All of p6

Question

Answer

What is the independent variable in a biology experiment?

The independent variable is the factor that is deliberately changed by the scientist to investigate its effect on the dependent variable.

What is the dependent variable in a biology experiment?

The dependent variable is the factor that is measured or observed during the experiment.

What are control variables?

Control variables are factors that are kept constant during an experiment to make sure the test is fair.

Why are repeats carried out in experiments?

Repeats are carried out to improve reliability identify anomalies and allow a mean to be calculated.

Why is a mean calculated from repeated results?

A mean is calculated to reduce the effect of anomalies and improve reliability.

What is an anomaly?

An anomaly is a result that does not fit the pattern of the other results.

What is reliability in experiments?

Reliability refers to how consistent results are when the experiment is repeated.

What is accuracy in experiments?

Accuracy refers to how close a result is to the true or accepted value.

What is validity in experiments?

Validity refers to whether the experiment actually tests what it is intended to test.

What is precision?

Precision refers to how close repeated measurements are to each other.

What is a fair test?

A fair test is one in which only the independent variable changes while all control variables remain constant.

Why are controls important in biology experiments?

Controls are important because they allow comparison and show that changes are caused by the independent variable.

What is qualitative data?

Qualitative data is descriptive information such as colour changes or observations.

What is quantitative data?

Quantitative data is numerical information such as temperature mass or time.

What is a source of error?

A source of error is something that reduces the accuracy of results.

How can reliability be improved?

Reliability can be improved by repeating experiments and calculating a mean.

How can accuracy be improved?

Accuracy can be improved by using more precise equipment and careful measurement techniques.

How can validity be improved?

Validity can be improved by carefully controlling variables.

What apparatus is used to measure liquid volume accurately?

A measuring cylinder pipette or burette is used to measure liquid volume accurately.

What apparatus is used to measure temperature?

A thermometer or temperature probe is used to measure temperature.

What apparatus is used to measure time?

A stopwatch is used to measure time.

What apparatus is used to measure mass?

A balance is used to measure mass.

What apparatus is used to measure pH?

A pH probe or pH paper is used to measure pH.

What is the SI unit for volume?

The SI unit for volume is cubic centimetres cm³ or millilitres mL.

What is the SI unit for temperature?

The SI unit for temperature is degrees Celsius °C.

What is the SI unit for mass?

The SI unit for mass is grams g.

What is the SI unit for time?

The SI unit for time is seconds s.

What is the formula for magnification?

Magnification = image size ÷ actual size.

How is percentage change calculated?

Percentage change = ((new value − original value) ÷ original value) × 100.

How is a mean calculated?

Mean = total of all values ÷ number of values.

How do you convert millimetres to micrometres?

Multiply by 1000.

How do you convert micrometres to millimetres?

Divide by 1000.

What should be included on graph axes?

Each axis should have a label and units.

When should a line graph be used?

A line graph should be used for continuous data.

When should a bar chart be used?

A bar chart should be used for categorical or discontinuous data.

What are the rules for drawing graphs in biology?

Graphs should use most of the grid have even scales labelled axes with units and neat plotted points using crosses.

What should a conclusion include in biology practicals?

A conclusion should describe the trend and support it using data from the results.

What should an evaluation include in biology practicals?

An evaluation should identify limitations sources of error and possible improvements.

What are the rules for biological drawings?

Biological drawings should use clear single lines no shading large size and ruled label lines that do not cross.

Why are stains used in microscopy?

Stains are used to make structures easier to see under the microscope.

What is diffusion?

Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration.

What factors affect diffusion rate?

Diffusion rate is affected by temperature concentration gradient surface area and diffusion distance.

How does temperature affect diffusion?

Higher temperature increases the kinetic energy of particles causing diffusion to occur faster.

How does surface area affect diffusion?

Larger surface area increases the rate of diffusion because more particles can move at once.

How does diffusion distance affect diffusion?

A shorter diffusion distance increases the rate of diffusion.

What is osmosis?

Osmosis is the net movement of water molecules through a partially permeable membrane from a dilute solution to a concentrated solution.

What happens to a plant cell in distilled water?

Water enters the cell by osmosis and the cell becomes turgid.

What happens to a plant cell in concentrated solution?

Water leaves the cell by osmosis and the cell becomes plasmolysed.

Why does potato mass increase in distilled water?

Water enters the potato cells by osmosis causing the mass to increase.

Why does potato mass decrease in concentrated solution?

Water leaves the potato cells by osmosis causing the mass to decrease.

What is active transport?

Active transport is the movement of substances against a concentration gradient using energy from respiration.

