Core praticals of Paper 1 Biology

Question 1

1.6 core practical: Investigate biological specimens using microscopes, including magnification
calculations and labelled scientific drawings from observations.

How to prepare before using the light microscope (solid)

Answer 1

1. Take a thin layer of cells from your sample (peel or use a cotton bud)
2. Add small amount of the correct chemical stain. These will allow you to see what is inside of the cell
3. Apply the cells to the glass slide (place it or rub it on)
4. Carefully add the coverslip and avoid air bubbles

Question 2

1.6 core practical: Investigate biological specimens using microscopes, including magnification
calculations and labelled scientific drawings from observations.

How to prepare before using the light microscope (liquid)

Answer 2

1. Add a few drops of the sample to the slide using a pipette
2. Cover the liquid/smear with a coverslip and gently press down to remove air bubbles
3. Wear gloves to ensure there is no cross-contamination of foreign cells

Question 3

1.6 core practicals

Calculations needed

Answer 3

Magnification = measured size/actual size

Actual size = measured size/magnification

Total magnification = objective lens magnification x eyepiece lens magnification

Question 4

1.6 core practical

How to use a light microscope and its components

Answer 4

1. Place the slide on the stage and look through the eyepiece lens
2. Turn the focus wheel to obtain a clear image
3. Start with the lowest objective lens magnification
4. Increase magnification of objective lens and refocus

Components:
Eyepiece - part of the microscope we look through to view specimens
Barrel - upper part of the microscope that can be moved up or down to focus the image
Turret - part of the miscroscope that is rotated to chaneg magnification lens in use
Lens - the part of the microscope that increases the magnification of the specimen
Stage - flat surface where we place the specimen