Skills for Biologists
Lab Notes
The Scientific Method:
1. Question – observation of the natural world
2. Hypothesis – potential answers to the question
3. Predictions – must be carefully worded and testable
4. Experimental design:
- Choosing subjects
- Study site
- Data
- Controls
- Sample sizes
- Confounding variables/factors
- Equipment
- Logistics
5. Collecting the data
6. Analysing and interpreting the data
7. Disseminate results
Practical 1 – Hypothesis testing:
Interspecific brood parasiting: When a different species enters the nest.
Intraspecific brood parasiting: When it is the same species but not the mother bird’s chick.
Evolutionary arms race.
Cuckoo matches their egg patterns with that of the host. Different cuckoos go with different
hosts. The female watches the host nest and then enters the nest and lays its eggs.
Chick kicks out the host eggs to get rid of the competition. Female removes a host egg and
lays its own.
Fully formed cuckoos keep eggs in their body for an extra 24 hours, so they are at a higher
stage of development when laid.
Phenotypic plasticity: Can alter phenotype as a result of the environment (i.e. according to
fear).
Practical 2 – Field identification of plants
Important terms:
1. Compound leaf: A leaf divided into separate leaflets, without any flange joining them
together along their common stalk.
2. Lanceolate leaf: A long narrow leaf, slightly wider below gradually tapering to its tip (lance
shaped).
3. Mucronate: A leaf otherwise blunt or rounded with a small, often sharp point at the tip.
4. Obovate leaf: A leaf with its broadest part above the middle tapering suddenly to its tip, and
more gradually to its base.
5. Palmate leaf: A compound leaf with more than three leaflets arising together from the top of
the leaf stalk.
6. Petiole: Leaf stalk.
7. Pinnate leaf: A compound leaf with separate leaflets arranged along the leaf stalk, usually in
opposite pairs, and often with a terminal leaflet as well.
, 8. Whorled leaves: Leaves arising three or more from a stem at the same level or point on it.
9. Pinnatifid leaf: A leaf deeply cut into pinnately arranged lobes, but not cut right to its midrib,
the lobes remaining connected by at least a narrow flange of leaf-blade bordering the
midrib.
10. Root leaves: Basal leaves (leaves arising from the base of the plant or of its erect stem, they
sometimes but not always form a spreading rosette).
11. Rosette: A circular arrangement of leaves, with all the leaves approximately at the same
height.
12. Stipule: A leaf like or scale like appendage at the base of a leaf stalk; often a pair of them
present.
13. Trifoliate leaf: A compound leaf with three leaflets only (as in clovers).
Producing a dichotomous key:
Using features of the plants, construct a dichotomous key which would enable someone to
discriminate between each of the 8 species you have studied.
Use features that have been highlighted in notes.
At each numbered step, you are confronted with a choice between two contrasting
alternatives.
Example: Petals 4 … 2 and petals 5 … 6
This means that if your plant has 4 petals then you proceed to question 2 but if it has 5
petals you go down to question 6. After further choice you will eventually reach an entry
which, together with the feature established at earlier stages in the key seems finally to
describe your plant and will give its name.
Practical 3 – The impact of environmental conditions and management on water quality in two
neighbouring lakes:
The populations and communities of organisms to be found in lakes is crucially dependent
on water quality.
Two important controls on water quality are environmental conditions and the management
of the lakes together with their catchment area.
Increased organic input and increased waterfowl density – influencing water quality.
Factorial experimental design – not only answers both questions but also examines whether
there is an interaction between the two factors.
Waterfowl are known to increase the nutrient input into lakes largely through faeces.
Positive interaction: The combined effect is greater than you would expect from a
knowledge of the individual effects.
Measurements:
pH:
- Measure of the concentration of hydrogen ions in water.
- Negative logarithm of the hydrogen ion concentration.
- Higher pH means fewer free hydrogen ions.
- A change of 1pH unit reflects a tenfold change in the concentration of hydrogen ions.
- Ranges from 0-14 (7=neutral, less than 7=acidic, more than 7=basic).
- In lakes it controls the solubility and biological availability of key nutrients (e.g.
phosphorous, nitrogen and CO2).
- Photosynthesis increases pH and respiration and decomposition lowers pH.
