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B - 4/5 Definitions

OCR Biology A2 - Unit 4 & 5 Definitions

QuestionAnswer
Stimulus A change in the environment that causes a response.
Homeostasis The maintenance of the internal environment in a constant state regardless of external changes.
Negative Feedback The reversal of a change in the internal environment to return to the optimum steady state.
Positive Feedback It increases any change that is detected by receptors.
Ectotherm An organism that relies on external sources of heat to regulate it's body temperature.
Endotherm An organism that can use internal sources of heat (such as those from metabolism) to maintain it's body temperature.
Excretion The removal of metabolic waste from the body.
Metabolic Waste Waste substances that may be toxic or produced in excess by cells.
Deamination The removal of the amine group from an amino acid to form ammonia.
Autotroph Organisms that use light or chemical energy and inorganic molecules to synthesise complex organic molecules.
Heterotroph Organisms that ingest and digest complex organic molecules, realising chemical potential energy within them.
Photosynthetic Pigment Molecules that absorb light energy. Each one only absorbs a specific range of wavelengths.
Limiting Factor The factor that is present at the lowest value.
Anabolic Reaction Large molecules are synthesised from smaller ones.
Catabolic Reaction Larger molecules are hydrolysed to produce small ones.
Respiratory Substrate An organic substance that can be used for respiration.
Gene A length of DNA that codes for one or more polypeptides.
Polypeptide A chain of amino acids joined together by peptide bonds.
Genome The entire DNA sequence of an organism.
Mutation A change in the amount of, or arrangement of, the genetic material in a cell.
Allele An alternative version of a gene (different DNA base sequence).
Homeobox Gene Controls the development of the body plan of an organism, including the polarity and the positioning or organs.
Phagocytosis The endocytosis of large molecules into a cell.
Meiosis A reduction division. The daughter nuclei have half the original number of chromosomes.
Locus The position of a gene on a chromosome.
Crossing Over Lengths of DNA are swapped from one chromatid to another.
Genotype The specific combination of alleles possessed by an organism.
Phenotype The characteristics that are expressed in the organism.
Homozygous An organism with two identical alleles for a particular gene.
Heterozygous Two different alleles for the same gene.
Codominant Alleles are codominant if they both contribute to the phenotype.
Dominant Always expressed in the phenotype even if a different allele for the same gene is present in the genotype.
Recessive An allele is only expressed in the phenotype in the presence of another identical allele.
Linkage Two or more genes are located on the same chromosome.
Epistasis The interaction of different gene loci so that one gene locus masks or suppresses the expression of another.
Ratio for Recessive Epistasis 9:3:4
Ratio for Dominant Epistasis 12:3:1
Ratio for Complimentary Action 9:7
Discontinuous Variation Qualitative differences between phenotypes. Differences fall into clearly distinguishable categories.
Continuous Variation Quantitative differences between phenotypes. A wide range of variation within the population.
Population A group of Individuals of the same species that can interbreed and produce fertile offspring.
Gene Pool Set of genetic information carried by a population.
Selection Pressure An environmental factor that confers greater chances of survival to reproduction age on some members of the population.
Carrying Capacity The maximum number of organisms an environment can sustain.
Biological Species Concept A species is a group of similar organisms that can interbreed and produce fertile offspring.
Phylogenetic Species Concept A group of organisms that share a common ancestor, and are in the same monophyletic group.
Monophyletic Group One that includes an ancestral organism and all it's descendant species.
Natural Selection Those organisms that are best adapted to their environments are more likely to survive to reproductive age and pass on their advantageous alleles.
Artificial Selection Humans select the organisms with favourable characteristics and allow them to breed over several generations.
Clone A genetically identical organism.
Vegetative Propagation The production of structures in an organism that can grown into new individual organisms.
Biotechnology The exploitation of living organisms or biological processes to improve industry and produce useful products such as food or drugs.
Metabolism The sum total of all the chemical reactions within an organism.
Asepsis The absence of unwanted microorganisms.
Immobilisation by Absorption Enzymes are mixed with an immobilising support and bind to it due to inter molecule interactions.
Immobilisation by Covalent Bonding Enzymes are covalently bonded to a support.
Immobilisation by Entrapment Enzymes are trapped in an Alginate bead.
Immobilisation by Membrane Separation A partially permeable membrane separates enzymes from the substrate.
Genomics The study of the whole set of genetic information.
Recombinant DNA Where DNA fragments from different organisms are joint together.
Transgenic An organism that contains DNA that has been added to it's cells as a result of genetic engineering.
Gene Therapy Using gene technology to treat some genetic disorders.
Xenotransplantation The transplantation of cell tissues or organs between animals of different species.
Ecosystem A group of living and non-living things occurring together, and the relationships between them.
Habitat The place where an organism lives.
Population All the organisms in one species who live in the same place and can interbreed.
Community All the populations who live in the same place and can interact.
Trophic Level The level at which an organism feeds.
Succession The directional change in a community of organisms over time.
Coppicing Cutting a tree trunk close to the ground to encourage new growth.
Pollarding Like coppicing but trunks are cut higher up.
Conservation Maintaining biodiversity and minting a variety of habitats and ecosystems.
Tropism A directional growth response in which the direction of the response is determined by the direction of the external stimulus.
Cerebrum Conscious thought and emotional responses. Also involved in reasoning and judgement.
Cerebellum Body position, balance and co-ordination of movement.
Medulla Oblongata Controls cardiac and involuntary muscles.
Hypothalamus Controls the bodies homeostatic mechanisms and much of the bodies endocrine function (as it regulates the pituitary gland).
Innate behaviour Instinctive behaviour that is genetically determined and rigid. It occurs without the need for thought.
Escape Reflex Involuntary response which follows a specific patter in response to a given stimulus. It's function is to avoid predators (or a potentially dangerous situation).
Kineses Rate of movement of an organism increases when they're in unfavourable conditions.
Taxes A 'directional' orientation response, in relation to the stimulus that triggered it.
Learned Behaviour Behaviour that is altered due to an experience, and may vary in each member of the species.
Habituation Animals learn to ignore certain stimuli because repeated exposure to the stimulus results in neither reward or punishment.
Imprinting Young animals becoming associated with another organism.
Classical Conditioning Animals learn to relate a pair of events and respond to the first in anticipation of the second.
Operant Conditioning Creating a specific behavioural reaction to a stimulus by adding an element of reward or punishment.
Latent Learning Animals explore new surroundings and retain information that is not of immediate use but may aid survival later.
Insight learning. Based on the ability to think and reason.
Social Behaviour Organisms of a particular species living together in groups with relatively defined roles for each member.
Created by: Sparksy
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