Microevolution Flashcards
Darwin’s four postulates
variation, inheritance, selection and not random over time.
Individuals within a population are variable.
Some variations are passed on to offspring.
Some individuals are more successful at surviving and reproducing than others.
The survival and reproduction of individuals are not random – individuals that survive and reproduce the most are those with the most favourable variations.
What is Cladogenesis?
the formation of a new group of organisms or higher taxon by evolutionary divergence from an ancestral form.
What is the difference between micro and macro evolution and what is the link between them?
microevolution- within species (intraspecific competition) = anagenetic change
macroevolution- variation between species= clade evolution
There is a link between these= speciation
What did Peter and Rosemary Grant do on la Isla daphne major
Case study on natural selection from over 40 years of research on Darwin’s finches on the tip of a volcano island
advantages;
*small study site
*ability to measure every species
*not a lot of vegetation variety so condition are tough (linked with beak morphology)
they caught the finches in nets and measure beak depth, length and number of individuals
How can we use the 4 postulates in the example of the galapagos ground finches?
Individuals were variable at the start
during a drought there was an 84% reduction in the population due to starvation (less seeds and harder seeds). which proves some individuals are more successful at surviving and reproducing than others over time. survival was non-random with respect to beak depth.
These larger-billed survivors went on to reproduce.
The ‘struggle for existence’ Malthus ideas (economics)
Malthus: Animal populations should outgrow limited resources very quickly.
Individuals with advantageous variations would do better in the struggle for survival.
These individuals would produce more offspring.
Adaptation
Organisms appear well ‘designed’ for their environment.
But the ‘designs’ are the result of chance and selection.
‘Adapted’ for different environments or niches.
An adaptation is:
- A trait that enables an organism to survive and reproduce better than if it lacked the trait.
Describe Fitness (species or genetic)
A measure of individual success in evolutionary terms.
OR
The average number of offspring produced by individuals with one genotype relative to the number produced by individuals with different genotypes.
Describe heritability
1.0= where heritability is perfect
The galapogos finches with larger beaks produced offspring with larger beaks and a heritability of h^2=0.65
the genetic drivers of this were ALX1 gene regulating activity of the expression of Bmp. This gene during embryo development can have upregulation or downregulation of the gene. ALX1, is involved in the facial development.
A definition of natural selection
“The differential reproductive success of different heritable phenotypes”
the finches have had a directional selection
What is microevolution linked to?
microevolutionary process are linked to the ecology of the different organisms
