Back to: ZOOLOGY 200 Level
It’s so good to see your learning spirit still burning bright. Today’s lesson is quite interesting—we’ll look at how animals are structured inside and out, and how they move. You may not always think about what goes on inside a worm or insect, but their body plans are a big reason they survive and adapt so well. Let’s find out how!
Segmentation, coelom, and locomotion
Segmentation
Segmentation refers to the division of an animal’s body into repeated sections or segments. This feature is especially seen in annelids like earthworms and arthropods like millipedes and insects.
Each segment can carry out a specific function, making the body more organised. For example, in an earthworm, each segment has muscles and bristles (called setae) that help with movement. In insects, segments have jointed legs, antennae, and wings that support various tasks.
This division allows for better coordination, flexibility, and specialisation. So, rather than the whole body doing the same thing, each part has its job—like a well-managed football team!
Coelom
The coelom is a fluid-filled body cavity located between the digestive tract and the body wall. Animals with a true coelom (called coelomates) include annelids, molluscs, arthropods, and vertebrates.
The coelom acts like a cushion for internal organs, allowing them to move independently of the body wall. It also provides space for the development of more complex organs and systems. For instance, in an earthworm, the coelom allows the digestive system to move food without disturbing the body structure.
Animals without a coelom (acoelomates) like flatworms, have solid bodies with no internal cavity, which limits their complexity. Those with a partial coelom (pseudocoelomates) like roundworms still benefit from some internal space but not as much control.
Locomotion
Locomotion is how animals move from one place to another. Different animals use different parts of their body to move, depending on their habitat and structure.
- Earthworms move by contracting their body segments in waves, using setae for grip.
- Insects use jointed legs and wings for walking and flying.
- Snails glide on a muscular foot and secrete mucus to move smoothly.
- Fish use fins and muscles to swim through water.
The type of locomotion an animal uses is closely linked to its environment and body structure, showing how well-adapted each species is to survive and thrive.
Summary
Segmentation helps animals divide their bodies into specialised parts for better coordination. The coelom provides internal support and space for organ development. Locomotion allows animals to find food, escape danger, and explore their habitats. Together, these features show just how smartly nature equips animals for life.
Evaluation
- What is segmentation, and which animals show this feature?
- Explain the role of the coelom in complex animals.
- Give two examples of locomotion in invertebrates.
- What is the difference between acoelomates and coelomates?
You’re grasping advanced concepts like a champion! Keep trusting your mind, and remember that every bit of knowledge takes you closer to your dreams. Afrilearn is right here with you—ready when you are for the next great topic!