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IB – 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 A discrete within a , with a specific .* biology A group of cells similar to each other, along with their associated intercellular substances, which perform the same function within a multicellular . A group of tissues which together as a single unit to perform a particular function within a . Organ A group of organs, vessels, , other tissues, and/or pathways which work together to perform a function within a multicellular organism. The passive movement of from a region of high concentration to a region of low concentration. The passive movement of molecules, across a partially permeable , from a region of lower solute concentration to a region of higher solute concentration.* Topic 2: Organic Compounds containing that are found in living Molecular (except hydrogencarbonates, carbonates and oxides biology of carbon).* that act as biological catalysts, speeding the rate at which biochemical reactions proceed but not altering the direction or of the reactions. A specific region of an enzyme where a binds and takes place. Denaturation A structural change in a that results in a loss (usually permanent) of its biological properties. Refer only to and pH as agents.* Degenerate Having more than one base triplet to for one amino .* Universal Found in all living organisms.* Cell Controlled release of in the form of ATP from organic compounds in cells.* Chemiosmosis is a processes that synthesizes ATP by the diffusion of across a biological membrane via the ATP synthase (a ) due to a gradient that forms on the other side of the membrane.

1 IB Biology – Definitions required by the syllabus

TOPIC WORD DEFINITION Topic 3: A heritable factor that controls a specific characteristic. (The differences between structural , regulator genes and genes coding for tRNA and rRNA are not expected at SL).* One specific form of a gene, differing from other by one or a few bases only and occupying the same gene locus as other alleles of the gene.* The whole of the genetic of an organism.* Gene 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 will not be used. Homologous A pair of containing the same linear gene chromosomes sequences, each derived from one parent. The alleles possessed by an organism.* 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 that has a recessive allele of a gene that does not have an effect on their phenotype.* cross Testing a suspected heterozygote by crossing it with a known homozygous recessive. (The term backcross is no longer used.)* 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: The study of relationships between living organisms and Ecology and between organisms and their environment.* A and its abiotic environment.* A group of organisms of the same who live in the same area at the same .* Community A group of living and interacting with each other in an area.* Species A group of organisms which can interbreed and produce fertile .* The environment in which a species normally or the location of a living organism.* An organism that fixes in the form of (producer) organic molecules; it "makes its own " and does not require previously formed organic materials from the environment; e.g. photoautotroph, chemoautotroph. An organism that requires chemical energy from already () formed organic molecules. that consumes decomposing organic , deriving primarily from microbes on the particles. Saprotroph Organism that feeds by secreting digestive onto () its food source and absorbing the products of . Fungi and are examples. Stage in a or web leading from primary producers (lowest trophic level) through primary consumers () to secondary and tertiary consumers (). Carrying Maximum average number or 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 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: An organism or that causes a .* and The removal of products from the body.

Topic 7: Nucleic Nucleosome Topic 8: , Chemiosmosis cell respiration, and

Topic 9: The loss of water vapour from the and stems of .* The transfer of from the male organ, where it is formed, to the receptive region of a organ, e.g. from anther to . 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 assortment* due to random alignment during metaphase I and II of . 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. colour in . Continuous variation occurs as a result.

4 IB Biology – Definitions required by the syllabus

TOPIC WORD DEFINITION Topic 11: Animal Active Immunity due to the production of 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 .* Artificial immunity Immunity due to inoculation with .* Resting potential The difference in electrical charge across the plasma membrane of a when not conducting impulses (i.e. resting). In humans, the value is around -70mV, meaning the inside is negative relative to the outside of the cell. Voltage change generated across the membrane of a nerve or 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 channels. The control of the water balance of the , tissue or of a living organism.* Option G: Ecology Gross production The amount of energy fixed by , 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. process in which chemical substances become more concentrated at each trophic level. Option H: Further Partial pressure The pressure exerted by an individual in a mixture of Human Physiology ; measured in kPa (or mm Hg).

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