lecture 2: evolution Flashcards
(20 cards)
false mutations
Mutations generally do not transform an organism that is already alive.
Mutations are inherited from parents to offspring.
Evolution does not occur on an
individual basis
nucleotide pairs
A (adenine) pairs with T (thymine)
C (cytosine) pairs with G (guanine)
locus
particular location of a gene on a chromosome
– BUT may have different versions (alleles) of that gene that code for
different versions of that trait.
allele and cause
two or more alternative forms of a gene
– result from slight differences in the DNA sequence of the gene
– cause slight differences in form and function
individual vs population
An individual is the reservoir of genetic information, but a population is where evolutionary change occurs.
genotype
You get 1 allele from each parent.
Your genotype = full genetic code.
SPECIATION
Allopatric = physical separation
Sympatric = same location, other barriers
Mnemonic: “A = Apart, S = Same place”
HARDY-WEINBERG CONDITIONS (No Evolution aka genetic equilibrium)
To stop evolution, allele freq should’nt change by:
No mutation
No gene flow (emigration and migration)
population must be large
Random mating
No natural selection
natural selection occurs if:
Variation in traits
Differences in fitness
population
a group of individuals of one species living together
phenotype
interaction of the genotype of an individual with its environment
not fixed
Phenotypic plasticity
the ability of a genotype to alter its phenotypic expression
under different environmental conditions
Phenotypic variation can be expressed as
Phenotypes vary with environment and exist in either
- discrete (same look, diff roles or morphology (due to the diff roles)
- continuous (same genes, diff look- body size, skin)
Evolution
is a change in the genetic composition of a population of a species
over time
the present form and function of individuals are
specializations to their
environment
What determines if a trait is favourable?
selection Pressures:
* Environmental conditions - abiotic factors
* Species interactions (predators, competitors) – biotic factors
types of natural selection
stabilizing: average traits have highest fitness
directional: only one extreme trait has highest fitness
disruptedL both extremes has highest fitness
biological concept
determines if it’s a different species.
if can interbreed and produce fertile offspring= same species
how does speciation occur (4 ways)
1) exchange of genes among individuals in a population stop (allopatric and sympatric)
2) isolated subpopulation= different selective pressures so different favurable traits= varying fitness
3) makes genetic composition of subpopulation different
4) after generations, if isolated subpopulation come back together and can no longer interbreed w/ eachother= diff species
what maintains speciation
1) premating (prevent mating)
separtion of mating events by space and time
behaviour (diff song calls)
mechanical or structural incompatibility
2) post mating
decrease surbival or reproductive success of offspring
