What Are Exoskeletons

About this printable What Are Exoskeletons science reading passage, NGSS-aligned (Grades 3-5)

This engaging 250-word reading passage introduces fourth-grade students to the concept of exoskeletons, aligning with NGSS standard 4-LS1-1 and the Disciplinary Core Idea LS1.A: Structure and Function. Students discover that some animals like insects, crabs, and spiders have their skeleton on the outside of their body instead of inside. The passage explains how exoskeletons are hard outer coverings that protect soft body parts, provide support, and prevent water loss. Unlike internal skeletons with bones that grow continuously, exoskeletons cannot grow with the animal. This leads to the fascinating process of molting, where animals must shed their old exoskeleton and grow a new, larger one. The passage compares exoskeletons to internal skeletons, helping students understand the diversity of animal structures. Audio integration supports diverse learners by providing multiple ways to access the content. The simplified differentiated version uses shorter sentences and familiar vocabulary while maintaining the same core science concepts. Both English and Spanish translations are included to support multilingual learners. Accompanying activities include comprehension questions, writing prompts, and graphic organizers that reinforce understanding of structure and function relationships in living organisms.

Written by Workybooks TeamPublished by Workybooks

Sample passage and quiz from What Are Exoskeletons

Beetle molting. — Insects shed shells to grow.

Most animals you know, like dogs and birds, have bones inside their bodies. But some animals are built differently. Insects (small animals with six legs like beetles and ants), crabs, and spiders have their skeleton on the outside of their body. This hard outer covering is called an exoskeleton.

An exoskeleton works like a suit of armor. It protects the soft body parts inside from getting hurt. The exoskeleton also gives the animal's body shape and support, just like your bones hold you up. Another important job of the exoskeleton is to keep water inside the animal's body so it doesn't dry out.

There is one big difference between an exoskeleton and the bones inside your body. Your bones grow as you grow. But an exoskeleton cannot grow. When an insect or crab gets too big for its exoskeleton, it must shed the old one. This process is called molting. The animal grows a new, larger exoskeleton underneath the old one. Then it crawls out of the old exoskeleton, leaving it behind like an empty shell. The new exoskeleton is soft at first, but it hardens in a few hours or days.

Interesting Fact: A cicada can live underground for 17 years, molting several times as it grows. When it finally comes above ground as an adult, you can often find its empty exoskeleton still clinging to a tree!