Population ecology
Definitions:
Ecology: The study of the interactions of organisms with their physical and biological
. environments and how these determine the distribution and make up of
. populations within an ecosystem.
Population ecology: The fluctuations in the size of a population and the physical and social
. factors that regulates these fluctuations.
Organism: An individual form of life, such as a bacterium, fungus, protect plant or
. animal, composed of a single cell or a complex of cells that are capable of
. growing and reproducing.
Individual: A single organism capable of independent existence.
Species: A group of closely related organisms that are very similar to each other and
. are usually capable of interbreeding and producing fertile offspring.
Population: A group of organisms of the same species that occupy the same area and
. can breed freely with each other.
Community: A group of different species that inhabit and interact in a particular area.
Ecosystems: Made up of groups of different species of organisms that interact with each
. other and with the environment.
Biosphere: The part of earth where living organisms are found.
Demography: The statistical study of populations. It is used to predict how the size of a
. population will change.
Ecological niche: All conditions and resources necessary for survival.
Habitat: A type of place or part of an ecosystem occupied by an organism.
Niche: The specific functional role of an organism.
. The way it goes about living its life (what the organism does, and what is
. (done to the organism)
, Key features of a population:
1. Size
= is the total number of individuals in a population.
Has an important effect on the ability of the population to survive.
Example: A small population is more likely to become extinct:
- In the case of random events or natural disaster
- Due to inbreeding where the population is more genetically alike
- With reduced variability it is harder to adapt to changes
2. Density
= the number of individuals in a given area.
If the individuals are too far apart they may only rarely encounter one another resulting in
little reproduction.
Too close together, disease can be easily spread.
3. Dispersion
= the way in which the individuals are arranged.
(Effects mating and the land)
Example: penguins - uniform
Example: Seeds dispersed by wind - random
Example: Elephant herds - clumped
Population size
= the total number of individuals in a population
It can increase or decrease over time with a change in one or more of the following.
Population parameters:
1. Natality - birth rate in animals or the production of seeds in plants
2. Mortality - death rate
3. Immigration - individuals move into a population and stay
4. Emigration - individuals leave a population and do not return
Population size = (Natality - Mortality) + (Immigration - Emigration)
Note: For humans, natality and mortality are measure in the number of births or deaths per
1000 people in a year
A population will:
- Grow when natality and immigration exceed mortality and emigration
- Decline when mortality and emigration exceed natality and immigration
- Remain stable when natality and immigration approximately equal natality and emigration
In a closed population, with no immigration or emigration, the only parameters affecting any
change in population size will be natality and mortality.
Definitions:
Ecology: The study of the interactions of organisms with their physical and biological
. environments and how these determine the distribution and make up of
. populations within an ecosystem.
Population ecology: The fluctuations in the size of a population and the physical and social
. factors that regulates these fluctuations.
Organism: An individual form of life, such as a bacterium, fungus, protect plant or
. animal, composed of a single cell or a complex of cells that are capable of
. growing and reproducing.
Individual: A single organism capable of independent existence.
Species: A group of closely related organisms that are very similar to each other and
. are usually capable of interbreeding and producing fertile offspring.
Population: A group of organisms of the same species that occupy the same area and
. can breed freely with each other.
Community: A group of different species that inhabit and interact in a particular area.
Ecosystems: Made up of groups of different species of organisms that interact with each
. other and with the environment.
Biosphere: The part of earth where living organisms are found.
Demography: The statistical study of populations. It is used to predict how the size of a
. population will change.
Ecological niche: All conditions and resources necessary for survival.
Habitat: A type of place or part of an ecosystem occupied by an organism.
Niche: The specific functional role of an organism.
. The way it goes about living its life (what the organism does, and what is
. (done to the organism)
, Key features of a population:
1. Size
= is the total number of individuals in a population.
Has an important effect on the ability of the population to survive.
Example: A small population is more likely to become extinct:
- In the case of random events or natural disaster
- Due to inbreeding where the population is more genetically alike
- With reduced variability it is harder to adapt to changes
2. Density
= the number of individuals in a given area.
If the individuals are too far apart they may only rarely encounter one another resulting in
little reproduction.
Too close together, disease can be easily spread.
3. Dispersion
= the way in which the individuals are arranged.
(Effects mating and the land)
Example: penguins - uniform
Example: Seeds dispersed by wind - random
Example: Elephant herds - clumped
Population size
= the total number of individuals in a population
It can increase or decrease over time with a change in one or more of the following.
Population parameters:
1. Natality - birth rate in animals or the production of seeds in plants
2. Mortality - death rate
3. Immigration - individuals move into a population and stay
4. Emigration - individuals leave a population and do not return
Population size = (Natality - Mortality) + (Immigration - Emigration)
Note: For humans, natality and mortality are measure in the number of births or deaths per
1000 people in a year
A population will:
- Grow when natality and immigration exceed mortality and emigration
- Decline when mortality and emigration exceed natality and immigration
- Remain stable when natality and immigration approximately equal natality and emigration
In a closed population, with no immigration or emigration, the only parameters affecting any
change in population size will be natality and mortality.
