Population key words

• Ecology

  The study of living things and their interactions with each other and their environment
• Ecosystems

  A characteristic community of interdependent species interacting with the abiotic components of their habitat
• Community

  All the members of all species in an area
• Habitat

  The place in an ecosystem where an organism lives
• Niche

  The role of an organism in an ecosystem, generally a feeding role
• Biotic

  All the living and organic components of an ecosystem
• Abiotic

  All the non living parts of an ecosystem
• Factors affecting population sizes

  - Birth rate

  - Death rate

  - Immigration

  - Emigration
• Birth rate

  The reproductive capacity of a population / The number of new individuals derived from reproduction per unit time
• Immigration

  The movement of individuals into a population of the same species
• Population

  An interbreeding group of organisms of the same species occupying a particular habitat
• Birth and immigration increase a population size
• Death and emigration decrease a population size
• Fugitive species

  Poor at competition, instead rely on a large capacity for reproduction and dispersal to increase their numbers. They invade a new environment rapidly.
• Equilibrium species

  Control their population by competition within a stable habitat
• Equilibrium species are species that control their population by competition rather than by reproduction and dispersal
• Lag phase in One-step growth curve

  Period of slow growth

  Period of adaptation or preparation for growth
• Exponential (log) phase in One-step growth curve

  As numbers increase more individuals become available for reproduction
• Environmental resistance

  Environmental factors that slow down the population growth
• Environmental resistance factors

  - Less food available

  - Concentration of waste products becomes increasingly toxic

  - Not enough space or nesting sites
• Environmental resistance factors for bacteria

  - Available food

  - Overcrowding

  - Competition

  - Accumulation of toxic waste
• Environmental resistance factors for animals

  - Predation

  - Parasitism and disease

  - Competition from other species for nesting sites and food
• Stationary phase in One-step growth curve

  Occurs when the birth rate is equal to the death rate. The population has reached its carrying capacity.
• Carrying capacity

  The maximum number which a population fluctuates in a given environment
• Death phase in One-step growth curve

  Factors that slow the population growth in the log phase become more significant and population size decreases until the death rate is greater than the birth rate and the graph has a negative gradient.
• Density dependent factors

  These are biotic factors that have more effect when there is a dense population e.g. disease and parasitism
• Density independent factors

  These are abiotic factors in the environment and they do not depend on the population density. The effect is the same regardless of the size of the population and is usually due to a sudden change in abiotic factors e.g. flood or fire.
• succession

  The change in structure and species composition of a community over time
• Climax community

  a stable community that has reached equilibrium with its environment, and no further change occurs
• Primary succession

  The change in structure and species composition of a community over time in an area that has not been previously colonised
• Pioneer species

  the first species to colonise a new area in an ecological succession
• Intraspecific competition

  Competition between individuals of the same species
• Interspecific competition

  Competition between individuals of different species
• secondary succesion

  The changes in a community following the disturbance or damage to a colonised habitat
• Gross primary production

  The rate of conversion of light energy into chemical energy by photoautotrophs
• Net primary production

  The plant biomass that is available to be consumed by the next trophic level