A2 Biology Unit 4

Front 1

Soil bacteria that remove nitrogen from the main nitrogen cycle by breaking down nitrates into nitrogen gas

Back 1

Denitrifying bacteria

Front 2

The increase in chemical nutrients in a water-based ecosystem that can lead to its destabilisation, often due to a rapid increase in the population of algae.

Back 2

Eutrophication

Front 3

An alternative version of a gene.

Back 3

Allele

Front 4

Molecule (nucleotide derivative) found in all living cells and involved in energy transfer. When it is hydrolysed energy is released.

Back 4

ATP

Front 5

Enzyme associated with stalked particles in mitochondria and chloroplasts. It catalyses the joining of ADP and inorganic phosphate to make ATP.

Back 5

ATP synthase

Front 6

Organism that makes its own food using simple inorganic molecules, such as carbon dioxide and water, and energy.

Back 6

Autotroph

Front 7

The number and variety of living things to be found in the world, an ecosystem or habitat.

Back 7

Biodiversity

Front 8

The maximum population size that can be maintained over a period of time in a particular habitat.

Back 8

Carrying capacity

Front 9

Type of metabolism: biochemical reactions that produce small molecules by hydrolysis of larger molecules.

Back 9

Catabolism

Front 10

The result of all the chemical reactions taking place in the cell cytoplasm.

Back 10

Cell metabolism

Front 11

Statistical test that can be carried out on data that are in categories. It enables the investigator to determine how closely an observed set of data corresponds to the expected data.

Back 11

Chi-squared test

Front 12

Organelles, in plant and some protoctist cells, where photosynthesis occurs.

Back 12

Chloroplasts

Front 13

A characteristic where both alleles contribute to the phenotype.

Back 13

Codominant

Front 14

A coenzyme that carries acetate from the link reaction of respiration to Krebs cycle.

Back 14

Coenzyme A

Front 15

Molecules that help enzymes carry out oxidation or reduction reactions. They work like shuttles, carrying atoms or molecules from one enzyme-controlled reaction to another.

Back 15

Coenzymes

Front 16

All the populations of different species that live in the same place at the same time, and who can interact with each other.

Back 16

Community

Front 17

A struggle between individuals for resources (like food or water) that are not present in amounts adequate to satisfy the needs of all the individuals who depend on those resources.

Back 17

Competition

Front 18

The active maintenance of biodiversity by man, including diversity between species, genetic diversity within species, and maintenance of a variety of habitats and ecosystems.

Back 18

Conservation

Front 19

Living organisms that feed on other living organisms.

Back 19

Consumers

Front 20

Describes the situation where there is wide phenotypic variation within the population. There are no distinct categories. It is controlled by many genes.

Back 20

Continuous variation

Front 21

Organisms that feed on dead organic matter, releasing molecules, minerals and energy that then become available to other living organisms in that ecosystem.

Back 21

Decomposers

Front 22

Type of oxidation involving the removal of hydrogen atoms from a substrate molecule.

Back 22

Dehydrogenation

Front 23

Movement of molecules down their concentration gradient. It may be through a partially permeable membrane.

Back 23

Diffusion

Front 24

Hydrolyse a large molecule to smaller molecules.

Back 24

Digest

Front 25

Having two sets of chromosomes (eukaryotic cell or organism). Denoted by 2n.

Back 25

Diploid

Front 26

Characteristic in which the allele responsible is expressed in the phenotype even in those with heterozygous genotypes.

Back 26

Dominant

Front 27

All the living organisms and all the non-living components in a specific habitat, and their interactions.

Back 27

Ecosystem

Front 28

Chemicals that take electrons from another compound. They are reduced while acting as oxidising agents.

Back 28

Electron acceptors

Front 29

Molecules that shuttle electrons between other molecules.

Back 29

Electron carriers

Front 30

The transport of large molecules or fluids into the cytoplasm of the cell, by the invagination (folding inwards) of the cell surface membrane to form a vesicle.

