Chapter 17 Selection & Evolution Flashcards
1
Q
Why is there phenotypic variation?
A
- genetic factors or environmental factors or a combination of genetic and environmental factors
- Vp = Vg + VE
- Phenotype = Genotype + Environment
2
Q
Define genetic variation.
A
- small differences in base sequences between individual organisms within a species population
3
Q
What processes cause genetic variation?
A
- Independent assortment of homologous chromosomes during metaphase I
- Crossing over of non-sister chromatids during prophase I
- Random fusion of gametes during fertilization
- These processes result in a new combination of alleles in a gamete or individual.
4
Q
Define variation.
A
- differences that exist between individuals of a species
- intraspecific variation
5
Q
Discontinuous variation.
A
- Qualitative differences in the phenotypes of individuals within a population.
- These differences fall into discrete & distinguishable categories.
- No intermediates.
6
Q
Continuous variation.
A
- Quantitative differences in the phenotypes of individuals within a population for particular characteristics.
- A range of values exist between two extremes.
7
Q
Genetic basis of discontinuous variation.
A
- Occurs solely due to genetic factors.
- Environment has no direct effect. Phenotype = genotype.
- Different genes have different effects on the phenotype.
- Different alleles at a single gene locus have a large effect on the phenotype.
8
Q
Genetic basis of continuous variation.
A
- Caused by an interaction between genetics & the environment. Phenotype = genotype + environment
- Different genes have the same effect on the phenotype & these add together to have an additive effect.
- Different alleles at a single gene locus have a small effect on the phenotype.
9
Q
What are polygenes?
A
A large number of genes have a combined effect on the phenotype.
10
Q
Aim of a t-test.
A
- Compare the means of 2 sets of data
- Determines if they are significantly different or not
11
Q
Conditions for a t-test.
A
- The sets of data must follow a rough normal distribution, be continuous & the standard deviations should be approximately equal.
- Null hypothesis must be given.
12
Q
Formula for calculating standard deviation.
A
- refer to revision notes page 7
13
Q
Formula for degrees of freedom.
A
v = (nA - 1) + (nB -1)
14
Q
Why does natural selection occur?
A
- Every individual within a species population has the potential to reproduce & have offspring which contribute to population growth.
- Environmental factors prevent certain individuals from making it to adulthood & reproducing.
- Individuals with advantageous phenotypes / alleles are most likely to survive to reproduce & pass on their alleles to the next generation.
15
Q
17.2 LO 2
A
