Unit 1: Science Inquiry Skills - Investigating Human Biology Study Notes

Overview of Human Biological Science

Definition: Human biological science is the scientific study of humans as individuals and as populations, including the study of the interaction between humans and their environment.
Nature of Knowledge: Scientific knowledge is not fixed or unchanging; it increases as new discoveries are made and existing knowledge is modified or discarded as evidence accumulates.
The Two Aspects of Science: * Process of Inquiry: A method for finding out about human beings and their living and non-living surroundings. * Body of Knowledge: Knowledge gained by systematic observation and testing of ideas.
Specialization: Due to the vast amount of information, human biologists specialize in specific fields, including: * Anatomy: Study of the structure of the body. * Anthropology: Relationships between biological, cultural, geographical, and historical aspects of humans. * Archaeology: Material evidence of the past (tools, weapons, art). * Biochemistry: Chemistry of living things. * Cytology: Study of cells. * Demography: Statistical study of populations. * Embryology: Development from fertilization to birth. * Genetics: How characteristics are passed from generation to generation. * Molecular biology: Macromolecules of the cell. * Nutrition: Food requirements of humans. * Palaeontology: Study of fossils. * Physiology: Functioning of living things. * Prehistory: The past before written records. * Primatology: Non-human members of the order Primates (apes, monkeys, lemurs, lorises, and tarsiers). * Psychology: Human behaviour. * Sociology: Nature of human society.

Methods of Scientific Investigation

Literature Review: A review of books, scientific journals, and the Internet to see what information has already been collected. This prevents duplication of work and allows science to build on past discoveries.
Observation: Gathering information using senses or instruments (microscopes, stethoscopes). Examples include: * Microbiologists observing bacteria using electron microscopes. * Archaeologists excavating sites to observe shelters and tools. * Primatologists noting animal behavior in the field.
Classification: Placing things into groups based on similarity of characteristics. Biologists use structural features to classify living things. For example, the classification of an animal as a mammal immediately identifies it as warm-blooded, having hair, and suckling young with milk.
Experimentation: Proposing a hypothesis (possible explanation) and designing a test that supports or disproves it by testing only one variable at a time.

The Scientific Method

Sequence of Investigation: 1. Recognition of a problem: Defining a question based on curiosity. 2. Collection of information: Observation and literature review. 3. Making a hypothesis: Suggesting a testable explanation. 4. Testing the hypothesis: Conducting experiments to collect data. 5. Collection of data: Recording measurements (quantitative) and observations (qualitative). 6. Analysis/Conclusion: Determining if the data supports or disproves the hypothesis.
Identifying Variables: * Independent Variable: The factor deliberately changed to determine its effect; also called the experimental or manipulated variable. * Dependent Variable: The factor that changes in response to the independent variable; also called the responding variable. * Controlled Variables: Factors kept the same for both the control and experimental groups to ensure a fair test.
Hypothesis Requirements: * Must be a definite statement, not a question. * Should be short and contain a single testable idea. * Usually links the independent and dependent variables (state the relationship/trend). * Must be testable (cannot test faith or personal taste).
Fair Test: An experiment involving an experimental group and a control group where only one variable differs.
Repetition: Performing the experiment many times or on a large number of subjects to account for natural variation and minimize the impact of uncontrolled variables.

Data Presentation and Interpretation

Tables: Organized ways to present numerical data. * Rules: Must have an informative title; data in columns; independent variable usually in the left column; headings must include units (e.g., $g$ , $cm$ , $months$ ).
Graphs: Show how one variable affects another. * Axes: Independent variable on the horizontal axis ( $x$ -axis); Dependent variable on the vertical axis ( $y$ -axis). * Line Graphs: Used for continuous data (e.g., mass, time, temperature). Includes a "line of best fit." * Bar/Column Graphs: Used for discrete (non-continuous) data. Bars have spaces between them. * Histograms: Used for frequencies or data grouped into categories. Columns are of equal width with no spaces between them.
Scientific Theory: A hypothesis that has been repeatedly tested and verified with an overwhelming amount of evidence (e.g., Einstein’s theory of relativity, Darwin’s theory of evolution).

Evaluating Investigations

Validity: The extent to which an experiment tests what it is supposed to test (a valid method fairly tests the hypothesis).
Accuracy: How correct or true the measurements are; dependent on using correct measuring equipment.
Reliability: How similar the results are for trials of the same test; increased by conducting multiple trials and averaging results.
Types of Experimental Error: * Human Error: A simple mistake (e.g., misreading a scale, calculation error). Should be avoidable with care. * Random Error: Unpredictable errors due to limitations in measurement precision (e.g., timing with a stopwatch). Impact is reduced by averaging multiple measurements. * Systematic Error: Occurs due to the way an experiment is designed or faulty equipment. Measurements are always too high or too low. Cannot be reduced by averaging; requires changing procedure or equipment.

Ethics in Human Research

Definition: Ethics are a set of moral principles or values; many institutions have ethics committees to approve research proposals.
Fundamental Ethical Principles: * Voluntary participation: Participants must not be pressured. * Informed consent: Participants must be fully informed of objectives, procedures, risks, and benefits before providing written consent. * Risk of harm: Harm must be minimized, and the benefit-to-risk ratio assessed. * Confidentiality: Ensuring identities are not revealed except to those directly involved. * Anonymity: Participants remain anonymous even to the researchers (a stronger guarantee of privacy than confidentiality).

Experimental Controls and Placebos

Placebo: An inactive substance or "dummy" treatment (tablet, injection, skin patch, etc.) that looks exactly like the real treatment.
Placebo Effect: Improvement in a patient's condition due to the belief that they are receiving real therapy.
Blind Experiments: Subjects do not know if they are receiving the drug or the placebo.
Double-blind Experiments: Neither the researcher nor the subjects know who is receiving the treatment or the placebo, reducing researcher bias.

Case Studies and Practical Examples

Robert Koch (1876): Demonstrated that $Bacillus\,anthracis$ (rod-shaped bacterium) caused anthrax in animals and humans.
Louis Pasteur: Investigated fermentation and infectious disease; demonstrated that micro-organisms in air cause disease; disproved spontaneous generation using sterilized nutrient solutions and filtered air.
Pollen and Hay Fever (Frank Murray): Scientists found that grass pollen ( $20$ to $30\,\mu m$ ) was too large to enter lungs (which requires particles $\le 10\,\mu m$ ). However, pollen swells and bursts in water into 1-micron granules ( $1\,\mu m$ ), allowing penetration into the lungs.
Francesco Redi (1668): Tested spontaneous generation by placing meat in open, sealed, and gauze-covered flasks; maggots only developed where flies could reach the meat.
Dr. William Bean: Studied fingernail growth for $35$ years. Observed that growth slowed with age: $0.123\,mm/day$ at age $32$ vs. $0.095\,mm/day$ at age $67$ .
Presslo Study: A randomized controlled trial of a blood pressure drug using $200$ people ( $50$ % male/female, aged $50-55$ ) where the control group received a sugar pill as a placebo.

Quantitative Data and Measurements

Volume Units: Measurements include $cm^3$ and $dm^3$ .
Concentration/Rates: Units include $kJ\,mol^{-1}$ , $mol\,dm^{-3}$ , and $g\,mol^{-1}$ .
Scientific Notation: Example: $6.02 \times 10^{23}$ .