Why are animals without skeletons usually small and live in water?

Animals without skeletons, also known as invertebrates, come in various sizes and habitats. While it is true that many small and aquatic animals lack skeletons, it is not accurate to generalize that all animals without skeletons are tiny and water-dwelling.

Size Variability Among Invertebrates:

Invertebrates display a wide range of sizes. Examples of large invertebrates include giant squids, which can grow to enormous lengths and weigh several tons. Some species of jellyfish also can reach colossal dimensions. The largest known jellyfish, the lion's mane jellyfish, can have a bell diameter of over 7 feet (2 meters) and tentacles stretching up to 120 feet (37 meters) long. On the other hand, there are microscopic invertebrates, such as certain single-celled organisms, that can only be observed under a microscope.

Skeletons Not Solely Determining Aquatic vs. Terrestrial Habitats:

The presence or absence of skeletons does not directly dictate whether an animal inhabits water or land. There are numerous invertebrate species that lack skeletons and thrive in terrestrial environments. Examples include insects, spiders, snails, and earthworms. Insects alone comprise the most diverse group of animal life on Earth, encompassing insects, with various habitats spanning terrestrial, aerial, and freshwater ecosystems.

Conclusion:

While some small and aquatic animals do lack skeletons, it is incorrect to assume this characteristic applies to all invertebrates. Size variation and habitat preferences differ widely among invertebrate species. Many invertebrates are large and live on land, while others are small and inhabit water. Skeletal composition and habitat are determined by specific evolutionary adaptations in different animal groups, and these traits do not exclusively define the size or primary environment of invertebrates.