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144 Cards in this Set

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

Denitrifying bacteria
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.
An alternative version of a gene.
Molecule (nucleotide derivative) found in all living cells and involved in energy transfer. When it is hydrolysed energy is released.
Enzyme associated with stalked particles in mitochondria and chloroplasts. It catalyses the joining of ADP and inorganic phosphate to make ATP.
ATP synthase
Organism that makes its own food using simple inorganic molecules, such as carbon dioxide and water, and energy.
The number and variety of living things to be found in the world, an ecosystem or habitat.
The maximum population size that can be maintained over a period of time in a particular habitat.
Carrying capacity
Type of metabolism: biochemical reactions that produce small molecules by hydrolysis of larger molecules.
The result of all the chemical reactions taking place in the cell cytoplasm.
Cell metabolism
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.
Chi-squared test
Organelles, in plant and some protoctist cells, where photosynthesis occurs.
A characteristic where both alleles contribute to the phenotype.
A coenzyme that carries acetate from the link reaction of respiration to Krebs cycle.
Coenzyme A
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.
All the populations of different species that live in the same place at the same time, and who can interact with each other.
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.
The active maintenance of biodiversity by man, including diversity between species, genetic diversity within species, and maintenance of a variety of habitats and ecosystems.
Living organisms that feed on other living organisms.
Describes the situation where there is wide phenotypic variation within the population. There are no distinct categories. It is controlled by many genes.
Continuous variation
Organisms that feed on dead organic matter, releasing molecules, minerals and energy that then become available to other living organisms in that ecosystem.
Type of oxidation involving the removal of hydrogen atoms from a substrate molecule.
Movement of molecules down their concentration gradient. It may be through a partially permeable membrane.
Hydrolyse a large molecule to smaller molecules.
Having two sets of chromosomes (eukaryotic cell or organism). Denoted by 2n.
Characteristic in which the allele responsible is expressed in the phenotype even in those with heterozygous genotypes.
All the living organisms and all the non-living components in a specific habitat, and their interactions.
Chemicals that take electrons from another compound. They are reduced while acting as oxidising agents.
Electron acceptors
Molecules that shuttle electrons between other molecules.
Electron carriers
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.
The ability to do work.
Double membrane. Double lipid bilayer. The nucleus is surrounded by one.
The combined action of biotic and abiotic factors that limits the growth of a population.
Environmental resistance
The tissue that covers the outside of a structure.
Organisms comprising cells with a true nucleus - protoctists, fungi, plants and animals.
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.
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.
Diffusion that is enhanced by the action of protein channels or carriers in the cell membrane.
Facilitated diffusion
Fusion of male and female gamete nuclei.
Specialised sex cells. In many organisms they are haploid and are produced by meiosis.
A length of DNA that codes for one (or more) polypeptides/proteins. Some may code for RNA and regulate other genes.
Total genetic information possessed by the reproductive members within a population of organisms.
Gene pool
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.
Genetic drift - also called allelic drift.
Describes the range of genetic information in a gene pool.
Genetic variation
All the genetic information within an organism/cell.
The alleles present within cells of an individual, for a particular trait/characteristic.
Intermediate 3-C compound produced during the Calvin cycle in the light-independent stage of photosynthesis by the enzyme RUBISCO.
Glycerate-3-phosphate (GP)
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.
Stacks of thylakoid membranes, found in a chloroplast.
Grana (s. granum)
The place where an organism or population of organisms lives.
Eukaryotic cell or organism having only one set of chromosomes. Denoted by n.
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.
Hardy-Weinberg principle
Cell or individual having only one allele for a particular gene.
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.
Eukaryotic cell or organism that has two different alleles for a specific gene.
The maintenance of a constant internal environment despite external changes.
Eukaryotic cell or organism that has two identical alleles for a specific gene.
Splitting of large molecules into smaller molecules with addition of water.
Mechanism that divides populations of organisms into subgroups.
Isolating mechanism
Third stage of respiration. It is aerobic and in eukaryotes it occurs in the matrix of the mitochondria.
Krebs cycle
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.
Light-dependent stage
Second stage of photosynthesis. Occurs in the stroma of the chloroplasts. ATP, reduced NADP and carbon dioxide are used to make organic molecules.
Light-independent stage
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.
Light intensity
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.
Limiting factor
Genes for different characteristics that are present at different loci on the same chromosome demonstrate this genetic property.
Stage of aerobic respiration that connects glycolysis with the Krebs cycle. In eukaryote cells it occurs in the mitochondrial matrix.
Link reaction
Specific position on a chromosome, occupied by a specific gene.
Member of a homologous pair of chromosomes that originally came from the female gamete.
Maternal chromosome
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.
Characteristic coded for by one gene.
Structural change to genetic material - either to a gene or to a chromosome.
A relationship between two organisms from which both benefit.
Coenzyme involved in respiration. It removes hydrogen atoms from substrates and carries them to the elctron transport chain in the mitochondria.
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.
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.
Natural selection
A process in which any change in a parameter brings about the reversal of that change so the parameter is kept fairly constant.
Negative feedback
The role that a species plays in an ecosystem.
Conversion of nitrogen gas into a form which is usable by plants, such as nitrate or ammonium ions.
