Unit 4, Topic 2: Continuity of life on Earth Flashcards
Define the term “evolution”
Change in the genetic compostion of a population during successive generations, which may result in the development of new species.
Define the term “macroevolution”
The variation of allele frequencies at or above the level of species over geological time, resulting in the divergence of taxonomic groups, in which the descendant is in a different taxonomic group to the ancestor.
Define the term “microevolution”
Small scale variation of allele frequencies within a species or population, in which the descendant is in the same taxonomic group as the ancestor.
Finish the sentence.
“Natural selection occurs when…
the pressures of environmental selection confer a selective advantage on a specific phenotype to enhance its survival and reproduction.”
Selection of a gene pool can be positive or negative. Is this T/F?
True
What are the three phenotypic selections? Draw diagrams to accompany answer
Stabilising, directional, disruptive
Explain microevolutionary change through the main processes of mutation, gene flow and genetic drift.
Mutations -> introduce a mutated, new allele which either survive or die out
Gene flow -> organisms migrate in or out of population which can introduce new allels or decrease no.
Genetic drift -> random acts of chance (bottle neck - segregates specific phenotypes), (founder affect - part of pop gets moved to new location and colonise) - > separates alleles
=> changes in allele frequencies of a population however it is not enough (time) to create a new species.
speciation and macroevolutionary change results from…
an accumulation of microevolutionary changes overtime
what are the four patterns of evolution (ways a new species can be created). accompany answer with simple diagram
Divergent, convergent, paralell, coevolution
Describe the modes of speciation.
Allopatric speciation - separated by physical barrier and creates isolated pop.
Parapatric speciation - occurs when a population occupies DIFFERENT niches. they differ by eological factors. Gene flow however they become reproductively isolated.
Sympatric speciation - speciation occurs within a single populaiton in the SAME place. e.g behavioural isolation (prefer different mating calls) or temporal isolation (different times of day) results in reproductive barrier. reduces gene flow, creating two isolated populations which face different selective pressures.
WHat are the five main mechanisms of isolation that influence gene flow?
Geographic, temporal, behavioural, morphological / mechanical, gametic isolation (fertilisation does not occur - not genetically compatible)
Explain how populations with reduced genetic diversity face an increased risk of extinction.
The environment of a population is always changing. With this comes selective pressures in which certain phenotypes will be favoured in order to promote population survival and reproduction. when genetic diversity is low, there are less phenotypic variations present and a lower chance that there is one present which will be able to positively respond to any environmental pressures. Therefore pops with reduced genetic diversity have a smaller chance of a phenotype being favoured and thus are at a higher risk of extinction.
