4.4-4.7 Flashcards
What is genetic diversity?
Number of different alleles of genes in a population
What are alleles and how do they arise?
Variations of a particular gene - different DNA base sequence
Arise by mutation
What is a population?
A group of interbreeding individuals of the same species
Explain the importance of genetic diversity?
Enables natural selection to occur
As in certain environments, a new allele of a gene might benefit its possessor
By resulting in a change in the polypeptide coded for that positively changes its protein
Giving possessor a selective advantage
What is evolution?
Change in allele frequency over many generations in a population
Occurring through the process of natural selection
Explain the principles of natural selection in the evolution of populations:
Mutation: Random gene mutations can result in (…) new alleles of a gene
Advantage: In certain (…) environments, the new allele might benefit its possessor as (…) so organisms has selective advantage
Reproductive success: Possessors are more likely to survive and have increased reproductive success
Inheritance: Advantageous allele is inherited by members of the next generation
Allele frequency: Over many generations, (…) allele increases in frequency in population
Describe 3 types of adaptations:
Anatomical- structural/physical features that increase chance of survival
Physiological- processes/chemical reactions that increase chance of survival
Behavioural- ways in which an organism acts that increase chance of survival
Explain directional selection, using an example:
Example- antibiotic resistance in bacteria
Organisms with an extreme variation of a trait have a selective advantage due to a change in the environment
Increased frequency of organisms with alleles for extreme trait. Normal distribution curve shifts towards extreme trait
Explain stabilising selection, using an example:
Human birth weight
Organisms with an average/modal variation of a trait have selective advantage. Environment stays the same. Increased frequency of organisms with alleles for average trait, normal distribution curve similar with less variation around the mean
What is a species?
A group of organisms that can produce fertile offsprings
Suggest why 2 different species are unable to produce fertile offspring
Different species have different chromosome numbers so offspring may have odd chromosome number
So homologous pairs cannot form- meiosis cannot occur to produce gametes
Explain why courtship behaviour is a necessary precursor to successful mating:
Allows recognition of members of the same species so fertile offspring produced
Allows recognition/attraction of opposite sex
Stimulates/synchronises mating/release of gametes
Indicates sexual maturity/fertility
Establishes a pair bond to raise young
Describe a phylogenetic classification system:
Species arranges into groups (taxa) based on their evolutionary origins and relationships
Uses a hierarchy:
- smaller groups are placed within larger groups
- no overlap between groups
Name the taxa in order:
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
How is each species universally identified?
A binomial consisting of the name of its genus and species
Suggest an advantage of binomial naming:
Universal so no confusion as many organisms have more than one common name
How can phylogenetic trees be interpreted?
Branch point=common ancestor
Branch=evolutionary path
If two species have a more recent common ancestor they are more closely related
Describe two advances that have helped to clarify evolutionary relationships between organisms:
- Advances in genome sequencing allowing comparison of DNA base sequence
- more differences in DNA base sequences so more distantly related/earlier common ancestor
- as mutations build up over time - Advances in immunology allowing comparison of protein tertiary structure
- higher amount of protein from one species binds to antibody against the same protein from another species so more closely related/more recent common ancestor
- as indicates a similar amino acid sequence and tertiary structure
- so less time for mutations to build up
What is biodiversity?
Variety of living organisms
Can relate to a range of habitats from a small local habitat to the earth
What is a community?
All populations of different species that live in an area
What is species richness?
Measure of the number of different species in a community
What does an index of diversity do?
Describes the relationship between:
- no. species in a community
- no. individuals in each species
Suggest why an index of diversity is more useful than species richness:
Also takes into account no. individuals in each species
So takes into account that some species may be present in small or high numbers
What is the formula for index of diversity?
d= N(N-1) / ∑n(n-1)
N= total no. organisms of ALL species
n= total no. organisms of each species
Describe how index of diversity values can be interpreted:
High= many species present and species evenly represented
Low= habitat dominated by one/a few species
Explain how some farming techniques reduce biodiversity:
Removal of woodland/hedgerows, monoculture and use of herbicide:
- reduces variety of plant
- so fewer habitats and niches
- less variety of food sources
Use of pesticides:
- predator population of pest decreases
Explain the balance between conservation and farming:
Conservation required to increase biodiversity
But when implemented on farms, yields can be reduced, reducing profit/income for farmers
To offset loss, financial incentives/grants offered
How can biodiversity be increased in areas of agriculture?
Reintroduction of field margins and hedgerows
Reduce use of pesticides
Growing different crops in the same area
Using crop rotation of nitrogen fixing crops instead of fertilisers
How can genetic diversity within or between species be measured?
Comparing frequency of measurable or observable characteristics
Comparing base sequence of DNA/mRNA
Comparing amino acid sequence of a specific protein
Explain how comparing DNA/mRNA/amino acids sequences can indicate relationships between organisms:
More differences in sequences= more distantly related/earlier common ancestor
As mutations build up over time
More mutations cause more changes in the amino acid sequence
Explain the change in methods of investigating genetic diversity over time:
Early estimates made by inferring DNA differences from measurable/observable characteristics
- many coded for by more than one gene
- many influenced by environment
Gene technologies allowed this to be replaced by direct investigation of DNA sequences
Explain the key considerations in quantitative investigation of variation within a species:
Collect data from random samples to remove bias
Use large sample size so representative
Ethical sampling must not harm organism
Calculate a mean value and standard deviation and interpret values
Used stats test to analyse whether there is a significant difference
