Pro subject in the app

Leaving Cert Biology glossary

114 key terms in plain English, grouped by strand and labelled Higher or Ordinary. The same definitions the H1 Owl app teaches, written from the published syllabus.

Filter terms114 terms

Nature of Science 17 terms

AccuracyHigher: How close a measured value is to the true or accepted value. Accuracy is improved by using correctly calibrated instruments and careful technique.
Anomalous resultHigher: A reading that clearly does not fit the pattern of the other results in a set. It should be recorded and investigated rather than deleted, and is normally left out when calculating a mean.
ControlHigher: A setup in an experiment that is identical to the others except that the independent variable is not applied. It provides a baseline for comparison so any change can be linked to the variable being tested.
ControlOrdinary: A part of an experiment set up in the same way but without the thing being tested. It is used to compare the results against.
CorrelationHigher: A relationship in which two variables change together in a consistent pattern. A correlation on its own does not prove that one variable causes the change in the other.
Dependent variableHigher: The factor that is measured as an outcome of an experiment. It is expected to respond to changes in the independent variable.
HypothesisHigher: A testable statement that predicts a relationship between variables and can be shown to be false. It is written before the investigation begins and is either supported or rejected by the data collected.
HypothesisOrdinary: An idea or statement that you can test with an experiment. The results either support it or show that it is wrong.
Independent variableHigher: The one factor that the investigator deliberately changes in an experiment. All other variables are kept constant so its effect can be measured fairly.
MagnificationHigher: How many times larger an image is than the actual object, calculated as image size divided by actual size. For a compound microscope the total magnification is the eyepiece power multiplied by the objective lens power.
MagnificationOrdinary: How many times bigger an image looks than the real object. With a microscope you multiply the eyepiece by the objective lens to get it.
ModelHigher: A simplified representation of a biological structure or process, which may be physical, diagrammatic, mathematical or computer based. Models help to explain and predict behaviour, but every model leaves out some detail of the real system.
Peer reviewHigher: The process in which independent scientists working in the same field examine a piece of research before it is published. They check the method, the data and the conclusions, which helps ensure that published science can be trusted.
PrecisionHigher: How closely repeated measurements agree with one another, and how finely an instrument can measure. A set of readings can be precise and still be inaccurate if there is a systematic error.
ReliabilityHigher: The extent to which an investigation gives the same result when it is repeated under the same conditions. Reliability is improved by repeating readings and calculating a mean.
ValidityHigher: The extent to which an investigation actually tests what it was designed to test. A valid design controls all other variables and includes a suitable control, so the results genuinely reflect the independent variable.
VariableOrdinary: Something in an experiment that can change, such as temperature or light. You change one variable and keep all the others the same.

