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exoskeleton

Definition

An exoskeleton is a rigid external skeleton that supports and protects the body of an animal. It is made up of many small plates that are joined together by flexible joints. The exoskeleton is made of a hard, tough material called chitin, which is also found in the cell walls of plants.

  • Exoskeletons are found in many different groups of animals, including insects, arachnids, and crustaceans. They provide a number of advantages to these animals, including:
  • Protection: The exoskeleton protects the animal's soft tissues from injury and from predators.
  • Support: The exoskeleton provides support for the animal's body, allowing it to move and hold its shape.
  • Gas exchange: In some animals, the exoskeleton helps with gas exchange. For example, the exoskeleton of insects is perforated with small holes that allow oxygen to pass through.
  • Water conservation: The exoskeleton helps to conserve water in some animals. For example, the exoskeleton of a crab is waterproof, which helps to prevent the crab from drying out.

Exoskeletons are not without their disadvantages. They can be heavy, and they can restrict the animal's movement. Additionally, the exoskeleton must be shed periodically as the animal grows. This process, called moulting, can be dangerous for the animal if it is not done properly.

How can the word be used?

The exoskeleton of a beetle is made up of chitin.

exoskeleton

Different forms of the word

Noun: exoskeleton, external skeleton.

Adjective: exoskeletonic, exoskeletal.

Verb: to exoskeltonize.

Synonyms: hard shell, external covering, crust.

Antonyms: endoskeleton, internal skeleton.

Etymology

The word "exoskeleton" comes from the Greek words exo (outside) and skeletos (dried up, skeleton). It was first used in English in the 19th century, and it is still used today to refer to the hard external covering that supports and protects the body of an animal.

Question

What is the difference between an exoskeleton and an endoskeleton?

AQA Science Exam Question and Answer

Question:

Explain the significance of an exoskeleton in arthropods and how it differs from an endoskeleton in vertebrates. Describe one advantage and one limitation of having an exoskeleton.

Answer:

The exoskeleton is a remarkable feature found in arthropods, such as insects, crustaceans, and spiders, serving as a rigid external structure that supports and protects their bodies. Unlike the internal endoskeleton of vertebrates, which consists of bones or cartilage, the exoskeleton is made of chitin, a tough and lightweight compound.

One advantage of an exoskeleton is its excellent protection against predators and the environment. The tough chitinous covering acts as a physical barrier, reducing the risk of injury and providing structural support. Additionally, the exoskeleton prevents water loss, helping arthropods thrive in various habitats.

However, the exoskeleton's rigid nature poses a limitation during growth. As arthropods grow, they need to moult and shed their old exoskeleton to accommodate their larger size. This process leaves them vulnerable until the new exoskeleton hardens. In contrast, vertebrates' endoskeleton grows with them, allowing continuous development without such vulnerable phases. Despite this drawback, the exoskeleton remains an adaptive and essential feature, contributing to the evolutionary success of arthropods.