Chapter 2: The Invisible Living World: Beyond Our Naked Eye

Flashcards covering the vocabulary and key concepts of grade 8 science regarding cell biology and microorganisms.

Lens

A curved piece of glass, thick in the middle and thin at the edge, used to make small things look bigger.

Organisms

All living beings, including plants and animals, that differ in size, shape, and structure.

Robert Hooke

A scientist who published Micrographia in 1665 and first used the word cell to describe the basic unit of life after observing thin slices of cork.

Cell

The basic unit of life, first described as small, empty spaces resembling a honeycomb.

Antonie van Leeuwenhoek

A Dutch scientist known as the Father of Microbiology who was the first to clearly see and describe bacteria and blood cells using improved lenses.

Onion peel

The thin, transparent layer from the inner surface of an onion bulb used in teacher demonstrations to study plant cells.

Safranin

A red-coloured stain used to give a pinkish colour to cells and help see them clearly under a microscope.

Glycerin

A substance used on microscope slides to prevent the drying of cells and improve clarity for better visualisation.

Cell membrane

The outer layer of a cell that encloses the cytoplasm and nucleus, and is porous to allow essential materials in and waste out.

Nucleus

A round structure in the middle of the cell that regulates growth and all activities occurring within the cell.

Cytoplasm

The material filling the space between the cell membrane and nucleus where most life processes take place.

Cell wall

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

Plastids

Tiny rod-shaped structures found in all parts of a plant; some, like chloroplasts, contain chlorophyll for photosynthesis.

Vacuole

A large, empty-looking space in plant cells that stores important substances, gets rid of waste, and maintains cell shape.

Neurons

Also known as nerve cells, these have an elongated shape and branched structure to carry messages quickly through the body.

Muscle cell

A thin, flexible, and spindle-shaped cell that helps in movement, such as pushing food through the food pipe.

Multicellular organisms

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

Yolk of an ostrich egg

The largest known single cell in the living world, measuring about $130\,\text{mm}$ to $170\,\text{mm}$ in diameter.

Microorganisms (Microbes)

Tiny creatures that cannot be seen with the naked eye and are found in water, soil, air, and inside bodies.

Unicellular organisms

Living beings made up of just one cell, such as bacteria and Amoeba.

Decomposition

The process where microorganisms like bacteria and fungi break down complex substances from dead organisms into simpler, nutrient-rich substances.

Biogas

A fuel source primarily composed of methane and carbon dioxide, released by bacteria decomposing waste in an oxygen-free environment.

Patent

A copyright given to a person so that no one else can copy, use, or sell their invention without permission.

Yeast

A unicellular fungus that respires and releases carbon dioxide, used in making breads and cakes to make them soft and fluffy.

Lactobacillus

A type of bacterium that feeds on lactose to produce lactic acid, which ferments milk into curd.

Rhizobium

Bacteria found in the root nodules of legumes that trap nitrogen from the air to increase soil fertility naturally.

Microalgae

Microscopic plant-like organisms like Spirulina and Chlorella that produce more than half of the Earth's oxygen supply.

Spirulina

A microalga called a superfood that is rich in protein (more than $60\%$ of its body weight) and vitamin B12.

Nucleoid

A region in a bacterial cell that contains genetic material, distinguishing it from cells with a well-defined nucleus.

Viruses

Microscopic and acellular entities that can only multiply when they enter a living host cell.