Organisation of Life 33 terms

Active siteHigher: The specific region of an enzyme where the substrate binds. Its shape is complementary to the substrate, which gives enzymes their specificity.
Active transportHigher: The movement of a substance across a membrane against its concentration gradient by means of carrier proteins. It requires energy from ATP, so it stops if respiration in the cell is blocked.
Amino acidHigher: The monomer or building block from which proteins are made, containing an amino group, a carboxyl group and a variable side chain. About twenty different amino acids are combined in different orders to make all the proteins of an organism.
CarbohydrateHigher: A biomolecule made of carbon, hydrogen and oxygen, with the hydrogen and oxygen usually present in a two to one ratio. Carbohydrates range from simple sugars such as glucose to polysaccharides such as starch and cellulose.
CarbohydrateOrdinary: A food type made of carbon, hydrogen and oxygen, such as sugar and starch. Carbohydrates give the body energy.
CellHigher: The basic structural and functional unit of all living organisms. Cells may be prokaryotic (no true nucleus) or eukaryotic (with a membrane-bound nucleus).
CellOrdinary: The basic unit that all living things are made of.
Cell membraneOrdinary: The thin layer around the outside of a cell. It controls what goes into and out of the cell.
Cell wallHigher: A rigid layer lying outside the cell membrane in plant, fungal and bacterial cells. In plants it is made of cellulose, and it gives support and stops the cell bursting when water enters by osmosis.
Cell wallOrdinary: A strong outer layer made of cellulose found around plant cells. It gives the cell support and keeps its shape.
ChloroplastHigher: A green organelle found in plant cells and algae that contains chlorophyll and is the site of photosynthesis. Its stacked internal membranes trap light energy and convert it into chemical energy.
ChloroplastOrdinary: The green part of a plant cell that holds chlorophyll. Photosynthesis happens here.
ChromosomeHigher: A long thread of DNA wound around proteins, carrying many genes in a fixed linear order. A human body cell contains 46 chromosomes arranged as 23 homologous pairs.
DenaturationHigher: A permanent change in the shape of a protein, such as an enzyme, usually caused by high temperature or extreme pH. It alters the active site so the enzyme can no longer function.
DiffusionHigher: The net movement of particles from a region of higher concentration to a region of lower concentration, that is down a concentration gradient. It is passive and needs no energy input from the cell.
DiffusionOrdinary: The movement of particles from where there are many of them to where there are fewer. It does not need any energy.
EnzymeHigher: A protein that acts as a biological catalyst, speeding up a specific reaction by lowering its activation energy without being used up in the process.
EnzymeOrdinary: A protein that speeds up reactions in living things without being used up.
EukaryoteHigher: An organism whose cells contain a true nucleus enclosed by a membrane, along with other membrane bound organelles. Animals, plants, fungi and protists are all eukaryotes.
LipidHigher: A biomolecule made of carbon, hydrogen and oxygen but containing proportionally far less oxygen than a carbohydrate. Fats and oils are formed from glycerol and fatty acids, and lipids act as long term energy stores and as membrane components.
MitochondrionHigher: A rod shaped organelle with a folded inner membrane where most of aerobic respiration takes place. Cells with high energy demands, such as muscle cells, contain very large numbers of mitochondria.
MitochondrionOrdinary: The part of a cell where respiration takes place. It releases the energy that the cell needs.
NucleusOrdinary: The part of the cell that holds the DNA and controls the cell.
OrganelleHigher: A distinct structure inside a cell that carries out a particular function, such as the nucleus, the mitochondrion or the ribosome. Dividing the work between organelles allows a single cell to run many processes at the same time.
OsmosisHigher: The movement of water molecules across a selectively permeable membrane, from a region of higher water concentration to a region of lower water concentration. It is a special case of diffusion involving only the solvent.
OsmosisOrdinary: The movement of water through a membrane from a weaker solution to a stronger one. It is a special kind of diffusion.
Phospholipid bilayerHigher: The double layer of phospholipid molecules that forms the basis of every cell membrane. The water attracting heads face outwards and the water repelling tails face inwards, creating a barrier that controls what enters and leaves the cell.
ProkaryoteHigher: An organism whose DNA lies free in the cytoplasm rather than inside a nuclear membrane, and whose cells have no membrane bound organelles. Bacteria are prokaryotes and possess a cell wall and ribosomes but no mitochondria.
ProteinHigher: A large biomolecule built from amino acids joined by peptide bonds and containing carbon, hydrogen, oxygen and nitrogen. Its folded three dimensional shape determines its role, for example as an enzyme, an antibody or a structural fibre.
ProteinOrdinary: A food type made of amino acids joined together. The body uses protein for growth and repair.
RibosomeHigher: A very small organelle made of RNA and protein that is the site of protein synthesis. Ribosomes may lie free in the cytoplasm or be attached to the endoplasmic reticulum, and they are found in prokaryotes as well as eukaryotes.
SubstrateHigher: The specific reactant that an enzyme acts upon. It binds to the active site to form an enzyme substrate complex and is then converted into the product or products.
VacuoleHigher: A sac filled with fluid and surrounded by a membrane. A mature plant cell has one large permanent vacuole containing cell sap, which stores substances and keeps the cell turgid.

