Biological Levels Of Organization

Levels of organization, least to most complex

Atom, molecule, macromolecule, organelle, cell, tissue, organ, organ system, organism

Atom

The smallest unit of an element (examples: carbon, hydrogen)

Molecule

Two or more atoms bonded together (examples: water, glucose)

Macromolecule

A very large molecule built from many smaller units (examples: protein, DNA)

Organelle

A tiny structure inside a cell that performs a specific job (examples: nucleus, mitochondrion)

Cell

The smallest unit of life

Tissue

A group of similar cells that work together to do the same job (example: muscle tissue)

Organ

A group of different tissues working together to perform a function (examples: heart, stomach)

Organ system

A group of organs working together (examples: circulatory system, digestive system)

Organism

A living thing that meets all the characteristics of life

Level that comes right before cell

Organelle

Level that comes right after tissue

Organ

Unicellular organism

Has one cell that performs all life functions independently

Multicellular organism

Has many cells; cells specialize and depend on each other

Examples of unicellular organisms

Bacteria, amoeba, yeast, paramecium

Examples of multicellular organisms

Humans, trees, mushrooms, dogs

Number of kingdoms of taxonomy in this class

Six

The 6 kingdoms

Archaebacteria, Eubacteria, Protista, Fungi, Plantae, Animalia

Prokaryotic kingdoms

Archaebacteria and Eubacteria (no nucleus; unicellular)

Kingdom of mushrooms and mold

Fungi

Kingdom that makes its own food by photosynthesis

Plantae

Kingdom of organisms that eat other organisms

Animalia

Structure

How something is built or shaped, and what it is made of

Function

The job that a structure does

Structure fits function (example)

A red blood cell has a large surface area to carry oxygen efficiently

Neuron structure and function

Long axon and dendrites; they send and receive electrical signals

How do cells of a multicellular organism work together?

Cells specialize and become dependent on one another for the good of the whole organism

Which is smaller: tissue or organ?

Tissue (tissues combine to make organs)

Which is larger: organelle or macromolecule?

Organelle (macromolecules help build organelles)