The cell is the basic unit of structure and function of a living thing.

Cells are specialized by size and shape for the job they do

Examples: human blood cell, sperm cell, neuron (nerve cell)


Tissues are made of a group of similar cells that work together to do a specific job in the body.Examples: connective tissue, muscle tissue, nervous tissue


Organs are made up of two or more tissues that work together to do a specific job.Example: liver, kidney, heart

Organ system

An organ system is a group of organs working together to perform particular jobs.

Example: skeletal system, muscular system, nervous system


Sum of all cells, tissues, organs and organ systems makes an organism. An organisms is made when a group of organ systems work together

example: Animals, plants, and humans are multicellular organisms while bacteria is an unicellular organism


A group of the same type of organisms all living together in the same place



Populations living together in one area



All the ecosystems around the world make up the biosphere