Ecosystems 5 Flashcards
When is random sampling used?
When you want to work out the average population of an area or compare the average of two areas
When is systematic sampling usually used?
When you want to investigate the change in a communities/population over a distance/area
Describe how you would randomly sample an area to estimate the population of stinging nettles in a field
Create a grid on the field (or on a map of the field)
Use a calculator to generate random numbers that are used as coordinates
Place the quadrate at the intersection of the coordinates
Estimate the abundance of nettles in the quadrat (e.g. using % cover)
Repeat many times so that the mean abundance calculated per quadrat is reliable
Multiple the number of plants per quadrat BY the number of times the quadrat fits into the total are of the field in order to work out the population in the whole field
Describe how you would systematically sample an area to investigate the effect of distance from a river on the population of a specific plant
Place a transect at 90O to the river
Place a quadrat at regular intervals along the transect
Estimate the abundance of the plant in the quadrat (e.g. using % cover)
Repeat the process with many transects which are parallel to each other
Plot a graph of distance on the x-axis against population of plant on the y-axis
Use spearman rank correlation to see if there is a significant correlation between them
How can a quadrat be used to measure percentage cover?
Count the number of small squares that are half or more filled with the plant
Work out what % each square is of the whole quadrat
Then multiply the number of squares half or more filled by the % each square is worth
What are the limitations of using percentage cover as a measure of abundance?
It is quite subjective
What are the advantages of using percentage cover as a measure of abundance?
It is quick and easy to do.
You don’t have to be able to identify individual plants
How can a quadrat be used to measure frequency of a plant?
Count the number of plants present in the quadrat
What are the limitations of using frequency as a measure of abundance?
It is time consuming
It cannot be used if you cannot identify individual plants
What is NPP?
Net primary production (NPP) is the chemical energy store in plant biomass after respiratory losses to the environment have been taken into account
What is a definition of gross primary production?
What does the GPP primarily depend on?
The total chemical energy stored in plant biomass, in a given area/volume, in a given time
This depends on the rate of photosynthesis
List the reasons why not all the energy is transferred from:
Sun 🡪 producer
Some of the radiation from the sun is reflected or absorbed (e.g. by clouds and dust) before it reaches the plant
Not all the light is the right wavelength to be absorbed by chlorophyll – so some is reflected
Some light doesn’t hit the chlorophyll molecules / chloroplasts
There might be another factor limiting the rate of photosynthesis (e.g. CO2 concentration or temperature)
Photosynthesis is not 100% efficient (so some of the energy which is absorbed is not converted into biomass)
What is a definition of net primary production?
The chemical energy stored in plant biomass after respiratory losses to the environment
What is the equation that links NPP with GPP?
NPP = GPP - R
How do you calculate net consumption of consumers?
The net production of consumers (N), such as animals, can be calculated as:
N = I – (F + R)
Where:
I represents the chemical energy store in ingested food
F represents the chemical energy lost to the environment in faeces and urine
R represents the respiratory losses to the environment.
