IB Biology – Definitions required by the syllabus IB Biology syllabus – definitions. * Definition given in IB Biology syllabus Summer homework directions: Study all the words for topics 1 through 6 (create a Quizlet, notecards, Kahoot…?). Share this with me via email. The first week of school we will have a vocabulary quiz. TOPIC WORD DEFINITION Topic 1: Cells Organelle A discrete structure within a cell, with a specific function.* biology Tissue A group of cells similar to each other, along with their associated intercellular substances, which perform the same function within a multicellular organism. Organ A group of tissues which work together as a single unit to perform a particular function within a multicellular organism. Organ system A group of organs, vessels, glands, other tissues, and/or pathways which work together to perform a body function within a multicellular organism. Diffusion The passive movement of molecules from a region of high concentration to a region of low concentration. Osmosis The passive movement of water molecules, across a partially permeable membrane, from a region of lower solute concentration to a region of higher solute concentration.* Topic 2: Organic Compounds containing carbon that are found in living Molecular organisms (except hydrogencarbonates, carbonates and oxides biology of carbon).* Enzyme Proteins that act as biological catalysts, speeding the rate at which biochemical reactions proceed but not altering the direction or nature of the reactions. Active site A specific region of an enzyme where a substrate binds and catalysis takes place. Denaturation A structural change in a protein that results in a loss (usually permanent) of its biological properties. Refer only to heat and pH as agents.* Degenerate Having more than one base triplet to code for one amino acid.* Universal Found in all living organisms.* Cell respiration Controlled release of energy in the form of ATP from organic compounds in cells.* Chemiosmosis Chemiosmosis is a processes that synthesizes ATP by the diffusion of hydrogen protons across a biological membrane via the ATP synthase (a transport protein) due to a proton gradient that forms on the other side of the membrane. 1 IB Biology – Definitions required by the syllabus TOPIC WORD DEFINITION Topic 3: Gene A heritable factor that controls a specific characteristic. (The Genetics differences between structural genes, regulator genes and genes coding for tRNA and rRNA are not expected at SL).* Allele One specific form of a gene, differing from other alleles by one or a few bases only and occupying the same gene locus as other alleles of the gene.* Genome The whole of the genetic information of an organism.* Gene mutation A change in the base sequence of a gene on DNA. This could be by substitution, deletion, or insertion of a base or bases. The terms point mutation or frameshift mutation will not be used. Homologous A pair of chromosomes containing the same linear gene chromosomes sequences, each derived from one parent. Genotype The alleles possessed by an organism.* Phenotype The characteristics of an organism.* Dominant allele An allele that has the same effect on the phenotype whether it is present in the homozygous or heterozygous state.* Dominant alleles mask the effects of recessive alleles. Recessive allele An allele that only has an effect on the phenotype when present in the homozygous state.* Codominant alleles Pairs of alleles that both affect the phenotype when present in a heterozygote. (The terms incomplete and partial will no longer be used.)* Locus The particular position on homologous chromosomes of a gene.* Homozygous Having two identical alleles of a gene.* Heterozygous Having two different alleles of a gene.* Carrier An individual that has a recessive allele of a gene that does not have an effect on their phenotype.* Test cross Testing a suspected heterozygote by crossing it with a known homozygous recessive. (The term backcross is no longer used.)* Sex linkage Genes found on sex chromosomes (X and Y chromosomes) are said to be sex linked. Genetic screening Testing an individual for the presence or absence of a gene.* Clone A group of genetically identical organisms or a group of cells artificially derived from a single parent cell.* 2 IB Biology – Definitions required by the syllabus TOPIC WORD DEFINITION Topic 4 and 5: Ecology The study of relationships between living organisms and Ecology and Evolution between organisms and their environment.* Ecosystem A community and its abiotic environment.* Population A group of organisms of the same species who live in the same area at the same time.* Community A group of populations living and interacting with each other in an area.* Species A group of organisms which can interbreed and produce fertile offspring.* Habitat The environment in which a species normally lives or the location of a living organism.* Autotroph An organism that fixes chemical energy in the form of (producer) organic molecules; it "makes its own food" and does not require previously formed organic materials from the environment; e.g. photoautotroph, chemoautotroph. Heterotroph An organism that requires chemical energy from already (consumer) formed organic molecules. Detritivore Animal that consumes decomposing organic particles, deriving nutrition primarily from microbes on the particles. Saprotroph Organism that feeds by secreting digestive enzymes onto (decomposer) its food source and absorbing the products of digestion. Fungi and bacteria are examples. Trophic level Stage in a food chain or web leading from primary producers (lowest trophic level) through primary consumers (herbivores) to secondary and tertiary consumers (carnivores). Carrying Maximum average number or biomass of organisms that capacity can be sustained in a habitat over the long term. Usually refers to a particular species, but can be applied to more than one. Random sample A method to ensure that every individual in a population has an equal chance of being observed. Evolution The process of cumulative change in the heritable characteristics of a population.* 3 IB Biology – Definitions required by the syllabus TOPIC WORD DEFINITION Topic 6: Human Pathogen An organism or virus that causes a disease.* Health and Physiology Excretion The removal of metabolic waste products from the body. Topic 7: Nucleic acids Nucleosome Transcription Translation Topic 8: Metabolism, Chemiosmosis cell respiration, and photosynthesis Topic 9: Plant Science Transpiration The loss of water vapour from the leaves and stems of plants.* Pollination The transfer of pollen from the male organ, where it is formed, to the receptive region of a female organ, e.g. from anther to stigma. Topic 10: Genetics Recombination The reassortment of genes or characters into different combinations from those of the parents. Recombination occurs for linked genes by crossing over and, for unlinked genes, by chromosome assortment* due to random alignment during metaphase I and II of meiosis. Linkage group Genes that are located on the same chromosome are part of a linkage group; the closer together the genes are, the lower the probability that they will be separated by crossing-over during meiosis in, and hence the greater the probability that they will be inherited together. Polygenic A trait or characteristic that is influenced by the expression inheritance of more than one gene, e.g. hair colour in humans. Continuous variation occurs as a result. 4 IB Biology – Definitions required by the syllabus TOPIC WORD DEFINITION Topic 11: Animal Active immunity Immunity due to the production of antibodies by the physiology organism itself after the body’s defence mechanisms have been stimulated by invasion of foreign micro-organisms.* Passive immunity Immunity due to the acquisition of antibodies from another organism in which active immunity has been stimulated, including via the placenta or in colostrum.* Natural immunity Immunity due to infection.* Artificial immunity Immunity due to inoculation with vaccine.* Resting potential The difference in electrical charge across the plasma membrane of a neuron when not conducting nerve impulses (i.e. resting). In humans, the value is around -70mV, meaning the inside is negative relative to the outside of the cell. Action potential Voltage change generated across the membrane of a nerve or muscle cell when the cell is activated by electrical, chemical or mechanical stimuli. In humans, the value is around +40mV. The action potential is propagated along the nerve by voltage-gated ion channels. Osmoregulation The control of the water balance of the blood, tissue or cytoplasm of a living organism.* Option G: Ecology Gross production The amount of energy fixed by autotrophs, in kJ m-2 yr-1. and Conservation Net production Gross production less the energy used by the autotrophs for their own respiration, in kJ m-2 yr-1. Biomass A quantitative estimate of the entire amount of living organisms in a particular habitat; it can be measured in terms of volume, mass, or caloric energy. Biomagnification process in which chemical substances become more concentrated at each trophic level. Option H: Further Partial pressure The pressure exerted by an individual gas in a mixture of Human Physiology gases; measured in kPa (or mm Hg). 5 .