Back 30

Endocytosis

Front 31

The ability to do work.

Back 31

Energy

Front 32

Double membrane. Double lipid bilayer. The nucleus is surrounded by one.

Back 32

Envelope

Front 33

The combined action of biotic and abiotic factors that limits the growth of a population.

Back 33

Environmental resistance

Front 34

The tissue that covers the outside of a structure.

Back 34

Epithelium

Front 35

Organisms comprising cells with a true nucleus - protoctists, fungi, plants and animals.

Back 35

Eukaryotes

Front 36

The process of gradual change in the inherited traits passed from one generation to the next within a population. It results in the formation of new species.

Back 36

Evolution

Front 37

A mechanism of secretion from a cell involving vesicles that fuse to the cell surface membrane and release their contents to the outside. It uses ATP.

Back 37

Exocytosis

Front 38

Diffusion that is enhanced by the action of protein channels or carriers in the cell membrane.

Back 38

Facilitated diffusion

Front 39

Fusion of male and female gamete nuclei.

Back 39

Fertilisation

Front 40

Specialised sex cells. In many organisms they are haploid and are produced by meiosis.

Back 40

Gametes

Front 41

A length of DNA that codes for one (or more) polypeptides/proteins. Some may code for RNA and regulate other genes.

Back 41

Gene

Front 42

Total genetic information possessed by the reproductive members within a population of organisms.

Back 42

Gene pool

Front 43

The random change in allele frequency in a population, as some alleles pass to the next generation and some disappear. This causes some phenotypic traits to become rarer or more common.

Back 43

Genetic drift - also called allelic drift.

Front 44

Describes the range of genetic information in a gene pool.

Back 44

Genetic variation

Front 45

All the genetic information within an organism/cell.

Back 45

Genome

Front 46

The alleles present within cells of an individual, for a particular trait/characteristic.

Back 46

Genotype

Front 47

Intermediate 3-C compound produced during the Calvin cycle in the light-independent stage of photosynthesis by the enzyme RUBISCO.

Back 47

Glycerate-3-phosphate (GP)

Front 48

Metabolic pathway. The first stage of respiration. It is anaerobic and occurs in the cytosol (cytoplasm). Although anaerobic, it involves oxidation as substrate molecules are dehydrogenated.

Back 48

Glycolysis

Front 49

Stacks of thylakoid membranes, found in a chloroplast.

Back 49

Grana (s. granum)

Front 50

The place where an organism or population of organisms lives.

Back 50

Habitat

Front 51

Eukaryotic cell or organism having only one set of chromosomes. Denoted by n.

Back 51

Haploid

Front 52

The concept that both genotype frequencies and gene frequencies will stay constant from generation to generation, within a large interbreeding population. It assumes mating is random, there is no mutation and no selection or migration.

Back 52

Hardy-Weinberg principle

Front 53

Cell or individual having only one allele for a particular gene.

Back 53

Hemizygous

Front 54

Organism that gains its nutrients from complex organic molecules. It digests them to simpler, soluble molecules and then respires some of them to obtain energy, or uses the products of digestion to synthesise the organic molecules it needs.

Back 54

Heterotroph

Front 55

Eukaryotic cell or organism that has two different alleles for a specific gene.

Back 55

Heterozygous

Front 56

The maintenance of a constant internal environment despite external changes.

Back 56

Homeostasis

Front 57

Eukaryotic cell or organism that has two identical alleles for a specific gene.

Back 57

Homozygous

Front 58

Splitting of large molecules into smaller molecules with addition of water.

Back 58

Hydrolysis

Front 59

Mechanism that divides populations of organisms into subgroups.

Back 59

Isolating mechanism

Front 60

Third stage of respiration. It is aerobic and in eukaryotes it occurs in the matrix of the mitochondria.