What is tested for using iodine solution?

Iodine solution is used to test for starch.

What is the positive result for starch with iodine?

A positive result is a blue-black colour.

What is the negative result for starch with iodine?

A negative result remains brown or orange.

What is Benedict’s solution used for?

Benedict’s solution is used to test for reducing sugars such as glucose.

How is Benedict’s test carried out?

Benedict’s solution is added to the sample and heated in a water bath.

What is the positive result for Benedict’s test?

A positive result changes from blue to green yellow orange or brick-red precipitate depending on sugar concentration.

What is the Biuret test used for?

The Biuret test is used to test for proteins.

What is the positive result for the Biuret test?

A positive result is a lilac or purple colour.

What is the ethanol emulsion test used for?

The ethanol emulsion test is used to test for lipids or fats.

What is the positive result for the ethanol emulsion test?

A positive result is a cloudy milky white emulsion.

What is DCPIP used for?

DCPIP is used to test for vitamin C.

What is the positive result for vitamin C using DCPIP?

The blue DCPIP solution becomes colourless.

Why must Benedict’s test be heated?

Heat is needed for the reaction between Benedict’s solution and reducing sugars to occur.

Why is a control used in food tests?

A control is used for comparison to make colour changes easier to identify.

What is an enzyme?

An enzyme is a biological catalyst made of protein that speeds up chemical reactions.

How does temperature affect enzyme activity?

As temperature increases enzyme activity increases until the optimum temperature is reached after which the enzyme denatures.

What happens when an enzyme denatures?

The active site changes shape permanently so the substrate no longer fits.

How does pH affect enzyme activity?

Enzymes have an optimum pH and extreme pH values can denature the enzyme.

Why must temperature be controlled in enzyme experiments?

Temperature must be controlled because it affects enzyme activity.

Why must pH be controlled in enzyme experiments?

pH must be controlled because it affects enzyme activity.

What is the independent variable in enzyme investigations?

The independent variable may be temperature pH or substrate concentration.

What is the dependent variable in enzyme investigations?

The dependent variable is usually the rate of reaction.

What gas is released during photosynthesis?

Oxygen is released during photosynthesis.

What gas is required for photosynthesis?

Carbon dioxide is required for photosynthesis.

What are the limiting factors of photosynthesis?

The limiting factors are light intensity carbon dioxide concentration and temperature.

What is the role of chlorophyll in photosynthesis?

Chlorophyll absorbs light energy for photosynthesis.

What colour does hydrogencarbonate indicator turn in high carbon dioxide?

It turns yellow.

What colour does hydrogencarbonate indicator turn in low carbon dioxide?

It turns purple.

Why is a water bath used in photosynthesis and enzyme experiments?

A water bath keeps temperature constant.

What is transpiration?

Transpiration is the loss of water vapour from leaves through stomata.

What factors affect transpiration rate?

Temperature humidity wind speed and light intensity affect transpiration rate.

How does temperature affect transpiration?

Higher temperature increases evaporation and diffusion causing faster transpiration.

How does wind speed affect transpiration?

Higher wind speed removes water vapour around the leaf increasing transpiration.

How does humidity affect transpiration?

Higher humidity decreases the water vapour concentration gradient reducing transpiration.

What apparatus is used to investigate transpiration?

A potometer is used to measure water uptake as an estimate of transpiration rate.

What is respiration?

Respiration is the chemical process in cells that releases energy from glucose.

What is aerobic respiration?

Aerobic respiration uses oxygen to break down glucose releasing energy carbon dioxide and water.

What is the word equation for aerobic respiration?

Glucose + oxygen → carbon dioxide + water.

What is anaerobic respiration?

Anaerobic respiration releases energy from glucose without using oxygen.

What is the word equation for anaerobic respiration in yeast?

Glucose → alcohol + carbon dioxide.

What is the word equation for anaerobic respiration in muscles?

Glucose → lactic acid.

What gas turns limewater milky?

Carbon dioxide turns limewater milky.

How does exercise affect heart rate?

Exercise increases heart rate to deliver more oxygen and glucose to muscles.

How does exercise affect breathing rate?

Exercise increases breathing rate to increase oxygen intake and carbon dioxide removal.

What should be controlled in exercise investigations?

The duration and intensity of exercise should be controlled.

What is sampling in ecology?

Sampling is collecting data from part of a habitat to estimate population information.

What is a quadrat?

A quadrat is a square frame used to estimate the abundance or distribution of organisms.

What is a transect?

A transect is a line across a habitat used to study changes in organisms across an area.