Invertebrates, Mollusks, Arthropods and Echinoderms
Science

Closed circulatory system explained in an easy to understand way.
Closed circulatory system
A circulation system in which blood flows within a network of vessels. Closed circulatory system. In a closed circulatory system, blood moves through a series of tubes called vessels, delivering nutrients and oxygen efficiently throughout the body.

Metamorphosis explained in an easy to understand way.
Metamorphosis
Changes in form as an animal becomes an adult. Metamorphosis. Metamorphosis is a biological process where an animal undergoes significant physical changes from its early stages to adulthood, like a caterpillar turning into a butterfly.

Open circulatory system explained in an easy to understand way.
Open circulatory system
A system in which blood moves through open spaces as well as vessels. Open circulatory system. In an open circulatory system, blood flows freely around the body's organs instead of being contained entirely within blood vessels.