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 parts
Animal 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?