3.5 population size and ecosystems 2 Flashcards
What is the definition of biodiversity?
The number of different species and individuals within each species in a given place at a given time
What are the steps of the capture-recapture technique?
1) Capture a sample. Count, mark, and release them
2) Recapture and count a second sample
3) count total number of recaptured organisms
What are the issues with the capture-recapture technique?
-trap has to be humane
-marking method can’t damage or visibly mark animals
-doesn’t account for immigration, emigration, births, and deaths
What is the equation for capture-recapture?
(1st capture x 2nd capture) / recapture
What are the steps for kick sampling?
1) Hold fine mesh net in downstream direction
2) Use one foot to kick substrate towards net
3) Work upstream so uncaught organisms flow downstream, prevents more organisms being caught than present
What are the steps for quadrat sampling?
1) Form measured grid
2) Select random coordinates using generator
3) Place quadrat at coordinates
4) Count number of individuals in a quadrat
5) repeat
6) Find mean per m2
7) Multiply by area of grid
What are line transects used for?
To see distribution of different species change along a habitat
What is a belt transect?
Quadrats are placed one after the other
What is a line transect?
Anything touching tape is recorded
What is an interrupted transect?
Quadrats placed at regular intervals
What is succession?
changes in a community over time due to changes in abiotic conditions caused by species present
How does secondary succession work?
-Occurs after existing vegetation is removed
-Soil is already fertile
-Seeds/spores easily dispersed by wind
-Rate of development is faster
Describe a pioneer community
-Can’t compete for resources
-Can fix Nitrogen and enrich soil
-Can tolerate extreme conditions
-Not influence by animals
-Early arrivals
Describe a climax community
-End point community
-Strongly influenced by other organisms
-Cant tolerate changes in soil water content
-Large seeds
-Good means of dispersal
-Specialised niche
How do humans affect succession?
-Farming
-Controlled fires
-Extinguishing forest fires
-Deforestation
-Soil erosion
