Populations Flashcards
What factors need to be considered when using quadrants?
Size of quadrat
How many to use
Position of quadrat
Why is measuring the abundance of a species not effective?
Counting all individuals is time consuming and damages habitats
How should you decide the position of a quadrat?
Random sampling (avoids bias), by generating random coordinates using a random number generator on a computer
Where should systematic sampling be used?
Transects are often used in tidal shores as there is transition
What are the two ways of measuring abundance within quadrats?
Frequency
Estimated percentage cover (shows density and distribution)
What will make the results representative of the population?
Large sample size
Tested in many areas
Mean result
Recap mark release recapture
Capture,mark,release, recapture!! (Ethics and methods of marking) - will a colour get rubbed off? Etc.
What could cause fluctuations in population size?
(Limiting factors) Temp - denaturation pH - enzymes Light - photosynthesis Humidity - transpiration and sweating Predation Minerals
What is intraspecific competition?
Competition between members of the same species
What is interspecific competition?
Competition between members of different species
Availability of resources determines…
Population size
Predator and prey relationships?
Trends, correlations, disease, climatic factors and other food sources
Population growth =
(Births + immigration) - (deaths + emigration)
Birth rate factors
Economy
Religion
Birth control
Politics
Death rate factors
Food supply Water Medical care Natural disasters War
Birth/death rate =
B/D per year/ population In year x1000
Demographic transition is…
Life expectancy up = birth rate down
Life expectancy down = birth rate up
Average life expectancy is..
The age at which 50% of the population are still alive
