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Complete Leaving Cert Biology Definitions

Terms in this set (217)

Aseptic Technique
any measures that are taken to exclude unwanted (especially pathogenic) microorganisms, as far as is possible, from an area or object.
Induced Immunity
the ability to resist disease caused by specific pathogens by the production of antibodies or by receiving antibodies from an outside source.
Scientific Method
a series of steps used in an investigation which strives to answer questions and explain the world around us
Hypothesis
a possible explanation for an observation, that can be tested
Data
the information gathered during a scientific investigation
Scientific theory
a well-established explanation that has been repeatedly tested and confirmed in many different ways and usually over long periods of time.
Scientific Law or Principle
a statement based on repeated experimental observations that describes what has been observed.
Control Experiment
An experiment carried out as a comparison to the test experiment, as a standard against which the actual experiment can be judged. It is identical to the test experiment, but without the variable that is being tested.
Continuity of Life
The fact that living things arise from other livings.
Metabolism
the sum of all the chemical reactions that occur in the cells of an organism.
Organisation
living things are made of cells, tissues, organs and organ systems.
Nutrition
The process by which organisms take in and use energy and materials from the environment.
Excretion
the removal of waste products of metabolism from the body of an organism.
Response
A change in a cell or organism as a result of it receiving a stimulus
Reproduction
the ability of an organism to produce new individuals of its own kind.
Biology
the study of living things
Ecology
the study of the how organisms interact with each other and with their environment.
Habitat
the place in which an organism lives.
Ecosystem
the interacting living and non-living components of a particular area.
Biosphere
the part of the Earth inhabited by living organisms.
Population
all the organisms of the same species in the same habitat.
Community
all the different populations living in the same habitat or area
Abiotic Factors
the influence of non-living parts of the environment on an organism.
Biotic Factors
The influences on an organism of other living things in its environment.
Edaphic Factors
soil features that influence the growth of plants or animals.
Climatic Factors
the influences of weather conditions on living organisms in the ecosystem
Producer
an organism that makes its own food from inorganic material, using energy from light (photosynthhetic) or from chemical reactions (chemosynthetic). Producers are also called autotrophs.
Consumer
an organism that cannot make its own food, but instead must obtain it by eating other organisms. Consumers sare also known as heterotrophs.
Food Chain
a series of organisms in which one is eaten by the next.
Trophic Level
The position of an organism in the food chain
Food Web
A series of interconnecting food chains.
Pyramid of Numbers
a chart showing the number of organisms at each trophic level in a food chain.
Ecological niche
The functional role of an organism in the community
Competition
The struggle between organisms for limited resources. Competition can take place within the same species (intra-specific) or between different species (inter-specific).
Intra-specific competition
The struggle for limited resources between organisms belonging to the same species
Inter-specific competition
The struggle for limited resources between organisms belonging to different species
Scramble competition
The struggle for limited resources, whereby each organism gets some of the resource
Contest competition
The struggle for limited resources where there is direct conflict between two individuals and only one is successful in gaining the resource - "the winner takes it all"
Adaptation
any change in the structure or behaviour of an organism that makes it better suited to its environment.
Predation
the catching and killing of an animal for food.
Predator
an animal that hunts and kills another animal (the prey) for food.
Prey
the animal that is eaten by a predator.
Symbiosis (symbiotic relationship)
A close relationship between two organisms of different species living together in which at least one benefits.
Parasitism
A close relationship between two organisms of different species in which one benefits (the parasite), while the other (the host) is harmed
Commensalism
A close relationship between two organisms of different species living together in which one benefits, while the other is unaffected
Mutualism
A close relationship between two organisms of different species that live together, in which both benefit
Nutrient recycling
the movement of essential elements from the abiotic environment into living organisms and back again
Nitrogen Fixation
the conversion of atmospheric nitrogen into nitrogen compounds such as ammonia (NH3) and nitrate (NO3).
Qualatitive study
A habitat survey that records the presence or absence of an organism
Quantitative study
A habitat survey that records the numbers of individuals of each species present
Frequency
the chance of finding a particular species in one quadrat throw
Percentage Cover
an estimate of the amount of ground in a quadrat covered by any species
Pollution
the addition of anything harmful to the environment.
Pollutant
Any substance that causes harm to the environment
Diffusion
the passive movement of molecules from areas of high concentration to area of low concentration.
