What is the carrying capacity?
The max population size of a species that an environment can sustain
Are biotic factors living or non-living and what are some examples?
Living
Competition for limited resources, new diseases, predation, parasitism
Are abiotic factors living or non-living and what are some examples?
Non-living
Temp, pH, light intensity, water availability
How is the population growth of an equilibrium species shown
One-step growth curve
4 steps of the one-step growth curve
- Lag
- Exponential
- Stationary
- Death
What happens in the lag phase of a one-step growth curve?
- enzymes are synthesised
- DNA is replicated
(In sexually reproducing organisms it is the time taken to reach sexual maturity + find a mate)
What happens in the exponential phase of a one-step growth curve?
- population doubles every unit of time
- abundant nutrients
What happens in the stationary phase of a one-step growth curve?
- birth & death rate are equal due to competition
- population reached its max size
What happens in the death phase of a one-step growth curve?
- nutrient depletion + waste accumulation => death rate higher than birth
Abundance definition
The number of individuals of a species in a given area/volume
What is an ecosystem?
A community of interdependent species interacting with their habitat. It’s comprised of biotic and abiotic elements and is dynamic
Primary productivity
The rate at which energy is converted by producers into biomass
What is succession?
The change in structure and species of a community over time
Where does primary succession start from?
Bare rock, where no organism lives
Where does secondary succession start?
From cleared land where communities have lived before
When does secondary succession happen?
After forest fires, tree felling etc
What does the speed of succession depend on?
- temperature
- proximity to a source of spores and seeds to be blown in
2 types of nitrifying bacteria and what do they do
- Nitrosomonas = convert ammonium to nitrite
- Nitrobacter = convert nitrite to nitrate
What do nitrogen-fixing bacteria do?
Convert nitrogen gas to ammonium
2 types of nitrogen-fixing bacteria and where are they found?
- Azotobacter = free living in soil
- Rhizobium = in root nodules of legumes
What do denitrifying bacteria do? & 1 type
Convert nitrate to nitrogen gas
Pseudomonas
What is significant about rhizobium and legumes
Have a symbiotic relationship
