Genetics - Variation and Evolution 174-178 Flashcards
what are the types of variation within a species
2 points
1) genetic variation
2) environmental variation
how do different genes cause genetic variation
4 points
1) an organisms characteristics are determined by genes inherited form their parents
2) these genes are passed on in gametes from which the offspring develop
3) most animals get some genes form the mother and some from the father
4) this combining of genes causes genetic variation
what characteristics are determined only by genes in animals
3 points
1) eye colour
2) blood group
3) inherited disorders
how is environmental variation caused
3 points
1) where the conditions where organisms live and grown cause differences between members of the same species
2) for example a plant grow in plenty of sunlight has green leaves and a plant growing in darkness would have yellow leaves
3) can also be things like getting a tan
what characteristics are determined by genes and the environment
4 points
1) weight
2) height
3) skin colour
4) condition of teeth
how can mutation introduce variation in a species
2 points
1) if the environment changed and the new phenotype (due to mutation) is more suited to the new environment
2) this mutation can become common throughout the species quickly by natural selection
what is the theory of evolution
all of today’s species have evolved from simple life forms that started to develop over 3 billion years ago
what is Darwin’s theory of evolution by natural selection
5 points
1) Darwin knew organisms in a species show wide variation in their characteristics, he also knew organisms have to compete for limited resources in an ecosystem
2) he concluded the organisms with the most suitable characteristics for the environment would be more likely to survive - ‘survival of the fittest’
3) the organisms that survive are more likely to reproduce an pass on genes for the characteristics that made them successful
4) the organisms that are less well adapted would be less like;y to survive and reproduce
5) overtime the beneficial characteristics become more common in the population and the species evolves
what is speciation
2 points
1) when over a long period of time the phenotype of organisms change so much because of natural selection that a completely new species is formed
2) it happens when populations of the same species change enough to become reproductively isolated
why do species become extinct
5 points
1) the environment changed to quickly
2) a new predator kills them all
3) a new disease kills them
4) they can’t compete with another species
5) a catastrophic event kills them
why was Darwin’s idea controversial
3 points
1) it went against religious beliefs about how life developed
2) Darwin couldn’t explain why these new characteristics appeared or how they were passed on from individual organisms to their offspring
3) there wasn’t enough evidence to convince many scientists
what was Lamarck’s differing idea about evolution
3 points
1) changes that an organism gets during its lifetime will be passed on to its offspring
2) he thought if a characteristic was used a lot by an organism, it would become more developed in its lifetime and this characteristic would be passed on to its offspring
3) for example if a rabbit used its legs to run a lot, then its legs would get longer and its offspring would be born with longer legs
why was Lamarck’s theory rejected
it didn’t have evidence to support it
