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Unit 4 Topic 2

Continuity of Life on Earth

Define evolution Evolution is the change in the genetic composition of a population during successive generations, which may result in the development of new species.
Define microevolution Microevolution is small-scale variation of allele frequencies within a species or population, in which the descendant is of the taxonomic group as the ancestor.
Define macroevolution Macroevolution is 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 from the ancestor.
What is evolutionary radiation? an increase in taxonomic diversity or morphological disparity
What is genetic drift? A change in the gene pool of a population as a result of chance; usually occurs in small populations
What is the bottle-neck effect? when a catastrophic event or a period of adverse conditions drastically reduces the size of a population.
What is the founder effect? a type of gene flow that occurs when a few individuals that have become isolated from a larger population do not carry all the alleles that were present in the original population.
What is viability? capability of living
What is fecundity? a measure of fertility, the capacity to reproduce
What are 5 examples of selection pressures? 1. competition between species for food/territories 2. predator-prey relationships 3. competition within species for food/water 4. competition within species for territories/nesting places 5. sexual selection -selection of traits that attract males
What are the three main types of phenotypic selection? 1. stabilising selection 2. directional selection 3. disruptive selection
What is stabilising selection? What does this look like on a graph? A form of selection that tends to advantage organisms similar to their parents; this usually occurs when the environment is very stable and unchanging, and selects against extremes of phenotypes. Peak narrows - mean does not change.
What is directional selection? What does this look like on a graph? a form of selection that selects against one of two extremes and leads to a change in a trait over time. Mean/peak shifts
What is disruptive selection? What does this look like on a graph? a form of selection that operates in favour of extremes and against intermediate forms. Two peaks form
What is gene flow? gene flow is the transfer of alleles that results from emigration and immigration between populations.
What is descent with modification? Descent with modification is Darwin's terminology indicating that life today has descended and evolved from common ancestors that were generally different from their modern descendants.
What is reproductive isolation? Reproductive isolation is the separation of populations that are unable to interbreed because of changes that produce physical, biological or behavioural barriers.
What is a pre-reproductive isolating mechanism? a mechanisms that prevents organisms from being able to interact to reproduce.
What are 4 examples of pre-reproductive isolating mechanisms? Geographical mechanisms temporal mechanisms behavioural mechanisms morphological mechanism
What is a post-reproductive isolating mechanism? a mechanisms that prevents fertilisation occuring or an embryo developing into viable offspring if reproduction does occur.
What are 3 examples of post-reproductive isolating mechanisms? gamete mortality zygote mortality hybrid sterility
What are the three modes of speciation? 1. allopatric 2. sympatric 3. parapatric
What is allopatric speciation? Speciation due to physical or geographic isolation.
What are some examples of things that can cause allopatric speciation? 1. water 2. mountains 3. continental drift 4. rising sea levels 5. climate change
What is sympatric speciation? speciation that occurs without physical or geographic isolation. Generally arises from reproductive isolation instead.
What is parapatric speciation? Speciation that occurs when populations are separated by an extreme change in habitat: populations may interbreed in bordering areas (hybrid zone)
What are the four patterns of evolution? 1. Divergent 2. Convergent 3. Parallel 4. Co-evolution
What is divergent evolution? a process whereby related species evolve new traits over time, away from the common ancestor, to give rise to new species. eg. koalas, Tasmanian devils and marsupial moles.
What is convergent evolution? a process whereby unrelated organisms evolve similar adaptations in response to similar environmental pressures. Eg. anteaters, echidnas, pangolins etc.
What is parallel evolution? a process whereby unrelated organisms evolve similar adaptations in response to the same environmental pressure. eg. sugar glider and flying squirrel
What is coevolution? a process whereby an evolutionary change in one species influences the evolution of another species.
Created by: Caitlyn_01
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