Lab Notes
The Scientific Method:
1. Question – observation of the natural world
2. Hypothesis – potential answers to the question
3. Predictions – must be carefully worded and testable
4. Experimental design:
- Choosing subjects
- Study site
- Data
- Controls
- Sample sizes
- Confounding variables/factors
- Equipment
- Logistics
5. Collecting the data
6. Analysing and interpreting the data
7. Disseminate results
Practical 1 – Hypothesis testing:
Interspecific brood parasiting: When a different species enters the nest.
Intraspecific brood parasiting: When it is the same species but not the mother bird’s chick.
Evolutionary arms race.
Cuckoo matches their egg patterns with that of the host. Different cuckoos go with different
hosts. The female watches the host nest and then enters the nest and lays its eggs.
Chick kicks out the host eggs to get rid of the competition. Female removes a host egg and
lays its own.
Fully formed cuckoos keep eggs in their body for an extra 24 hours, so they are at a higher
stage of development when laid.
Phenotypic plasticity: Can alter phenotype as a result of the environment (i.e. according to
fear).
Practical 2 – Field identification of plants
Important terms:
1. Compound leaf: A leaf divided into separate leaflets, without any flange joining them
together along their common stalk.
2. Lanceolate leaf: A long narrow leaf, slightly wider below gradually tapering to its tip (lance
shaped).
3. Mucronate: A leaf otherwise blunt or rounded with a small, often sharp point at the tip.
4. Obovate leaf: A leaf with its broadest part above the middle tapering suddenly to its tip, and
more gradually to its base.
5. Palmate leaf: A compound leaf with more than three leaflets arising together from the top of
the leaf stalk.
6. Petiole: Leaf stalk.
7. Pinnate leaf: A compound leaf with separate leaflets arranged along the leaf stalk, usually in
opposite pairs, and often with a terminal leaflet as well.
, 8. Whorled leaves: Leaves arising three or more from a stem at the same level or point on it.
9. Pinnatifid leaf: A leaf deeply cut into pinnately arranged lobes, but not cut right to its midrib,
the lobes remaining connected by at least a narrow flange of leaf-blade bordering the
midrib.
10. Root leaves: Basal leaves (leaves arising from the base of the plant or of its erect stem, they
sometimes but not always form a spreading rosette).
11. Rosette: A circular arrangement of leaves, with all the leaves approximately at the same
height.
12. Stipule: A leaf like or scale like appendage at the base of a leaf stalk; often a pair of them
present.
13. Trifoliate leaf: A compound leaf with three leaflets only (as in clovers).
Producing a dichotomous key:
Using features of the plants, construct a dichotomous key which would enable someone to
discriminate between each of the 8 species you have studied.
Use features that have been highlighted in notes.
At each numbered step, you are confronted with a choice between two contrasting
alternatives.
Example: Petals 4 … 2 and petals 5 … 6
This means that if your plant has 4 petals then you proceed to question 2 but if it has 5
petals you go down to question 6. After further choice you will eventually reach an entry
which, together with the feature established at earlier stages in the key seems finally to
describe your plant and will give its name.
Practical 3 – The impact of environmental conditions and management on water quality in two
neighbouring lakes:
The populations and communities of organisms to be found in lakes is crucially dependent
on water quality.
Two important controls on water quality are environmental conditions and the management
of the lakes together with their catchment area.
Increased organic input and increased waterfowl density – influencing water quality.
Factorial experimental design – not only answers both questions but also examines whether
there is an interaction between the two factors.
Waterfowl are known to increase the nutrient input into lakes largely through faeces.
Positive interaction: The combined effect is greater than you would expect from a
knowledge of the individual effects.
Measurements:
pH:
- Measure of the concentration of hydrogen ions in water.
- Negative logarithm of the hydrogen ion concentration.
- Higher pH means fewer free hydrogen ions.
- A change of 1pH unit reflects a tenfold change in the concentration of hydrogen ions.
- Ranges from 0-14 (7=neutral, less than 7=acidic, more than 7=basic).
- In lakes it controls the solubility and biological availability of key nutrients (e.g.
phosphorous, nitrogen and CO2).
- Photosynthesis increases pH and respiration and decomposition lowers pH.
