Year 7 Biology: MRS GREN & Microscopes Notes

This set of flashcards will help you review key concepts related to MRS GREN life processes and microscope usage, essential for your Year 7 Biology exam.

What does MRS GREN stand for?

Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition.

What is the process of respiration?

A chemical reaction that releases energy from glucose using oxygen.

What is the role of the nucleus in a cell?

Controls cell activities and contains DNA (genetic information).

Which part of the microscope do you look through?

Eyepiece lens.

How is total magnification calculated?

Total magnification = Eyepiece lens magnification × Objective lens magnification.

Why is a stain added to a slide specimen?

To add contrast so that the colourless cells can be seen clearly.

What organelle controls what enters and leaves the cell?

Cell membrane.

Give an example of movement in a plant and one in an animal.

Plant: Leaves move towards light (phototropism); Animal: A dog runs after a ball.

Why must the specimen be thin when viewed under a microscope?

Light must pass through it — if it's too thick, details can't be seen.

Compare the process of nutrition in plants and animals.

Plants make food through photosynthesis; animals take in nutrients from food.

How do you focus a microscope safely?

Start at the lowest power, lower the stage fully, then use coarse focus to raise it until the image appears.

What is the role of mitochondria in a cell?

Where respiration happens — it releases energy.

Which three parts are found only in plant cells?

Cell wall, vacuole, chloroplasts.

Why is a coverslip placed at an angle when preparing a slide?

To avoid air bubbles in the specimen.

Why does respiration occur in all living cells, even in plants at night?

Because respiration is necessary for energy production, which occurs regardless of light.

How does sensitivity help an organism survive in its environment?

Sensitivity allows organisms to detect changes in their surroundings and respond appropriately.

If the total magnification is 400x, why might you need to reduce the light at this power?

Higher magnification may require less light to avoid glare and to see details clearly.

Compare the functions of chloroplasts and mitochondria in plant cells.

Chloroplasts convert light energy into chemical energy (photosynthesis); mitochondria release energy from that chemical energy.

Why is the statement "Plants don’t respire because they make their own food" incorrect?

Plants also need to respire to release energy for cellular processes; they respire all the time, day and night.

What problem could air bubbles under the coverslip cause, and how can you avoid it next time?

Air bubbles can obstruct the view of the specimen; you can avoid it by placing the coverslip at an angle and lowering it gently.

🧠 1. MRS GREN – The Seven Life Processes

Front: What does MRS GREN stand for?

Back: Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition.

Front: What is movement?

Back: The ability to change position or move parts of the body (e.g. a cat chasing a mouse; a plant bending to light).

Front: Define respiration.

Back: A chemical process in cells that releases energy from glucose using oxygen.

Front: Why is respiration essential?

Back: It provides the energy needed for all life processes such as growth, repair, and movement.

Front: What does sensitivity mean in biology?

Back: The ability to detect and respond to changes (stimuli) in the environment, such as light or temperature.

Front: What is growth?

Back: The increase in size or number of cells — making an organism bigger or more developed.

Front: Define reproduction.

Back: The ability of living things to produce offspring of the same kind.

Front: What is excretion?

Back: Removing waste products produced inside the body — e.g. CO₂, sweat, urine.

Front: What is nutrition?

Back: Taking in or making food to obtain nutrients and energy.

Front: How do animals and plants differ in nutrition?

Back: Animals eat other organisms; plants make their own food through photosynthesis.

Front (Challenge): Why are viruses not considered living?

Back: They do not carry out all seven life processes independently — they can only reproduce inside host cells.

🔬 2. Microscopes

Front: What is the function of the eyepiece lens?

Back: It magnifies the image, usually ×10.

Front: What does the objective lens do?

Back: Provides additional magnification (×4, ×10, or ×40).

Front: What is the total magnification if the eyepiece is ×10 and the objective is ×40?

Back: 10 × 40 = 400× total magnification.

Front: Why must specimens be thin?

Back: So that light can pass through for a clear image.

Front: What is the purpose of the mirror or lamp?

Back: To shine light through the specimen.

Front: What does the coarse focus knob do?

Back: Moves the stage up and down to find rough focus.

Front: What does the fine focus knob do?

Back: Brings the image into sharp focus.

Front: Why should you start on the lowest magnification?

Back: It gives a wider view and helps locate the specimen easily before zooming in.

Front (Challenge): Why might you need to reduce light at high magnification?

Back: Because the image can appear too bright, making details harder to see.

Front (Challenge): How can you estimate the actual size of a cell under the microscope?

Back: Measure its image size and divide by the total magnification.

🧫 3. Making and Viewing Slides

Front: What is the purpose of methylene blue when making a cheek-cell slide?

Back: It stains colourless cells, adding contrast so structures are visible.

Front: Why is the coverslip lowered at an angle?

Back: To avoid trapping air bubbles that can distort the image.

Front: Why must the specimen be thin?

Back: Thick specimens block light, preventing clear viewing.

Front: What do you use to collect cheek cells?

Back: A clean cotton bud rubbed gently on the inside of the cheek.