Biology U4 T2 - Continuity of Life on Earth

Question 1

Evolution

Answer 1

the change in genetic composition of a population during successive generations which may result in the development of new species

Question 2

Microevolution

Answer 2

small-scale change in the variation of allele frequencies where the descendant is of the same taxonomic group as the ancestor and does not produce a new species

Question 3

Macroevolution

Answer 3

the accumulation of changes to allele frequencies at or above species level over geological time. The descendant is in a different taxonomic group to the ancestor and leads to a new species

Question 4

Evolutionary radiation

Answer 4

the increase in taxonomic diversity or morphological disparity

Question 5

Allele frequency formula

Answer 5

allele frequency =(2×(number of homozygotes)+(number of heterozygotes))/(2×(number of individuals) )

Question 6

Positive and negative allele frequency selection

Answer 6

• Positively selected for results in an increased percentage
• Negatively selected for results in a decreased percentage

Question 7

Phenotypic selection

Answer 7

Stabilising
o Most of population has common allele, fairly set, most suited to environment

Directional
o More individuals favour the previously extreme allele, change in environment, short time or extreme becomes stabilised

Disruptive
o Both extremes are favoured, short period of time, following random event, survival mechanism

Question 8

Microevolutionary change

Answer 8

Mutation
Random, new trait

Gene flow
Two separate populations come together, no new traits

Genetic drift
Random death, bottleneck effect, founder effect

Question 9

Speciation

Answer 9

A group within a species separates and develops unique characteristics

Question 10

Species diversification patterns

Answer 10

• Divergent shows one species evolving into more
• Convergent is when two species have similar environmental pressures
• Parallel shows a recent common ancestor with similar/same environmental pressures
• Coevolution shows evolution of one species based off another species (competition/predation)

Question 11

Modes of speciation

Answer 11

• Allopatric sees a barrier formed (geographical isolation) and the second population evolves separately
• Parapatric sees new niche (habitat fragmentation) and the species in the new niche evolve separately
• Sympatric sees genetic polymorphism (mutation) and the two populations live in different areas

Question 12

Mechanisms of isolation

Answer 12

Spatial isolation
Geographic isolation (larger space) (Isolation by physical/geographic barriers (seismic activity/natural disasters))
Decreased gene flow and breeding access (Oceans, mountains, rivers, deserts)
Habitat fragmentation (smaller space) (Portioning of singular habitat, Decreased genetic diversity/gene flow, Fallen trees, roads, dams)

Temporal isolation
Temporal (Breeding seasons, reproductive cycle length)
Anatomical differences
Pre-zygotic (Failure to fertilise or keep zygote alive)
Post-zygotic (Offspring cannot reproduce)

Question 13

Impacts of reduced genetic diversity

Answer 13

The lack of genetic diversity means a limited gene pool, lessened ability to adapt, reproductive unfitness