VCE Biology - Unit 4, AOS 2

Gene pool

the complete set of alleles present within a particular population

Gene

a section of DNA that carries the code to make a protein

Allele

an alternate form of a gene

Population

a group of individuals of the same species living in the same location

Allele frequency

the proportion of certain alleles in a gene pool

Genotype

the genetic composition of an organism at a particular gene locus

Phenotype

the physical or biochemical characteristics of an organism that are the result of gene expression and the environment

Genetic diversity

the variation in genetic makeup or alleles within a population

Mutation

a permanent change to a DNA sequence

Mutagen

an agent that can cause mutations in DNA

deleterious

used to describe alleles that have an overall negative effect on individual fitness when expressed

heritability

the transmission from parent to offspring (i.e. encoded in genes)

germline cell

a cell involved in the generation of gametes in eukaryotes

somatic cell

any cell in an organism that is not a germline cell

point mutation

a mutation that alters a single nucleotide in a DNA sequence

block mutation

a mutation that affects a large chunk of DNA, or an entire gene

silent mutation

a mutation in which a nucleotide is substituted for another, changing the codon, but still coding for the same amino acid. Therefore, there is no effect on protein structure

missense mutation

a mutation in which a nucleotide is substituted for another, changing the codon and coding for a different amino acid. Therefore, there can potentially be an effect on protein structure

nonsense mutation

a mutation in which a nucleotide is substituted for another, changing the codon to a stop codon, prematurely ceasing translation of the gene's mRNA. Therefore, there is an effect on protein structure

frameshift mutation

a mutation that involves the insertion or deletion of one or two nucleotides, altering every codon from that point forward

degenerate

a property of the genetic code which means that a single amino acid can be coded for by more than one codon

reading frame

the order in which nucleotide triplets or codons are divided into a consecutive, non-overlapping sequence

aneuploidy

when a cell or organism varies in the usual amount of chromosomes in its genome by the addition or loss of a chromosome

polyploidy

when an organism contains additional sets of chromosomes in its genome

pressure

A factor in the environment that impacts the ability to survive and reproduce

Competition

interactions between organisms in which both are negatively impacted when vying for the same limited resource. Can exist within or between species

natural selection

a mechanism through which organisms that are better adapted to their environment have an increased chance of surviving and passing on their alleles

fitness

a measure of how well an organism survives and reproduces in its environment

advantageous phenotype

a biochemical, physical, or behavioural trait that increases an organism's fitness in its local environment

selective advantage

an organism conferred a beneficial allele, which increases its chances of survival against a specific environmental selection pressure

disadvantageous allele

an allele that encodes for a biochemical, physical, or behavioural trait that lowers an individual's fitness in its local environment

evolution

the change in the genetic makeup of a population over successive generations

genetic drift

a random event that dramatically alters a population's gene pool

bottleneck effect

the reduction in genetic diversity that occurs when a large proportion of a population is removed due to a chance event

founder effect

the reduction in genetic diversity that occurs when a population is derived from a small unrepresentative sample of the original population

unrepresentative sample

a small selection of individuals from a larger group that does not reflect the characteristics of the larger group

inbreeding

sexual reproduction between two related individuals

adaptive potential

the ability for a population to adjust to new environmental selection pressures

interbreeding

when two individuals living in different populations mate and have offspring

gene flow

the flow of alleles in and out of a population due to the migration and interbreeding of individuals between two populations

immigration

the movement into a population

emmigration

the movement out of a population

species

a group of individuals who are able to breed with each other and produce viable and fertile offspring

allopatric speciation

the geographical separation of a population from a parent population resulting in the formation of a new species

sympatric speciation

the divergence of a species from an original species without the presence of a geographical barrier

viable

able to survive

fertile

the ability to produce offspring

geographical barrier

a physical factor that prevents gene flow, and thereby stops two populations from breeding together

ecological niche

the specific environmental conditions and resources or selection pressures within a particular environment

selective breeding

the changing of a population's gene pool due to humans altering the breeding behaviour of animals and plants to develop a selected trait. (also known as artificial selection)

desirable trait

a heritable phenotype that humans select for during selective breeding

deleterious allele

an allele that has an overall negative effect on individual fitness when expressed

recessive allele

a trait that can be masked by a dominant allele on a homologous chromosome

homozygous

having identical alleles for the same gene on homologous chromosomes

antimicrobial agent

an agent that kills or slows the growth of microorganisms. Examples include antiseptics, disinfectants, antifungals, antivirals, and antibacterial agents

antimicrobial resistance

the ability of a microorganism to survive exposure to an antimicrobial agent

bacterial conjugation

the process in which bacteria exchange genetic material via direct cell-cell contact

normal flora

naturally occuring, non-pathogenic microbes present in an organism

virulence

the potential of a pathogen or disease to cause serious illness of harm

antigenic drift

small and gradual mutations in the genes encoding for viral surface antigens

antigenic shift

sudden and significant mutations in the genes encoding for viral surface antigens

viral recombination

the combination of surface antigens from two or more different strains of a virus to form a completely new virus subtype

epidemic

a dramatically increased occurrence of a disease in a particular community at a particular time

pandemic

an epidemic that has spread across multiple countries and/or continents

fossil record

the information derived from fossils. The fossil record is arranged in chronological order and helps us map the history of life on Earth, placing species in the appropriate geologic time frame

