Summary WJEC (England) Eduqas A-Level Biology 2. Continuity of Life - 6. variation & evolution
12 views 0 purchase
Course
Continuity of life
Institution
WJEC
I achieved a high A* Grade in my final A-Level exams using these notes!!!
I believe you can achieve an A* if you can memorise these notes! Simply use blurting, a method of active recall, to write everything you remember from the notes, then identify the parts you couldn’t remember, then repeat ...
a. Variation of phenotype = genetic (genotype / epigenetic modification) & environmental factors
b. Continuous & discontinuous variation
Continuous – normal distribution Discontinuous – bar chart
- Range of phenotypes – intermediates between - Distinct groups of characteristics – no
extremes intermediates
- Polygenic – trait controlled by many genes - Monogenic
- Environment factors = major - Environmental factors = minor
heritable & non-heritable variation
Heritable Non-heritable
- Gene mutations - Environment (non-epigenetic): diet
- Crossing over
- Independent assortment
- Random mating
- Random fertilisation
- Environment: epigenetic modifications
c. Competition = selection pressure: survival & breeding success = natural selection
Interspecific: same species
Intraspecific: different species
d. Selection
pressure: environmental factor = affects organisms ability to survive = changes allele frequency in pop when limiting
- Food supply
- Breeding/nesting site availability
- Climate
- Human impacts: habitat loss = no breeding sites
Natural selection:
- conditions change = selection pressures affect survival of phenotypes in population
- mutation = selective advantage
- survive & reproduce = pass selected alleles to offspring
- repeat over several generations = allele frequency increase over time
Stabilising: extreme values selected against = more average (higher peak)
Directional: 1 extreme value selected for/against = curve moves in one direction
Disruptive: average selected against = 2 peaks
e. Population genetics – allele frequencies in gene pool
stable environment = stable allele proportions (change with selection pressures)
gene pool: total alleles for all genes in population
genetic drift: chance variations in allele frequencies in population
- significant in small/isolated populations – small number of alleles have high frequency
founder effect: small number isolate from large pop & establish new – have reduced genetic variation = genetic drift
f. Allele frequency: expressed as proportion/percentage of total alleles for that gene
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller tnotes. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $3.91. You're not tied to anything after your purchase.