Back 60

Krebs cycle

Front 61

First stage of photosynthesis. Occurs in the thylakoid membranes of the chloroplasts. It involves using light energy to make ATP. Other products are reduced NADP and oxygen.

Back 61

Light-dependent stage

Front 62

Second stage of photosynthesis. Occurs in the stroma of the chloroplasts. ATP, reduced NADP and carbon dioxide are used to make organic molecules.

Back 62

Light-independent stage

Front 63

A measure of the amount of energy associated with light. Can be calculated using the formula I = 1/d^2 where d is the distance between source and object receiving the light.

Back 63

Light intensity

Front 64

Where the rate of a natural process is affected by a number of factors, this is the one whose magnitude determines the rate of the process.

Back 64

Limiting factor

Front 65

Genes for different characteristics that are present at different loci on the same chromosome demonstrate this genetic property.

Back 65

Linkage

Front 66

Stage of aerobic respiration that connects glycolysis with the Krebs cycle. In eukaryote cells it occurs in the mitochondrial matrix.

Back 66

Link reaction

Front 67

Specific position on a chromosome, occupied by a specific gene.

Back 67

Locus

Front 68

Member of a homologous pair of chromosomes that originally came from the female gamete.

Back 68

Maternal chromosome

Front 69

Type of nuclear division by which the chromosome number is halved. It involves two divisions. It produces cells that are genetically different from each other and from the parent cell.

Back 69

Meiosis

Front 70

Characteristic coded for by one gene.

Back 70

Monogenic

Front 71

Structural change to genetic material - either to a gene or to a chromosome.

Back 71

Mutation

Front 72

A relationship between two organisms from which both benefit.

Back 72

Mutualism

Front 73

Coenzyme involved in respiration. It removes hydrogen atoms from substrates and carries them to the elctron transport chain in the mitochondria.

Back 73

NAD

Front 74

Coenzyme involved in photosynthesis. It accepts hydrogen atoms from photolysis of water during the light-dependent stage and carries them to the light-independent stage.

Back 74

NADP

Front 75

Mechanism for evolution. Organisms that are well adapted to their environment are more likely to survive and reproduce, passing on the alleles for the favourable characteristics.

Back 75

Natural selection

Front 76

A process in which any change in a parameter brings about the reversal of that change so the parameter is kept fairly constant.

Back 76

Negative feedback

Front 77

The role that a species plays in an ecosystem.

Back 77

Niche

Front 78

Conversion of nitrogen gas into a form which is usable by plants, such as nitrate or ammonium ions.

Back 78

Nitrogen fixation

Front 79

Failure of members of a homologous pair of chromosomes, or of a pair of chromatids, to separate during nuclear division.

Back 79

Non-disjunction

Front 80

Structures within cells. Each carries out a specific function.

Back 80

Organelles

Front 81

Chemical reaction involving loss of electrons, gain of oxygen or loss of hydrogen atoms.

Back 81

Oxidation

Front 82

The formation of ATP, in the presence of oxygen, by chemiosmosis.

Back 82

Oxidative phosphorylation

Front 83

A membrane that is permeable to certain substances, such as water, but is not permeable to other substances.

Back 83

Partially permeable membrane

Front 84

Member of a pair of homologous chromosomes that originally came from the male gamete.

Back 84

Paternal chromosome

Front 85

Observable characteristics of an organism.

Back 85

Phenotype

Front 86

Organism that can make its own food using energy obtained from light.

Back 86

Photoautotroph

Front 87

Enzyme-catalysed reaction where water molecules are split, using light energy. It occurs in photosystem II, during the light-dependent stage of photosynthesis.

Back 87

Photolysis

Front 88

Formation of ATP in the presence of light energy. It takes place in thylakoid membranes of chloroplasts, during the light-dependent stage of photosynthesis.

Back 88

Photophosphorylation

Front 89

Chemicals that absorb light energy. Found in thylakoid membranes, in photosystems. Various types absorb energy associated with light of a specific wavelength.

