You know that the structure of cells in plants allows plants to convert sunlight into energy that the plants can use for growth and reproduction. In a very similar way, cells in humans and animals take in energy from the sun through the food they eat. You will learn more about the cells of animals in this activity. 

The energy taken in by humans and animals is converted into useful forms that allow them to live, move, and grow.

The following diagram shows what an animal cell looks like. You may notice that it is very similar to a plant cell, except it does not have chloroplasts or a cell wall like plant cells do.

Click on the + sign if you would like to look at this image more closely.

When cells combine and work together to do a particular job, they are called tissues.

When tissues combine to do a particular job, they are called organs. When organs combine to do a particular job, they are called body systems.

In humans and animals, the digestive system is the system involved in taking in food and converting it into a form that can be used by the body.

The circulatory system works with the digestive system to carry nutrients throughout the body to provide all cells with energy.

This image shows you different systems in the body.