Topic 2: Community of life on Earth

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

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

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

the reduction of a species to zero individuals

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

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

the mechanism by which evolution occurs; descent with modification

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)

will become more prevalent in the population

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

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

• stabilising selection • directional selection • disruptive selection

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

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

• 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

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

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

• 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

• 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

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)

macroevolution

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

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

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