biology u4aos2

allele frequencies

proportion of a particular allele appearing at a certain gene locus in a gene pool

allele frequency calculation

total number of particular allele / total number of alleles in population

gene pool

the collection of all the genes and alleles within a specific population

the larger the gene pool…

the greater the genetic diversity

genotype

an organisms unique genetic composition of genes and alleles

phenotype

an individuals observable traits

mutations

responsible for introducing new alleles into a population via changes to DNA

what induces mutations?

mutagens

mutations can be…

advantageous, neutral or deleterious

evolutionary significance to mutations

their ability to create and introduce new alleles into a population, increasing genetic diversity

heritable mutations

must occur in germline cells

point mutations

changes to a single nucleotide in a gene

silent mutation

substitution mutations that have no effect on amino acid sequence due to degeneracy

missence mutation

substitution mutations which code for a different amino acid, altering primary structure and folding of a polypeptide

nonsense mutation

substitution mutations which prematurely end the translation of a gene’s mRNA, affecting the stop codon so the gene is not fully translated and polypeptide is too short to function as intended

frameshift mutation

addition or deletion of one or two nucleotides which alters the reading frame of following nucleotides, disrupting codons and structure of protein

block mutations

alteration of the chromosomes structure by deleting, duplicating, inverting or translocating a cluster of nucleotides during meosis

aneuploids

addition or loss of a chromosome in a cell or organism

polyploidy

organism contains additional sets of chromosomes in its genome

environmental selection pressures

select for the individuals best adapted to a specific environment, promoting their survival and passing on alleles

environmental factors that influence survivability of organisms

competition, disease, predation and climate change

natural selection

the selection of the phenotype most suited to overcome environmental selection pressure

four basic conditions that facilitate natural selection

variation, selection pressure, selective advantage, heritability

variation

individuals in a population vary genetically, leading to phenotypic differences

selection pressure

impacts survivability of organisms within their population and their ability to reproduce

selective advantage

individuals with phenotypes that are more advantageous under the selection pressure and can survive and reproduce more successfully

heritability

advantageous trait must be heritable, allowing it to be passed from parent to offspring

effect of selection pressures on genetic diversity

can decrease, eventual evolution, determines which phenotypes are fitter

genetic drift

changes to a population’s allele frequencies due to sudden and random occurrences

the bottleneck effect

large proportion of a population is wiped out by a random event, decreasing population size and allele frequencies, thus, lower genetic diversity

founder effect

small unrepresentative sample of individuals separates from larger population to colonise. new region and start a new population

risks with low genetic diversity

inbreeding and lower adaptive potential (populations become vulnerable to selection pressures due to absence of advantageous alleles)

gene flow

introduction or removal of alleles between populations through either migration or interbreeding

forms of migration

immigration of emmigration

speciation

populations genetically diverge until they become a distinct species

types of speciation

allopatric of sympatric

isolating mechanisms

pre-reproductive and post-reproductive

allopatric speciation

formation of a new species as a result of a geographical barrier

galapagos finches

18 species caused by allopatric speciation

sympatric speciation

formation of a new species in populations located in the same geographical location by different selection pressures acting on different phenotypes

howea palms

2 species on lorde howe island caused by sympatric speciation

howea palms species

howea forsterina and howea belmoreana

how did howea palms form two species?

pH of soil. F high pH, B low pH

selective breeding

humans selectively developing desirable traits in plants and animals by altering the breeding process of a population

requirements for selective breeding

variation and selection pressure