Osmosis
the movement of water from an area of high water concentration to an area of low water concentration across a selectively permeable membrane
Osmoregulation
The activities of organisms to maintain the concentration of a solution at an optimum
Turgor
the firm state of plant cell due to the outward pressure of the cytoplasm against the cell wall, caused by water entering the cell by osmosis
Active Transport
A process requiring energy (ATP), whereby chemicals are taken into a cell against the concentration gradient
Haploid Cell (n)
cell that has one set of chromosomes present in the nucleus
Diploid Cell (2n)
cell that has two sets of chromosomes present in the nucleus
Mitosis
a form of nuclear division in which one nucleus divides into two, each with the same number of identical chromosomes as another and the original cell
Cancer
a group of disorders in which cells lose their ability to control the rate and frequency of mitosis.
Enzyme
biological catalyst made of protein
Active Site
the part of an enzyme that binds to the substrate, and catalyses the reaction to form the product
Native Enzyme
an enzyme that functions normally
Denatured enzyme
An enzyme that has lost its shape and cannot function
Immobilised enzymes
enzymes that are trapped in a soft permeable gel or attached to an inactive support
Bioprocessing
the use of living cells, their components or enzymes to make products of commercial or scientific value or destroy harmful wastes.
Photophosphorylation
the addition of a phosphate to ADP to form ATP using light energy
Respiration
the controlled release of energy from food. It is an essential characteristic of all living things.
Aerobic respiration
the controlled release of energy from food using oxygen.
Anaerobic respiration
the controlled release of energy from food without the use of oxygen. (It is sometimes known as fermentation)
Gene
a sequence of nucleotides which codes for the synthesis of a protein, i.e. It encodes a specific characteristic
Gene expression
The decoding of a gene into a sequence of amino acids (i.e. Protein)
DNA triplet
a sequence of bases that codes for one amino acid.
Genome
an organism's complete set of DNA, including its genes (like a full 'cookbook' of gene recipes)
Protein Synthesis
the combination of the transcription of a region of DNA followed by translation into protein
Transcription
the copying of information in the nucleus from a DNA molecule to an RNA molecule
Translation
The conversion of the mRNA code into the amino acid sequence in a protein
Genetic Engineering
the artificial manipulation or alteration of the genes of an organism
Gene Cloning
the production of many copies of a specific gene which occurs when a genetically modified organism (GMO) replicates the DNA during normal cell division.
Biotechnology
the use of organisms (or other biological systems) to provide useful products or processes.
Recombinant DNA
DNA that is altered using the techniques of DNA technology.
Genetically modified organism (GMO)
an organism with artificially altered DNA.
Cloning Vector
A piece of DNA that can have a foreign gene inserted into it and then used to deliver that gene into a cell, tissue or organism.
DNA Profiling
the process of making a unique pattern of bands (like a barcode) from the DNA of a person, which can be distinguished from the pattern of another person's DNA.
The Law of Segregation (Mendel's 1st Law)
states that each characteristic is controlled by a pair of factors (genes) which separate at gamete formation such that a gamete receives only one of each pair.
Allele
an alternative form of a gene
Heterozygous
The alleles in a pair are different
Homozygous
The alleles in a pair are the same
Dominant Allele
An allele that masks its (recessive) partner. A dominant allele is one that is always expressed if it is present
Recessive Allele
An allele whose expression is masked by the dominant allele
Locus of a gene
The position of a gene on a chromosome
Phenotype
The physical make-up of an organism
Monohybrid cross
A genetic cross which studies the inheritance of one trait
Dihybrid cross
A genetic cross which studies the inheritance of two different traits
The Law of Independent Assortment (Mendel's 2nd Law)
states that during gamete formation, either one of a pair of alleles is equally likely to combine with either one of another pair of alleles.
Linked genes
genes that are located on the same chromosome and are inherited together
Incomplete Dominance
The heterozygous genotype produces a phenotype that is intermediate betweeen those produced by the homozygous genotypes.
Sex-Linked characteristics
A characteristic that is controlled by a gene that is carried on a sex chromosome.
Variation
the difference between living things in a population caused by genes and environment.
Mutation
a change in the sequence of a DNA molecule.
Mutagen
an agent that cause mutations.
Carcinogen
any factor that results in a DNA mutation that causes cancer
Evolution
The change in the genetic characteristics in a population over a long period of time, resulting in new species. Evolution is the result of the process of natural selection.
Prokaryote
an organism that has no nucleus or other membrane-bound organelles.
