Need to know definitions
IB Biology Syllabus 2009
2.4.4 Define diffusion
Diffusion is the passive movement of particles from a region of high concentration to a region of low concentration.
Osmosis is 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.
3.6.1 Define enzyme
Enzymes: Globular proteins which act as catalysts of chemical reactions.
Active site: Region on the surface of an enzyme to which substrates bind and which catalyses a chemical reaction involving the substrates.
3.6.4 Define denaturation.
Denaturation is a structural change in a protein that results in the loss (usually permanent) of its biological properties
3.7.1 Define cell respiration.
Cell respiration is the controlled release of energy from organic compounds in cells to form ATP.
4.1.2 Define gene, allele and genome.
Gene: a heritable factor that controls a specific characteristic. (The 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.
4.1.3 Define gene mutation
Gene mutation: a change to the base sequence of a gene
4.2.2 Define homologous chromosomes
Homologous chromosomes: chromosomes with the same genes as each other, in the same sequence but do not necessarily have the same allele of those genes.
4.3.1 Define genotype,
Genotype: the alleles of 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.
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.
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 one copy of a recessive allele that causes a genetic disease in individuals that are homozygous for this allele.
Test cross: testing a suspected heterozygote by crossing it with a known homozygous recessive.
4.3.7 Define sex linkage
Sex linkage: when the gene controlling the characteristic is located on the sex chromosome and so we associate the characteristic with gender.
4.4.11 Define clone
Clone: a group of genetically identical organisms or a group of cells derived from a single parent cell.
5.1.1 Define species
Species: a group of organisms that can interbreed and produce fertile offspring.
Habitat: the environment in which a species normally lives or the location of a living organism
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.
Ecosystem: a community and its abiotic environment
Ecology: the study of relationships between living organisms and between organisms and their environment.
5.1.6 Define trophic level.
Trophic level: the trophic level of an organism is its position in the food chain. Producers, primary consumers, secondary consumers and tertiary consumers are examples of trophic levels.
5.4.1 Define evolution
Evolution is the cumulative change in the heritable characteristics of a population
6.3.1 Define pathogen.
Pathogen: an organism or virus that causes a disease
6.5.4 Define resting potential and action potential (depolarization and repolarization).
Resting potential: the electrical potential across the plasma membrane of a cell that is not conducting an impulse.
Action potential: the reversal and restoration of the electrical potential across the plasma membrane of a cell, as an electrical impulse passes along it (depolarization and repolarization).
9.2.5 Define transpiration.
Transpiration is the loss of water vapour from the leaves and stems of plants.
10.2.4 Define linkage group.
Linkage group: A pair or set of genes on a chromosome which tend to be inherited together.
10.3.1 Define polygenic inheritance.
A single characteristic that is controlled by two or more genes
11.1.3 Define active
Active immunity is immunity due to the production of antibodies by the organism itself after the body's defence mechanisms have been stimulated by antigens.
Passive immunity is immunity due to the acquisition of antibodies from another organism in which active immunity has been stimulated, including via the placenta, colostrum, or by injection of antibodies
11.3.1 Define excretion
Excretion is the removal from the body of the waste products of metabolic pathways.
11.3.5 Define osmoregulation.
Osmoregulation is the control of the water balance of the blood, tissue or cytoplasm of a living organism
3.2.1 Distinguish between organic and inorganic compounds.
Compounds containing carbon that are found in living organisms (except hydrogencarbonates, carbonates and oxides of carbon) are regarded as organic
Autotroph: an organism that synthesizes its organic molecules from simple inorganic substances.
Heterotroph: an organism that obtains organic molecules from other organisms.
Consumer: an organism that ingests other organic matter that is living or recently killed.
Detritivore: an organism that ingests non-living organic matter.
Saprotroph: an organism that lives on or in nonliving organic matter, secreting digestive enzymes into it and absorbing the products of digestion.
Absorption occurs when the food enters the body as the food molecules pass through a layer of cells and into the bodies tissues. This occurs in the small intestine which has many villi that are specialised for absorption.
Assimilation occurs when the food molecules becomes part of the bodies tissue. Therefore, absorption is followed by assimilation.
6.3.5 Distinguish between antigens
Antigens are foreign substances which stimulate the production of antibodies.
Antibodies are proteins that defend the body against pathogens by binding to antigens on the surface of these pathogens and stimulating their destruction. Antibodies usually only bind to one specific antigen.
6.4.1 Distinguish between ventilation, gas exchange and cell respiration.
Ventilation is the process of bringing fresh air into the alveoli and removing the stale air. It maintains the concentration gradient of carbon dioxide and oxygen between the alveoli and the blood in the capillaries (vital for oxygen to diffuse into the blood from the alveoli and carbon dioxide out of the blood into the alveoli).
Gas exchange is the process of swapping one gas for another. It occurs in the alveoli of the lungs. Oxygen diffuses into the capillaries from the air in the alveoli and carbon dioxide diffuses out of the capillaries and into the air in the alveoli.
Cell respiration releases energy in the form of ATP so that this energy can be used inside the cell. Cell respiration occurs in the mitochondria and cytoplasm of cells. Oxygen is used in this process and carbon dioxide is produced.
7.3.2 Distinguish between the sense and antisense strands of DNA.
The sense strand (coding strand) has the same base sequence as mRNA with uracil instead of thymine. The antisense (template) strand is the template of DNA which is transcribed.
9.3.2 Distinguish between pollination, fertilization and seed dispersal.
Pollination = transfer of pollen grain from anther to stigma Fertilization = Fusion of the male gamete (in the pollen grain) with female gamete (in ovule) to form a zygote Seed dispersal = Seeds are moved away from parental plants to reduce competition.
10.2.2 Distinguish between autosomes and sex chromosomes.
Sex chromosomes are the ones that determine your gender. These are X and Y (XX in females, XY in males).