Scientists are not positive about how many species of animals exist on Earth. A study completed in 2010 by the Census of Marine Life predicts that there are approximately 7.77 million animals on Earth. Of those approximate 7.77 million animals, only 953,434 have been identified and catalogued. That means that there are many species of animals that have yet to be discovered.

The animal kingdom is extremely diverse. Insects, such as the praying mantis, fish, such the largemouth bass, and mammals, such as a spider monkey are all in the animal kingdom.

Animals have the following characteristics in common.

1. Animals are multicellular.
2. Animals have eukaryotic cells that do not have cell walls.
3. Animals are heterotrophic.
4. Animals typically reproduce sexually.

Typical animal cells have the same organelles. Each organelle performs a specific function in the cell.

Let's look at a typical animal cell.

Directions: Scroll over the letters to view the name of the structure and the function. Take notes on the structure and function of the parts of this cell.

As stated above, this is a typical animal cell. Animal cells are highly specialized and have differences in their structures based on their job, or function, within the organism. The image below shows the structure of some of the specialized animal cells.