- Created by: Marybillinge
- Created on: 13-11-19 09:32
Population: An interbreeding group of organisms of the same species in a particular habitat.
Carrying capacity: Maximum number around which a population fluctautes in an enviornment.
Population number will fluctuate depending on various factors: Birthrate, death rate, immigration and emigration
Populations will increase in size when:
Births + immigrants > deaths + emigrants
Standard growth curves
- Cells adjust to new conditions
- Takes a wile for enzyme production
- The bacteria adjust to new conditions, synthesising carriers to absorb nutreints and enzymes to digest.
- May involve switching on genes
Log (exponential) phase:
- As numbers increase, as long as there is not factors limiting growth, more individuals become availble for reproduction. Bacterial cells divide at a constant rate and the population doubles per unit time. The cell numbers increases logarithmically and so the exponential phase is also called the log phase.
- Occurs when birth rate is equal to the death rate. The population has reached its maximum size, which is the carrying capacity for that particular enviornment
- The actual number depends on the resources available
The death phase:
- Death rate is greater than birth rate
- Waste products such as ethanol kills cells
- Net decrease of population
- Nutreints exhausted and waste too toxic
- Some dead will act as a nutrient source for others
Environmental resistance relates to any factor that slows down population growth and can cause it to crash
- Less food available
- Build up of waste products
- Not enough space
- available food
- Over crowding
- Buildup of waste
- Parasitism and disease
- Light intensity
Density- dependent or independent
Biotic factors are density dependent - when some factors play a more significant role in population size if the population is higher, they are often biotic factors
Density independent: Abiotic factors effect the population regardless of the population density.