LIFE SCIENCE
DEFINITIONS & TERMS
Grade 12 IEB
Prepared by: George Cox
Date: August 2025
This document contains key definitions and terms for the Life Science IEB
Curriculum for Grade 12, compiled for study and revision purposes.
,LIFE SCIENCE............................................................................................................................................. 1
Population Ecology.................................................................................................................................... 3
Core Concepts.................................................................................................................................................. 3
Population Dynamics........................................................................................................................................ 3
Sampling Methods............................................................................................................................................ 3
Species Interactions..........................................................................................................................................4
Succession & Organisation............................................................................................................................... 4
Human Impact................................................................................................................................................... 4
Endocrine System.......................................................................................................................................5
Core Concepts.................................................................................................................................................. 5
Major Glands & Hormones................................................................................................................................5
Disorders of the Endocrine System...................................................................................................................6
Applications & Issues........................................................................................................................................ 6
Meiosis.........................................................................................................................................................7
Core Concepts.................................................................................................................................................. 7
Meiosis Overview.............................................................................................................................................. 7
Phases of Meiosis............................................................................................................................................. 7
Significance of Meiosis......................................................................................................................................8
Errors in Meiosis............................................................................................................................................... 8
Attitudes & Issues............................................................................................................................................. 8
Genetics.......................................................................................................................................................9
Mendelian Genetics.......................................................................................................................................... 9
Patterns of Inheritance...................................................................................................................................... 9
Mutations & Variation........................................................................................................................................ 9
Human Genome Project (HGP)...................................................................................................................... 10
Genetic Engineering........................................................................................................................................10
Medical & Agricultural Applications................................................................................................................. 10
Modern Tools & Debates.................................................................................................................................10
Reproduction.............................................................................................................................................12
Plant Reproduction..........................................................................................................................................12
Human Reproduction...................................................................................................................................... 13
Male Reproductive System...................................................................................................................... 13
Female Reproductive System..................................................................................................................13
Puberty & Gametogenesis....................................................................................................................... 13
Menstrual & Ovarian Cycles.................................................................................................................... 13
Fertilisation & Development..................................................................................................................... 14
Contraception...........................................................................................................................................14
Reproductive Health................................................................................................................................ 14
Evolution....................................................................................................................................................15
Core Concepts................................................................................................................................................ 15
Historical Figures............................................................................................................................................ 15
Mechanisms of Evolution................................................................................................................................ 15
Human Evolution.............................................................................................................................................16
Evidence for Evolution in Humans.................................................................................................................. 16
Evolutionary Patterns & Events.......................................................................................................................16
Controversies & Applications.......................................................................................................................... 16
, Population Ecology
Core Concepts
● Individual – A single organism of a species.
● Population – A group of individuals of the same species living in a specific area at a
given time.
● Community – All the different populations of organisms living and interacting in the
same area.
● Ecosystem – A community of organisms interacting with each other and their physical
environment.
Population Dynamics
● Immigration – Movement of individuals into a population.
● Emigration – Movement of individuals out of a population.
● Mortality – Death rate within a population.
● Natality (Births) – Number of new individuals born into a population.
● Population Size – The total number of individuals in a population; changes due to
immigration, emigration, births, and deaths.
● Limiting Factors – Environmental factors that restrict population growth.
● Density-Dependent Factors – Limiting factors influenced by population density (e.g.
competition, disease, predation).
● Density-Independent Factors – Limiting factors that affect populations regardless of
density (e.g. drought, fire, floods).
● Environmental Resistance – The sum of limiting factors that prevent a population from
growing indefinitely.
● Carrying Capacity (K) – The maximum population size that an environment can
sustainably support.
Sampling Methods
● Mark-Recapture – A technique for estimating population size where individuals are
captured, marked, released, and later recaptured.
● Quadrats – A square sampling frame used to estimate population size and distribution
of plants or slow-moving animals.
● Census – A direct count of every individual in a population (rare in ecology due to
practical limits).
● Random Sampling – A method ensuring each part of the area has an equal chance of
being sampled, reducing bias.
, Species Interactions
● Predator-Prey Relationship – Interaction where one species (predator) feeds on
another (prey), helping regulate population sizes.
● Competition – When individuals or species compete for limited resources (food, water,
space, mates).
○ Intraspecific Competition – Competition within the same species.
○ Interspecific Competition – Competition between different species.
● Ecological Niche – The role and position a species has in its environment, including its
use of resources.
● Resource Partitioning – Division of resources by species to reduce competition (e.g.
different feeding times/places).
Succession & Organisation
● Ecological Succession – The gradual process of change in species composition in a
habitat over time.
○ Primary Succession – Succession starting on a bare surface with no soil (e.g.
volcanic lava).
○ Secondary Succession – Succession following a disturbance where soil
remains (e.g. after a fire).
Pioneer Species – The first species to colonise a new habitat.
● Social Organisation – Group behaviours that enhance survival:
○ Herds/Flocks – Predator avoidance strategy (e.g. zebra).
○ Packs – Cooperative hunting (e.g. wild dogs).
○ Dominant Breeding Pair – Only one pair reproduces in a group (e.g. wild dogs).
○ Division of Labour – Task specialisation among castes (e.g. termites).
Human Impact
● Exponential Growth – Rapid human population growth without limits.
● Ecological Footprint – Measure of human demand on ecosystems, compared between
developed and developing countries.
● Sustainable Harvesting – Use of resources at a rate that does not exceed their
renewal.
● Biodiversity – Variety of living organisms in an ecosystem, valued aesthetically and
ecologically.
