Speciation and Macroevolution Flashcards
4.2.9 Recall that speciation and macroevolutionary changes result from accumulation of microevolutionary changes over time.
4.2.10 Identify that diversification between species can follow four patterns: divergent, convergent, parallel, and coevolution
Describe the process of speciation (macroevolution)
Natural selection is the driving force of evolution and causes some alleles to increase or decrease in frequency, depending on their effect on the viability and fecundity of the organism. Environmental conditions change over time, altering the environmental selective pressures on a population. Allele frequencies change through gene flow, genetic drift, mutations and natural selection. Eventually the population change may change so much through an accumalation of microevolutionary changes that it is deemed a new species.
4.2.9 Recall that speciation and macroevolutionary changes result from accumulation of microevolutionary changes over time.
4.2.10 Identify that diversification between species can follow four patterns: divergent, convergent, parallel, and coevolution
Describe the process of speciation (macroevolution)
Natural selection is the driving force of evolution and causes some alleles to increase or decrease in frequency, depending on their effect on the viability and fecundity of the organism. Environmental conditions change over time, altering the environmental selective pressures on a population. Allele frequencies change through gene flow, genetic drift, mutations and natural selection. Eventually the population change may change so much through an accumalation of microevolutionary changes that it is deemed a new species.
4.2.9 Recall that speciation and macroevolutionary changes result from accumulation of microevolutionary changes over time.
4.2.10 Identify that diversification between species can follow four patterns: divergent, convergent, parallel, and coevolution
Describe the patterns of speciation.
When different species originate from a common ancestor, they diversify as they continue to accumalate genetic variations through mutations and genetic drift. Different mutations and selection pressures drive this divergence. In some cases, similar environmental selection pressures can lead to genetically distinct species sharing similar morphology or behaviours. There are four different patterns of speciation: divergent, convergent, parallel, and coevolution.
4.2.9 Recall that speciation and macroevolutionary changes result from accumulation of microevolutionary changes over time.
4.2.10 Identify that diversification between species can follow four patterns: divergent, convergent, parallel, and coevolution
What is divergent evolution?
Divergent evolution involves the differentiation of distinctly different species from a common ancestor. It results when populations become isolated and they accumalate genetic differences. For example, homologous features may become different, with a different function. It represents the evolutionary pattern in which species sharing a common ancestry become more distinct due to differential selection pressure which gradually leads to speciation over an evolutionary time period. Darwin’s finches are one example of divergent evolution as they moved to two different isalnds with different environments and food sources. Different beaks, body size and behaviours allowed access to these different seed types.
4.2.9 Recall that speciation and macroevolutionary changes result from accumulation of microevolutionary changes over time.
4.2.10 Identify that diversification between species can follow four patterns: divergent, convergent, parallel, and coevolution
Explain covergent evolution and provide an example.
Convergent evolution involves the evolution of similar features through natural selection in unrelated groups of organisms. These features are termed analogous structures. Unrelated species that have adapted to a particular environment in similar ways are said to have converged and evolved similarities in their phenotypes - but remain seperate species that do not interbreed. Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. For example, sharks and dolphins look relatively similar despite being entirely unrelated.
4.2.9 Recall that speciation and macroevolutionary changes result from accumulation of microevolutionary changes over time.
4.2.10 Identify that diversification between species can follow four patterns: divergent, convergent, parallel, and coevolution.
Explain parallel evolution and provide an example.
This type of evolution occurs when two species evolve independently of each other, maintaining the same level of similarity. It usually occurs between unrelated species that are geograhically isolated. Parallel evolution implies that two or more lineages have changed in similar ways, so that the evolved descendants are as similar to each other as their ancestors were. The evolution of marsupials in Australia, for example, paralleled the evolution of placental mammals in other parts of the world.
4.2.9 Recall that speciation and macroevolutionary changes result from accumulation of microevolutionary changes over time.
4.2.10 Identify that diversification between species can follow four patterns: divergent, convergent, parallel, and coevolution.
Explain coevolution and provide an example.
Coevolution results in simultaneous phenotypic adjustments between two species that are very reliant on each other. Each species exerts a strong selective force on the other (predator/prey). Microevolution causes small changes which cayse a corresponding selection pressures in the associated species. As a result, the gene pool of both populations changes in a particular direction. Mimicry is an example of coevolution. It occurs when one organism evolves to look like the other in order to benefit itself. The mimic benefits the situation while the organism it mimics is unaffected.
4.2.11. Describe the modes of speciation; allopatric, sympatric, parapatric
4.2.12 Understand that the different mechanisms of isolation
- geographical, reproductive, spatial, and temporal influence gene flow.
What are isolating mechanisms?
Isolation of groups of organisms in a population through spatial or temporal can result in the seperation of a lineage. Geographical and temporal isolation limits gene flow between populations and microevolution occurs due to genetic drift. New mutations appear in seperated populations and eventually new species arise. Once new species form, isolation mechanisms keep the groups speerate and usually prevent interbreeding between the species. Genetic isolation can be prezygotic (before reproduction) or postzygotic (occurring after reproduction).
4.2.11. Describe the modes of speciation; allopatric, sympatric, parapatric
4.2.12 Understand that the different mechanisms of isolation
- geographical, reproductive, spatial, and temporal influence gene flow.
Describe prezygotic isolating mechanisms.
Prezygotic isolation occurs before the formation of a zygote can take place. In most cases mating does not even occur. Therefore it is an obstacle to mating or to fertilisation if mating occurs.
4.2.11. Describe the modes of speciation; allopatric, sympatric, parapatric
4.2.12 Understand that the different mechanisms of isolation
- geographical, reproductive, spatial, and temporal influence gene flow.
Define habitat isolation.
two species live in the same general area but not the same kind of place.
4.2.11. Describe the modes of speciation; allopatric, sympatric, parapatric
4.2.12 Understand that the different mechanisms of isolation
- geographical, reproductive, spatial, and temporal influence gene flow.
Define temporal isolation.
Occurs when two species mate at different times of the year. Lions and tigers can potentially interbreed, but usually occupy different habitats.
4.2.11. Describe the modes of speciation; allopatric, sympatric, parapatric
4.2.12 Understand that the different mechanisms of isolation
- geographical, reproductive, spatial, and temporal influence gene flow.
Define temporal isolation.
Occurs when two species mate at different times of the year. Frogs live in the same pond but dbreed during different seasons (summer vs spring).
4.2.11. Describe the modes of speciation; allopatric, sympatric, parapatric
4.2.12 Understand that the different mechanisms of isolation
- geographical, reproductive, spatial, and temporal influence gene flow.
Define behavioural isolation.
Occurs when two species have different courtship behaviours. Certain groups of birds will only respond to species-specific mating calls.
4.2.11. Describe the modes of speciation; allopatric, sympatric, parapatric
4.2.12 Understand that the different mechanisms of isolation
- geographical, reproductive, spatial, and temporal influence gene flow.
Define mechanical isolation.
occurs when physical differences prevent copopulation/pollination. Certain breeds of dog are morphologically incapable of mating due to size.
4.2.11. Describe the modes of speciation; allopatric, sympatric, parapatric
4.2.12 Understand that the different mechanisms of isolation
- geographical, reproductive, spatial, and temporal influence gene flow.
Define gametic isolation.
Reproductive Isolation where mating does occur, but male and female gametes cannot bind to form a zygote. For example, surface proteins on the eggs of one species prevent sperm of the wrong species from entering.
