evolution by natural selection Flashcards
1
Q
four observations
A
- more offspring are produced than required
- natural variation : no two individuals are exactly alike
- change in environment leads to different reproduction : differential reproduction / survival of the fittest
- characteristics were heritable
2
Q
how did darwin explain natural selection?
A
- only operates on variation in inherited characteristics
- survival of best adapted to environmental conditions
- produce most offspring
3
Q
how does natural selection occur?
A
- large number of offspring
- great deal of variation among offspring
- change in environment, competition becomes evident
- some favourable traits allow offspring to adapt
- less favourable traits will die
- reproduce, carrying favourable traits
- eventually all individuals will have desirable trait (evolution by natural selection)
- possible new species may arise
4
Q
natural selection
A
- not random
- variations arise (mutations, and recombination of genes)
- not perfect
- process, changing
5
Q
what causes genetic variation?
A
- germ-line point mutations
- duplication of genes or swapping positions
- whole chromosomal deletion / duplication
- sexual reproduction (combination of alleles)
- variety of genotypes form
6
Q
why do offspring differ from their parents?
A
- genetic variation
- effect of environmental factors
- variety of phenotypes
7
Q
why are only some offspring selected for survival?
A
- environmental pressures : competition; climatic factors; predation; disease; parasitism
- favourable phenotypic characteristics
8
Q
what is the result of natural selection?
A
- favourable genotype becomes more frequent
- possible new species
9
Q
peppered moth
A
- originally light matching lichen covered trees
- become black, to match darker trees and soot after lichen was killed by pollution
10
Q
other mechanisms of evolution
A
- polyploidy : doubling or trebling of basic sets of chromosomes (hybridisation), can not mate with parent species
- gene flow : movement of genes between populations (migration)
- genetic drift : random changes in frequency of characteristics in population
