All Biology Definitions for Leaving Cert

All Biology Definitions for Leaving Cert

The Scientific Method

  • Scientific Method is a process of investigation where problems are identified and their explanations are tested by carrying out experiments.
  • Observation : An unbiased, accurate report of an event.
  • Hypothesis : An educated guess based on observations.
  • Experiment : An experiment is designed to test a hypothesis.
  • Data : Consists of measurements, observations/information gathered during an experiment.
  • Replicate : A repeat of an experiment.
  • Control : A comparison used to provide a standard against which the actual experiment can be judged.
  • Theory : A hypothesis that has been supported by different experiments.
  • Principle/Law : A theory that has shown to be valid against long-term testing.
  • Ethics : Refers to whether issues are right or wrong

 

Characteristics of Life

  • Continuity of life : Living things that arise from other living things of the same type (Biogenesis)
  • Metabolism : Sum of all the chemical reactions in an organism.
  • Characteristics of life : The common features shared by living organisms.
  • Organisation : Living things are composed of cells, tissues,organs and organ systems.
  • Nutrition : Process by which an organism obtain and uses food.
  • Excretion : Removal of waste products of metabolism.
  • Response : The reaction of organisms to stimuli in their environment.
  • Reproduction : The production of new individuals.

 

Nutrition

  • Biomolecules : Molecules found in living things are composed of atoms where elements bonded together in different ratios to form biomolecules. Such as Carbohydrates, Lipids, Proteins and Vitamins.
  • Organic Compounds : Carbon atoms bonded together make up most of the chemical compounds in living things.
  • Monosaccharides : Single sugar molecules such as Glucose.
  • Disaccharides : 2 sugar molecules bonded together such as Sucrose,Lacotse and Maltose.
  • Polysaccharides : Made up of many sugar molecules bonded together. Eg  – Starch, Glycogen and Cellulose
  • Phospholipids : Fat-like substances where one of the fatty acids is replaced/added a phosphate group.
  • Anabolic reactions :  Convert smaller molecules into larger ones. (Using energy)
  • Catabolic reactions : Complex molecule is broken down to simple molecules. (Releasing energy)

 

Ecology

  • Ecology : The study of the relationships of living organisms with one another and with the environment.
  • Ecosystem : A community of organisms and their abiotic environment.
  • Biosphere : Part of the earth in which life can occur.
  • Habitat : Place in the environment where an organism lives.
  • Population : All the member of the same species living in an area.
  • Community : Plants and animals sharing the resources of a particular habitat.
  • Niche : The functional role of an organism in an ecosystem. Eg – How it feeds, what it eats, who eats it etc.
  • Abiotic Factors : Non-living factors.
  • Biotic Factors : Living Factors.
  • Climatic Factors : Refers to weather over a long period of time.
  • Edaphic factors : Aspects of the soil that influence an ecosystem such as the soil pH, soil type,moisture, air and mineral content of soil.
  • Producers : Autotrophs that carry out photosynthesis.
  • Consumers : Organisms that take in food from another organisms.
  • Primary Consumers : Organisms which feed directly on producers. Eg – Rabbits
  • Secondary Consumers : Carnivores that feed on primary consumers. Eg – Fox
  • Tertiary Consumers : Carnivores that feed on secondary consumers. Eg – Badger
  • Food chain : The pathway along which energy is transferred in an ecosystem.
  • Food web : 2 or more interlinked food chains.
  • Trophic level : Is a feeding stage/energy level in a food chain.
  • Pyramid of numbers : Based on numbers of organisms at each trophic level in a food chain.
  • Nutrient recycling : The way in which elements (Carbon and Nitrogen) are exchanged between the living and non-living components of an ecosystem.
  • Nitrogen Fixation : Conversion of nitrogen gas into ammonia (NH3), ammonium (NH4+) or nitrate ( NO3)
  • Nitrification : The ammonia is converted to nitrites and then to nitrates by nitrifying bacteria.
  • Dentrification : Conversion of nitrates to nitrogen gas. It is carried out by denitrifying bacteria in the soil.
  • Pollution : Any harmful addition to the environment.
  • Pollutants : Substances that cause the undesirable change to the environment.
  • Conservation : The wise management of our natural resources.
  • Competition : Occurs when organisms actively struggle for a resource that is in short supply.
  • Intra-specific competition : This takes place between members of the same species. Eg – Buttercups compete with each other for light,water and minerals.
  • Inter-specific competition :  Occurs between members of different species. Eg – Foxes and thrushes compete for earthworms.
  • Contest competition : Involves an active physical contest between 2 individuals. Eg – Robins actively defend a territory for feeding, nesting and reproduction.
  • Scramble competition : Involves all the competing organisms getting some of the resources. Eg – Seedlings competing for space around parent plant.
  • Adaptations : Ways in which organisms are specialised either in structure/behavior to survive competition.
  • Predation : An organism that lives by killing and consuming other living things. Eg – Ladybirds kill greenfly.
  • Parasitism : Living organism that feeds on another living organism of a different species knows as host, generally causing harm to the host.
  • Ectoparasites/Exoparasites : Live on the body of the host. Eg – greenfly on rose bushes.
  • Endoparasites : Live on the inside of the body of the host. Eg – Disease causing bacteria in the human body (Streptococcus)
  • Symbiosis : Relationship between 2 organisms of different species that live in close association to the benefit of both organisms.
  • Saprophytes : Lives on dead organisms.
  • Quantitative study : A study to find out the number of organisms that exist in an ecosystem.
  • Qualitative study :  A study to find out the type(s) of organism that exist in an ecosystem.