Structures and Processes of Life 39 terms

Aerobic respirationHigher: The controlled release of energy from glucose using oxygen, producing carbon dioxide, water and a large yield of ATP. It begins in the cytoplasm and is completed inside the mitochondria.
AlleleHigher: One of two or more alternative forms of the same gene, found at the same locus on homologous chromosomes. An organism carries two alleles for each gene, one inherited from each parent.
AlveolusHigher: One of the microscopic air sacs found at the ends of the bronchioles in the lungs. Its very thin moist wall and dense covering of capillaries allow rapid gas exchange between the air and the blood.
AlveolusOrdinary: A tiny air sac in the lungs. Oxygen and carbon dioxide are swapped here between the air and the blood.
AmylaseOrdinary: An enzyme that breaks starch down into a sugar called maltose. It is found in saliva in the mouth.
Anaerobic respirationHigher: The release of energy from glucose without oxygen, giving a much smaller yield of ATP. In human muscle the glucose is converted to lactic acid, while yeast produces ethanol and carbon dioxide.
ArteryHigher: A blood vessel that carries blood away from the heart. Arteries have thick muscular and elastic walls with a narrow lumen to withstand high pressure, and they contain no valves apart from those at the exit of the heart.
ArteryOrdinary: A blood vessel that carries blood away from the heart. It has thick strong walls because the blood is at high pressure.
ATPHigher: Adenosine triphosphate, the molecule that carries energy in a form cells can use immediately. Energy is released when the bond holding its third phosphate group is broken, leaving ADP and phosphate.
CapillaryHigher: The smallest type of blood vessel, with a wall only one cell thick. Capillaries form dense networks that bring blood close to every cell, allowing oxygen, nutrients and wastes to be exchanged.
CapillaryOrdinary: A very tiny blood vessel with a wall only one cell thick. Oxygen and food pass through it to the cells.
ChlorophyllHigher: The green pigment held in chloroplasts that absorbs light energy, mainly from the red and blue regions of the spectrum. It reflects green light, which is why most leaves look green.
ChlorophyllOrdinary: The green colour found in plant leaves. It takes in light energy for photosynthesis.
DigestionOrdinary: The breaking down of food into small pieces the body can take in. Enzymes speed this process up.
DNAHigher: Deoxyribonucleic acid, the molecule that stores genetic information in the sequence of its bases. This code directs the production of proteins.
DNAOrdinary: The chemical in the nucleus that carries the genetic code. It decides the features that a living thing has.
Dominant alleleHigher: An allele whose characteristic appears in the phenotype whenever the allele is present, including in a heterozygote. It masks the effect of the matching recessive allele.
GeneHigher: A section of DNA that codes for a particular characteristic, usually by directing the making of a protein. Each gene occupies a fixed position, called its locus, on a chromosome.
GeneOrdinary: A short piece of DNA that controls one feature, such as eye colour. Genes are passed on from parents to their children.
GenotypeHigher: The particular combination of alleles that an organism carries for a trait. It is homozygous when the two alleles are identical and heterozygous when they are different.
HaemoglobinHigher: The iron containing red pigment carried inside red blood cells. It binds oxygen in the lungs to form oxyhaemoglobin and releases that oxygen in tissues where the oxygen concentration is low.
HomeostasisHigher: The maintenance of a stable internal environment in the body despite changes in the surroundings. Factors such as body temperature, blood glucose and water balance are held within narrow limits, usually by negative feedback.
InsulinHigher: A hormone secreted by the pancreas when the blood glucose concentration rises. It causes body cells to take up glucose and the liver to store it as glycogen, which lowers blood glucose again.
MeiosisHigher: A form of cell division that halves the chromosome number, producing four genetically varied haploid gametes from one diploid parent cell.
MitosisHigher: A form of cell division that produces two genetically identical diploid daughter cells. It is used for growth, repair and asexual reproduction.
PhenotypeHigher: The observable characteristics of an organism, produced by its genotype interacting with the environment. Two organisms with different genotypes can show the same phenotype.
PhloemHigher: The living plant tissue that transports dissolved food, mainly sucrose, from the leaves to the rest of the plant. This movement is called translocation and can travel up or down the plant.
PhloemOrdinary: The living tubes in a plant that carry food made in the leaves to the rest of the plant.
PhotosynthesisHigher: The process by which green plants use light energy, captured by chlorophyll, to convert carbon dioxide and water into glucose and oxygen.
PhotosynthesisOrdinary: How green plants use light energy to make food (glucose) from carbon dioxide and water, giving out oxygen.
RespirationHigher: The release of energy from glucose in cells. Aerobic respiration uses oxygen and takes place mainly in the mitochondria, producing carbon dioxide and water.
RespirationOrdinary: How cells release energy from glucose. It happens mainly in the mitochondria.
TranspirationHigher: The loss of water vapour from a plant, mostly through the stomata of the leaves. It creates the pull that draws the transpiration stream of water upwards through the xylem.
VeinHigher: A blood vessel that carries blood back towards the heart. Veins have thinner walls and a wider lumen than arteries, and they contain valves that stop the low pressure blood flowing backwards.
VeinOrdinary: A blood vessel that carries blood back to the heart. It has thinner walls and valves to stop the blood flowing backwards.
VillusHigher: One of the many tiny finger like projections lining the small intestine. Villi greatly increase the surface area for absorption, and each one contains blood capillaries for sugars and amino acids and a lacteal for the products of fat digestion.
VillusOrdinary: A tiny finger shaped bump on the inside of the small intestine. Villi give a large surface for absorbing digested food.
XylemHigher: The plant tissue made of dead, hollow, lignified cells that carries water and dissolved minerals upwards from the roots. It also contributes to the support of the plant.
XylemOrdinary: The tubes in a plant that carry water and minerals up from the roots. The cells are dead and hollow.

