Answer:
Cell, Organ
Explanation:
The level of organization of an organism refers to the order in which the organism exists starting from Its most basic unit. The levels of organisation are cell, tissue, organs, organ system.
ATOMS are the smallest unit of matter comprising both living and non-living things. Molecules consists of these atoms held together by chemical bonds. Cells are the fundamental basic units of all organisms. All living organisms are made up of CELLS. However, a group of cells can cooperate and work together, performing the same function. These cells are said to be TISSUES.
Tissues that work together to perform a certain task forms structures called ORGAN. Organs in living organisms include liver, brain, etc. In the same vein, organs can collectively work together to perform certain functions in the organism's body. This collection of organs is called ORGAN SYSTEM. For example, In humans, we have, circulatory system consisting of the heart organ.