 

Cells

  • Protoplasm : Is all the living parts of a cell.
  • Ultrastructure : The fine detail of a cell as seen as with an electron microscope.
  • Chromatin : Name given to chromosomes when they are not dividing.
  • Ribosomes : Very small organelles made of protein and RNA. Function is to make proteins.
  • Organelles : Distinct structures suspended in cytoplasm.
  • Prokaryotic cells : Cells do not have a nuclear membrane surrounding their DNA. Eg – Monera
  • Eukaryotic cells : These cells have a membrane bound nucleus and organelles.
  • Tissue : A group of similar cells specialised to carry out the same function.
  • Tissue culture : Cells grown on a sterile nutrient medium outside an organism.
  • Organ : A structure, containing different tissues, which has a specific function.
  • Organ system : A group of organs and tissues working together to carry out a specific function.
  • Catalyst : A substance that speeds up the rate of a chemical reaction(metabolism) without itself taking part in the reaction.
  • Enzymes : Defined as biological catalysts, protein in nature. Enzymes speed up the reactions in the cell without being used up in the reaction.
  • Substrate : The substance an enzyme reacts with.
  • Product : Is formed when an enzyme reacts with a substrate.
  • Active site : The region of the enzyme that binds with the substrate.
  • Denatured enzyme : An enzyme which has lost its shape and can no longer carry out its function.
  • Bioprocessing : Use of enzyme-controlled reactions to produce a product.
  • Bioreactor : A vessel used to carry out enzyme controlled reactions.
  • Batch processing : Fixed amount of nutrients added at beginning and emptied at the end of production.
  • Immobilised enzymes : Enzymes that are fixed/attached to each other or to an inert material.
  • Phosphorylation : Addition of phosphate to a molecule.
  • Protease : An enzyme which digests protein.
  • Cell continuity : All cells develop from pre-existing cells.
  • Chromosome : Coiled threads of DNA and protein that become visible in the nucleus at cell division.
  • Haploid cell : A cell which contains one of every chromosome type or pair.
  • Diploid cell : A cell which contains two of each type of chromosome (in homologous pairs).
  • Homologous pair : Consists of 2 chromosomes that each have genes for the same features at the same positions.
  • Interphase : The phase in the cell cycle when the cell is not dividing.
  • Mitosis : A form of cell division that produces two daughter cells, genetically identical to each other and to the parent cell.
  • Meiosis : A form of cell division that produces four genetically different daughter cells, each of which has half the number of chromosomes of the parent cell.
  • Cancer : Group of disorders in which certain cells lose their ability to control both the rate of mitosis and the number of times mitosis takes place.
  • Selectively permeable : Cell membranes allow the passage of some materials but not others.
  • Diffusion : The movement of a substance from its area of higher concentration to its area of lower concentration. (Passive process)
  • Active transport : The movement of a substance(usually ions) from its area of lower concentration to its area of higher concentration. (Opposite of diffusion)
  • Osmosis : The diffusion of water across a selectively permeable membrane, from its area of higher concentration to its area of lower concentration.
  • Hypotonic sol : Has a low concentration of solutes and thus a higher concentration of water than another solution.
  • Hypertonic sol : Has a higher concentration of solutes and thus a lower concentration of water than another solution.
  • Isotonic sol : Has the same concentration of solutes and water as another solution.
  • Turgor / Turgor pressure : Is the pressure of the cytoplasm and vacuole against the cell wall.
  • Phagocytosis : Process where large particles are engulfed by the cell and become incorporated into a vacuole within the cell.

