Genetic Diversity Flashcards
What differences will individuals have?
Differences between their DNA base sequence
What are teh small differences in DNA base sequence called?
Genetic variation
How does genetic diversity come about?
Genetic variation is transferred from one generation to the next
What is genetic diversity?
The number of difference alleles of genes in a population
Origins of genetic diversity?
Meiosis- independent serration of homologous chromosomes during metaphase
Crossing over- the chromatids break and recombine with another non-sister chromatid at the chiasma
Random fertilisation- any one of the sperm can fertilise the egg
Non-disjunction- failure to separate in anaphase 1&2 results in different number of chromosomes in each cell
Mutations- change in base sequence of DNA
Chromosomal mutations- changes in whole sets of chromosomes leads to polyploidy
High genetic diversity?
Higher adaptive capacity
Potential for long term survival
High resilience
Low genetic diversity?
Lower adaptive capacity
Weak potential for long term survival
Low resilience
What is carrying capacity?
The maximum size a population can be
What prevents population size exceeding the carrying capacity?
Environmental resistance
What abiotic factors contribute to environmental resistance?
Food availability, temperature
What biotic factors contribute to environmental resistance?
Predation, disease
How does natural selection come about?
There is genetic diversity in the population
New alleles arise due to random mutations
Population experiences a selection pressure
Individuals with the advantageous allele survive to reproduce
The advantageous allele is inherited by offspring
Anatomical adaptations?
Neck length
Fur colour
Physiological adaptations?
Muscle contraction efficiency
Rate of gas exchange
Behavioural adaptations?
Courtship displays
What is directional selection?
Individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce
Those with the allele pass it on to their offspring
Over time most organisms will carry the allele
Example of directional selection?
Antibiotic resistance
What is stabilising selection?
Individuals with characteristics towards the middle of the range are more likely to survive and reproduce
Occurs when the environment isn’t changing and it reduces the range of possible characteristics
Example of stabilising selection?
Human birth weight
Disruptive selection?
The average phenotype is selected against
Example of disruptive selection?
Evolution of beak sizes in Darwin’s finches on the Galápagos Islands
