This summary is from the IEB syllabus for Life Science. As someone who used to struggle to understand the syllabus I found that making very short summaries with the most important facts helped my brain process all of the mass information that is in the subject. This document is a brief outline of a...
Population parameters – can make population size change
1. Natality
2. Mortality
3. Immigration
4. Emigration
• When all four can happen = open population
• 3 & 4 can’t happen = closed population
GROWTH
Growth curve – show how size of population changes
Geometric – numbers increase slowly (not a lot of reproduction) = lag phase
Accelerating growth phase – grows faster
Limiting factor = anything that slows down population growth (eventually could stop growth
permanently)
1. Amount of food
2. Space
3. Predation
The effect of these factors = environmental resistance
Decelerating growth phase – when limiting factors start to have an effect
Equilibrium phase – level of reproduction and death is equal
LOGISTIC GROWTH IS ALWAYS A NEGATIVE FEEDBACK
MEASURING POPULATION SIZE
DIRECT TECHNIQUES
Census – counting every individual
, Shira Woolf HUGE population ecology summary 2
Number of quadrants
Average number of sampled plants per quadrant = Total number of sampled plants
Population size = Average number of sampled plants per quadrant X total study area
Area of quadrant
INDIRECT TECHNIQUES
Marcy recapture
INTERACTIONS IN THE ENVIRONMENT
Ways populations interact in the communities:
1. Predation
2. Competition
3. Sometimes two species live permanently in a close association: (3 different types)
4. Parasitism
5. Mutualism
6. Commensalism
1. PREDATION
Predator eats prey
In a dynamic equilibrium- predators control the prey population and prey control the predator
population
Both benefit from the relationship
e.g. African Wild dog
àcamouflages well
à good eye sight
àrun fast over long distance
à intelligent and hunt in packs communicate with one another
e.g. The Great White Shark
à sharp eye sight
àdark upper body to camouflage near the surface
à fast swimmer
2. COMPETITION
Happens when there is a limited amount of resources that both need
Density dependant factors become stronger
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