3.2 natural selection Flashcards
what are the key points of evolution
- living oganisms that reproduce ssexually show a great deal of variety in their appearance
- organisms produce excess offspring - because many don’t survive to reproduce so there is competition between members of the same species
- organisms that inherit characteristics that give them an advantage are most likely to survive and pass it on to their offspring
- organisms that inherit characteristics that put them at a disadvantage will be more likely to die out before they reproduce
what is survival of the fittest
- organism with the greatest ability to survive and reproduce in the environment it’s living in is most likely to survive
what is natural selection
the process by which fitter individuals who are better adapted to the environment are more likely to survive and reproduce and pass on advantageous alleles to their offspring
what tends to cause a change in the frequency of a particular allele
- always driven b a change in the organisms environment, o9r by the organism moving to a slightly different environment
define evolution
the process by which the frequency of alleles in a gene pool changes over time as a result of natural selection
what is a niche
an organisms role within a habitat
whats are the ways that organisms can be adapted to their niches
- anatomical adaptations
- physiological adaptations
- behavioural adaptations
how are organisms adapted to their niches anatomically, give an example
- involves the form and structure of an organism, physical adaptations
- loop of henle in desert animals allowing them to produce concentrated urine and minimise water loss
how are organisms adapted to their niches physiologically, give an example
- involves the biochemical pathways (hormones) or enzymes of an organism
- e.g. diving mammals being able to stay underwater for longer due to their dramatic drop in heart rate
how are organisms adapted to their environment behaviourally, give an example
- involves an organism’s changes to programmed instinctive behaviour to be better adapted for survival
- e.g. mating calls
define species (again)
a group of organisms sharing a number of structural and evolutionary features, which are capable of interbreeding and producing fertile offspring
what is speciation, what is it a result of
- the formation of a new species
- the result of isolation parts of a population
how does speciation occur
- part of the population is isolated from the rest
- the two isolated populations experience different conditions
- natural selection acts on them in different directions
- as a result, the genotype and the phenotype of the isolated groups change
- this can continue to the point where if members of the split population are reunited, they can no longer interbreed
what is the common way that speciation happens in plants
- hybridisation
- two closely related species breed to form fertile hybrids that are better adapted to the niche
- in some cases, the hybrids do not produce fertile offspring when crossed over with their parent plant, so a new species is formed
- the new species may out-compete the parent plants
describe each different type of reproductive isolating mechanisms
- geographical isolation - a physical barrier e.g. river / mountain range
- ecological isolation - two populations inhabit the same region but develop preferences for different parts of the habitat
- seasonal (temporal) isolation - the timing of flowering or ssexual receptiveness in some parts of te population drifts away from the norm for the group
- behavioural isolation - changes occur in the courtship, ritual, display or mating pattern so that some animals don’t recognise others as being potential mates
- mechanical isolation - a mutation occurs that changes the genitalia of animals making it physically impossible to mate with some members of the population
