Biology Exam revision

STUDY YOU BIG GRONK

abiotic factor

non-living environmental factor with which organisms interact e.g. water, oxygen, sunlight, wind, soil etc.

adaptation

features (structural, physiological and behavioural) that enhance an organism's ability to survive and reproduce within their and changing environmental conditions

amensalism

an association between species in which one is inhibited or killed, and the other species is unaffected

behavioural adaptation

action or activities performed (innate or learned) in response to a stimuli that increase the chances of an organism surviving and successfully reproducing in a particular environment

biodiversity

the variety of all living organisms on planet earth including plants, animals, fungi, protists and bacteria; the genetic material (DNA) they contain; and the ecosystems in which they live

biotic factor

living environmental factor with which organisms interact e.g. competition, predation, disease, food availability etc.

commensalism

an interaction between species in which only one species benefits but the other species is not harmed

consumer

the members of the community that rely either directly or indirectly on producers for their source of energy; known as heterotrophs

cool burning

a fire management technique used by Indigenous Australians encourages new growth and helps maintain biodiversity

decomposer

the members of the community that rely on decaying matter for their energy source and return nutrients to the soil

density-dependent model

S-curve; a model of population growth that is limited by an environment's carrying capacity and is capped at a specific number

ecosystem diversity

the variety of physical environments in which an organism can live and interact e.g. rainforests, deserts, ocean, arctic etc.

exponential model

J-curve; a model of population growth as a result of births and deaths only; it also assumes that the number of immigrants equals the number emigrants over time

genetic diversity

the variety of genes present within a given species; larger populations will tend to show greater genetic diversity compared to smaller ones; genetic variation is brought about through mutations to genes

habitat

the location or place where an organism lives at a given time

keystone species

a species that has a disproportionately large effect on its environment relative to its abundance; it plays a critical role in maintaining the structure of its ecosystem

limiting factor

an abiotic or biotic factor that limits the ability of a particular species to survive and successfully reproduce

microhabitat

a smaller section within a habitat where an organism will experience slightly different environmental conditions compared to the overall habitat

mutation

a change made to a gene or chromosome that brings a new allele variation into a population

mutualism

a partnership between two different kinds of organism where both benefit

optimum tolerance range

the zone where an abiotic factor is within an optimum range for a species to survive and reproduce

parasitism

an interaction between species where one (the parasite) benefits and the other species (the host) is harmed

physiological adaptation

internal features (cell/tissue/organ/system) that relate to the functioning of an organism, and increase the chances of surviving and successfully reproducing in a particular environment

population

a group of organisms of the same species living and reproducing together in a given area

predation

an interaction between animals that occurs when one animal species (the predator) kills and feeds on another animal (the prey)

primary ecological events

primary factors that affect the size of a population including births, deaths, immigration and emigration

producers

the members of the community that supply the energy needs to the consumers by producing organic compounds; known as autotrophs

secondary ecological events

secondary factors that affect the size of a population including density-dependent and density-independent factors

species diversity

the variety of different organisms living in a given habitat or region e.g. the number of different species living in the Amazon rainforest

structural adaptation

anatomical features that relate to size, shape, structures, limbs etc. that increase the chances of an organism surviving and successfully reproducing in a particular environment

zone of intolerance

the zone where there is too little or too much of an abiotic factor for a species to adequately survive and reproduce, hence no organisms can survive in this range

asexual reproduction

the production of offspring from just one parent, no need to find a mate, resulting in large numbers of offspring being produced relatively quickly

binary fission

a form of asexual reproduction where there is an equal division of the complete organism into two identical offspring

budding

a form of asexual reproduction where a new individual develops through cell division as an outgrowth on the parent

clones

identical offspring produced from asexual reproduction

cutting

a cloning technique used in agriculture where a section of a plant (stem, root or leaf) is removed and planted in soil or water

embryo splitting

a cloning technique used in horticulture to produce clones in livestock (stockbreeding) that utilises the splitting of an embryo to produce offspring from quality male and female livestock

external fertilisation

where animals release their gametes into the external environment and fertilisation occurs outside the body

fragmentation

a form of asexual reproduction where part of the organism breaks off and regenerates into a new individual

grafting

a cloning technique used in agriculture that involves transferring part of one plant onto the cut stem of another plant (known as rootstock)

hermaphrodite

an organism that contains both male and female reproductive organs

internal fertilisation

where males deliver sperm directly into the female's reproductive tract and fertilisation occurs inside the body

parthenogenesis

a form of asexual reproduction that involves the development of a new individual from an unfertilised egg which does not require sperm from the male

sexual reproduction

a form of reproduction where two parents contribute genetic material to the offspring resulting in genetically diverse individuals

spore formation

a form of asexual reproduction that involves the creation of new cells through mitosis; spores are then released into the environment when conditions are favourable