Heterotroph
An organism that cannot make its own food, but instead must obtain it by eating other organisms. Also called consumers
Saprophytic organism
organisms that feed on dead organic matter.
Autotrophs
organisms that make their own food from simple inorganic raw materials such as water and carbon dioxide, using energy and light (photosynthetic autotrophs) or from chemical reactions (chemosynthetic autotrophs). Also called producers
Aerobe
A bacterium that requires oxygen for respiration
Anaerobe
A bacterium that does not require oxygen for respiration
Facultative Anaerobes
An organism that can respire with or without oxygen.
Obligate anaerobes
Organisms can only respire in environments without oxygen
Antibiotics
chemicals produced by bacteria and fungi which kill or inhibit the growth of other bacteria
Pathogen
a disease-causing organism.
Digestion
the physical and chemical breakdown of food into smaller soluble particles that can be absorbed into by the circulatory system
Portal System
a blood pathway that begins and ends in capillaries.
Homeostasis
the maintenance of a constant internal environment in an organism.
Endotherms
animals whose body temperature is independent of the environment temperature
Ectotherms
animals whose blood temperature varies with the environmental temperature
Neuron (or neurone)
a nerve cell
Receptor
a cell that can detect a stimulus
Stimulus
a change in the environment of a cell or organism that, if strong enough, results in an impulse.
Threshold
the minimum intensity of stimulus needed to generate an impulse.
The "All-or-nothing" Law
states that an impulse is only generated if the stimulus is at or above the threshold.
The Refractory Period
the slight delay that occurs after a neuron has carried an impulse, during which the neuron does not respond to a stimulus: it is resetting itself in preparation for the next impulse
Synapse
a specialised junction at which a neuron comes close enough to a target cell to allow it to pass a signal to that target cell. The target cell could be another a neuron, a muscle cell or a gland
Synaptic Cleft
the tiny gap between a neuron and its target cell at a synapse.
Ligaments
strong, slightly elastic fibres that connect bone to bone. Their function is to prevent dislocation
Tendons
strong, flexible, inelastic fibres that connect muscle to bone
Antagonistic Pair
two muscles that that have opposite effects to each other, as one contracts, the other relaxes
Exocrine Glands
Glands that release substances through ducts
Endocrine Glands
ductless, and secrete hormones in to the bloodstream
Hormone
a chemical messenger produced by an endocrine gland and carried in the blood to another part of the body where it has a specific effect.
Immunity
the ability of organisms to defend themselves against pathogens and toxins
General Defence System
The part of the immune system consisting of barriers to prevent the entry of all pathogens, and prevent their initial spread.
Specific Defence System
A part of the immune system that protects against particular pathogens. It involves white blood cells either producing specific antibodies or directly destroying infected or abnormal cells
Antigen
A foreign (non-self) chemical that stimulates the production of antibodies
Antibody
A specific protein produced by lymphoctyes in response to the presence of an antigen
Active Immunity
The body's defences to fight off disease and infection, whereby the body produces its own antibodies
Natural Active Immunity
The ability to protect against and fight infections and toxins that is acquired due to normal infection
Artificial Active Immunity
Immunity acquired when a person is given a dose of inactivated pathogen. This is also known as vaccination
Vaccine
a dose of inactivated pathogen, which doesn't cause disease, but triggers the production of antibodies
Passive Immunity
The ability to protect against and fight infections and toxins that occurs when someone is given antibiotics made by another organism
Natural Passive Immunity
The ability to protect against and fight infections and toxins that occurs when a baby gets antibodies from its mother
Artificial Passive Immunity
immunity that occurs when a person is injected with antibodies made by another organism.
Virus
a small non-cellular infectious particle that replicates only inside the living cells of other organisms.
Gonad
an animal organ that produces sex cells
Ovulation
the release of an egg from the ovary.
Secondary sexual characteristics
the features that distinguish males from females, other that the presence of the sex organs. They develop at puberty under the control of sex hormones
The Menstrual Cycle
a series of changes that occurs in the female reproductive system every 28 days on average, if fertilisation does not take place
Menopause
The time during which a woman gradually stops menstruating and therefore cannot reproduce anymore (usually occurs between 45-55)
Fertile Period
The time during the menstrual cycle in which fertilisation is most likely to occur.
Menstruation
the shedding of the blood-filled lining of the womb (the endometrium).
