Unit 4 Definitions

Pregunta	Respuesta
Community	All the populations of different species interacting together in a habitat at a given time
Habitat	The conditions in which an organism lives, which is composed of both biotic and abiotic factors
Environment	A well defined area in which an organism lives e.g. hedgerow or pond, oakwood or rocky shore
Population	The members of one species living in one habitat at a given time
Niche	Where an organism lives in a habitat and its role in the habitat
Ecosystem	Self contained ecological unit of community of living organisms in conjunction with the non-living components of their environment (community + environment)
Random Sampling	Used to avoid bias in collecting data to ensure that the data obtained is valid
Abundance	Counting the number of individuals of a species in a given space
Systematic sampling	Samples are taken at regular intervals within a set sample area
Percentage cover	An estimate of the area within a quadrat that a particular plant species covers
Mark-release-recapture	Known number of animals caught, marked and released. Some time later given number of individuals are collected and randomly and mark recorded.
Frequecy	Th likelihood of a particular species occuring in a quadrat
Mark-recapture-release method relies on what assumptions?	1 - Marked individuals distribute themselves evenly 2 - Population has a definitive boundary 3 - Mark is not toxic 4 - Mark is not lost 5 - Few births or deaths
Mark-recapture-release equation	no of organisms in sample 1 X no of organisms in sample 2 -------------------------------------------- no of marked organisms recaptured
Factors that affect population size	Abiotic and biotic factors
Definition of abiotic factors	Non-living part of the environment
Examples of abiotic factors	Light, temp, wind, water availability, humidity, salinity (salt), water movement, O2 concentration, soil, pH
Definition of biotic factors	The effect of living organisms and how they interact (tend to have greater impact in later stages of succession)
Examples of biotic factors	Symbiosis, mutualism, parasitism, disease
Symbiosis	Intimate relationship between members of 2 species, the survival of a species relies on the success of another species e.g. bee pollinating plants
Mutualism	A type of symbiosis between a pair of species that is mutually beneficial e.g. Lichen - algae + fungus
Parasitism	A type of symbiosis where the host gives and the parasite takes e.g. ivy growing on a tree
Disease	Caused by pathogens
Interspecific Competition	Competition between organisms of different species
Intraspecific Competition	Competitions between organisms of the same species
Phosphorylation	The process of adding a phosphate group (ADP+ Pi = ATP)
Light Dependent Reaction	Stage of photosynthesis in which light energy is required to produce ATP and reduced NADP
Oxidation	Loss of electrons, combining oxygen with a substance
Reduction	Gain of electrons, loss of oxygen from a substance
Electron Carrier Molecules	A chain of carrier molecules along which electron pass releasing energy in the form of ATP
Photolysis of Water	Light energy splits water molecule, yielding electron, hydrogen ions and oxygen (light-dependent reaction)
Calvin Cycle	A biochemical pathway (part of the light-independent reaction) where CO2 is reduced to form carbohydrate CO2 + RuBP = GP =TP = Glucose or RuBP
Limiting Factor	A variable that limits the rate of a chemical reaction
Glycolysis	First part of cellular respiration in which glucose is broken down (in the cytoplasm) to 2 molecules of Pyruvate
Link Reaction	Process linking glycolysis to the Krebs cycle (in the matrix of the mitochondria), where the 2 molecules of pyruvate are converted into CO2 and Acetylcoenzyme A
Krebs Cycle	Introducing acetylcoenzyme A into a cycle of oxidation-reduction reactions (in the matrix of the mitochondria ) that yield some ATP and large number of electrons
Electron Chain Transport	Use of electron from Krebs cycle to synthesis ATP via a series of oxidation-reduction reactions
Anaerobic Respiration	Releasing energy from glucose without oxygen (produces lactate = lactic acid)
Trophic Levels	Each stage in a food chain
Consumer	An organism that obtains its energy by feeding on other organisms
Gross production	Total quantity of energy that plants in a community convert into organic matter
Net Production	Gross production - respiratory losses
Energy Transfer	(Energy available after the transfer/energy available before the transfer) x 100
Pyramid of Number	A pyramid drawn with bar lengths proportional to the number of organisms present
Pyramid of Biomass	A pyramid drawn with bars proportional to the mass of the plants/animals
Pyramid of Energy	A pyramid drawn with bars proportional to the energy stored in organisms
Biological Control	Controling pests by introducing pedators
Chemical Control	Controlling pests by using various chemicals
Integrated Pest Control System	Controlling pests by using both biological and chemical controls
Selective Breeding	Breeding of organism by human selection of parents for certain characteristics
Saprobiotic Micro-organisms	An organisms that gets its food from the dead or decaying remains of other organisms
Greenhouse Gases	Gases such as methane and CO2 which trap more heat energy raising the Earth temp
Ammonification	Production of ammonia from urea and proteins
Nitrification	Converting ammonia into nitrites then nitrates
Nitrogen fixation	Conversion of nitrogen gas into nitrogen-containing compounds
Denitrification	Conversion of soil nitrates into nitrogen gas
Leaching	Process by which nutrients are washed from the soil into watercourses
Eutrophication	Consequences of an increase in nutrients in watercourses that leads to a decrease in biodiversity
Succession	The changes in an ecosystem, over time, of the species that occupy it
Pioneer Species	A species that can colonise bare rock of ground. They are the first plant that colonise the bare ground
Climax Community	The stable, final community that exists in balanced equilibrium
Conservation	Management of the Earth's natural resources in such a way that maximum use can be made of them in the future
Genotype	The genetic composition of an organism
Phenotype	The (visible) characteristic of an organism, often resulting from its genotype and the environment
Gene	A length of DNA that codes for a polypeptide
Allele	One form of a gene
Homologous Chromosomes	A pair of chromosomes that have the same gene loci and determine the same features
Dominant	An allele that is always expressed in the phenotype
Recessive	An allele that is only expressed in the phenotype if there is another identical allele
Heterozygous	When the alleles are different for a particular gene
Homozygous	When the alleles are the same for a particular gene
Sex Linkage	Any gene that is carried on the X or Y chromosome (Women = XX Men = XY)
Co-dominance	Both alleles are equally dominant and are both expressed in the phenotype
Multiple Alleles	More than 2 possible alleles for a particular gene
Gene Pool	Al the alleles of all the genes of all the individuals of a population at a given time
Allelic Frequency	The number of times that allele occurs within a gene pool
Stabilising Selection	Selection that favours average individuals
Directional Selection	Selection that favours individuals at one extreme
Speciation	The evolution of new species from existing species
Geographical Isolation	When a physical barrier prevent 2 populations from breeding with one another

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