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

Flashcards covering the vocabulary of Chapter 2, including cell structures, levels of organization, and various microorganisms.

Lens

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

Organisms

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

Robert Hooke

A scientist who published the book Micrographia in 1665 and was the first to use the word cell to describe the basic unit of life.

Cell

The basic unit of life, first described by Robert Hooke as small, empty spaces in a thin slice of cork resembling 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 from the inner surface of an onion bulb used to study plant cell structure.

Safranin

A red-coloured stain used in laboratory activities to give cells a pinkish colour for clearer visualization.

Methylene blue

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

Glycerin

A liquid used when mounting specimens on slides to prevent the drying of cells and improve clarity.

Cell membrane

The porous outer layer of a cell that encloses the cytoplasm and nucleus, allowing essential materials to enter and waste to exit.

Nucleus

A round structure in a cell covered by a thin membrane that regulates all cell activities and growth.

Cytoplasm

The space between the cell membrane and the nucleus filled with compounds like carbohydrates and proteins, 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 compact structure.

Plastids

Tiny rod-shaped structures found in all parts of a plant; some contain chlorophyll for photosynthesis while others help in storage.

Vacuole

A large space in plant cells used to store substances, remove waste, and maintain shape; they are small or absent in animal cells.

Neurons (Nerve cells)

Elongated, branched cells in the human body that carry messages quickly to different parts of the body.

Tissue

A group of similar cells that work together to perform a specific function.

Organ

A structure made of different tissues organized together to perform specific tasks in the body.

Organ system

A group of several organs that work together to perform a major body function.

Multicellular organisms

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

Unicellular organisms

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

Microorganisms (Microbes)

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

Soil suspension

A mixture of fine soil particles and water used to observe microscopic creatures living in the soil.

Viruses

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

Decomposition

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

Biogas

A mixture of gases, primarily carbon dioxide and methane, produced by bacteria decomposing waste in an oxygen-free environment.

Ananda Mohan Chakrabarty

A scientist who in 1971 developed a special bacterium capable of breaking down oil spills to clean the environment.

Patent

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

Yeast

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

Lactobacillus

A bacterium that feeds on lactose in milk and ferments it 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 without chemical fertilisers.

Microalgae

Microscopic plant-like organisms that live in water and produce more than half of the Earth's oxygen supply.

Spirulina

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

Nucleoid

An area in a bacterial cell that contains genetic material but lacks a well-defined nuclear membrane.

Electron microscope

A high-powered tool that magnifies a cell about $1,000,000$ times to observe subcellular components.