Science revision notes

The Criterions

(Criterion A) What is the main function of the digestive system?

Main function of the digestive system: break down food into smaller molecules for absorption and provide nutrients and energy to the body.

(Criterion A) Name three organs of the digestive system and one role for each.

Three organs and one role each:

• Mouth: mechanical (chewing) and chemical digestion (saliva/enzymes).

• Stomach: churns food and begins protein digestion with acid and enzymes.

• Small intestine: most chemical digestion and absorption of nutrients into the bloodstream

(Criterion A) How do villi in the small intestine help nutrient absorption?

Villi are small, finger-like projections in the small intestine that increase surface area for absorption, allowing for more efficient uptake of nutrients and minerals into the bloodstream.

(Criterion A) Describe the pathway of air from the nose to the alveoli.

Pathway of air: nose/mouth → pharynx → larynx → trachea → bronchi → bronchioles → alveoli.

(Criterion A) Explain how oxygen moves from the alveoli into the blood.

Oxygen moves from alveoli into blood by diffusion down a concentration gradient across the thin alveolar and capillary walls; it then binds to hemoglobin in red blood cells.

(Criterion A) Trace the path of blood through the heart starting at the right atrium.

Blood path starting at right atrium: right atrium → right ventricle → pulmonary artery → lungs (pick up O₂, release CO₂) → pulmonary veins → left atrium → left ventricle → aorta → body → returns via vena cavae → right atrium.

(Criterion A) What is the difference between pulmonary and systemic circulation?

Pulmonary vs systemic circulation: pulmonary circulation moves blood between heart and lungs for gas exchange; systemic circulation moves oxygenated blood from the heart to body tissues and returns deoxygenated blood to the heart.

(Criterion A) How is carbon dioxide transported from body cells to the lungs?

Carbon dioxide is carried from body cells to the lungs dissolved in plasma, bound to hemoglobin, and mainly converted to bicarbonate ions in the blood.

(Criterion B) What is the purpose of a control variable in an experiment?

The purpose of a control variable in an experiment is to keep certain conditions constant to ensure that the results are influenced only by the independent variable, thus helping to validate the experiment's outcomes.

(Criterion B) How do you formulate a testable hypothesis? Give an example.

To formulate a testable hypothesis, you must make a prediction that can be tested through experimentation or observation. This is typically structured in the format of an 'If…then…' statement. For example: 'If plants are given more sunlight, then they will grow taller than plants that receive less sunlight.

(Criterion B) Name three variables in an experiment and classify each as independent, dependent, or controlled.

Three variables can be:

1. Independent Variable: The variable that is changed or controlled in an experiment. Example: Amount of sunlight given to plants.

2. Dependent Variable: The variable that is measured or tested in an experiment. Example: Height of the plants.

3. Controlled Variables: Variables that are kept constant to ensure a fair test. Example: Type of soil, amount of water, and temperature.

(Criterion B) Describe proper steps to take when collecting quantitative data with a ruler and timer.

1. Gather Materials: Ensure you have a ruler, timer, and any objects you will measure.

2. Set Up the Experiment: Define what you are measuring and how it will be measured. Ensure the environment is consistent.

3. Calibrate the Timer: Make sure the timer is functioning properly and set to zero before starting.

4. Perform Measurements: For each measurement, use the ruler to measure carefully and make note of the value. Start the timer at the beginning of each trial and stop it at the designated endpoint.

5. Record Data: Write down each measurement clearly in a data table, noting the time taken for each measurement consistently.

6. Repeat Trials: Conduct multiple trials to ensure accuracy and reliability of the data collected.

7. Analyze Data: After collecting all data, review and analyze it for patterns or trends.

(Criterion B) How do you identify and reduce a major source of experimental error?

To identify a major source of experimental error, analyze the data for inconsistencies or unexpected results that do not align with predictions. Once a potential error source is identified, implement strategies such as improving precision in measurement, standardizing conditions among trials, and conducting multiple trials to reduce variability and enhance the reliability of results.

