Unit 7 - Inheritance Flashcards
Define phenotype (2)
- Expression of genetic constitution of a genotype
- And its interaction with the environment
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 2 recessive alleles
Mutation is one cause of genetic variation in organisms. Give TWO other causes of genetic variation. (2)
- Crossing over
- Independent segregation
- Random fertilisation
In genetic crosses, the observed phenotypic ratio obtained in the offspring are often NOT the same as the expected ratios. Suggest TWO reasons why. (2)
- Small sample size
- Fusion/fertilisation of gametes is random
- Linked genes
- Epistasis
- Lethal genotypes
Name the relationship between 2 alleles when both alleles appear in the phenotype. (1)
- Co-dominance
Name the type of gene interaction when one gene affects the expression of another. (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
- The data is categoric
Define gene pool (1)
- All the alleles of each gene in a population at a given time.
Define species (1)
- Organisms that can interbreed to produce fertile offspring
The conditions under which the Hardy-Weinberg principle applies (5)
- No mutations occur
- Random mating
- Large population
- Population is isolated (so no migration)
- No selection
What are the two equations used in the Hardy-Weinberg equation (2)
- p + q = 1
- p² + q² + 2pq = 1
Describe allopatric speciation (5)
- Geographical isolation
- Reproductive isolation/Gene pools remain separate
- Different selection pressures
- Variations due to mutations
- Different ALLELES passed on/Change in frequency of ALLELES
- Eventually different species cannot interbreed to produce fertile offspring
Why does speciation take a long time? (3)
- Initially few organisms will have the favourable allele/mutation
- Individuals with the favourable allele will reproduce more and have more offspring.
- Takes many generations for the allele to become the most common allele
Natural selection in resistant strains (5)
- Some organisms naturally resistant
- Due to mutations
- These survive when non-resistant ones are killed (due to pesticide/antibiotic)
- And they reproduce and pass on the favoured allele
- Increase in frequency of allele for resistance
Describe sympatric speciation (5)
- NOT geographically isolated
- Mutation causes reproductive isolation
- Gene pools kept separate/no gene flow
- Different alleles passed on
- Cannot breed to produce fertile offspring
Define community (1)
- All organisms of every species in the same area at a given time
Mark, Release, Recapture - Assumptions (4)
- No migration
- No losses due to predation
- Marking does not affect survival
- Birth rate and death rate are equal
Describe how you could estimate the size of a population using random sampling (4)
- Use a grid
- Method of obtaining random coordinates (RNG)
- Count number/frequency in a quadrat
- Large sample AND calculate mean
- Valid method of calculating total number of plant (e.g mean number of plants per quadrat multiplied by number of quadrats)
Why do you need a large sample size? (1)
- So more representative
Why random sampling? (1)
- To avoid bias
The scientist used % cover rather than frequency to record the abundance of algae present. Suggest why (1)
1.Too many to accurately count / too small / overlap
Describe use of systematic sample to count plants (4)
- Systematic sampling, place quadrats at regular intervals
- Transect line from/to….
- Count number/frequency in a quadrat
- Large sample AND calculate mean number per quadrat
Effect of increased plant/animal diversity on ecosystem (3)
- Increase in diversity of plants leads to more variety of food for animals
- Increase in diversity of animals leads to an increase in predator species
- Increase in more different niche/habitat
Define niche (3)
- Role a species plays in a community
- Includes food resources
- No two species can occupy identical niche
Succession (5)
- Colonisation by pioneer species
- Pioneer species change the abiotic conditions (GIVE EXAMPLE HOW)
- Environment becomes less hostile for new species
(Accept older species being outcompeted) - Increase in biodiversity
- To climax community
Predator-prey relationship (4)
- As pest numbers increase, there’s also more food for predators so they increase too.
- Increased predation of pests/prey reduces numbers of prey
- Low number of pests result in less food for predators so their numbers decrease
- Low predator numbers allow prey population to increase as less eaten.
Succession - competition (3)
- Pioneer species increase and then decreases
- Principle of a species changing the conditions / a species makes the conditions
- New / named species better competitor / pioneer species outcompeted
Give TWO features of a climax community (2)
- Same species present over a long time / stable community
- Abiotic factors constant
- Stable populations
Suggest ONE reason for conserving woodlands. (1)
- Conserving habitats
- Conserving endangered species
- Reduces global warming (as CO2 is taken up)
- Source of medicines, etc
