2a: Levels of organisation

Question 1

What are the levels of organisation within organisms, in order from smallest to largest?

Answer 1

organelles, cells, tissues, organs, organ systems

Question 2

Describe organelles

Answer 2

Organelles are structures within cells which carry out particular functions for that cell.
Example: mitochondria that release energy from nutrients for the cell to use.

Question 3

Describe cells

Answer 3

The basic unit of life; the building blocks of tissues. Many organisms are only one cell. In a multicellular organism you may find specialised cells, designed to perform a particular function, such a nerve cell which sends electrical impulses around the body of an animal.

Question 4

Describe tissue

Answer 4

A group of similar cells which perform a particular function. For example, a collection of muscle cells which form a muscle tissue which functions by contracting and moving the skeleton.

Question 5

Describe organ

Answer 5

A group of tissues that work together to carry out a particular function, such as the stomach or heart. The heart for example, contains muscle, nervous and connective tissue, which all work together to perform the heart’s function of pumping blood around the body.

Question 6

Describe organ system

Answer 6

A group of organs that work together to carry out a particular function, such as the mouth stomach and intestines in the digestive system.