Selection And Evolution Flashcards
What is variation?
*Variation= presence of different characteristics (phenotypes)
*Phenotype results from interaction of genotype and environment
Phenotypic variation= Genetic variation + Environmental variation
Vp=Vg+Ve
Two types of variation:
1. Discontinuous variation
2. Continuous variation
What is the difference in the type of distribution in discontinuous and continuous variation?
In discontinuous variation we have discontinuous distribution.
In continuous variation we have normal distribution.
What is the difference in the number of genes controlling phenotype in continuous vs discontinuous variation?
In discontinuous there is one/ few genes (monogenic).
In continuous variation there are many genes (polygenic)
What is the difference in the effect of different alleles at single gene locus in discontinuous and continuous variation?
In discontinuous variation it is large and different genes have different effects.
In continuous variation it is small and genes have an additive effect.
What is the difference in the type of data in discontinuous and continuous variation?
Discontinuous variation is qualitative
Continuous variation is quantitative
Describe the difference in the number of categories/ intermediates in discontinuous and continuous variation
In discontinuous variation there is distinct categories and no intermediate.
In continuous variation there is a range of phenotypes and many intermediates.
Describe the effect of environment on the phenotype on discontinuous and continuous variation
In discontinuous variation there is little or none.
In continuous variation the environment has effect and helps smooth the curve.
Give examples of discontinuous and continuous variation
Discontinuous variation: albinism, sickle cell anemia, haemophilia, Huntingdons disease
Continuous variation: height, mass
Describe genetic variation and its main sources.
Genetic variation is when the phenotype results from interaction of genotype and environment.
Main source of genetic variation:
1) meiosis and fertilisation
*Crossing over at prophase I
*Independent assortment at metaphase I
*Random fertilisation/mating
2(Mutations!
*Primary source of variations
*Results in new alleles
How does the environment influence phenotype.
Phenotype results from interaction of genotype and environment.
Environmental factors that can influence are:
Nutrients/diet
Water availability
Light intensity
Disease/parasites
Temperature
Chemicals/mutagens
Lifestyle and culture etc
Environment effect usually greater on polygenes
➡️ polygenes= many genes controlling one trait
➡️ phenotype affected by environment shows continuous variation
How does the environment influence phenotype?
The environment may…
1. Limit/ modify gene expression
*Size/ mass/ height
2. Trigger/ switch on gene
*Examples:
a) low temp and charge in animal colour
b) High temperature and gender in croc/ curly wing in drosophila
c) UV light and melanin production
d) wavelength of light and plant growth
3. Induce mutation which affect phenotype
Describe how the environment of low temperature can cause a change in animal colour.
*Dark pigmentation in Himalayan rabbits
➡️Controlled by both genotype and environment
At low temp:
*Allele for dark pigment expressed
*Forming dark tips at ears, paws, paws, nose and tail
➡️Coldest part of rabbit
Describe how the enviroment of high temperature can determine gender in crocs/curly wing in drosophila
Gender of crocodiles depend on temperature of eggs!
*Temperature of 32-34 degrees celcius=males
*below 32/above 34=females
In fruit flies eith the curly wing mutation….
*Temperature of 19 degrees celcius=straight wings
*Temperature of 25 degrees=curly wings
Describe how the enviroment of UV light and melanin production
After a few hours of exposure to UV radiation:
*Melanocytes produce melanin in skin
➡️Causing skin to tan/form dark spots/freckles
➡️Protecting cells from DNA damage
Describe how the enviroment of wavelength of light affects plant growth
*Red and blue light are most effective for plant growth
*Blue light=helps with seed germination
*Red light=helps flower bloom, but leaves will have stretched and elongated appearance.