Camrbian Explosion

a period (~ 535 mya) of rapid diversification of multicellular life, characterised by the evolution of hardened body parts such as shells or bones

Extinction

The dying out of a species on a global or reigonal level

Fossil

the preserved body, impressions, or traces of a dead organism

Fossilisation

The process by which an organism becomes a fossil

Sediment

Naturally occurring solid material, such as earth and rock, that is broken down into very fine pieces and typically settles at the bottom of liquid

Sedimentary rock

rock that has formed through the accumulation of sediment that hardens under pressure

Permineralised fossil

Fossil formed when mineral-rich groundwater deposists minerals like silica and calcite into organic material, creating a mineral relic

Mould fossil

Fossil formed when a living thing decomposes underneath sediment, creating a cavity in the shape of the dead organism

Cast fossil

Fossil formed when a mould fossil is filled with sediment

Trace fossil

Fossil or structure indicating the presence of organisms, rather than the organisms themselves (e.g. nests, footprints, and burrows)

Relative dating

A dating technique used to determine the relative age of a fossil by comparing its position to other fossils or rock in surrounding rock strata

Absolute dating

A dating technique used to determine the absolute age of a fossil by measuring the relative amounts of radioisotopes to their products. Also known as radiometric dating

Fossil succession

The principle that fossils of the same age will be in the same layer of sedimentary rock, and fossils foudn in higher or lower sedimentary layers will be younger or older, respectivley. Also known as faunal succession

Relative age

The age of a fossil as determined by relative dating techniques. Describes the age of a fossil compared to other fossils, instead of a fossil's exact age in years

Stratum (pl. strata)

A layer of sedimentary rock

Index fossil

A group of widespread fossils which existed for a short period and have a known age. Can be used as a refrence to easily determine the age of unknown fossils

Transitional fossil

A fossil that shows traits that are common to both its ancestral group and its descendant group. They are particularyly important when the descendant species is physically very distinct from the ancestral species, such that the transitional fossil can help demonstrate evolutionary changes between the two

Absolute age

An estimate of age (in years) of a fossil or rock

Radioactive isotope

A radioactive atom of a specific element. This atom breaks down into a predictable and stable product. Also known as a radioisotope

Half-life

The time taken for half the mass of a radioisotope sample to break down into its products

dating period

The range of time since fossilisation in which a particular radioisotope series can be used. Beyond this period, most of the radioisotope will have broken down into its products, meaning that it is too difficult to estimate the fossil's age

radiocarbon dating

A form of absolute dating used to determine the ag eof a fossil by measuring the properties of radiocarbon, a radioactive isotope of carbon. Alos known as carbon dating and radioactive carbon dating

Structural morphology

The study of physical structures to establish relatedness

Homologous structures

Features present in two or more species that may look and function very differently in each species, but are derived from a common ancestor

Divergent evolution

The process in which a common ancestor evolves into two or more descendant species

Analogous structures

Features present in two or more species that fulfil the same function but do not originate from a common ancestor

Convergent evolution

The process in which distantly related species evolve similar traits over time due to the action of similar selection pressures

Vestigial structures

Features that have lost all or most of their usefulness as a result of evolution by natural selection

Molecular homology

The study of the similarities in the nuceotide sequences of DNA or amino acid sequences in proteins between organisms to establish relatedness

Conserved genes

Genes that have remained largely unchanged throught evolution, and are found across the genome's of many differnt species

Haemoglobin (Hb)

A protein foudn in red blood cells that is responsibl for the transport of oxygen in the body

Cytochrome c

An enzyme found in mitochondira that carries electrons in aerobic and anaerobic respiration reactions

mitochondrial DNA (mtDNA)

circular DNA found in the mitochondria - is maternal

DNA

A double-stranded nucleic acis chain made up of nucleotides. DNA carries the instructions for proteins which are required for cell and organism survival

Nucleotide

The monomor subunit of nucleic acids. Made up of a nitrogen-containing base, a five-carbon sugar molecule (ribose in RNA and deoxyribose in DNA), and a phosphate group