The Invisible Living World: Beyond Our Naked Eye Flashcards

Summary of vocabulary and key concepts from Grade 8 Science Chapter 2 regarding the discovery of cells and the world of microorganisms.

Lens

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

Organisms

A general term used to describe all living beings, including both plants and animals.

Robert Hooke

The scientist who published Micrographia in $1665$ and first used the word cell to describe the basic unit of life.

Cell

The basic unit of life, first named by Robert Hooke after observing honeycomb-like compartments in a thin slice of cork.

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.

Onion peel

The thin, transparent layer from the inner surface of an onion bulb used to study plant cell structure.

Safranin

A red-coloured stain used in microscopy to provide a pinkish colour to cells, making them easier to see.

Glycerin

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

Methylene blue

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

Cell membrane

The porous outer layer of a cell that encloses the cytoplasm and nucleus, separating the cell from others while allowing materials to enter and exit.

Nucleus

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

Cytoplasm

The substance filled 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 and strength.

Plastids

Tiny rod-shaped structures in plant cells, such as chloroplasts, which contain chlorophyll for photosynthesis or help in storage.

Vacuole

A large space in plant cells used to store substances, remove waste, and maintain shape; in animal cells, they are small or usually not present.

Neuron

Also known as a nerve cell, it has an elongated and branched structure designed to carry messages quickly throughout the body.

Tissue

A level of biological organisation consisting of a group of similar cells working together.

Organ

A structure formed by different tissues organised together to perform a specific function within the body.

Multicellular organisms

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

Ostrich egg yolk

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

Microorganisms

Also called microbes, these are tiny living beings—such as protozoa, algae, fungi, and bacteria—that cannot be seen with the naked eye.

Unicellular organisms

Organisms made of just one cell, such as Amoeba or bacteria, which carry out all life functions within that single cell.

Viruses

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

Decomposition

The process where microorganisms break down complex substances from dead plants and animals into simpler, nutrient-rich substances.

Biogas

A fuel mixture of carbon dioxide and methane produced when bacteria decompose waste in an oxygen-free environment.

Ananda Mohan Chakrabarty

A scientist ($1938$–$2020$) who developed a bacterium in $1971$ capable of breaking down oil spills to clean the environment.

Yeast

A unicellular fungus that respires and releases carbon dioxide, used to make bread and cakes soft and fluffy.

Lactobacillus

A bacterium that ferments the sugar (lactose) in milk into lactic acid to form curd.

Rhizobium

Bacteria found in the root nodules of legumes that trap nitrogen from the air to help plants grow naturally.

Microalgae

Microscopic plant-like organisms, such as Spirulina, that produce more than half of the Earth's oxygen supply.

Spirulina

A microalga considered a superfood because it is rich in vitamin $B_{12}$ and contains more than $60$ per cent protein by body weight.

Nucleoid

A region in bacterial cells that contains genetic material without a well-defined nuclear membrane.

Electron microscope

A high-powered tool that can magnify a cell about $10,00,000$ times to observe subcellular components.