Infertility
the inability to produce offspring
In-Vitro Fertilisation
The removal of eggs from the ovary and fertilising them outside the body
Ejaculation
the release of semen from the penis
Insemination
the release of semen into the vagina. It may be natural or artifcially
Fertilisation
the fusion of the sperm nucleus with the nucleus of the egg to form a diploid zygote.
Implantation
the embedding of the fertilised egg into the lining of the womb (endometrium)
Morula
a solid ball of cells formed from a zygote by mitosis
Blastocyst
A hollow, fluid-filled ball of cells formed from a morula
Germ Layers
layers of cells in the blastocyst from which all adult tissues and organs will form.
Gestation
the length of time spent in the womb from fertilisation to birth. This is usually 38 week in humans
Lactation
the production of milk by the breasts of the female
Root Pressure
the force which can push water up a stem from the root.
Transpiration
the loss of water vapour from the surface of a plant
Tropism
a growth response of a plant to an external stimulus.
Phototropism
a plant growth response to light
Geotropism
a plant growth response to gravity
Hydrotropism
a plant growth response to water
Chemotropism
a plant growth response to chemicals
Thigmotropism
a plant growth response to touch
Growth Regulator
a chemical that controls the growth of a plant.
Vegetative Propagation
the asexual reproduction of plants.
Asexual Reproduction
reproduction that involves only one plant, and does not involve gametes
Pollination
the transfer of pollen from the anther to a stigma of a flower of the same species.
Cross-Pollination
the transfer of pollen from the anther to a stigma on a different plant of the same species
Self-Pollination
the transfer of pollen from an anther to a stigma on the same plant.
Seed dispersal
the transfer of a seed away from the parent plant.
Dormancy
A resting period when a seed does not germinate even though the environmental conditions are suitable for growth.
Germination
The re-growth of an embryo, after a period of dormancy.
Antibiotic resistance
Occurs when some bacteria are no longer killed or inhibited by a particular antibiotic
Aquatic factors
Environmental information relating to aquatic habitat
Balanced diet
A healthy eating habit, whereby all the essential nutrients are included in the correct proportions
Bioreactor
A vessel in which microorganisms or enzymes are used to make useful products
Biomolecules
Chemicals made by an organism
Carnivore
Animal that feeds only on (other) animals
Centromere
The location on a chromosome where the two sister chromatids are attached
Chemosynthetic
Organisms that use the energy from chemical reactions to make food
Chromatid
One of two identical copies DNA making up a replicated chromosome joined together at a centromere
Chromatin
The fibrous loose mixture of DNA and protein that chromosomes loosen to form. Nuclear material takes this form during interphase
Chromosomes
Tightly coiled structures found in the nucleus. They are composed of DNA and protein, and they consist of a particular set of genes. They are only visible as individual structures during nuclear division.
Conservation
The wise management of our environment to ensure the survival of organisms and their habitat
Contraception
Methods used to prevent fertilised or implantation
Genotype
The genetic make-up of an organism
Food pyramid
A guide to healthy eating indicating the proportions of different types of food to be eaten in a day
Genetics
The study of inheritance
Herbivore
Animal that feeds only on plants
Homologous structures
Structures that display a similar basic pattern, but have a different function
Infection
The harmful colonisation of an organism by another species
Meiosis
The division of a diploid nucleus, resulting in four genetically different haploid daughter nuclei
Neurotransmitter
A chemical released by neutrons at synapses, which transmits signals across the synaptic cleft from the neuron to a target cell
Omnivore
An animal that feeds on plants and animals
Photosynthetic
Organisms that use the energy from light to make food
Primary sexual characteristics
The sex organs and associated glands
Reflex action
A very fast, automatic and involuntary response to an unexpected stimulus. It is not controlled by the brain.
Sterile
The absence of any living things
'all-or-nothing' law:
A law that states that an impulse is only generated if the stimulus is at or above the threshold.
Codon
A codon is a sequence of three DNA or RNA nucleotides that correspond to a specific amino acid (or astop signal) during protein synthesis.
Clone
genetically identical offspring of an organism.
Glycolyis
the first stage of respiration that converts glucose into pyruvic acid and occurs in the cytosol.
In Vitro Fertilisation
The removal of eggs from the ovary and their fertilisation outside the body.
Natural Selection
the process by which members of a species with traits that allow them to survive in their environment, reproduce and pass on these traits to their offspring.
Zygospore
a zygote with a resistant coating that can survive adverse conditions.
Zygote
a diploid cell produced by the fusion of two gametes.
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