Topic 2: Community of life on Earth

Question 1

define microevolution

Answer 1

refers to the small-scale variations of alleles, in which the descendant is of the same taxonomic group as the ancestor

Question 2

define macroevolution

Answer 2

the variation of allele frequencies at or above the level of species over geological time - results in the divergence of taxonomic groups

Question 3

what is evolutionary radiation?

Answer 3

an increase in taxonomic diversity or morphological disparity / rapid increase in the diversity of a clade

Question 4

define extinction

Answer 4

the reduction of a species to zero individuals

Question 5

define mass extinction

Answer 5

widespread event defined as a loss of 75% of all species in existence across the planet (over a “short” geological period)

Question 6

what is comparative genomics

Answer 6

field of biological research in which the genomic sequences and associated gene products of different species are compared using computer-based analysis

Question 7

define natural selection

Answer 7

the mechanism by which evolution occurs; descent with modification

Question 8

explain natural selection using the two key terms

Answer 8

individuals that are better suited to the environment have higher VIABILITY and are therefore more likely to survive and have higher FECUNDITY (ability to produce offspring)

Question 9

what happens to ‘selected traits’

Answer 9

will become more prevalent in the population

Question 10

what is positive selection

Answer 10

-type of selection pressure
- favours a particular allele, resulting in an increase in frequency

Question 11

what is negative selection

Answer 11

-type of selection pressure
- acts against a particular alleles, resulting in a decrease in frequency

Question 12

what are the three types of phenotypic selection

Answer 12

• stabilising selection
• directional selection
• disruptive selection

Question 13

define stabilising selection

Answer 13

intermediate phenotypes are better suited to environment over extreme phenotypes
- tends to narrow (stabilise) the normal curve, leading to a decrease in genetic variance –> more common when environmental conditions are stable and extreme phenotypes are disadvantageous

Question 14

define directional selection

Answer 14

occurs when one extreme phenotype is better suited to the environment over all other phenotypes
- shifts the normal curve towards the favoured phenotype - also leads to reduced genetic variation
- (individuals with a moderate phenotype will remain within the population)
- occurs due to gradual or sustained change in environmental conditions

Question 15

define disruptive selection

Answer 15

• individuals at either end of the ‘normal range’ are favoured over individuals in the middle (both extremes)
• leads to bimodal spread - giving rise to increased genetic variation in two distinct pop.s

Question 16

what is gene flow

Answer 16

(migration)
- genes flow between populations
- alleles are added/ removed from gene pool due to movement of fertile individuals between populations

Question 17

what is genetic drift

Answer 17

when chance or random events cause unpredictable changes in allele frequencies from one generation to the next
- founder effect + bottleneck effect are the mechanisms that drive this

Question 18

explain the founder effect

Answer 18

• colonising chance event
• small group of individs are separated from the larger OG pop. and colonise a new area
• this smaller pop. doesn’t have the same diverse gene pool as the OG - resulting in dif. allele freqeuncies

Question 19

explain the bottleneck effect

Answer 19

• catastrophic chance event
• OG pop is significantly reduced in number - leading 2 smaller gene pool and large decline in allele frequency
• reduced genetic variation– predisposes species to the risk of extinction

Question 20

‘recall that speciation and macroevolutionary changes result from an accumulation of microevolutionary changes’

Answer 20

microevolution - observed thru genetic and phentypic changes – lead to new variation but no new species
macroevolution - changes occur over extended period - give rise to a new species (speciation)

Question 21

microevolution + time =

Answer 21

macroevolution

Question 22

what is divergent evolution

Answer 22

process by which distinct species arise from a common ancestor (speciation)
- isolated populations experience dif selective pressures - drives different adaptations

Question 23

what is convergent evolution

Answer 23

different, unrelated species evolve from their respective ancestral species to have similar analogous structures that perform comparable functions
- exposed to similar selective environmental pressures
- still remain different species

Question 24

what is parallel evolution

Answer 24

two species w/ a common ancestor evolve similar traits independent of one another
- similar selective pressures post separation

Question 25

what is coevolution

Answer 25

the influence of species on each other and their evolution
- dif species evolve in tandem by exerting selection pressures on each other

Question 26

what does allopatric mean

Answer 26

• speciation - occurs as a result of geographic isolation separating pop.s of a species (e.g. mountain or river)
• leads to reproductive isolation - where alleles are no longer exchanges between pop.s

Question 27

what is parapatric speciation

Answer 27

occurs when pop/s from the same species become reproductively isolated without geographical separation - while continuing to exchange genes
- signif. variation in habitat conditions

Question 28

what is sympatric speciation

Answer 28

when pop.s from the same species become reproductively isolated and diverge w/out geographical separation
- can occur via temporal (time) isolation (e.g. breeding times dont align with each other)

Question 29

define spatial isolation

Answer 29

any form of isolation that leads to physical separation (e.g. natural disasters)

Question 30

what is habitat fragmentation

Answer 30

• the breakup of a species’ territory
• isolated gene pools - preventing exchange of alleles and results in genetic drift

Question 31

what is geographical isolation

Answer 31

• pop. separated by physical barriers

Question 32

what is temporal isolation

Answer 32

• isolated in time
• individs prevented from mating because they breed at dif times

Question 33

what is reproductive isolation

Answer 33

any form of isolation that prevents gene flow
- sptial and temporal both result in this
- can also link to behavioral isolation

Question 34

what does SNPs stand for/ mean

Answer 34

Single Nucleotide Polymorphism
- a point mutation (single base) in a segment of DNA that occurs in MORE THAN 1% of the pop.

Question 35

why dont SNPs impact cellular function

Answer 35

• mostly occur in the introns (DNA between genes) and therefore has little effect on cellular function
• as a result - not ‘selected’ out of the population and can be used to determine the timing of splits between species