Patterns of inheritance and Evolution Flashcards
(23 cards)
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
