Introduction to Biology and Laboratory Rules, revision notes

Overview

Biology is the study of living things and their life processes. This first chapter sets up the skills every later chapter relies on: working safely in the laboratory, communicating findings, and carrying out a fair scientific investigation.

You are also introduced to the fields and careers biology opens up, from medicine and pharmacy to biotechnology and environmental science.

Communicating in biology means presenting observations so another person can check them: labelled diagrams drawn with a sharp pencil, data tables with clear column headings and units, and line graphs plotted with a sensible scale and axis titles. A measurement without a unit, or a diagram without a label, cannot be credited as evidence in an exam answer.

Because this chapter is a foundation, its skills resurface in almost every practical topic that follows: a hypothesis for an osmosis experiment, a data table for an enzyme investigation, or a safety precaution for handling a specimen. Mastering variables and drawing conventions here saves time revising them chapter by chapter later.

The scientific method itself is worth memorising as a sequence: state the aim, propose a hypothesis, identify the variables, list the apparatus and materials, follow a numbered procedure, tabulate the results, and end with a conclusion that refers back to the hypothesis. Missing any one of these seven parts is a common reason a Paper 3 answer loses marks even when the science is correct.

SPM biology values precise vocabulary as much as correct facts, so this chapter also builds the habit of using exact terms, 'diffusion' instead of 'spreading', 'variable' instead of 'factor', because examiners award marks for stating a relationship in the language of the syllabus, not merely for expressing the right idea in everyday words.

Field trips and simple ecological surveys also fall under this chapter's scope, since observing organisms in their natural habitat and recording environmental data such as light intensity or soil pH follows the same fair-test principles used indoors, just applied outdoors where fewer variables can be controlled.

Fields and careers biology leads to

Content Standard 1.1 expects a named field of biology to be matched to the type of career it leads to, not just a list of definitions recited from memory. Medicine and pharmacy apply biology to diagnose disease and develop new drugs; a related career such as a pharmacist or medical officer draws directly on this field.

Biotechnology uses living organisms or their products to make something useful, such as insulin produced by genetically modified bacteria, and leads to careers like a biotechnologist or genetic engineer. Microbiology studies bacteria, fungi and viruses and underlies careers in food safety and public health, such as a food microbiologist.

Environmental science and ecology study organisms in relation to their surroundings and lead to careers such as a conservation officer or an environmental consultant, while forensic science applies techniques such as DNA profiling to careers in criminal investigation. Agriculture and animal husbandry apply biology to improve crop yield and livestock health, leading to careers such as an agronomist or a veterinarian.

Safety and rules in the biology laboratory

Content Standard 1.2 is tested through specific hazards rather than a general instruction to 'be careful'. Chemical hazards such as a corrosive acid or alkali call for gloves and safety goggles, with immediate rinsing under water if splashed on skin; heat hazards from a Bunsen burner call for tied-back hair, a heatproof mat, and turning the flame to yellow (safety flame) whenever it is not actively heating something.

Glassware is checked for cracks before it is heated, held by its neck or base rather than the middle when hot, and a test tube being heated is pointed away from anyone nearby rather than towards a face. Sharp instruments such as a scalpel or a mounted needle are held with the cutting edge pointing away from the body and disposed of in a designated sharps container rather than a normal bin.

Living specimens used in an investigation, such as small invertebrates collected for an ecology study, are handled gently and returned to the habitat they were taken from wherever this is possible, while preserved specimens and used chemicals are disposed of through the correct waste stream rather than down a sink.

Communicating in biology: drawings, tables and graphs

A biological drawing needs a title stating what is shown and its magnification, an unbroken outline drawn with a sharp pencil and no shading or colouring, and straight label lines that do not cross and end exactly on the structure named, with every label written horizontally. The proportion between the parts drawn should match the actual specimen rather than being drawn from imagination.

A results table carries the unit inside the column heading, such as 'Time / s' or 'Volume / cm³', so that every value entered in that column is a plain number; the variable that was deliberately changed is conventionally placed in the leftmost column, with the values it produced set out to its right in the order the readings were taken.

A line graph is used for continuous data such as time, temperature or concentration, plotted with a scale that uses at least half of the available graph paper and joined with a single best-fit line or smooth curve rather than dot-to-dot segments; a bar chart is reserved for discrete or categorical data, such as blood group or plant species, where the categories have no continuous numerical order.

Scientific investigation in biology: from aim to conclusion

An investigation into how temperature affects the rate of germination of mung bean seeds illustrates the full sequence Content Standard 1.4 expects. The aim is stated as a purpose, such as 'to investigate the effect of temperature on the percentage germination of mung bean seeds', and the hypothesis then adds direction: 'as temperature increases from 10 °C towards an optimum of about 30 °C, the percentage germination increases, after which it decreases at higher temperatures'.

The manipulated variable here is temperature, the responding variable is the percentage of seeds that germinate within a set number of days, and fixed variables include the number of seeds used, the amount of water supplied and the type of seed. The apparatus and materials are listed before a numbered procedure is written, each step specific enough that another student could repeat the method exactly.

