Unit 7 Flashcards
(33 cards)
Define Phenotype (2)
- Expression of genetic constitution of an organism
- And its interaction with the enviroment
Define Genotype (1)
- The genetic constitution of an organism
If a gene is sex-linked on the X chromosome, why is the phenotype more common in XY organisms? (2)
- Males have one allele
- Females need two recessive alleles
Mutation is one cause of genetic variation in
organisms.
Give two other causes of genetic variation.(2
- Crossing over
- Independent segregation
- Causes random fertilisation
In genetic crosses, the observed phenotypic ratios obtained in the offspring are often not the same as the expected ratios.
Suggest two reasons why. (2)
- Small sample size
- Fusion of gametes is random
- Linked Genes
- Epistasis
- Lethal Genotypes
Name the relationship between two alleles when both alleles appear in the phenotype (1)
Co-Dominance
Name the relationship between the two alleles when both alleles appear in the phenotype (1)
Epistasis
Explain what it means when two genes are linked (1)
On the Same chromosome
Which statistical test could the scientist use to
determine whether his observed results were
significantly different from the expected results?
Give the reason for your choice of statistical test.
(2)
- Chi Squared Test
- Categorical Test
Define Gene Pool (1)
All alleles in a population
Define species (1)
Organisms that can breed together and produce fertile offspring
The conditions under which the
Hardy-Weinberg Principle
applies (5)
- No mutations
- Random mating
- Large Population
- Isolated Population
- No selection pressure
What are the two equations used in the Hardy-Weinberg equation? (2)
- P + Q = 2
- P2 + Q2 = 2PQ = 1
Describe Allopatric Speciation (5)
- Geographical Isolation
- Reproductive separation
- Different selection pressures
- Variation due to mutations
- Different alleles passed on
- Eventually different species cannot interbreed to produce fertile offspring
Why does speciation take a long time? (3)
- Initially few animals with favourable allele
- Individuals with allele will have more offspring
- Takes many generations for favourable mutation to become the most common allele
Natural Selection in Resistant Strains (5)
- Some individuals in population are naturally resistant
- Due to mutation
- These survive when non-resistant are killed
- To reproduce and pass on the allele for resistance
- Increase in frequency of allele for resistance
Describe sympatric speciation (4)
- Not Geographically isolated
- Mutation causes reproductive isolation
- Gene pools kept separate
- Different alleles are passed on
- Cannot breed to produce fertile offspring
Define Community (1)
All groups of populations living and interacting with each other in an area
Assumptions with Mark, Release and Recapture (5)
- No Immigration
- No losses to predation
- Marking does not affect survival
- Birth rate and Death rate equal
- All belongs to one population
Outline method of Mark, Release and Recapture (4)
- Capture sample, mark then release
- Ensure marking isn’t harmful to survival
- Allow time for organism to randomly distribute before collecting a second sample
- (Population =) number in first sample × number in second sample divided by number of marked fish in second sample/number recaptured
Describe how you could estimate the size of a population using random sampling (4)
- Use a grid
- Method of obtaining random numbers, example random number generator
- Count number in a quadrat
- Large sample and calculate the mean
- Valid method of calculating total number of plants, example mean number of plants per quadrat
Why repeat/large sample size? (1)
So representative
Why random? (1)
Avoid bias
The scientist used percentage cover rather
than frequency to record the abundance of
algae present. Suggest why. (1)
Too many to accurately count