 

Genetics

  • Species : A group of similar organisms capable of interbreeding and producing fertile offspring.
  • Variation within a species : In a group of successfully interbreeding organisms the individual members show different characteristics.
  • Heredity : The transmission of traits from parents to offspring.
  • Mutation : Is a spontaneous inheritable change in the structure of the genetic material.
  • Mutagens : Agents that cause mutations.
  • Gene(point) mutations : Are changes in a single gene.
  • Chromosome mutations : Large changes in the number and structure of the chromosomes.
  • Evolution : Defined as a change of a population of 1 species that gives rise to 1 or more new species.
  • Natural selection : A mechanism of evolution whereby the best-adapted individuals survive and produce more offspring. Or inheritable change within a population in response to change in the environment by natural selection over time.
  • Gene : Part of a chromosome, made of DNA and controls a single characteristic/trait.
  • Gene expression : The process whereby genetic information, encoded in a gene, is transferred to its functional product.
  • DNA profiling : A process of making unique patterns in the non-coding regions of an individual’s DNA. Or examining DNA for a pattern or band to compare.
  • Genetic screening : Testing DNA to identify the presence or absence of particular genes.
  • Transcription : Copying of a sequence of genetic bases from DNA onto mRNA. (Making mRNA using DNA template)
  • Translation : Conversion of a sequence of genetic bases on mRNA into a sequence of amino acids.
  • Chromosome : Found in the nucleus, made of DNA and protein and contain genes along their length.
  • Homologous chromosomes : Pairs of chromosomes that contain genes for the same characteristics at the same positions on the chromosomes.
  • Gametes : Haploid cells that are capable of fusion.
  • Allele : Different forms of the same gene. They occupy the same position(locus) on homologous chromosomes.
  • Locus : The position of the gene on the chromosome.
  • Genotype : The genotype is the kind of genes present in the cell.
  • Phenotype : This is the expression of the gene in the environment. This is how genes affect the appearance of the organism.
  • Progeny : Refers to offspring that are produced.
  • Homozygous : When 2 alleles for a particular characteristic are the same.  Eg – TT = Tall and tt = short
  • Heterozygous : When 2 alleles for a particular characteristic are different.  Eg – Tt = Tall
  • Dominant : A dominant allele is one that is always expressed in the phenotype. Generally written with a capital letter.
  • Recessive : A recessive allele is not expressed in the presence of the dominant allele, but only when both recessive alleles are present. Generally written with a small letter.
  • Incomplete dominance : The condition in which both alleles in the heterozygous condition are expressed in the phenotype, and an intermediate phenotype results.
  • Fertilisation : Fusion of a haploid sperm and an egg to form a diploid zygote.
  • The Law of Segregation : An individual has 2 genes for a character. These segregate at gamete formation. Only 1 of a pair of such genes can be carried in a single gamete. At fertilisation, the new organism will have 2 genes for each trait, one from each parent.
  • The Law of Independent Assortment : When gametes are formed, each member of  a pair of alleles can be inherited with any one from another allele pair.
  • Linkage : That genes are located on the same chromosome.
  • Sex linkage : A characteristic is controlled by a gene on an X/Y chromosome.
  • Pedigree : A diagram showing the occurance and appearance of a particular genetic trait from one generation to the next.
  • Genetic engineering : The artificial manipulation/alteration of genes.
  • DNA Ligase : An enzyme that is used to stick DNA molecules from sources firmly together.
  • Restriction enzymes : Enzymes that DNA at specific places.
  • Genetically Modified organisms ( GMOs) : Living things whose DNA has been altered artificially.

 

Diversity of Organisms

  • Autotrophs : Organisms which can make their own food from simple inorganic substances. Eg – Green plants
  • Photosynthetic : A type of nutrition where organisms make their own food using light energy. Eg – purple sulphur bacteria
  • Chemosynthetic : A type of nutrition where organisms make their own food using energy from chemical reactions. Eg – nitrifying bacteria.
  • Heterotrophs : Organisms which cannot make their own food. Eg – Animals, fungi
  • Saprophytes : Organisms that take in food from dead organic matter. Eg – Bacteria of decay
  • Parasites : Organisms that take in food from a live host and cause harm. Eg – Disease-causing bacteria
  • Pathogens : Micro-organisms that cause disease.
  • Antibiotics : Chemicals produced by some bacteria and fungi that inhibit the growth or reproduction of other bacteria and fungi.

