Chapter 2 – Classifying Animals: Lesson 2 – Which Animals are Invertebrates?

Standard – S3.B.2 – Continuity of Life

S3.B.2.1 – identify and describe characteristics of plants and animals that help with their survival- S.3.B.2.1.1 – identify adaptations of plants and animals that have helped them survive- S.3.B.2.1.2 – identify and describe plant and animal characteristics that are necessary

for survival- S.3.B.2.1.3 – identify characteristics for plant and animal survival in different

environments (desert, forest, ocean)

Characteristics of Animals: Objectives –

In this lesson, students will describe and identify characteristics of animals.

Students will also –

- Discuss different characteristics of animals for survival- Identify adaptations that animals use for their survival- Identify how animals adapt to different environments- Observe an aquarium or terrarium- Explore characteristics of ants and how they survive in their environment- Identify and describe the functions of basic structure of animals- Classify living things based on similarities- Know the five main animal groups- Describe basic needs of animals- Describe how animals go through life cycles

Big Ideas:

Animals, including vertebrates and invertebrates, can be classified according to their characteristics.

Scientists study fossils to learn about animals that lived long ago. Some animals that lived long ago have become extinct

Some modern animals resemble extinct animals. Other modern animals are in danger of becoming extinct.

Which Animals are Invertebrates? – Vocabulary

1. Arthropod – an invertebrate that has pointed legs, a body with two or more sections and a hard outer covering

2. Invertebrate – an animal that does not have a backbone

Chapter 2: What Animals are Invertebrates? – Lesson 2: Invertebrates

Main Idea: The many kinds of invertebrates can be grouped according to their traits.

Traits of Invertebrates

Most of the animals on Earth are invertebrates. An invertebrate is an animal that does not have a backbone. Some types of invertebrates live on land and some types live in water.

Invertebrates: sponges, sea stars and sea urchins, worms, corals and jellies, snails and squids, and arthropods.

Sponges

Sponges are animals that move very little. Their bodies are full of holes. Sponges filter tiny bits of food from the water.

Sea Stars and Sea Urchins

Sea stars and sea urchins have spiny body coverings. Neither animal has a head, but they both have a mouth. They move and capture food using tiny suction cups called tube feet.

Worms

Worms have soft, tube-shaped bodies with no legs, eyes, or shells. Worms live in water, in soil, or even inside other animals.

Corals and Jellies

Corals and jellies are underwater animals. They have soft bodies, but some corals have a hard outer skeleton. They both have mouths and arm-like parts called tentacles. When food floats by, these animals use their tentacles to grab it and put it into their mouth.

Snails and Squids

Snails, squid, octopus, clams, oysters, and scallops all belong to the same group called mollusks. They have soft bodies. All of these animals, except for the octopus, have a shell.

How do vertebrates differ from invertebrates?How are sea stars and sea urchins alike?What do corals and jellies use to grab food?

Arthropods

The largest group of invertebrates is the arthropod group. An arthropod is an invertebrate that has jointed legs, a body with two or more sections, and a hard outer covering. The hard outer covering is called an exoskeleton. An exoskeleton protects and supports the animal.

Arthropods – butterflies and ants, centipedes and millipedes, spiders, crabs, lobsters, and crayfish

Butterflies and Ants

There are several groups of arthropods. The largest group includes butterflies and ants. These insects have six legs and three body sections. They may or may not have wings.

Centipedes and Millipedes

Centipedes and millipedes have segmented bodies. Centipedes have one pair of legs on each segment. Millipedes have two pairs of legs on each segment.

Spiders

Spiders have eight jointed legs, two body sections, jaws, and fangs. Many spiders spin webs.

Crabs, Lobsters, and Crayfish

Another group of arthropods includes crabs, lobsters, and crayfish. Many animals in this group have an exoskeleton that is very hard, like a shell.

More Information about Arthropods

Almost 80% of all animals are arthropods. About three-quarters of arthropods are insects All arthropods have a line of symmetry that divides their left and right sides The exoskeleton provides protection for the body and limbs of the arthropod. The head

has sense organs and a mouth The number of segments arthropods vary greatly among the different groups

Lesson 2 Review Questions:

1. Why are insects, lobsters, and spiders all classified as arthropods?2. Write a sentence using the vocabulary word invertebrate.3. A certain centipede has 15 segments on its body. Each segment has 2 legs. Use a number

pattern to find how many legs the centipede has.4. In older times, sailors from Norway told of a sea creature called the Kraken. The Kraken

was said to be more than a mile long and have tentacles strong enough to sink a ship! Today we know that these legends were probably based on a real animal, the giant squid. Choose an invertebrate and write a story about your own legendary creature.

No Brain, No Bones, No Problem!

A “jellyfish” is not a fish! It isn’t jelly, either. In fact, jellies, to use their scientific name, are invertebrate animals: animals that get along fine without a spine. Everything about the giant Antarctic jelly is extreme. Its bell (the rounded shape at the top) can be over three feet wide. Its tentacles can be 30 feet long. Jellies use their long tentacles to sting and catch their food.

Scientists think jellies have been around since before the dinosaurs. Not bad for an animal with no bones, no blood, no heart… not even a brain!

Most jellies simply float wherever the ocean currents take them. Others, like the Antarctic jelly, can move through the water by expanding and contracting their bells.

Background on Stinging Jellies

Jellies use some of the most sophisticated poisons on Earth. Jellies have stinging cells in their tentacles that stun or kill prey that touches them. The poisons are especially strong and quick-acting so that the prey will quickly be paralyzed or dead, allowing the delicate jelly to safely ingest it.

Most jelly stings cause little more than pain or a rash to a human. But the sting of the Australian box jelly, or sea wasp, can be deadly. Swimmers, surfers, and divers can be stung when they run into the jelly’s tentacles. Even a tiny amount of poison – as little as a grain of salt – can kill!

Luckily, people can prevent stings simply by wearing nylon (wet suits) over the skin. The layer of nylon prevents the jelly’s stinging cells from firing.