Download Amount of light - Noadswood Science

Distribution of Organisms
• LO: To identify physical factors
• Describe a range of sampling techniques
• Evaluate validity of data
Distribution of organisms
• A habitat is the place where an organism lives
• The distribution is where the organism is found
• Environmental factors affect where an organism
is found.
eg amount of light
.
Sampling the distribution of organisms
• Watch the video
• Make notes on each method
• Click on:
http://www.scienceunleashed.ie/videos.aspx
Some transects are a little bit more tricky – see
video clip…..
http://www.youtube.com/watch?v=5QknA9RRU
h8
Sampling techniques
1. Quadrats – usually 1m2
thrown randomly. Used to
compare different areas
such as, flat vs hilly
2. A transect line - to find out
how distribution of an
organism changes across a set
area by placing quadrats
along atransect line eg
20meters
Physical Factors
• Suggest what physical factors could affect,
for example, the distribution of daisies in a
field
1.
2.
3.
4.
5.
6.
Amount of light (shady or under a tree vs open
field)
Temperature
Amount of water:- soil moisture levels or
humidity
Amount of carbon-dioxide
Amount of oxygen
Wind
For each one explain why they could affect
the distribution of daisies
How to measure abiotic factors
1.
Temperature can be recorded using
a simple thermometer or with digital probes or data-loggers.
1.
Light levels can be monitored with a lux-meter to record the amount of light
reaching the vegetation canopy or the soil surface.
2.
Humidity can be monitored with the use of a whirling hygrometer or digital
probes.
3.
a)
i)
ii)
Soil characteristics can be monitored by;
soil moisture with
soil probes,
or by collecting and drying soil samples in an oven;
a)
i)
ii)
iii)
Soil pH can be determined with:
soil probes,
indicator solution
or a Litmus test.
For 1-4 Explain
which method
you think is
best & why.
Physical/ Abiotic or (non-living) Factors
There are 2 important rules when measuring
abiotic factors
1) Repeat readings must be taken (one sample is
not enough), the bigger the sample size the more
reliable the data
2) All samples must be taken at the same time ( or
as close together as can realistically be achieved)
otherwise data is not valid.
Biotic (living) factors
• Biotic or living factors include:
1. other animals (prey and predator),
2. parasites,
3. competition between members of the same
species,
4. and relations between different species
(symbiotic, mutualistic).
Improving your fieldwork study
1) Take a larger sample size
Eg use as many quadrats and transects as possible as
bigger samples are more representative of a whole
population.
2) Use random samples
Eg do not stand in one spot and throw you quadrat –
maybe mark the area and co-ordinates (like a grid) and
use a random number generator to pick areas to study
How can you ensure results are valid?
Define the term valid
• Valid results answer the original question
• Results are not valid if you do not control all the variables
Come up with a question to investigate regarding
organism distribution.
State the:
• independent,
• dependent
• and control variables.
Mean, median and mode
• Sing-a-long to Frere Jacques:
http://www.bing.com/videos/search?q=Frere+Jacques+Music&doc
id=4657862726582310&mid=5838395127D379C0D77E583839512
7D379C0D77E&view=detail&FORM=VIRE5
• ‘Mean is adding, then dividing,
• mode is most, mode is most,
• median in the middle, median in the
middle,
• range is high then take low’