 

Fungi/Protista(Amoeba)/Viruses

  • Mycology : Study of fungi.
  • Hypha : Tube/filament in a fungus.
  • Mycelium : Made up of network of fine tubular filaments( Hyphae)
  • Chitin : Fungus’ have rigid cell walls containing chitin.
  • Sporulation : Process of making spores.
  • Aseptic/Asepsis : The exclusion of micro-organisms.
  • Sterile : The absence of  micro-organisms/ free from micro-organisms.
  • Osmoregualtion : The control of water and salt balance in an organism.
  • Bacteriophage : A virus that infects bacteria.
  • AIDS ( Acquired Immunodeficiency Syndrome) : A collection of disorders following infection by the HIV (Human Immunodeficiency Virus ). HIV virus contains RNA.

 

Plants

  • Meristem : Zone of active cell division in plants.
  • Dermal tissue : A single layer of cells covering the different parts of the plant. Eg – epidermis
  • Vascular tissue : The tissues involved in transport within the plant, xylem and phloem.
  • Ground tissue : All the other tissues within the plant.
  • Cuticle : Living cells often with a waxy layer covering over the outer surface.
  • Herbaceous : Plants do not contain wood/lignin. Eg – buttercup
  • Woody : They possess woody tissue Eg – Oak
  • Transpiration : Loss of water vapour from the leaves and other aerial parts of a plant.
  • Lenticels : Openings in the stems of plants that allow gas exchange.
  • Stimulus : Anything that brings about a response in an organism.
  • Response : The effect the stimulus has on the organism activity. Plants respond to light by growing.
  • Tropism : The growth response of a plant to an environmental stimulus.
  • Phototropism : Growth of plants in response to light.
  • Geotropism : Growth of plants in response to gravity.
  • Thigmotropism : Growth of plants in response to touch.
  • Hydrotropism : Growth of plants in response to water.
  • Chemotropism : Growth of plants in response to chemicals.
  • Growth regulators : A chemical that controls growth in plants.
  • Phytoalexins : When a plant is infected by a micro-org, the plant is able to produce stress proteins.
  • Asexual : Reproduction involves only 1 parent.
  • Sexual reproduction : Involves the union of 2 sex gametes.
  • Gametes : Haploid cells capable of fusion.
  • Stamens : Male parts of the flower.
  • Carpels : Female parts of the flower.
  • Pollination : The transfer of pollen from an anther to a stigma of a flower from the same species.
  • Self-Pollination : The transfer of pollen from an anther to a stigma on the same plant.
  • Cross-Pollination : The transfer of pollen from an anther to a stigma on a different plant of the same species.
  • Fertilisation : Union of the male and female gametes to form a diploid zygote.
  • Non-endospermic seed : Has no endopserm when fully formed.
  • Endopspermic seed : Contains some endosperm when fully formed.
  • Dispersal : The tranfer of a seed/fruit away from the parent plant.
  • Dormancy : Resting period when seeds undergo no growth and have reduced cell activity/metabolism.
  • Germination : The regrowth of the embryo, after a period of dormancy, if the environmental conditions are suitable.
  • Vegetative propagation : Asexual reproduction in plants. Eg – Strawberry
  • Clone : A group of cells/organisms that are genetically identical to each other and are produced by mitosis.
  • Runners : Horizontal stems that run.grow above ground and from which new plants grow.
  • Root tuber : A swollen, underground root that remains dormant during winter and from which new plants may grow.
  • Bulb : Modified bud.
  • Micropropagation : Involves growing large numbers of plant from small pieces of plant tissue( single cells).
  • Tissue culture : The growth of tissues outside the organism on an artificial medium. Eg – Micropropagation of plants
  • Leaf venation : The way in which veins in the leaf are arranged is called leaf venation.

 

Blood

  • Serum : Is plasma with fibrinogen removed. This prevents plasma from clotting and serum can be stored by hospitals for transfusions.
  • Granulocytes : Formed in the red bone marrow. They are phagocytic ( Actively seek out and engulf bacteria)
  • Monocytes : Non granular and are also phagcytic. They often leave the capillaries in search of foreign material.
  • Lymphocytes : Formed in the bone marrow and matured in the lymph nodes. They recognise proteins(antigens) on the cell membranes of invading organisms and respond by making antibodies which kill the invaders.
  • Blood pressure : The force the blood exerts against the wall of a blood vessel.
  • Pulse : Contraction of a wall of an artery/ The rate at which the heart beats.
  • Valves : Control the direction of blood flow.
  • Portal system : A blood pathway that begins and ends in capillaries.
  • Hepatic portal vein : Carries blood rich in food form from the small intestines to the liver.
  • Diastole : When heart chambers relax.
  • Systole : When heart chambers contract.
  • Lymphatic System : A secondary circulatory system consisting of fine tubes ending blindly among the tissues.
  • Lymph nodes : Along the lengths of these tubes are swellings called lymph nodes.
  • Lymphatic vessels : The tubes that carry lymph.