DEFINITIONS & TERMS
Grade 12 IEB
Prepared by: George Cox
Date: August 2025
This document contains key definitions and terms for the Life Science IEB
Curriculum for Grade 12, compiled for study and revision purposes.
,LIFE SCIENCE............................................................................................................................................. 1
Population Ecology.................................................................................................................................... 3
Core Concepts.................................................................................................................................................. 3
Population Dynamics........................................................................................................................................ 3
Sampling Methods............................................................................................................................................ 3
Species Interactions..........................................................................................................................................4
Succession & Organisation............................................................................................................................... 4
Human Impact................................................................................................................................................... 4
Endocrine System.......................................................................................................................................5
Core Concepts.................................................................................................................................................. 5
Major Glands & Hormones................................................................................................................................5
Disorders of the Endocrine System...................................................................................................................6
Applications & Issues........................................................................................................................................ 6
Meiosis.........................................................................................................................................................7
Core Concepts.................................................................................................................................................. 7
Meiosis Overview.............................................................................................................................................. 7
Phases of Meiosis............................................................................................................................................. 7
Significance of Meiosis......................................................................................................................................8
Errors in Meiosis............................................................................................................................................... 8
Attitudes & Issues............................................................................................................................................. 8
Genetics.......................................................................................................................................................9
Mendelian Genetics.......................................................................................................................................... 9
Patterns of Inheritance...................................................................................................................................... 9
Mutations & Variation........................................................................................................................................ 9
Human Genome Project (HGP)...................................................................................................................... 10
Genetic Engineering........................................................................................................................................10
Medical & Agricultural Applications................................................................................................................. 10
Modern Tools & Debates.................................................................................................................................10
Reproduction.............................................................................................................................................12
Plant Reproduction..........................................................................................................................................12
Human Reproduction...................................................................................................................................... 13
Male Reproductive System...................................................................................................................... 13
Female Reproductive System..................................................................................................................13
Puberty & Gametogenesis....................................................................................................................... 13
Menstrual & Ovarian Cycles.................................................................................................................... 13
Fertilisation & Development..................................................................................................................... 14
Contraception...........................................................................................................................................14
Reproductive Health................................................................................................................................ 14
Evolution....................................................................................................................................................15
Core Concepts................................................................................................................................................ 15
Historical Figures............................................................................................................................................ 15
Mechanisms of Evolution................................................................................................................................ 15
Human Evolution.............................................................................................................................................16
Evidence for Evolution in Humans.................................................................................................................. 16
Evolutionary Patterns & Events.......................................................................................................................16
Controversies & Applications.......................................................................................................................... 16
, Population Ecology
Core Concepts
● Individual – A single organism of a species.
● Population – A group of individuals of the same species living in a specific area at a
given time.
● Community – All the different populations of organisms living and interacting in the
same area.
● Ecosystem – A community of organisms interacting with each other and their physical
environment.
Population Dynamics
● Immigration – Movement of individuals into a population.
● Emigration – Movement of individuals out of a population.
● Mortality – Death rate within a population.
● Natality (Births) – Number of new individuals born into a population.
● Population Size – The total number of individuals in a population; changes due to
immigration, emigration, births, and deaths.
● Limiting Factors – Environmental factors that restrict population growth.
● Density-Dependent Factors – Limiting factors influenced by population density (e.g.
competition, disease, predation).
● Density-Independent Factors – Limiting factors that affect populations regardless of
density (e.g. drought, fire, floods).
● Environmental Resistance – The sum of limiting factors that prevent a population from
growing indefinitely.
● Carrying Capacity (K) – The maximum population size that an environment can
sustainably support.
Sampling Methods
● Mark-Recapture – A technique for estimating population size where individuals are
captured, marked, released, and later recaptured.
● Quadrats – A square sampling frame used to estimate population size and distribution
of plants or slow-moving animals.
● Census – A direct count of every individual in a population (rare in ecology due to
practical limits).
● Random Sampling – A method ensuring each part of the area has an equal chance of
being sampled, reducing bias.
, Species Interactions
● Predator-Prey Relationship – Interaction where one species (predator) feeds on
another (prey), helping regulate population sizes.
● Competition – When individuals or species compete for limited resources (food, water,
space, mates).
○ Intraspecific Competition – Competition within the same species.
○ Interspecific Competition – Competition between different species.
● Ecological Niche – The role and position a species has in its environment, including its
use of resources.
● Resource Partitioning – Division of resources by species to reduce competition (e.g.
different feeding times/places).
Succession & Organisation
● Ecological Succession – The gradual process of change in species composition in a
habitat over time.
○ Primary Succession – Succession starting on a bare surface with no soil (e.g.
volcanic lava).
○ Secondary Succession – Succession following a disturbance where soil
remains (e.g. after a fire).
Pioneer Species – The first species to colonise a new habitat.
● Social Organisation – Group behaviours that enhance survival:
○ Herds/Flocks – Predator avoidance strategy (e.g. zebra).
○ Packs – Cooperative hunting (e.g. wild dogs).
○ Dominant Breeding Pair – Only one pair reproduces in a group (e.g. wild dogs).
○ Division of Labour – Task specialisation among castes (e.g. termites).
Human Impact
● Exponential Growth – Rapid human population growth without limits.
● Ecological Footprint – Measure of human demand on ecosystems, compared between
developed and developing countries.
● Sustainable Harvesting – Use of resources at a rate that does not exceed their
renewal.
● Biodiversity – Variety of living organisms in an ecosystem, valued aesthetically and
ecologically.
