evolution of species 3.6 Flashcards
(21 cards)
mutation
a random change to genetic material, they are spontaneous and are the only source of new allele
what could the change in genetic material be
the number or types of bases found in DNA or the number or length of chromosomes
mutant
if the change in the genotype result in a change in phenotypes
types of mutations
neutral, advantageous and disadvantageous
neutral
results in a protein which doesn’t affect the organisms, eg: many silent mutations
advantageous
results in a protein which confers in an advantage on the organisms, eg: 6 fingers
disadvantageous
the mutation results in a protein which confers a disadvantage in an organisms, eg: cystic fibrosis
mutagenic agents
environmental factors which increase the chance of mutations occurring
examples of mutagenic agents
ionising radiation, UV radiation and chemical mutagens (mustard gas)
variation
within a population makes it possible for a population to evolve over time in response to changing environmental conditions
adaptation
an inherited characteristic that makes an organism well suited to survival in it’s environment or niche
the types of adaptation
structural and behavioural
selection pressures
- every species produces far more offspring that the environment can sustain
- this often leads to many offspring dying before reaching reproductive age
things that lead to selection pressure
competition, lack of food, overcrowding, predation and disease
natural selection
when the best adapted individuals in a population survive to reproduce, passing on the favourable alleles that confer the selective advantage and the offspring who’s phenotypes are least well suited to the environment die before reproductive age
speciation
the process of the formation of a new species
the stages of speciation
1) isolation
2) mutation
3) natural selection
isolation in speciation
species become cut off from the other members of the species for a very long time or permanently by an isolation barrier
different isolation barriers
geographical
-mountains and rivers
ecological
-different habitats including temperature, pH or humidity
behavioural
-different breeding seasons
mutation in speciation
different mutations occur in each sub-population and any new variations which arise in one group is not shared by the other group
natural selection in speciation
natural selection selects for different mutations in each group, due to different selection pressures and each sub-population evolves until they become so genetically different that they are two different species, therefore they can not interbreed successfully
