What is the abundance of an organism?
How many individuals are found in an area. (Population size)
What is the distribution of an organism?
Location of an organism in a habitat. (Part of a field)
Why are samples taken instead of investigating a whole ecosystem or area?
It is too time consuming. A sample allows you to gain an estimate to size up to the total area.
How is abundance estimated?
Count the number of individuals in a sample area and work out the percentage cover.
Describe the two ways you can study the distribution of an organism.
- Measure how common an organism is in 2 sample areas and compare.
- Study distribution changes across a transect line.
Describe the sampling technique used to collect ground insects.
- Use a pooter
- Suck into the mouthpiece connected to a tube, and have the longer tube over an insect, this will suck the insects into the jar.
Describe the sampling technique used to collect flying insects.
- Use a sweep net
- Sweep a large net to catch flying insects or those in long grass.
Describe the sampling technique used to collect insects further under the ground.
- Pitfall traps
- Dig a hole to place a jar with possibly some food to attract the crawling invertebrates such as beetles and spiders
- Cover it with leaves or a roof so rainwater doesn’t enter and the insects can’t escape.
Describe the sampling technique used to collect water organisms.
- Kick sampling/pond nets
- Wade through the first sample area and kick the river bank to disturb the mud,
- Hold the pond net in front of you downstream to capture any organisms released into the flowing water.
Describe the sampling technique used to collect insects in trees or bushes.
- Tree beating
- Place a large white cloth or paper under a tree or bush
- Shake or beat the tree to dislodge invertebrates which will fall onto the cloth.
How are unknown organisms identified?
Using keys
- Dichotomous - correct answer to a question tells you which question to go to or the organism eventually.
- Spider - yes no questions
Describe the process of capture-recapture and how it is used to estimate animal population.
- Capture a sample of the population, mark them and release back into environment
- Recapture at a later date. Count the number of organisms and the number marked.
Use formula to estimate.
population size = (no. in 1st sample x no. in 2nd sample)/(no. in 2nd sample marked)
What assumptions have been made when conducting capture-recapture?
- No population change (births or deaths)
- When marking animals the chance of survival hasn’t been affected (e.g. more visible to predator).
Describe the method used to sample plants.
- Place a quadrat on the ground and record and count the no. of organisms within each section.
- Take a number of samples and take a mean, the more samples the more reliable your results are.
- Work out the whole population of an organism by multiplying the mean per area by total area.
What biotic factors affect distribution of an organism?
- Competition between species, there may be a different distribution if competition did/didn’t exist.
What abiotic factors affect distribution of an organism?
- Temperature, moisture, light intensity and soil pH.
- E.g. light intensity is higher where there are less trees covering the grass, so daisies are more common in the open due to more light intensity.
How do you measure abiotic factors?
- Temperature - thermometer
- Soil pH - take a sample of soil, wet it and use indicator or a pH probe.
- Light intensity - data logger
For species, what are the consequences when biodiversity is lost?
The removal of one species affects another, for example the species that is removed maybe prey for a predator which could endanger that species.
State 4 examples of how biodiversity is lost.
Deforestation
Agriculture
Hunting and fishing
Pollution
What is random sampling?
Random sampling is where the area to be sampled is selected by chance.
What are the advantages of random sampling and how can it be carried out when sampling plants?
The investigation will not be bias.
Mark out a grid, generate coordinates and use a random number generator to pick the coordinates.
What is non-random sampling?
E.g a transect, the sampling is conducted over a selected area if that is where you want to investigate.
For species, what are the consequences when biodiversity is lost?
The removal of one species affects another, for example the species that is removed maybe prey for a predator which could endanger that species.
What are the consequences of deforestation?
- Reduces the number of trees
- Removes habitats for some species
- Some species food source has been lost
- Affects the food chain as there is no producer, then no consumers or predators.
