Grade 8 Science: The Invisible Living World

Lens

A curved piece of glass shaped like a lentil seed—thick in the middle and thin at the edge—that makes small things look bigger.

Organism

A general term for any living being, whether it is a plant or an animal.

Robert Hooke

The scientist who in 1665 published Micrographia and first used the word 'cell' to describe the basic unit of life after observing a thin slice of cork.

Cell

The basic building block of all living beings, first described by Robert Hooke as small compartments reminding him of a honeycomb.

Antonie van Leeuwenhoek

A Dutch scientist known as the Father of Microbiology; he was the first to clearly see and describe tiny living things like bacteria and blood cells.

Onion peel

The thin, transparent layer pulled from the inner surface of an onion bulb, often used to study plant cells under a microscope.

Safranin

A red-coloured stain used in microscopy to give a pinkish colour to cells, such as those in an onion peel, to make them clearly visible.

Methylene blue

A blue-coloured stain used to increase contrast and improve the visibility of material, such as human cheek cells, under a microscope.

Cell membrane

The porous outer layer of a cell that encloses the cytoplasm and nucleus, separating one cell from another and regulating the entry and exit of materials.

Nucleus

The central, small round structure in a cell that regulates growth and all activities occurring within the cell.

Cytoplasm

The jelly-like substance filling the space between the cell membrane and the nucleus where most life processes take place.

Cell wall

An extra outer layer found in plant, fungal, and bacterial cells that provides rigidity, strength, and a firm structure.

Plastids

Tiny rod-shaped structures in plant cells; examples include chloroplasts, which contain chlorophyll for photosynthesis.

Vacuole

A large, empty-looking space in plant cells (usually small or absent in animal cells) that stores substances, handles waste, and maintains cell shape.

Neurons

Also known as nerve cells, these are long, branched cells that carry messages to different parts of the body quickly.

Muscle cells

Thin, flexible, spindle-shaped cells that contract and relax to allow movement, such as pushing food through the food pipe.

Multicellular organisms

Living beings made up of many cells, such as humans, animals, and most plants.

Ostrich egg yolk

The largest known single cell in the living world, measuring between