NCERT Class 9 Science Chapter 2 - Cell: The Building Block of Life

A complete set of vocabulary flashcards covering key terms, cell division types, origin of life research, biological hierarchy, and microscopy limits from NCERT Class 9 Science Chapter 2.

Cell

The basic structural and functional unit of life, and the smallest unit that can carry out all life processes.

Structural Unit

The role of cells as the fundamental building blocks of all living organisms, forming tissues, organs, organ systems, and whole organisms.

Functional Unit

The characteristic of the cell where each individual cell performs all essential life processes, including nutrition, growth, respiration, transport, excretion, and reproduction.

Law of Cell Origin

The principle stating that all new cells are formed only from pre-existing cells.

Mitosis

A type of cell division occurring in somatic cells where one parent cell forms two identical daughter cells, maintaining the chromosome number for growth, repair, and replacement.

Meiosis

A type of cell division occurring in reproductive cells where one parent cell forms four non-identical daughter cells with half the chromosome number for gamete formation.

Somatic Cells

Body cells that undergo mitosis to produce identical daughter cells for body growth and repair.

Gametes

Reproductive cells, such as sperm and eggs, formed through meiosis with half the chromosome number of the parent cell.

Simple Microscope

An optical instrument that magnifies objects up to about $1500$ times, helping in observing larger cells and simple structures.

Compound Microscope

An optical instrument that magnifies objects up to about $2,00,000$ times, allowing detailed study of tiny cells and tissues.

Electron Microscope

An advanced microscope used to observe the ultra-structure of cells, including internal organelles.

Puga Valley

A valley located in Ladakh, India, featuring hot springs near the boiling point of water (\text{Temp} \thicksim 100^\bar{\text{o}}\text{C}) that resemble environmental conditions on early Earth $\text{about } 3.5\text{ billion}$ years ago.

Birbal Sahni Institute of Palaeosciences

A research institute in Lucknow whose scientists studied hot springs in Puga Valley to understand early cell origin and protective membrane formation.

Thermophiles

Unicellular, heat-loving bacteria that live in extreme high-temperature environments such as hot springs.

Calcium Carbonate ($\text{CaCO}_3$)

A compound deposited rapidly around hot springs that shielded early organic molecules from harmful radiation and aided in forming the first protective cell membrane.

Unicellular Organism

An organism made up of only a single cell that carries out all functions of life, such as bacteria and yeast.

Multicellular Organism

An organism made up of millions of cells working together, such as plants, fish, birds, and humans.

Tissue

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

Organ

A body structure formed by different tissues working together to carry out specific functions.

Organ System

A group of several organs working together to perform major body functions.

Respiratory System

An organ system in the body formed by the nasal pores, nasal cavity, trachea, and lungs working together.

Limit of Resolution of Human Eye

The ability of the human eye to see two close objects as separate and distinct, which equals about $0.1\,\text{mm}$ from a viewing distance of about $25\,\text{cm}$.

Near Point of the Eye

The distance of about $25\,\text{cm}$ from which the human eye can distinguish two points separated by $0.1\,\text{mm}$ as distinct.