4.2.3 Speciation and Macroevolution Flashcards
define 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— QCAA
Results from the accumulation of microevolution changes over time to create new species
Define speciation
the evolutionary process by which new and distinct speacies are formed
In macroevolution, diversification can follow these four processes: ___?
- Divergent evolultion
- Convergent evolution
- Parallel evolution
- Coevolution
Understand what divergent evolution is
Descandants becoming different from one common ancestor. Occurs from environment pressures (like a competition for resources, new niches becoming available etc.)
*Any individual with a variation (from mutation) can expoit resources for an advantage
*Eventually these 2 groups will become so different they wont be able to breed together
Understand what convergent evolution is
The independent development of two different species, becoming similar because of similar environments
Understand what parallel evolution is
Independent evolution of similar traits in species that once shared a common ancestor
They continue staying similar without becoming one species or getting further apart (parallel along the evolution line)
Understand what coevolution is
- Occurs when 2 or more species reciprocally affect each other’s evolution
- Results in simultaneously phenotypic changes between community member
Results in the species to rely on each other (ex. Predator/prey or parasite/prey)
What are the three modes of speciation
- Allopatric
- Sympatric
- Parapatric
Understand what allopatric speciation is
When a species is divided geographically (mountain or river forming) which separates this species meaning they could evolve traits separately from one another; eventuating into too much genetic variation to breed together, meaning they become different species over time
*gene flow needs to be greatly reduced
Understand what sypmatric speciation is
Either a species population will become different without any physical separation (rare) through reproductive cycles varying or behavioural differences causing isolation
or more commonly: through polyploidy in the zygote (more than two sets of chromosomes resulting in more genetic variation as more phenotypes are possible to be present) —these new species will be tetraploid (4n) rather than diploid (2n) meaning the tetraploid can’t reproduce with the diploid.
Understand what parapatric speciation is
A species population becomes reproductively isolated due to the significant variation of habitat conditions (partial spatial separation) without becoming geographically separated.
Over time these species may have a hybrid zone however they typically won’t interbreed, eventuating to speciation
What are the different factors that affect isolation?
- Spatial isolation
- Temporal Isolation
- Reproductive
What is spatial isolation
*Hint: Usually associated with allopatric speciation
isolation that leads to physical separation
Can occur by:
- natural disasters (separating a population into groups, reducing the amount of species which can result in gentic drift)
- habitual fragmentation (natural or human caused which can result in a reduced gene pool and genetic drift)
- geographic isolation (physical barriers)
What is temporal isolation
*Hint: Usually associated with sympatric speciation
-Indiviuals are prevented from breeding as their reproductive cycles are out of sync (different times)
What is reproductive speciation
*Hint: spatial and temporal isolation can lead to it
any isolation preventing gene flow between indivuals
Including:
-hybrid inviability/ steribility (species offspring that cannot reproduce e.g. a mule)
How can population size effect genetic diversity
What is a population bottleneck?
Events that substantially reduces the size of a population and thus its genetic diversity
-could be from floods, fires, over hunting etc
Results in:
allele frequencies in new groups may be different from original (some alleles may be missing)
new population will be more vulnerable to genetic drift
Explain how a population with small genetic diversity face and increased risk of extinction
•Without genetic variation, a population cannot evolve in response to changing environmental variables –> may face increased risk of extinction.
e.g. tasmanian devils