Results are tabulated with temperature in the left-hand column and percentage germination in the column beside it, and the conclusion restates the relationship found, for example, that germination rate increased with temperature up to 30 °C and then fell at 40 °C, while stating clearly whether this supports or does not support the original hypothesis.

Precision, accuracy and reliability in practical work

Precision describes how close a set of repeated readings are to one another, while accuracy describes how close a single reading is to the true or accepted value; a stopwatch that consistently reads 0.5 seconds fast gives precise but inaccurate times, because the readings agree with each other but not with the real duration, usually as a result of a fault such as a zero error that was never corrected before the readings were taken.

Reliability refers to whether an investigation would give a consistent conclusion if it were repeated by someone else under the same conditions, and it is improved less by taking one very careful reading than by repeating every reading, commonly three times, and calculating a mean, since this reduces the effect of one anomalous result on the overall trend.

An anomalous reading is identified by comparing it against the other repeats for the same manipulated-variable value, not by whether it matches a value the student already expects; once identified, it is excluded from the mean and, where marks allow, the reason for the anomaly is stated, such as a reading taken before the reaction had properly started.

Field investigations and ecological sampling techniques

A field investigation, such as comparing plant species diversity at increasing distance from a river bank, still needs a clearly stated aim and, where a relationship is being tested, a hypothesis, but the degree of control over variables is lower than indoors because factors such as light intensity, soil moisture and wind exposure change naturally across a site.

Quadrats are placed to avoid bias, commonly using random coordinates generated along two measuring tapes laid at right angles, and the organisms or percentage cover within each quadrat frame are recorded in a table before being compared between sampling points. A line transect is used instead of scattered quadrats when a gradient, such as distance from the water's edge, is the factor being investigated.

Because uncontrolled variables cannot be removed outdoors, reliability in a field investigation is improved by increasing the number of sampling points and, where practical, repeating the survey at a similar time of day, rather than by attempting to eliminate natural variation altogether.

Key concepts to master

• Fields and careers in biology, Biology branches into areas such as medicine, genetics, microbiology and ecology, each leading to specific careers.
• Laboratory safety, Correct handling of apparatus, chemicals and specimens, plus fire and glassware rules, prevents accidents.
• Manipulated, responding and fixed variables, A fair test changes one manipulated variable, measures the responding variable, and keeps all other (fixed) variables constant.
• Hypothesis, A testable statement predicting how the responding variable depends on the manipulated variable.
• Scientific investigation, The ordered steps of aim, hypothesis, variables, apparatus, procedure, results and conclusion.
• Biological drawing, Clear line drawings with a title, magnification and labels using straight, non-crossing label lines.
• Communicating in biology, Findings are recorded as labelled diagrams, data tables with units placed in the column heading, and graphs with a sensible scale; each format has its own conventions, and an answer loses marks if a label, a unit or an axis title is missing.
• SI units and precision, Standard units such as cm, g, s and °C are used throughout biology so that measurements can be compared and repeated by anyone. Readings within one table are recorded to the same number of decimal places so precision is not overstated.
• Choosing apparatus, A metre rule or measuring cylinder measures length or volume, a stopwatch measures time, a thermometer measures temperature, and a beam balance measures mass. Matching the apparatus to the quantity being measured is itself an examinable skill.
• Controlling a fair test, Besides changing the manipulated variable and measuring the responding variable, every other factor that could affect the result is kept fixed. Without this control, a change in the responding variable cannot be attributed to the manipulated variable alone.
• Types of scientific report, A report may be a full write-up from aim to conclusion, or a structured Paper 3 answer with headed sub-sections; SPM usually expects the structured form, where each part is clearly labelled rather than written as continuous prose.
• Precision versus accuracy, Accuracy is how close a reading is to the true value, while precision is how consistent repeated readings are with each other; a set of readings can be precise, meaning close together, without being accurate if the apparatus itself is faulty.
• Ethics and care of living specimens, Specimens used in practical work, such as small organisms in an ecology study, are handled gently and returned to their original habitat where possible, since unnecessary harm to living things is avoided in any investigation.
• Recording field observations, Outdoor investigations, such as a simple quadrat survey, still need a stated aim, a way of sampling that avoids bias, and a table of results, even though fewer variables can be tightly controlled than in a laboratory setting.

Quick recall checklist

1. Can you define and explain Fields and careers in biology?
2. Can you define and explain Laboratory safety?
3. Can you define and explain Manipulated, responding and fixed variables?
4. Can you define and explain Hypothesis?
5. Can you define and explain Scientific investigation?
6. Can you define and explain Biological drawing?
7. Can you define and explain Communicating in biology?
8. Can you define and explain SI units and precision?
9. Can you define and explain Choosing apparatus?
10. Can you define and explain Controlling a fair test?
11. Can you define and explain Types of scientific report?
12. Can you define and explain Precision versus accuracy?
13. Can you define and explain Ethics and care of living specimens?
14. Can you define and explain Recording field observations?

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