Evolution & Speciation Flashcards
Ageing
Change in individual over time
Metabolism
Organism changing the environment
Evolution
Permanence change in a population over time, due to external pressures and random genetic mutations. These changes may not be observable from one generation to the next but the process over time will cause visible change to the species.
Lamarcks Theory
“Use and disuse, life evolves as environments change” Certain organs and traits can be “developed” as a result of an environmental need (selection pressure) as they are used more often and therefore are more developed. The more developed organs will be inherited by offspring and thus a species will evolve. Individuals therefore lose characteristics they do not require, or use.
Giraffe Example (Lamarck)
Giraffes stretch their neck to reach food high in trees - this strengthens and lengthens the neck and is passed on to offspring.
Darwins Decent with Modification
Individuals in a population vary in their heritable characteristics - some of which are more suited to the environment and are therefore selected for, and give rise to visible change in the species as a whole.
Natural Selection
Environmental pressures give advantage to certain traits - therefore some individuals within the population are more likely to survive and pass on their genes - causing the species to change and evolve over time
Four basic principles of evolution by natural selection
- Individuals are not identical
- Some of the variation between individuals is heritable
- All populations are cabale of exponential growth but have limited resources… therefore….
- Variations that increase survival and reproductive success are more likely to be passed down to others
Therefore…..
The heritable features that define a population will change over time.
Speciation
Formation of new and distinct species by splitting a single lineage into two or more genetically seperate ones
What drives speciation
- Barrier formed
- New Habitat
- Genetic Change
Allopatric Speciation
Formation of species that are geographically isolated from one another ( Selection pressures are slightly different and mutations aren’t being transferred within the two groups, thus speciation occurs. )
Peripatric Speciation
small groups of individuals break off from the larger group and form a new species
Parapatric Speciation
Species spread out over a large area and individuals only mate with those in their own geographic region - various niches within the same habitat
Sympatric Speciation
No physical barriers & close proximity BUT a new species spontaneously develops through genetic change
Herbert Spencer described evolution as …
Survival of the fittest
Herbert spencer definition of fitness
The contribution made to a population of descendants by an individual relative to the contribution made by others in its present population. (all about relativity)
Selection Pressure
Evolutionary force that causes a particular phenotype to be more favourable in certain environmental conditions - considered the driving force of evolution via natural selection
How do selection pressures have such an effect over a short period of time?
Their ability to vary and change DNA within a population can happen rapidly due to high reproduction rates and very large population sizes.
2 key points of antibiotic resistance
- Natural selection is a process of editing rather than creating
- Natural selection depends on time and place
Mutation
Permanent change to the base code of DNA
Gametic cell
Gametes - involved in sexual reproduction
Somatic cell
Not involved in reproduction - any mutations to these cells CAN NOT be passed fown
Effect of mutation
- Some result in no change, others cause a functional change (+/-) and rarely, they are fatal.
Rates of mutation (mammals compared to bacteria)
Estimated mutation rate in all species is 1 per 100,000 genes per generation. - therefore rate of reproduction significantly influences rate of mutation. Mammals have much slower rates of mutation compared to bacteria - which mutate fast thereby evolve quickly
Is evolution goal oriented
No, evolution does not aim to achieve a specific outcome.
Genetic Drift
Unpredictable fluctuations in allele frequency from one generation to the next - smaller populations are more vulnerable_
Genetic Drift result
Loss of certain alleles/alter the allele frequency, a small subset of survivors are left to rebuild the entire population therefore their alleles become dominating.
Intersexual Selection
Form of natural selection in which individuals of one sex (usually females) are choosy in selecting their mate of the other sex. Also known as mate selection (higher genetic fitness of offspring)
Intrasexual Selection
Form of natural selection in which their is competition amongst one group of the same sex (males) for mates of the opposite sex (responsible for the formation for deer horns etc)
Coevolution
Changes in at least two species genetic compositions that reciprocally affect each others evolution
Light zone in germinal centre
B-Cells proliferate and activate
Dark zone in germinal centre
B cells start adding point mutations - small changes
Antibiotic resistance
Bacteria’s ability to vary and change their DNA within a population can happen rapidly due to high reproduction rates and very large population sizes. When a person is infected with staph, there may be a few bacteria that are drug resistant by chance. Over time, the population can become resistant as those that aren’t die off and the drug resistant staph survive, reproduce and descendants inherent drug resistance.
Evolution in germinal center
Once b cells add the point mutations, they go into the light zone and compete. Each B-cell has lsightly different antibodies (due to mutation) and those that are stronger survive, and the weaker ones die. = antibodies get better and stronger over time, allowing us to develop a better antibody to fight the infection.
Are mutations directed
NO - Mutations are NOT directed. They are simply random but may OR MAY NOT bring advantage when that pressure is there. Without a selection pressure the mutation means nothing.
Species
a group of populations who’s members have the potential to interbreed and produce viable fertile offspring.