(Criterion B) Explain why repeated trials are important for reliability.

Repeated trials increase reliability by reducing random error and showing consistency of results.

(Criterion B) When is a line graph more appropriate than a bar graph?

Line graph: for continuous data showing trends over a range (e.g., time). Bar graph: for comparing discrete categories.

(Criterion C) How do you calculate the mean of a data set and what does it tell you?

Add all the values together and divide by the number of values; the mean gives the average or central tendency of the data.

(Criterion C) What does a scatter plot show about the relationship between two variables?

A scatter plot shows how two variables vary together, indicating whether there is a positive, negative, or no correlation and suggesting the strength and pattern of their relationship.

(Criterion C) How can you tell if data supports or refutes your hypothesis?

Compare the measured results to the predicted outcome—if the results consistently match the prediction within expected uncertainty, the data supports the hypothesis; if results conflict or significantly differ, the data refutes it.

(Criterion C) What is the median of a data set, how do you find it, and why is it useful?

The median is the middle value when data are ordered; find it by ordering values and selecting the middle one (or averaging the two middle values if even count); it is useful because it represents the central value without being skewed by extreme outliers.

(Criterion C) Explain the difference between correlation and causation with an example.

Correlation means two variables change together (e.g., ice cream sales and sunburns increase in summer) but does not prove one causes the other; causation means one variable directly causes the change in the other (e.g., touching a hot stove causes a burn).

(Criterion C) What conclusions can you draw from a graph showing global temperature rising over decades?

The graph indicates a long‑term warming trend in Earth’s average temperature, which suggests climate change and warrants investigation into causes and impacts.

(Criterion C) How do uncertainties or measurement errors affect your confidence in results?

Larger uncertainties reduce confidence because they widen possible true values; reporting error margins and repeating measurements helps quantify and reduce uncertainty.

(Criterion C) Describe how to use evidence to make a scientific claim and include a brief reason and data link.

State the claim clearly, cite specific data as evidence (e.g., measured values or trends), and provide reasoning that links the evidence to the claim (claim → evidence → reasoning); example: “Claim: average water temperature rose 1°C over 30 years (evidence: yearly temperature data), therefore increased local evaporation likely contributed to higher rainfall (reasoning: warmer water increases evaporation rates)”.

(Criterion D) Give one example of how human activity affects local water quality and a mitigation strategy.

Agricultural runoff adds nitrates and phosphates causing algal blooms; mitigation includes buffer strips, reduced fertilizer use, or constructed wetlands to filter runoff.

(Criterion D) What does SHEEEP stand for?

SHEEP stands for:

• Social

• Health

• Environmetal

• Etical

• Economics

• Politics

(Criterion D) Describe a technological solution that reduces the impact of earthquakes or floods.

Earthquake base isolators decouple buildings from ground motion to reduce shaking; flood defenses like levees and floodwalls protect communities from rising water.

(Criterion D) Explain how understanding food chains helps manage an ecosystem.

Knowing producer–consumer–decomposer links predicts effects of species removal or introduction, guiding conservation, pest control, and habitat restoration to maintain balance.

(Criterion D) How can the design of a building use knowledge of forces to improve safety?

Engineers distribute loads using trusses, beams, and shear walls and choose materials strong in tension/compression to resist forces like gravity, wind, and earthquakes, improving stability and safety.

(Criterion D) How can sustainable urban planning reduce heat island effects, and give one specific strategy?

Sustainable urban planning reduces heat islands by increasing shade and surface reflectivity to lower local temperatures; one strategy is planting urban trees and creating green roofs to provide shade and evapotranspiration cooling.

(Criterion D) Describe one way climate change can affect human societies and one adaptation response.

Sea‑level rise can flood coastal communities; adaptation includes building sea walls, relocating infrastructure, or implementing managed retreat and flood‑resilient planning.

(Criterion D) Explain how engineers use the scientific method when developing a new product.

Engineers define the problem, propose design hypotheses, build prototypes, test and collect data, analyze results, and iterate the design based on evidence until requirements are met.