Populations Flashcards
What is a niche?
The role a species plays within its habitat
Every species occupies its own niche
What is a biotic factor?
Living factors that affect an organisms environment
What is an abiotic factor?
non living factors that affect an organisms environment
What is a habitat?
The place where an organism normally lives
What is a population?
all of the organisms of one species in a particular habitat
What is a community?
all of the populations of different species living in the same place at the same time
What is an ecosystem?
combination of all biotic and abiotic factors in a particular area
What are the stages of the population growth curve?
- Lag phase
- Exponential phase
- Transitional phase
- Stationary phase
- Decline/death phase
What happens in the lag phase?
Slowest phase of population growth
- Starts with a very low no. of individuals
- Takes time to reproduce and the population to grow
Birth rate higher than death rate
What happens in the exponential growth phase?
Happens when there are no abiotic or biotic factors to limit growth (food, oxygen, habitats)
- The population grows rapidly, doubling in a short period of time
- Limited intraspecific competition
What happens in the transitional phase/stationary phase?
Population growth slows and stabilises.
- Fluctuations due to a change in abiotic and biotic factors
- K (carrying capacity) is reached
Birth rate= death rate
What happens in the death phase?
The death phase
- Organisms start to die due to lack of resources (oxygen, glucose) or due
to too much CO2 or a build up of toxins (such as ethanol being produced with yeast)
What is carrying capacity?
the maximum stable population size of a species that an ecosystem can support
What happens to population growth in a closed batch culture?
Nutrients run out and toxic waste products build up so the organism goes into a death phase
What happens to pop. Growth in a non closed culture?
No death phase
Limiting factors affect the population growth leading to stabilisation at the carrying capacity
What is migration?
Movement of organisms in/out of a particular area
What is immigration?
Individuals move into the area increasing the population size
What is emigration?
individuals move out of the area, decreases the population
What are density independent factors?
Factors that can change/limit a
population regardless of its size.
Eg of a density independent factor?
Natural disasters
Suggest reasons why the maximum population size fluctuates
Food availability
Number of predators
Disease
Temperature
What factors affect human birth rate?
Economic factors
Cultural expectations
Religious expectations
Social pressures
Availability of birth
control
What factors affect human death rate?
Life expectancy at birth
Food supply
Safe drinking water and effective sanitation
Medical care
Natural disasters
War
What are age population pyramids?
• Show % male and female per age group
