What are Invertebrates?
Invertebrates are animals that lack an internal backbone. Most invertebrates are symmetrical, except for sponges, and have distinct front and rear ends. Well-known invertebrate phyla include:
- Porifera, including sponges
- Arthropoda, including insects, arachnids, and crustaceans
- Mollusca, including snails and octopuses
- Annelida, Nematoda, Platyhelminthes
- Echinodermata, including starfish
- Cnidaria, including jellyfish
What are the Different Phyla of Invertebrates?
Did you know that sponges are “sessile” animals? That means they don’t move around. Instead, they live by pumping large volumes of water through their bodies and filtering out tiny organisms and organic particles of food.
Sponges have existed for a very long time. Fossils of sponges that are 60 million years old have been discovered. As of 2023, there are over 9,500 species of sponges that have been classified scientifically under the phylum Porifera.
Arthropods are a diverse group of invertebrates that include creatures we encounter every day, such as insects, spiders, crabs, and centipedes. They have a hard outer skeleton called an exoskeleton that protects their bodies and gives them a framework for their muscles. Their segmented bodies and jointed appendages allow them to move in many ways. Arthropods can be found in a variety of locations, such as trees and oceans.
- Insects: Insects are arthropods with three body segments and three pairs of legs, two of which are wings. They are the most diverse group of animals on Earth, with over a million species.
- Arachnids: Arachnids include spiders, scorpions, and ticks. They have two body segments and four pairs of legs, and many are venomous. Spiders spin silk to create webs for catching prey.
- Crustaceans: Crustaceans are mostly aquatic arthropods, such as crabs, lobsters, shrimp, and barnacles. They have a hard outer shell that they shed periodically as they grow, and some have claws or pincers for catching prey or defending themselves.
Mollusks have soft bodies that are often covered (wholly or partially) by a hard shell. They include snails, clams, octopuses, and squid. They’re found in many different habitats, from the deepest parts of the ocean to the highest mountains.
Did you know that the largest mollusk is the giant squid, which can grow up to 43 feet long? Some mollusks, like the octopus, have highly developed nervous systems and can solve puzzles and open jars to get to their food. Some snails can hibernate for up to three years when the weather gets too harsh. And some mollusks, like the cone snail, are venomous and can be dangerous to humans.
Worms are a diverse group of invertebrates that can be found in soil, water, and even other animals. They break down old plants and animals, which helps new things grow and they are also an important food source for other animals.
- Annelids are another group of invertebrates that includes earthworms, leeches, and marine worms. They move in various ways and some feed on detritus or filter-feed.
- Platyhelminthes, or flatworms, are invertebrates with flattened bodies. They include tapeworms and planarians and some are parasites.
- Nematodes, also known as roundworms, are found in many different habitats and play an important role in soil ecosystems by breaking down organic matter and cycling nutrients.
Echinoderms have a special body shape where their body parts are arranged in a circle around a center point. They live in the ocean and include creatures like sea stars, sea urchins, and sea cucumbers.
Echinoderms can regenerate lost body parts, including entire bodies from a single arm. Some echinoderms form symbiotic relationships, such as certain species of crabs that attach sea anemones to their shells for extra protection. Echinoderms move using tube feet, which can also be used to grab onto things or catch prey.
Cnidarians are a fascinating group of invertebrates that live in the ocean and include jellyfish, sea anemones, and coral. They have tentacles to catch food and can be found in many habitats, from deep ocean to shallow reefs.
Cnidarians produce fluorescent proteins that allow them to glow in the dark, which scientists have utilized to create fluorescent animals for research purposes. Some jellyfish species are even immortal, able to revert to their juvenile form and regrow when faced with stress or damage. Coral reefs are diverse ecosystems that provide habitat for marine life such as fish, sea turtles, and sharks, and many species call coral reefs their home.
To get to know the invertebrate animals, Montessori nomenclature cards are used.
Nomenclature refers to a system of terms or symbols, especially in a particular scientific discipline or art. It is used in biology to classify types and groups of animals and plants.
How to Use the Montessori Zoology Nomenclature Cards
A collection of three sets of cards mounted on cardstock or laminated, if desired.
- Poriferans or sponges
- Annelids, Nematodes, Platyhelminthes
Each set should be color-coded with marking and arranged together based on classification.
The card set, also known as 3-part cards, consist of an image card, a label card, and a control card that displays both the image and label.
- Invite 1-3 children to bring 1 packet of the animals under 1 phylum of invertebrates.
- Using the image cards, go through all the animals and see which ones the children know, and isolate the unfamiliar ones.
- Ask if you have corresponding 3D objects for the animals, then match.
- Give a three-period lesson for the unfamiliar animals.
- At the end of the second period, shuffle all the cards and pass them out to the children face down. The children pick them up and hold them like playing cards.
- Ask for cards by the name of their object.
- The child with the matching card lays it in the middle of the table.
- In the third period, reshuffle the cards and pass them out face down. The children keep the cards in a pile in front of them.
- The children take turns turning over the top card and naming it.
- If a child does not know, another child or the adult may give the item’s name.
- Repeat the presentation for other types of invertebrates.
Get to know the animals under each type of invertebrates with these nomenclature cards:
You’ll also find the anatomy nomenclature cards and booklet from the link above.