Back 89

Photosynthetic pigments

Front 90

Apparatus to measure rate of photosynthesis by collecting and measuring the volume of oxygen produced in a certain time.

Back 90

Photosynthometer

Front 91

Group of photosynthetic pigments in the thylakoid membrane. Consists of a primary reaction centre and accessory pigments.

Back 91

Photosystem

Front 92

Characteristic coded for by many genes. Examples include height and intelligence in humans. More influenced by environmental factors than are characteristics determined by a single gene.

Back 92

Polygenic

Front 93

Large polymer molecule made of many amino acids joined by peptide bonds.

Back 93

Polypeptide

Front 94

Eukaryotic organisms or cell with more than two sets of chromosomes.

Back 94

Polyploid

Front 95

All of the organisms of one species, who live in the same place at the same time, and who can breed together.

Back 95

Population

Front 96

The study of the gene pools and the allele and genotype frequencies of populations of organisms.

Back 96

Population genetics

Front 97

The primary photosynthetic pigments in a photosystem. In PSI has a peak absorption of 680 nm. In PSII the absorption peak is 700 nm.

Back 97

Primary pigment reaction centre

Front 98

Autotrophic organisms (plants, some protoctists and some bacteria) that convert light energy to chemical energy, which they then supply to consumers.

Back 98

Producers

Front 99

The rate of production of new biomass by producers. It is the energy captured by their chlorophyll and used to synthesise organic molecules.

Back 99

Productivity

Front 100

A polymer of many amino acids joined by peptide bonds. May also be called a polypeptide.

Back 100

Protein

Front 101

Eukaryotic organism that cannot be classified as belonging to the other four kingdoms. It includes algae, protozoa and slime moulds. Some members of this phylum are photosynthetic. Some have undulipodia and some have cilia.

Back 101

Protoctist

Front 102

Force produced as hydrogen ions flow, through ATP synthase channels, down their concentration gradient. The force causes ADP and Pi to combine and form ATP.

Back 102

Proton motive force

Front 103

A square frame used for sampling in fieldwork.

Back 103

Quadrat

Front 104

Characteristic in which the allele responsible is only expressed in the phenotype if there is no dominant allele present.

Back 104

Recessive

Front 105

Chemical reaction involving the gain of electrons, gain of hydrogen atoms or loss of oxygen atoms.

Back 105

Reduction

Front 106

5-carbon compound, present in small amounts in stroma of chloroplasts. It is a carbon dioxide acceptor. It is regenerated from triose phosphate.

Back 106

Ribulose bisphosphate (RuBP)

Front 107

Enzyme that catalyses the carboxylation (addition of carbon dioxide) to ribulose bisphosphate.

Back 107

Ribulose bisphosphate carboxylase (rubisco)

Front 108

Organisms (like bacteria and fungi) that feed by secreting enzymes onto food, and absorbing digested nutrients across their outer walls.

Back 108

Saprotrophs

Front 109

Environmental factor that confers greater chances of surviving and reproducing on some members of the population than on others.

Back 109

Selection pressure

Front 110

Recessive alleles carried on the X chromosome will always be expressed in males. As there are few genes on the Y chromosome, in humans, most genes showing this characteristic are on the X chromosome.

Back 110

Sex linkage

Front 111

Production of new organisms involving fusion of nuclei from male and female gametes, usually from unrelated individuals. Increases genetic variation in the population.

Back 111

Sexual reproduction

Front 112

A group of similar organisms that can interbreed and produce fertile offspring. A group of organisms with similar morphology, physiology, embryology and behaviour, and that all occupy the same ecological niche.

Back 112

Species

Front 113

A type of natural selection in which the allele and genotype frequency within populations stays the same because the organisms are already well adapted to their environment.

Back 113

Stabilising selection

Front 114

Any change in the environment of an organism that causes a response.

