Animal Symmetry: Transitioning from Vertebrates to Invertebrates!

5th Grade

What are Invertebrates?

• Animals without backbones

• What percent of animals are Invertebrates?

• 97 percent of all animals are invertebrates!

Invertebrates are the only animals that can have no symmetry

What is animal symmetry?

Animal Symmetry

Symmetry: the balanced arrangement of partsAnimal Symmetry: the balanced arrangement of parts, characteristic of many animals

Different Types of Animal Symmetry

• 1) Bilateral Symmetry

• 2) Radial Symmetry

• 3) No Symmetry

Bilateral Symmetry

• there is one line of symmetry that divides an an animal into halves that are mirror images

Bilateral Symmetry

Where would you draw the line of symmetry?

Radial Symmetry

Radial Symmetry

*Animals with radial symmetry have many lines of symmetry that all go through a central point

Radial Symmetry

No Symmetry

Animal Symmetry

Which one has bilateral symmetry and which one is radial symmetry?

Animals with NO symmetry tend to have very simple body plans

Depending on symmetry, animals share general characteristics.

Animals with Radial Symmetry

• The external body parts of animals with radial symmetry are equally spaced around a central point

• Ex. sea stars, jelly fish, sea urchins

Characteristics of animals with Radial Symmetry

• All live in water

• Most do NOT move very fast

• They tend to stay in one spot, are moved along by water currents, or creep along the bottom of the ocean

Characteristics of animals with Bilateral symmetry

*Are larger and the most complex

*They have a front end that typically goes first as the animal moves along

*Can move quickly and more efficiently than animals with radial symmetry because bilateral symmetry allows for a streamlined body

Characteristics of animals with Bilateral symmetry

*most animals with bilateral symmetry have sense organs in their front ends that pick up information about what is in front of them

Ex. a tiger has eyes, ears, nose, and whiskers on its head

*sense organs help animals with bilateral symmetry obtain food and avoid enemies

Bilateral Symmetry

Bilateral Symmetry

1) What is symmetry? 2) How are bilateral symmetry and radial

symmetry alike? How are they different? 3) What kind of symmetry does a grasshopper

have? 4) What general characteristics do animals with

radial symmetry share? 5) What four body characteristics do animals

with bilateral symmetry usually have? 6) How would having sense organs in front be

helpful to an animal?