Chapter 19: Evolution And Natural Selction Flashcards
What observations did Darwin make that led him to develop his theory of evolution?
- found marine fossils on the Andes mountains 100 of miles from nearest ocean
- island finches resembled mainland finches with different physical characteristics
- similarity between the crib t species and living species in same species
- favorable variations were kept
How does evolution occur, what happens in the molecular level within a population for evolution to occur?
- species have diverged from a common ancestor and changed over time
- natural selection
- beneficial traits increase in allele frequency
- EVOLUTION CANNOT OCCUR W/ OUT MUTATION
Mutations
- alteration in a base pairing of DNA, change in alleles
- ultimate source of genetic variation in a population add alleles into gene pool more variation
- caused by mishaps in DNA or r environmental phenomena
- MUTATIONS CAN BE GOOD OR BAD
Genetic drift
- NOT NATURAL SELECTION
- random change in alleles by CHANCE
- impact is greater in small pop
- all individuals are homozygous
- alleles become fixed until new alleles are introduced
- small pop can lose the beneficial allele and less genetic variation
Bottleneck
- extreme form of genetic drift
- caused by contagious disease habitat loss and over hunting at the same time
- close to complete loss of population
- huge loss of alleles homozygosity increases less genetic variation
- northern elephant seal and cheetah
What is the founder effect and what type of alleles would you find in this population?
- small group breaks off and finds a place and restarts a new population
- allele frequencies does not represent the og pop
- genetic diversity greatly reduced
Why does inbreeding occur within a population and why is it bad
- no random breeding between close relatives
- genetic drift
- reduced genetic diversity
- increases homozygosity and increases recessive alleles
- lots of bad mutations
What is gene flow and migration
- movement of alleles among different populations
- populations of same species existing in separate locations
- maintains allele frequency and genetic variation
Natural selection
- genetic change within a population
- those with a better chance of survival reproduces while the others don’t
- ex rabbits running speed increased overtime slow bunnies died
- conditions necessary: variation, gene must be heritable, differential reproductive success
What is sexual selection and how does it differ from natural selection
- non random mating, they choose specific mates
- natural selection are organisms better adapted to environment, sexual through preference
- females choose and are picky because she wants the best genes for her offspring
- males pass allele for attractive traits
- females pass alleles that influence mate preference
What does survival of the fittest mean?
Those are who are fit will pass on their genes
What is fitness, how is it measured, and what
-a measure of the reproductive output of an individual with a given phenotype compared with the reproductive output of individual with alternate phenotypes
Adaptation
Process where organisms become better matched to their environment
-specific traits give them an advantage, leading for better fitness and better adapted to environment
Can selection changes over time and what is it determined by
Favored trait can change by environment and there is a change in alleles frequency
What is selective pressure and example
Traits make individual most fit in that environment
-white mouse in light sand and dark brown mouse in dark brown environment
What is directional pressure and example
- allele frequencies shift in constant direction, one extreme phenotype favored over the other
- ex peppered moth. Light moth on light trees when their was coal in the air dark moths are proffered switched back and forth.
- selective pressures are environmental changes and predation.
