Removing unwanted materials from the body is called excretion.

Here are the answers to your questions:

1. Removing unwanted materials from the body is called excretion.

   $$\boxed{\text{Excretion}}$$

2. Living things increase in number by reproduction.

   $$\boxed{\text{Reproduction}}$$

3. Changing position or direction from one place to another is called movement (or locomotion).

   $$\boxed{\text{Movement}}$$

4. Vertebral column are also known as the spine (or backbone).

   $$\boxed{\text{Spine}}$$

5. Living things are also called organisms.

   $$\boxed{\text{Organisms}}$$

6. Two groups of animals are:

   • a) Vertebrates
   • b) Invertebrates
   $$\boxed{\text{a) Vertebrates, b) Invertebrates}}$$