A4.1 - speciation (5s) Flashcards
(18 cards)
What is speciation?
Speciation is the process by which new species appear.
When does speciation occur?
Speciation only occurs by splitting of pre-existing species.
What are the consequences of speciation?
Speciation increases the total number of species on Earth, and extinction decreases it.
What is not an example of speciation?
Gradual evolutionary change is not speciation, even though individuals of that species from different points in evolutionary time may have very different traits.
What is required for speciation to occur?
For speciation to occur, there must be prolonged reproductive isolation of separated populations of species.
What is reproductive isolation?
When two populations of a species are not able to interbreed.
What are the causes of variation in each population?
- Mutation
- Meiosis
- Sexual reproduction
How is reproductive isolation reached?
Geographic isolation is a means of achieving reproductive isolation.
When does geographic isolation occur?
When physical barriers prevent individuals from different populations meeting.
What is a natural example of geographic isolation?
- Hawaiian tree snails separated by volcanos.
What is a human example of geographic isolation?
Great Wall of China
Why will natural selection result in different traits becoming more prevalent in isolated populations.
Each population will:
- have different variants (from mutation, meiosis and sexual reproduction)
- experience different selection pressures, leading to increases in the frequency of the adaptation traits in the population, and therefore,
- have different adaptations that are advantageous, leading to their selection, with increases survival and reproduction
What is genetic divergence?
An increase in the genetic differences between 2 populations.
How do we know speciation has occurred?
Speciation has occurred when interbreeding individuals from the two populations become impossible as no fertile offspring is produced.
How does natural selection lead to speciation?
- natural selection requires that variation exists within a species
- variation arises randomly due to mutation
- natural selection is caused by selection pressures in the environment
- natural selection occurs when there is competition for resources
- well-adapted individuals survive and reproduce
- genes that are advantageous are selected for
- geographical factors may lead to reproductive isolation
- genetic divergence may also lead to reproductive isolation
- prolonged reproductive isolation leads to speciation
- genetic divergence increases further
what is an example of a case study on how populations of the original species may show divergence in characteristics due to differential selection?
The separation of bonobos and common chimpanzees by the Congo river, which prevented the individuals from meeting and interbreeding.
- differences in the population began to arise as new alleles and combinations of alleles formed at random
- to the north-east and south-west of the Congo river are different habitats and food resources, as well as different challenges such as the presence of snakes
What physical differences could be seen from the case study between chimpanzees and bonobos?
physical differences: in comparison to the chimpanzees, bonobos tend to:
- be smaller
- have a darker face
- have longer limbs compared with their body length
What behavioral differences could be seen from the case study between chimpanzees and bonobos?
behavioral differences: in comparison to the chimpanzees, bonobos tend to:
- have higher-pitched vocalisations
- hunt less, and forage in larger groups
- be more nomadic and have a matriarchal society, while chimpanzee groups have an alpha-male, with males tending to be more aggressive and territorial
