Chapter 19: Evolution And Natural Selction Flashcards
(40 cards)
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.
What is stabilizing selection and example
- the intermediate form of a trait is favored
- reduced phenotypic variation
- maintains midrange phenotypes
- ex weaver birds. Fat birds get eaten easily so birds maintain an average weight because there is not enough food and they can escape easily
- selective pressure are food availability and predation
What is disruptive selection and an example
- forms of a trait at both extremes are favored
- intermediate forms are not let
- ex Coho salmon. large bodied males can produce a lot of offspring and right for land, small males are good at sneaking into territories and fertilizing eggs, the middle sized can’t hold territories or make a lot of offspring
- selective pressure are competition for territory and ability to fertilize
How is evolutionary change measured and how to calculate alleles?
- it is measured by allele frequency
- p= # of copies of the allele/ total # copies of all alleles in population
What is hardy Weinberg and what are the conditions need to be at equilibrium?
- the opposite of evolution, evolution does not occur, allele frequencies do not change
- conditions: no mutations, no selection among genotypes, no gene flow, population size is infinite/no genetic drift, mating is random
What are the 5 lines of evidence supporting evolution?
- Fossil record
- Biogeography
- comparative morphology
- Molecular biology
- Lab & field experiments
What are complete fossil records that we have found, does evolution occur within a straight line, why did species change within the fossil record, why do they look different but have similar traits?
- horse and whale
- evolution does not occur in a straight line but branched
- they look similar but are different because they adapt to different environments
What is a missing link and what info does it provide?
-missing links provide link between groups of species believed to share a common ancestor, shows change through natural selection
What is radiometric dating, how are radioisotopes used, what is a half life?
- dates materials
- radioisotopes are a form of an element with an unstable nucleus, the nucleus breaks down the atoms of radioisotope becomes atoms of other elements, and decays at a constant rate, predictable products
- half life is the time it takes for half of a radioisotopes atoms to decay into a product, almost for dating fossils
