Chapter 9 - Changes In Genetic Makeup Of Populations Flashcards
Lactose intolerance/tolerance
Arose due to?
The ability to be lactose tolerant arose due to a mutation in our ancestors - we were all lactose intolerant.
Inherited variations
- Charles Darwin proposed?
- Inherited variation can arise from?
- Can only have evolutionary change if there is genetic variation in a population that can be inherited.
- • genetic basis - action of one gene or several genes.
• chromosomal basis - gain entire set of chromosomes (polyploidy), gain or lose single chromosomes (aneuploidy).
Gain = trisomy Los = monosomy
Variation due to a single gene
- Continuous variation
- Discontinuous variation
- Discrete variation
- Controlled by many genes at different loci and often greatly influenced by environment.
- Controlled by a small number of genes, limited number of phenotypic variant in the population.
- Inherited traits controlled by a single gene with a maximum of two alleles. E.g. ABO blood types, hair colour, flower colour, wing pattern.
Chromosomal variation
- Polyploidy
- Aneuploidy
- An organism with more than two paired sets of chromosomes, most species = diploids, to to be larger and more superior.
- An organism that has a chromosome number that differs by a small number from the standard chromosomes number for its species; loss or gain in chromosome numbers in a diploid organism = fatal.
Genes in populations
Define
- Population
- Genotype
- Alleles
- Gene pool
- Phenotype
- Interbreeding group of organisms of the same species living in the same region at the same time.
- The set of genes in an organism’s DNA responsible for a particular trait.
- Variations of a gene
- The sum of all the genotypes (alleles) of all the members in a population.
- The physical expression of an organism’s genes.
Genes in populations: Hardy-Weinberg principle/equation
Their prediction?
If the population was large with random mating, environment stayed the same, and no immigration/emigration, then the frequency of alleles will remain the same over generations.
Change agents in populations: selection
- Selection
• 3 natural selective pressures
- The mechanism by which some individuals with particular features have a greater chance than others of surviving and leaving fertile offspring.
• physical agents - climate, food availability
• biological - disease, predation, competition
• chemical - pollutants in soil and water
Change agents in population: gene flow (or migration)
The movement of genes from one population to another.
• migrants must interbreed with the population they enter, and leave progeny, if gene flow is to have an evolutionary impact.
Change agents in population - chance events: genetic drift
A mechanism of evolution in which allele frequencies of a population change over generations due to chance.
- Chance has a role in determining whether a given individual survives and reproduces.
- infrequently-occurring alleles face a greater chance of being lost.
Change agents in population - chance events: bottleneck effect
- Size of a population is suddenly drastically reduced for at least one generation, resulting in few survivors.
- Mainly due to disaster - bushfire, flood, disease, introduction of a new predator.
Change agents in population - chance events: founder effect
- A few individuals from a population start a new populations with a different allele frequency than the original population.
- All subsequent generations will only have the limited variation that the founder carries.
Speciation: Allopatric
Two steps of allopatric speciation
- A population of species becomes geographically isolated, resulting in two isolated groups of the same species.
- Over many generations, each isolated population will accumulate genetic differences (in appearance and at the molecular level, which helps them to survive) due to different selection pressures and genetic drift. Eventually, the differences are so great that the two isolated groups can no longer interbreed and produce fertile offspring. So, they are now considered different species.
Speciation: sympatric
what?
Process (hint: VSAS)
*sympatric means occurring in the same geographical area
- Species in the same geographic location becoming two different species.
- Process:
- Variation
- Selection pressure, something has changed
- A certain species survives/adapts better than others, pass on the advantageous genes
- Eventually new species is created.
Define
- Subspecies
- Biological fitness
- Selective advantage
- Adaptation
- Selective pressure
- Becoming different species, physically isolated but if they were to be reintroduced they would still be able to interbreed.
- Measured by the relative proportion of fertile offspring left behind by an individual in the next generation.
- Relative higher genetic fitness of a phenotype compared with other phenotypes controlled by the same gene.
- The inherited characteristic that allows an individual to survive and reproduce.
- Any phenomena which alters the behaviour and fitness of living organisms within a given environment.
Mutation
Define
The alteration of the nucleotide sequence of the genome of an organism.
