Ib Biology Definitions

Front 1

Diffusion

Back 1

Passive movement of particles from a region of high concentration to a region of low concentration

Front 2

Osmosis

Back 2

Passive movement of water molecules, across a partially permeable membrane, from a region of lower solute concentration to a region of higher solute concentration

Front 3

Enzyme

Back 3

Mainly proteins that function as biological catalysts

Front 4

Active site

Back 4

Region of enzyme molecule where substrate molecule binds

Front 5

Denaturation

Back 5

A structural change in a protein that results in a loss (usually permanent) of its biological properties (due to high heat or too high/low pH)

Front 6

Cell respiration

Back 6

Controlled release (transfer) of energy from organic compounds in cells to form ATP

Front 7

Gene

Back 7

A heritable factor that controls a specific characteristic

Front 8

Allele

Back 8

One specific form of a gene, differing from other alleles by 1 or a few bases only & occupying the same gene locus as other alleles of the gene

Front 9

Genome

Back 9

The whole of the genetic information of an organism

Front 10

Mutation

Back 10

A change in chemical structure (i.e. base sequence) of DNA of a chromosome

Front 11

Homologous chromosome

Back 11

Chromosomes in a diploid cell which contain same sequence of genes but are derived from different parents

Front 12

Genotype

Back 12

Alleles of an organism

Front 13

Phenotype

Back 13

Characteristics/appearance (structural, biochemical etc.) of an organism

Front 14

Dominant allele

Back 14

Allele that has same effect on phenotype whether it is present in homozygous or heterozygous state

Front 15

Recessive allele

Back 15

Allele that has an effect on phenotype only when present in homozygous state

Front 16

Codominant alleles

Back 16

Pairs of alleles that both affect phenotype when present in heterozygous state

Front 17

Locus

Back 17

Particular position on homologous chromosomes of a gene

Front 18

Homozygous

Back 18

Having 2 identical alleles of a gene

Front 19

Heterozygous

Back 19

Having 2 different alleles of a gene

Front 20

Carrier

Back 20

An individual that has 1 copy of a recessive allele that causes a genetic disease in individuals that are homozygous for this allele

Front 21

Test-cross

Back 21

Testing a suspected heterozygote by crossing it with a known homozygous recessive

Front 22

Sex linkage

Back 22

Genes carried on only 1 of sex chromosomes & show different pattern of inheritance in crosses where male carries the gene from those where the female carries the gene

Front 23

Clone

Back 23

Group of genetically identical organisms or a group of cells derived from a single parent cell

Front 24

Species

Back 24

Group of organisms that can interbreed and produce fertile offspring

Front 25

Habitat

Back 25

Environment in which species normally lives or location of a living organism

Front 26

Population

Back 26

Group of organisms the same species which live in same habitat at same time

Front 27

Community

Back 27

Group of populations of organisms living & interacting with each other in a habitat

Front 28

Ecology

Back 28

Study of relationships between living organisms & between organisms & their environment

Front 29

Trophic level

Back 29

Level in food chain defined by method of obtaining food & in which all organisms are same number of energy transfers away from original source or energy (photosynthesis)

Front 30

Evolution

Back 30

Cumulative change in heritable characteristics of a population

Front 31

Pathogen

Back 31

Organism or virus that causes a disease

Front 32

Evolution

Back 32

Cumulative change in heritable characteristics of a population

Front 33

Pathogen

Back 33

Organism or virus that causes a disease

Front 34

Resting potential

Back 34

Potential difference across membrane of a neurone when it's not being stimulated (repolarised)

Front 35

Action potential

Back 35

Rapid change (depolarisation) in membrane potential of an excitable cell (e.g. a neurone)

Front 36

Transpiration

Back 36

Loss of water vapour from leaves & stems of plants

Front 37

Linkage group

Back 37

Genes carried on any 1 chromosome

Front 38

Polygenic inheritance

Back 38

Inheritance of phenotypic characters (e.g. height, eye colour) determined by collective effects of several different genes

Front 39

Active immunity

Back 39

Immunity due to production of antibodies by organism itself after body's defence mechanisms have been stimulated by antigens

Front 40

Passive immunity

Back 40

Immunity due to acquisition of antibodies from another organism in which active immunity has been stimulated, including via: placenta, colostrum, or by injection of antibodies

Front 41

Excretion

Back 41

Removal from the body of the waste products of metabolic pathways

Front 42

Osmoregulation

Back 42

Control of water balance of blood, tissue or cytoplasm of living organism