HSC Biology Terms and Definitions

Do you often find that you get lost in the sea of HSC Biology Terms and Definitions?

Do your eyes glaze over when your teacher starts talking in ‘Biologese’ because you don’t know what any of the words mean?

Fear no more!

I hereby seek to dispel the mystery of Biologese with the following HSC Biology Terms and Definitions complete with useful examples!

Let’s dive in!

60+ HSC Biology Terms and Definitions:


TermDefinitionExample and related concepts
Sexual reproductionGenetic information comes from two sexes, and gametes must meet and fuseFor humans, the egg and sperm will meet. For flowers, the ovule and the pollen will meet.
Asexual reproductionDoesn’t require an egg and sperm (gametes) to meet, and usually comes from one organismBacteria can split from a single cell in a process called binary fission
GameteGametes are cells which can give rise to a new organism when they meet with a gamete of the opposite gender.Gametes usually have a haploid chromosomes (half the number of chromosomes in an adult).
External fertilisationEgg and sperm meet outside the female bodyFish and frogs can release their eggs and sperm outside their body. Water assists in keeping them moist.
Internal fertilisationEgg and sperm meet inside the female bodySeen in humans, dogs and cats
Binary fissionType of asexual reproduction where bacteria ‘split’ in half, each half becomes a new daughter cellWhen comparing the life cycle between prokaryotes and eukaryotes, there are similarities that can be drawn. Both replicate their DNA, and both increase the size of the cell to create two daughter cells except this occurs in the organism level for bacteria, and the cell level for humans.
BuddingType of yeast asexual reproduction where cells grow bigger until a little ‘bud’ forms on the mother cell. This bud grows bigger until it is big enough to break off.Great demonstration of budding is the immortal hydra
MitosisCell division where daughter cells have the same number of chromosomesHuman somatic cells replicate by mitosis. The new daughter cells are identical to the mother cell.
MeiosisThe process by which cells are replicated but it is different from mitosis because 1 parent cell gives rise to 4 daughter cells, which are different because of crossing overHaploid gametes are produced from meiosis. It is important that the daughter cells aren’t identical to the mother cells.
DNA replicationMaking new copies of DNA so new cells can have a copyDNA replication is a semi-conservative process which means that the two new DNA molecules that are made contains one strand of the original DNA
TranscriptionThe process of copying information encoded in DNA into a ‘photocopy’ or RNA so the ribosome can read itDNA is hard to read because it is so long and the structure is different. mRNA is a direct copy of the sequences in DNA, making it easier to use the information encoded in the genome
TranslationRibosome ‘reading’ the mRNA which tells it to recruit certain amino acids. Results in a polypeptide chaintRNAs carry amino acids to the growing polypeptide chain
PolypeptidesPolypeptides are short proteins made up of chains of amino acidsPolypeptides are usually smaller than proteins but larger than peptides and amino acids
ChromosomeA chromosome is a package of DNA, which is a long DNA molecule that is coiled tightly for easy storage and movementHumans have 46 chromosomes (26 pairs)
GeneA gene codes for a particular characteristic. A gene is a section of our DNA moleculeThe gene for eye colour
AlleleAllele is a form of a gene. For each gene, we have two alleles - one from mum and one from dadA blue eye allele and a brown eye allele
PhenotypeThis is the physical characteristic of a genotypeBrown eyes are coded for by genotype ‘Aa’
GenotypeA genotype is the genetic code for a characteristicAa
Homozygous genotypesGenotypes where the two alleles are the sameAA or aa
Heterozygous genotypesGenotypes where the two alleles are differentAa or Bb
Simple dominanceWhere one allele is completely dominant over the other (the recessive allele)Where greenness is dominant over yellowness (of Mendel’s peas)
Monohybrid crossA Medelian cross where the two individuals have the same genotypeCross of AA and AA or Aa and Aa
Co-dominanceWhere two or more alleles have equal dominance (which gives rise to a third outcome)Snapdragons experiment, where a red one and a white one will cross to form a pink one. Red and white are co-dominant.
Sex-linked genesA common genetic variation that occurs in >1% of the population>1% of people have a C T nucleotide mutation in a specific part of their DNA
Single nucleotide polymorphism (SNP)A common genetic variation that occurs in >1% of the population>1% of people have a C T nucleotide mutation in a specific part of their DNA
DNA sequencingFinding out what the sequence of DNA isIllumina technology is commonly used at and can find the sequence (CTTAGACCGA…) of almost all of the 3 billion base pairs that you have

Genetic Change

TermDefinitionExample and related concepts
MutagenAnything causing mutationsCigarette smoke
MutationA change in DNA sequencePoint mutations are one nucleotide differences in a gene (CTAGTA CTTGTA)
Genetic flow/gene mutationIntroducing genes of one population into another by breeding between two populationsA bee carrying the pollen from one population of flowers to another can be considered genetic flow
Genetic diversityVariation in a genetic pool for a particular characteristicGenetic diversity is the reason why some people have black hair, others have brown hair, and others still can have blonde or red hair.
BiotechnologyUsing biology for industryWe can use massive cultures of bacteria to make drugs at the industrial scale
Artificial inseminationTaking semen from a male animal and inserting it into a female uterusFarmers pick which cows mate to ensure that the cow with the best characteristics mate and to prevent inbreeding
Artificial pollinationTaking pollen or stamen from one plant into the pistil of anotherThe characteristics of flowers can be mixed
CloningCreating a genetically identical copy of an organismWhole organism cloning of dolly the sheep
Transgenic organismsSpecies which are the result of genetic modification'Anti-freeze strawberries’

