Variation Flashcards
20.1, 10.5, 10.6
How can you group data?
Continuous, discontinuous
Interspecific, intraspecific
Environmental, genetic, both
Genetic explanation
Interspecific variation
Considers the variation between different species
Intraspecific variation
Is the variation within a specific species/group.
Environmental causes definition
Interaction of environmental and genetic factors
Environmental causes examples
Chlorosis- yellow leaves
Etiolation- long thin growth
Genetic causes examples
Gene mutations
-changes to DNA sequence can lead to changes in proteins coded for and can affect physical and metabolic characteristics and if these in gametes and not somatic body cells then variation
-multiple alleles
Chromosome mutations
Meiosis/sexual reproduction
-independent assortment and crossing over
-chance which parental alleles combine
Discontinuous variation definition
Each characteristic falls into one of a few discrete categories
Discontinuous variation examples
Blood type, flowering vs non-flowering, biological sex
Continuous variation definition
There are no definite categories: the characteristics exist along a range of possible values between 2 extremes
Continuous variation examples
Leaf length, stomatal density, height
Describe the likely genetic explanations for discontinuous variation
Often due to monogenic inheritance
-single gene locus, multiple alleles
-patterns of dominance, recessiveness, codominance
-multiple genes acting epistatically
Continuous variation plotted on graph usually result in…
Normal distribution curve
-mean,mode and median are the same
-bell shape is symmetrical around the mean
-50% of values are less and 50% are more than the mean
-extremes are few
Describe the likely genetic explanations for continuous variation
Polygenic inheritance
-multiple genes influencing a particular characteristic
-multiple genes with multiple alleles
-tend to show normal distribution
