil informs us of the timeline of evolution

Question 2

List the four postulates regarding populations proposed by Darwin and Wallace’s theory of evolution by natural selection

Answer 2

Genetic variation
Genetics are passed to offspring
Death of some
Survival and reproduction are not determined by chance but depends at least in part on heritable characteristics

Question 3

Define gene pool, gene flow and allele frequency;

Answer 3

Gene pool - A set that contains all of the alleles of all of the genes from all of the individuals in a population.
Allele frequency - An alleles proportion in a gene pool

Question 3

Define Hardy-Weinberg principle and its conditions

Answer 3

Hardy-Weinberg principle - Population geneticists use the term equilibrium population for the hypothetical non-evolving population in which allele frequencies do not change as long as the following conditions are met.
1. There must be no mutation
2. There must be no gene flow
3. The populations must be very large
4. All matings must be random with not endency for certain genotypes
5. There must be no natural selection. That is, all genotypes must reproduce with equal success.

Question 4

Define homologous and vestigial structures, and describe how their existence supports the theory of evolution;

Answer 4

Homologous structures - structures that are similar these show that there is a common ancestor.
Vestigial structure - Structure which no longer perform the function of which they originally evolved to do in the species ancestor
These support evolution as it provides evidence of common traits when sharing ancestors as well as providing evidence even when said structure does not aid the species

Question 5

define analogous structures; describe how biochemical and genetic analyses support the notion of evolution of all organisms from a common ancestor

Answer 5

Analogous structure - Non - homologous structures which serve similar functions evolved from convergent evolution as such they resemble each other. Consider birds and bees
By analysing biochemical and genetics (DNA barcoding is visual similarities of DNA coding) we are able to note similarities that may be genetically connected and traits which may have evolved due to environmental conditions. These imply and last universal common ancestor (LUCA)

Question 6

Define artificial selection, and list some examples of artificial selection and some examples that natural selection is occurring in present time

Answer 6

Artificial selection - Agrarian civilisations selecting certain traits in species.
Wild mustard plant has variated into kale, broccoli, cabbage and cauliflower
Cows bos indicus and bos taurus divided by north and south.
Natural selection example are insect becoming resistant to insecticides and the peppered moth darkening after the industrial revolution

Question 7

Define genetic drift, population bottleneck and the founder effect

Answer 7

Genetic drift - ‘drift in equilibrium’ shift in gene frequencies
Population bottleneck - A drastic size reduction in a population that results in less genetic variation
Founder effect - few individual become isolated from the main population and this results in divergent evolution

Question 8

Define adaptation, sexual selection, directional selection, stabilising selection and disruptive selection.

Answer 8

Adaptation - The process of change by which an organism or species becomes better suited to its environment. This may be a physical or behavioural change.
Sexual selection - A special kind of selection that acts on traits that help an animal acquire a mate. (peacocks)
Directional selection - Favours individuals with one extreme value of a trait (Finch beak size)
Stabilising selection - Favours individuals with the average value of a trait (beards)
Disruptive selection - Favours individuals on both extremes of a trait (horses and giraffes)