Infectious Disease

TermDefinitionExample and related concepts
PathogenA foreign body that can cause diseaseChickenpox
AntigenMolecules made of protein which are on the surface of cells that trigger the immune response when they detect infectious pathogensThe Rhesus antigen causes our blood type to be + or -
AntibodyMade by plasma cells which specifically target a pathogen by binding to itStarts getting released after the innate immune system can’t defeat the infection
EpidemicAn infectious disease spreading across a wide rangeAIDS epidemic
Innate immune systemMade up of neutrophils, macrophages and other cells to attack any non-specific responseAny bacteria or virus entering gets attacked by the same molecules. E.g. regardless if it is S. aureus or E. coli, they get attacked by cytokines and other molecules
Adaptive immune systemMade up of T cells and B cells and attack a specific pathogenT cells and B cells prepare chemicals and molecules to specifically attack either S. aureus or E. coli
CytokinesProteins that immune cells use to communicate with each otherCells can release growth factors (GFs), interferons (IFs) and interleukins (ILs)
Cell differentiationHow cells become specialised for their different functions. They all start off exactly the sameWhite blood cells specialise from stem cells
QuarantineIsolation after coming from another country to make sure they don’t spread potential diseasesWaiting to see if plants/animals have introduced infectious diseases prevents introducing the disease to an unimmune public
Passive immunityInjection of someone else’s antibodiesIf you wait for your body to respond to neutralise snake bites, it’ll be too late. We use another animals’ antibodies and inject it into the affected person. These antibodies will act to neutralise the bite without needing an immune reaction
Active immunityMaking your own antibodiesAfter a vaccine, your body responds by making antibodies against the infectious agent

Non-Infectious Disease and Disorders

TermDefinitionExample and related concepts
HomeostasisA process involving feedback networks (positive and negative) that means that organisms (like humans) can adapt to changes in their environmentWhen it is warm, mammals have mechanisms like sweating which allow us to adapt to the environment. If we did not have these mechanisms, our enzymes would denature!
EnzymesA protein that is responsible for lowering the activation energy of a reaction, making it occur fasterBromalain is an enzyme found in pineapple and kiwi fruit.
Lock and key model of substrate specificity for enzymes.
Enzymes will become denatured if the temperature or pH changes outside of its optimal range.
SubstratesMolecules part of a chemical reaction which react together to form the productsSubstrates are the molecules which go into enzymes
OptimalBest for efficiency of a reactionOptimal temperature of most human chemical reactions and their enzymes is around 37 degrees Celsius (this is our human body temperature is around this range)
Endotherm organismsOrganisms which control their own body temperature, independently of the outside environment‘Warm blooded’ animals, such as humans and other mammals
EctothermOrganisms which do not control their own body temperature, and rely on the outside environment‘Cold blooded’ animals, such as lizards and other reptiles
Adaptive advantageAn advantage of a particular characteristic which helps the organism to adapt to the environment, according to the theory of evolution by natural selectionAn adaptive advantage for a frog living in a green forest is that it has green skin which allows it to camouflage, and thus survive and pass on its genetic characteristics to its offspring
HormonesChemicals which are used to control organs in the bodyAnti-diuretic hormone (ADH) can tell the kidney to reabsorb more water, and so the need to urinate is decreased
DiseaseDisturbance in normal structure and function caused by something outside the bodyCan be caused by improper diet or radiation exposure
DisorderDisturbance in normal body structure and function caused by something inside the bodyCan be caused by genes, birth defects
CancerUncontrolled growth of cellsStomach cancer is when stomach cells keep dividing and don’t stop
IncidenceHow many new cases of this disease in x time?Estimated 14,320 new melanoma cases diagnosed in 2018
PrevalenceHow many people have had this disease in x time?At the end of 2013, 53,215 people were living with melanoma
MortalityNumber of deaths in a given time or locationSkin cancer mortality in Australia is estimated to be 3.9% of all deaths in 2018
EpidemiologyThe study of how a disease occurs and spreads and where it is most prevalentEpidemiology allows us to understand why a disease starts and spreads and how to tackle it
Genetic engineeringChanging the characteristics of an organism by changing its genesMice that glow due to the insertion of a gene that makes fireflies glow

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Gia-Yen Luong has been an Art of Smart coach for 3 years, coaching a range of subjects including HSC English, Legal Studies, Biology, Chemistry and General Maths. She is in her final year of a mega double degree in Law/Science (Neuroscience). She graduated high school with an ATAR of 99.9 and spends most of her time trying to convince people that it’s wholly possible to get such a mark while still having a normal life during Year 12. She enjoys reading, podcasts and Clash of Clans. In effect, she is a true nerd.