Patterns of inheritance and Evolution Flashcards
what is interspecific variation
differences between different species
what is intraspecific variation
differences between individuals of the same species
what is continuous variation
- can be measured (quantitative)
- no categories
- controlled by genes/environment
- line graph
what is discontinuous variation
- cannot be measured - qualitative
- categories
- controlled by genes only
- bar graph
what are genetic factors that influence phenotypic variation
Polygenic
- controlled by many genes
Monogenic
- controlled by 1 gene
what are the environment factors that influence phenotypic variation
- diet, climate, lifestyle, nutrients
Etiolation - plants grow abnormally due to lack of sunlight
Chlorosis - don’t produce enough chlorophyll due to lack of magnesium
how can you create genetic variation
Crossing over
- chromatids twist around each other and swap alleles
- contain some genes but different alleles
Independent assortment
- chromosomes align on metaphase randomly
- one chromosome from each pair passes into a daughter cell
Random fertilisation
- any sperm can fertilise any egg
what is sex linkage
- any gene that is carried on the X/Y chromosome
- recessive conditions on sex chromosomes are more likely to appear in men as there is no dominant allele on the X
what are autosomal genes
- chromosome that is not a sex chromosome
- genes on the same chromosome are linked
how are autosomal genes linked
- crossing over in meiosis prophase 1
- closer genes less likely they are separated
- independent assortment in meiosis 1
- genes on the same autosome are linked stay together during independent assortment
what is epistasis
when one gene masks or supresses the expression of another
example of epistasis
Humans
- widow’s peak controlled by one gene and baldness
- alleles that code for baldness it doesn’t matter if you don’t have the allele for Widow’s peak - already bald
- baldness gene masks the expression of the widow’s peak gene
what is genetic bottleneck
- random reduction in population which changes gene pool
- original population
- large number of population die
- reduced population - some alleles lost from the original population
- reproduction
- new population - genetic diversity greatly reduced
what is the founder effect
- small group leaves with varying genes
- migration
what is the genetic drift
characteristics are passed on by chance rather than due to factors that affect the individuals ability to survive and reproduce
what is speciation
- development of a new species
- occurs when population of the same species become reproductively isolated
- changes in alleles frequency leads to change in phenotype
what is allopatric speciation
- geographic isolation
- separate gene pools and no interbreeding between the two populations
- variation due to mutations
- different abiotic/biotic factors
- selected organisms survive and reproduce
- leads to changes in allele frequency
- new species created
- cannot interbreed
what is reproductive isolation
- changes in alleles and phenotypes of two populations to prevent them from breeding together successfully
- seasonal changes - flowering and mates
- mechanical changes - changes in genitalia prevent successful reproduction
- behavioural changes - different courtship
what is sympatric speciation
- don’t have to be geographically isolated to become reproductively isolated
- occurs when members of two different species interbreed and from fertile offspring
- hybrid formed has different amounts of chromosomes
- can no longer interbreed
- stops gene flow
- random mutations
what is artificial selection
- selectively breeding plants and animals for desirable characteristics
- humans select individuals with desirable characteristics
dairy cow example of artificial selection
- female with high milk yield and male cow whose mother had a high milk yield
- breed them together
- select offspring with highest milk yield
- breed
- milk quality
- large udders
- calm temperature
- lactation period
wheat example of artificial selection
- large ear plants bred with large ear plant
- offspring selected with large ears are breed
- process repeated over generations to produce very large ears
- tolerance to cold
- short stalks
what are the problems with artificial selection
- health problems - traits may be exaggerated
- reduces genetic diversity / gene pool
- more susceptible to genetic disease
Pugs - small nasal passage and difficult to breathe