Back 114

Stimulus

Front 115

Pores between guard cells in the epidermis of leaves.

Back 115

Stomata

Front 116

Fluid-filled matrix of chloroplasts where the light-independent stage of photosynthesis takes place.

Back 116

Stroma

Front 117

Formation of ATP from ADP and Pi during glycolysis and the Krebs cycle.

Back 117

Substrate-level phosphorylation

Front 118

A directional change in a community of organisms over time.

Back 118

Succession

Front 119

Inner membrane in chloroplast. Site of photosystems and ATP synthase.

Back 119

Thylakoid

Front 120

A group of cells, with a common origin and similar structures, which performs a particular function; for example, blood, bone, epithelium, muscle, nerves, xylem and phloem.

Back 120

Tissue

Front 121

The formation of an RNA molecule, using a length of DNA as a template. Complementary base pairing is used. The enzyme RNA polymerase catalyses the reaction.

Back 121

Transcription

Front 122

A line taken through a habitat, which helps with systematic sampling of changes across a habitat.

Back 122

Transect

Front 123

Stage of protein/polypeptide synthesis in which the amino acids are assembled at ribosomes. The order in which the amino acids are joined together, by peptide bonds, is determined by the sequence of codons on the mRNA, which is itself determined by the sequence of nucleotide triplets on the coding strand of a length of DNA (gene).

Back 123

Translation

Front 124

3-carbon compound formed when a molecule of glycerate phosphate is reduced using NADPH, during the Calvin cycle in the light-independent stage of photosynthesis.

Back 124

Triose phosphate (TP)

Front 125

The level at which an organism feeds in a food chain.

Back 125

Trophic level

Front 126

Cell formed, during sexual reproduction, from the fusion of two gametes.

Back 126

Zygote

Front 127

Pigments found in chloroplasts of plant (and some protoctist) cells. Each molecule consists of a hydrocarbon tail and a porphyrin ring head with a magnesium atom.

Back 127

Chlorophyll

Front 128

The formation of a new species.

Back 128

Speciation

Front 129

The non-living factors influencing an ecosystem

Back 129

Abiotic factors

Front 130

The living factors influencing an ecosystem

Back 130

Biotic factors

Front 131

In succession, the term used to decribe the final stable population that is reached under one set of environmental conditions

Back 131

Climax community

Front 132

Opportunistic species that are the first to colonise newly-formed habitatssuch as volcanic islands.

Back 132

Pioneer community

Front 133

A way of showing energy transfer in food chains by quantifying the organic material at each trophic level.

Back 133

Pyramid of biomass

Front 134

The most accurate way of displaying energy flows through food chains.

Back 134

Pyramid of energy

Front 135

A way of showing the hierarchy of food chains that reflects the population at each trophic level.

Back 135

Pyramid of numbers

Front 136

Three-carbon compound that is the end product of glycolysis

Back 136

Pyruvate

Front 137

Site of electron transport chain involved in aerobic respiration

Back 137

Inner mitochondrial membrane

Front 138

Man route by which energy enters an ecosystem

Back 138

Photosynthesis

Front 139

Calculated as the difference between gross productivity less the respiratory loss.

Back 139

Net productivity

Front 140

Process by which bacteria in soil convert ammonia into nitrate that can be taken up by plants.

Back 140

Nitrification

Front 141

Bacteria in soil that convert ammonia into nitrate that can be taken up by plants.

Back 141

Nitrifying bacteria

Front 142

The process by which excess chemicals added to the soil can be carried into lakes and rivers through the watr table.

Back 142

Leaching

Front 143

Change in biotic or abiotic factors that causes a change in allele frequencies within a population.

Back 143

Directional selection

Front 144

A statistical measure of how well correlated two sets of variables are, that works even if the realtionship is non-linear.

Back 144

Spearman's rank correlation coefficient. (Figures of +1 or -1 indicate a perfect correlation.)