Interactions of Life 25 terms

Abiotic factorHigher: A non living physical or chemical influence in an ecosystem, such as light intensity, temperature, pH, salinity or water availability. Abiotic factors help decide which species can survive in a habitat.
AdaptationHigher: A structural, behavioural or physiological feature that improves an organism's chance of surviving and reproducing in its habitat. Adaptations build up over many generations through natural selection.
AdaptationOrdinary: A feature that helps a living thing survive where it lives. For example, thick fur keeps an animal warm.
BiodiversityHigher: The variety of living organisms in an area, covering the number of different species present and the genetic variation within them. Greater biodiversity generally makes an ecosystem more stable and better able to recover from change.
BiodiversityOrdinary: The number of different kinds of living things in an area. More biodiversity usually means a healthier habitat.
Biotic factorHigher: A living influence on the organisms in an ecosystem, such as predation, competition, parasitism or the availability of food. Biotic factors can change both the size and the distribution of populations.
CommunityHigher: All the populations of different species that live and interact together in the same habitat. The community plus the non living surroundings makes up the ecosystem.
CompetitionHigher: The struggle between organisms for a resource that is in short supply, such as food, water, light, space or mates. It is called intraspecific when it occurs within one species and interspecific when it occurs between species.
CompetitionOrdinary: When living things struggle for something that is in short supply. They may compete for food, water, light or space.
ConsumerOrdinary: An animal that gets its food by eating other living things.
DecomposerHigher: An organism, such as a bacterium or fungus, that breaks down dead organisms and waste, recycling nutrients back into the ecosystem.
DecomposerOrdinary: A living thing, such as a fungus or bacterium, that breaks down dead material and recycles nutrients.
EcosystemHigher: A community of living organisms together with the non-living parts of their environment, interacting as a system through energy flow and nutrient cycling.
EutrophicationHigher: The enrichment of a body of water with nutrients such as nitrates and phosphates, often from fertiliser runoff or sewage. It triggers rapid algal growth that blocks light, and when the algae die the decomposing bacteria use up the dissolved oxygen so fish and other animals die.
Food chainOrdinary: A diagram that shows what eats what in a habitat. It starts with a green plant and the arrows show the way the energy moves.
Food webHigher: A set of interconnected food chains showing the feeding relationships within a community. A web is more realistic than a single chain because most organisms eat, and are eaten by, more than one species.
HabitatHigher: The particular place where an organism lives, providing the conditions and resources it needs. A rocky seashore and a hedgerow are examples of habitats.
HabitatOrdinary: The place where a plant or an animal lives. A pond and a hedge are two examples of habitats.
Nitrogen fixationHigher: The conversion of nitrogen gas from the air into compounds such as ammonia that plants are able to use. It is carried out mainly by nitrogen fixing bacteria, some of which live in the root nodules of legumes.
PopulationHigher: All the members of a single species living in a particular habitat at a given time. Population size is limited by factors such as food supply, predation, disease and competition.
PopulationOrdinary: All the members of one species living in the same place. An example is all the rabbits in one field.
ProducerHigher: An organism, usually a green plant, that makes its own food by photosynthesis and forms the base of a food chain.
ProducerOrdinary: A green plant that makes its own food by photosynthesis and starts a food chain.
Pyramid of numbersHigher: A diagram in which the width of each bar represents the number of organisms at each trophic level. It is usually widest at the producer level, but it can be inverted when one large producer such as a tree supports many consumers.
Trophic levelHigher: A feeding level in a food chain. Roughly 10 percent of the energy at one trophic level is passed on to the next, with the rest lost mainly as heat.

No term matches that. Try a shorter word, or search all four subjects.

More subjects: Maths · Chemistry · Physics. Or test yourself with the Maths question of the day.

Get the free study guide

H1 Owl is now on the App Store: download it for iPhone. Sign up here and get The Leaving Cert Maths Game Plan, our free PDF study guide, straight away, plus occasional study tips.

Occasional emails, no spam. Under 16? Ask a parent to sign up for you.