6.1.2 patterns of inheritance Flashcards
describe the process of natural selection
- mutation
- causes variation
- selection pressure
- those that are better adapted will survive
- reproduce
- pass on the beneficial alleles to their offspring
- the advantageous alleles increase in the population
- over many generations
what is speciation
- formation of new species through evolution
- cumulative change over time in the inherited characteristics of a population
what must occur for speciation to happen
- isolation
- random mutations
- change in allele frequency
2 types of isolation
sympartic and allopartic
what is allopartic speciation
when the population occupy different environments - geographic isolation
- a new river separates them/ building roads separates the
what is sympartic speciation
when the pop. are reproductively isolated within the same habitat - hybrids (liger) - more common in plants bcs they can still produce offspring
how does random mutations result in speciation
diff environments or selection pressures - diff characteristics are selected against or for
how does changes in allele frequency over many generations lead to speciation
results in large changes in phenotype - no longer interbreed - reproductively isolated
what are selection pressures
environmental factors that act selectively on certain phenotypes leading to natural selection
what are 3 types of selection pressures
- directional
- stabalising
- disrupted
describe directional selection
when 1 extreme is selected for than another
- e.g. whether the peppered moth is black or white depends on the environment - will only be black OR white
describe stabalising selection
average selected for
e.g. birth weights - if overweight OR underweight = health issues - therefore must be average bcs that = healthy
describe disrupted selection
different extremes selected for
e.g. finch beak sizes can be thick or thin
define gene pool
sum total of all the alleles in an interbreeding pop. at a given time - some more common than others
define the Hardy-Weinberg principle
in a stable population with no disturbing factors the allele frequency will remain constant from 1 gen to the next - therefore no evolution
conditions for Hardy-Weinberg
- reproduce by sexual reproduction only
- mating is random
- population is large
- no migration, mutation, or selection
what criticises the Hardy-Weinberg principle
- species are always changing
- disrupting this eqm WILL lead to evolution
factors affecting rate of evolution
- genetic drift - bottleneck and founder effect
- gene flow
what is genetic drift
random changes in freq. of alleles in a pop.
- unlike natural selection which is driven my adaptive changes, genetic drift occurs due to CHANCE
- often in SMALLER pop.
- overtime there is a significant change in the allele freq
- some favoured more or lost entirely from gene pool
bottleneck as an example of genetic drift
- if large pop. suffers a dramatic fall in n.o - reduces gene pool ( now has become a small pop)
- a major environmental change e.g hunting/climate change/natural disasters - genetic diveristy dec. and alleles lost
- modern pop. descend from only a few survivors
founder effect as an example of genetic drift
- small n.o of individuals migrate and start a new pop. in a diff area
- only some of alleles from parents are present
- changes in allele freq occur due to chance bcs some alleles become dominant over others in gene pool
what is gene flow
- movement of genes from 1 pop to another via immigration of emmigrationwh
what is variation
the differences in the observable characteristics and genetic material - can be intra or interspecific
what 3 things cause variation due to meiosis
- crossing over in P1
- independent assortent in M1
- random fertilisation
discrete/discontinuous vs continuous data
d
- monogenic
- distinct categories
- no intermediates - fall in either group
- environment has little to no effect
- non-numerical
c
- polygenic
- pop lie within range
- intermediates
- numerical
- environment and genetic has an effect
e.g height
phenotypic variation
- diff in environment
e.g. body mass in animals = lifestyle/diet/climate
e.g. yellowing in leaves of plants = low light = genes for chlorophyll are switched off + availability of mineral ions like Mg2+ + viruses
chi-squared
measures the difference between observed and expected results
- if X2 is significantly different (v high or v low) than c.v then diff is significant - at p0.05 theres a 95% chance results are not due to chance - reject null hypothesis
- vice versa for similar