Nitrogen fixation
Failure of members of a homologous pair of chromosomes, or of a pair of chromatids, to separate during nuclear division.
Structures within cells. Each carries out a specific function.
Chemical reaction involving loss of electrons, gain of oxygen or loss of hydrogen atoms.
The formation of ATP, in the presence of oxygen, by chemiosmosis.
Oxidative phosphorylation
A membrane that is permeable to certain substances, such as water, but is not permeable to other substances.
Partially permeable membrane
Member of a pair of homologous chromosomes that originally came from the male gamete.
Paternal chromosome
Observable characteristics of an organism.
Organism that can make its own food using energy obtained from light.
Enzyme-catalysed reaction where water molecules are split, using light energy. It occurs in photosystem II, during the light-dependent stage of photosynthesis.
Formation of ATP in the presence of light energy. It takes place in thylakoid membranes of chloroplasts, during the light-dependent stage of photosynthesis.
Chemicals that absorb light energy. Found in thylakoid membranes, in photosystems. Various types absorb energy associated with light of a specific wavelength.
Photosynthetic pigments
Apparatus to measure rate of photosynthesis by collecting and measuring the volume of oxygen produced in a certain time.
Group of photosynthetic pigments in the thylakoid membrane. Consists of a primary reaction centre and accessory pigments.
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.
Large polymer molecule made of many amino acids joined by peptide bonds.
Eukaryotic organisms or cell with more than two sets of chromosomes.
All of the organisms of one species, who live in the same place at the same time, and who can breed together.
The study of the gene pools and the allele and genotype frequencies of populations of organisms.
Population genetics
The primary photosynthetic pigments in a photosystem. In PSI has a peak absorption of 680 nm. In PSII the absorption peak is 700 nm.
Primary pigment reaction centre
Autotrophic organisms (plants, some protoctists and some bacteria) that convert light energy to chemical energy, which they then supply to consumers.
The rate of production of new biomass by producers. It is the energy captured by their chlorophyll and used to synthesise organic molecules.
A polymer of many amino acids joined by peptide bonds. May also be called a polypeptide.
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.
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.
Proton motive force
A square frame used for sampling in fieldwork.
Characteristic in which the allele responsible is only expressed in the phenotype if there is no dominant allele present.
Chemical reaction involving the gain of electrons, gain of hydrogen atoms or loss of oxygen atoms.
5-carbon compound, present in small amounts in stroma of chloroplasts. It is a carbon dioxide acceptor. It is regenerated from triose phosphate.
Ribulose bisphosphate (RuBP)
Enzyme that catalyses the carboxylation (addition of carbon dioxide) to ribulose bisphosphate.
Ribulose bisphosphate carboxylase (rubisco)
Organisms (like bacteria and fungi) that feed by secreting enzymes onto food, and absorbing digested nutrients across their outer walls.
Environmental factor that confers greater chances of surviving and reproducing on some members of the population than on others.
Selection pressure
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.
Sex linkage
Production of new organisms involving fusion of nuclei from male and female gametes, usually from unrelated individuals. Increases genetic variation in the population.
Sexual reproduction
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.
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.
Stabilising selection
Any change in the environment of an organism that causes a response.
Pores between guard cells in the epidermis of leaves.
Fluid-filled matrix of chloroplasts where the light-independent stage of photosynthesis takes place.
Formation of ATP from ADP and Pi during glycolysis and the Krebs cycle.
Substrate-level phosphorylation
A directional change in a community of organisms over time.
Inner membrane in chloroplast. Site of photosystems and ATP synthase.
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.
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.
A line taken through a habitat, which helps with systematic sampling of changes across a habitat.
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).
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.
Triose phosphate (TP)
The level at which an organism feeds in a food chain.
Trophic level
Cell formed, during sexual reproduction, from the fusion of two gametes.
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.
The formation of a new species.
The non-living factors influencing an ecosystem
Abiotic factors
The living factors influencing an ecosystem
Biotic factors
In succession, the term used to decribe the final stable population that is reached under one set of environmental conditions
Climax community
Opportunistic species that are the first to colonise newly-formed habitatssuch as volcanic islands.
Pioneer community
A way of showing energy transfer in food chains by quantifying the organic material at each trophic level.
Pyramid of biomass
The most accurate way of displaying energy flows through food chains.
Pyramid of energy
A way of showing the hierarchy of food chains that reflects the population at each trophic level.
Pyramid of numbers
Three-carbon compound that is the end product of glycolysis
Site of electron transport chain involved in aerobic respiration
Inner mitochondrial membrane
Man route by which energy enters an ecosystem
Calculated as the difference between gross productivity less the respiratory loss.
Net productivity
Process by which bacteria in soil convert ammonia into nitrate that can be taken up by plants.
Bacteria in soil that convert ammonia into nitrate that can be taken up by plants.
Nitrifying bacteria
The process by which excess chemicals added to the soil can be carried into lakes and rivers through the watr table.
Change in biotic or abiotic factors that causes a change in allele frequencies within a population.
Directional selection
A statistical measure of how well correlated two sets of variables are, that works even if the realtionship is non-linear.
Spearman's rank correlation coefficient. (Figures of +1 or -1 indicate a perfect correlation.)