 

Excretion

  • Homeostasis : The ability of an organism to maintain a constant internal environment.
  • Ectotherms : Gain/Lose heat from or to their external environment.
  • Endotherms : Generate their own heat from metabolic reactions.
  • Active transport : Energy is used to move molecules against a concentration gradient. Eg – low conc to high concentrations

 

The Nervous System

  • Neuron : A nerve cell
  • Threshold : The minimum stimulus needed to cause an impulse to be carried.
  • The ‘All or nothing Law’ : States that if the threshold is reached an impulse is carried, but if the threshold is not reached no impulse is carried.
  • Refractory period : Short timespan after a a neuron has carried an impulse during which a stimulus fails to cause a response.
  • Synapse : A region where 2 neurons come into close contact.
  • Synaptic cleft : The tiny gap between the 2 neurons at a synapse.
  • Reflex action : An automatic,involuntary, unthinking response to a stimulus.

 

Endocrine System/Skeleton

  • Exocrine glands : Release their product into ducts/tubes.
  • Endocrine glands : A ductless gland that produces hormones which are released directly into the bloodstream.
  • Hormone : A chemical messenger produced by an endocrine gland and carried by the bloodstream to another part of the body where it has a specific effect.
  • Ligaments : Strong, fibrous,slightly elastic tissues that connect bone to bone.
  • Tendons : Strong,flexible,inelastic fibres that connect muscle to bone.
  • An antagonistic pair : 2 muscles that have opposite effects to each other.

 

The Human Defence System

  • Pathogen : An organism that causes disease.
  • Immunity : The ability to resist infection.
  • The general defence system : Acts against all potential pathogens attempting to gain entry to the human body and is divided into 2 lines of defence.
  • The specific defence system : Attacks particular pathogens.
  • Antigen : A foreign molecule that stimulates the production of antibodies.
  • Anitbody : A protein produced by white blood cells (lymphocytes) in response to an antigen.
  • Induced immunity : The ability to resist disease caused by specific pathogens.
  • Active immunity : The person produces antibodies in response to invading antigens. This gives long lasting production.
  • Natural active immunity : When a pathogen enters the body in the normal way.
  • Artificial active immunity : When a pathogen is medically introduced into the body.
  • Vaccine : Injected or taken orally into the body, is a small quanitity of a microbe that is dead or is treated in some way to reduce its effect. The vaccine stimulates the production of the corresponding antibody, giving resistance to the microbe, eg – polio, whooping cough.
  • Passive immunity : Antibodies produced in another individual are given to the person.
  • Natural passive immunity : Antibodies pass from mother to child across the placenta and in the milk.
  • Artificial passive immunity : Antibodies produced in another animal/human are given, eg – antitetanus injection.

 

Human Reproduction

  • Gamete : A haploid cell.
  • Gonad : An organ that produces sex cells in animals.
  • Ejaculation : The release of semen from the penis.
  • Secondary sexual characteristics : Are features that distinguish males from female apart from the sex organs.
  • Infertility : The inability to produce young.
  • Ovulation : The release of an egg from the ovary.
  • The menstrual cycle : Series of events that occurs every 28 days on average in the female if fertilisation has not taken place.
  • Insemination : The release of semen into the vagina, outside the cervix.
  • Fertilisation : Occurs when the nucleus of the sperm fuses with the nucleus of the egg, forming a diploid zygote.
  • Birth control : Involves methods to limit the number of children born.
  • Abortion : Termination of pregnancy.
  • Contraception : The deliberate prevention of fertilisation/pregnancy.
  • Implantation : The embedding of the fertilised egg into the lining of the uterus.
  • In vitro fertilisation (IVF) – Involves removing eggs from an ovary and fertilising them outside the body.
  • Morula : A solid ball of cells formed from a zygote by mitosis.
  • Blastocyst : A hollow ball of cells formed from a morula.
  • Germ layers : Basic layers of cells in the blastocyst from which all adult tissues and organs will form.
  • Gestation : The length of time spent in the uterus from fertilisation to birth.
  • Lactation : The secretion of milk from mammary glands(breasts) of the female.

 

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