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Summary Life Sciences IEB Paper 1 Definitions

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Complete set of definitions for IEB Paper 1 Life Sciences Matric Exam: Evolution, DNA, RNA and Meiosis, Genetics and Genetic Engineering, and Population Ecology.

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POPULATION ECOLOGY:
Population: A group of individuals belonging to the same species
(so they can interbreed) that live in the same area at the same time.
Individual: A single, separate organism, animal or plant capable of
independent existence.
Biosphere: The part of the Earth where living organisms are found.
Ecosystem: Made up of groups of different species of organisms
that interact with each other and the physical environment.
Organism: An individual form of life composed of a single cell or a
complex of cells that are capable of reproducing and growing.
Population: A group of individuals belonging to the same species
(so they can interbreed) that live in the same area at the same time.
Community: A group of different species that inhabit and interact
in a particular area.
Species: A group of closely related organisms that are very similar
to each other and are usually capable of interbreeding and
producing fertile offspring.
Natality: Birth rate in animals or the production of seeds in plants
(in humans it’s the number of births per 1000 people per year).
Mortality: Death rate (in humans it’s the number of deaths per
1000 people per year).
Immigration: Individuals move into a population and stay.
Emigration: Individuals leave a population and don’t return.
Carrying capacity: The population density that the environment
can support.
Environmental resistance: The total number of factors that stop a
population from reproducing at its maximum rate.
Density independent factors: Factors that limit the growth of a
population as a result of natural factors and not because of the
density or number of organisms.
Density dependent factors: Factors that have a greater effect
when the population density is high.
Interspecific: between different species

,Intraspecific: within a species
Stable population: A population in which numbers decrease when
its size exceeds the carrying capacity but increase again when
numbers fall below the carrying capacity ie one that fluctuates
around the carrying capacity.
Unstable population: A population that develops if the population
exceeds the carrying capacity.
Population pyramid: Age-sex pyramid bar graph, shows
composition of a nation’s population at a time of census.
Predation: A biological interaction where one species, the predator,
kills and eats another species, the prey. Predator and prey evolve
together and are part of the same environment.
Food web: An interconnected set of all the food chains in an
ecosystem.
Competition: When two or more individuals compete for the same
resources that are in short supply.
Ecological niche: All the conditions necessary for an organism to
survive and reproduce.
Specialisation: The structural and behavioural adaptations that
enable individuals of different species to co-exist.
Social organisation: Structure of relationships within a group of
organisms (jobs/tasks divided between members).
Eusocial: Most advanced form of social organisation(specialized
traits).
Resource partitioning: The evolutionary process whereby species
with similar requirements living in the same habitat, evolve
specialized traits that enable them to vitalize resources
differently(separate niches).
Ecological succession: A predictable pattern of gradual change
over time in the types of species in a community following a
disturbance.
Climax community: Semi-stable stage, endpoint of succession.
May be various possible endpoints, dependent on variety, number of
species and environmental fluctuations.

, Biome: A collection of plants and animals that have common
characteristics for the environment they exist.
Ecological footprint: A measure of human demand on the earth’s
ecosystems. Represents the amount of biologically productive land
and sea area necessary to supply the resources a human population
consumes and to assimilate the waste generated.
Biocapacity: The amount of productive land and water available to
produce the resources we use and to absorb the waste we produce.
Ecological debtor country: A country with an ecological deficit.
Ecological creditor country: A country that does not have an
ecological deficit.


DNA, RNA, CELL DIVISION, PROTEIN SYNTHESIS AND
MEIOSIS:
Chromatin: Chromosomal material made up of DNA, RNA and
histone proteins as found in a non-dividing cell.
Purines: Made up of two fused rings of nitrogen, carbon and
hydrogen (guanine and adenine).
Pyrimidines: Made up of one ring of similar atoms and are
therefore much smaller than purines (thymine, cytosine and uracil).
Replication: The process of making a new DNA molecule from an
existing DNA molecule that is identical to the original molecule. This
takes place in the nucleus during interphase.
Transcription: The process by which DNA makes and codes RNA.
Protein: A polymer (long chain) of monomers (small units) called
amino acids.
Translation: The process by which a specific protein is formed from
a chain of amino acids due to the sequence of codons in the mRNA
which, in turn, was coded by the DNA.
Tetracyclines: prevent the attachment of tRNAs carrying amino
acids.
Chloramphenicol: Prevents the formation of peptide bonds.

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