somatic cell nuclear transfer

(SCNT) a cloning technique that uses somatic cell genetic material to create a clone of an animal

tissue culture

a cloning technique used in agriculture to produce large quantities of plants rapidly; tissue is taken from plants, grown in a culture medium and treated with hormones and nutrients

vegetative propagation

a form of asexual reproduction in plants where there is a separation and formation of a new plant from either leaves, stems or underground roots (runners, tubers, rhizomes and bulbs)

autosomal dominant gene

a dominant gene found on an autosome (non-sex chromosome)

autosomal recessive gene

a recessive gene found on an autosome (non-sex chromosome)

dihybrid cross

a cross between two individuals with different alleles at two gene loci

filial generation

the offspring of a parental generation

linked genes

genes found closely together on the same chromosome that are unlikely to be separated by crossing over

monohybrid cross

a cross between two individuals with different alleles at a single locus

pedigree chart

a visual display using symbols to follow the inheritance of a particular trait through a family over a number of generations

Punnett square

a table showing the random combination of gametes and the genotypes of the resulting offspring

test cross

a cross between an unknown genotype for a dominant trait e.g. BB or Bb with a homozygous recessive for the same trait

X-linked dominant gene

a dominant gene found on the X chromosome; sex linked

X-linked recessive gene

a recessive gene found on the X chromosome; sex linked

codominance

the pattern of dominance where a heterozygote expresses both of the alleles for a given gene in the phenotype

complete dominance

the pattern of dominance where one allele (D) completely dominates or hides the other allele (d) and is shown in the phenotype

epigenetics

the interaction of certain chemicals with DNA, affecting the way genes are expressed

genotype

the complete set of alleles present in the DNA of an individual organism; the alleles at a single gene location

hemizygous

a genotype in males where only one allele is present on the X chromosome

heterozygous

a genotype with two different alleles at a specific gene region e.g. Aa; hybrid

homozygous

a genotype with two of the same alleles at a specific gene region e.g. AA or aa; pure breed

incomplete dominance

the pattern of dominance where a heterozygote expresses an intermediate form (blended) of the alleles for a given gene in the phenotype

multiple allele system

when there are more than two possible alleles within a population for a particular gene e.g. ABO blood type

phenotype

the physical expression of their genotype (the observable characteristics) and the influence of the organism's environment

acrocentric

relates to the position of centromere on a chromosome; located very close to one end

allele

an alternative form of a gene; written with upper and lower case letters; e.g. AA, Aa or aa

autosomes

non-sex chromosomes; chromosomes 1-22 in humans

blastocyst

the cell stage of a zygote at Day 6 (64-200 cells) where the cells start to specialise into tissues

centromere

the region of the chromosome where the sister chromatids are held together; the attachment point of the spindle fibres during prophase

chiasma

the point between non-sister chromatids where crossing over occurs

chromatid

a single chromosome structure; non-replicated prior to S-phase in cell cycle

chromatin

the uncondensed form of a chromosome where the DNA is wrapped tightly around histone proteins forming nucleosomes

chromosome

structures found within the nucleus of almost all eukaryotic cells, composed of a single strand of DNA; found in the cytoplasm of prokaryotes

crossing over

a common event that results in the genetic exchange between non-sister chromatids of homologous pairs of chromosomes

diploid

cells that contain two copies of each chromosome (2n); somatic cells in humans

embryo

the cell stage during development between 2 and 8 weeks

fertilisation

the union of male and female gametes to form a zygote

foetus

a human embryo from 8 weeks onwards

gametes

the haploid sex cells involved in sexual reproduction; sperm and ova

gene

coded sections of DNA that carry the information for the production of a protein/trait

gene locus

the position/location of a gene on a chromosome

genome

the total sum of genetic information (DNA) within a haploid cell of an organism

genomics

the study of an organism's genome

germ cell

the diploid cell located in the gonads from which meiosis begins to produce gametes

gonads

the reproductive organs in which gametes are produced; testes and ovaries

haploid

cells that contain only one copy of each chromosome (n); sex cells in humans

histones

proteins around which DNA is coiled within the nucleus

independent assortment

the random alignment of maternal and paternal chromosomes during Metaphase I which creates variation of chromosome combinations produced in the gametes

karyotype

the image or picture of the full set of chromosomes from an individual's cell arranged in pairs according to their length, position of the centromere and banding patterns

metacentric

relates to the position of centromere on a chromosome; located in the centre

monogenic trait

a trait controlled by one gene; leads to only a small amount of variation of the trait within the population

monosomy

an individual with one less chromosome; one copy of a chromosome instead of two (2n-1)

non-disjunction

when chromosomes fail to segregate evenly to opposite poles during meiosis I or II; results in uneven chromosome number in the gametes

ovum

the haploid (n) female gamete (pl. ova)

polar bodies

the unused cells during meiosis in females; the cells that do not go on to full maturity