Living beings appeared on Earth billions of years ago. Archaeologists can infer the age of their existence from the biological fossils discovered and tell us how animals evolved.
About 1 billion years ago, spineless invertebrates appeared in the ocean, much like today's jellyfish and sponges. It was not until more than 400 million years ago that vertebrates began to appear. These were primitive fish. Some fish developed lungs and could breathe air directly. They came to land and, like today's frogs, were able to live both in water and on land. They were called amphibians and appeared more than 300 million years ago.
Reptiles come from amphibians. Around 200 million years ago, dinosaurs began to dominate the Earth. However, 65 million years ago, they suddenlyement and mysteriously disappeared, including many of their reptilian relatives. and birds and mammals took their place.
Mammals were particularly weak during the time of the dinosaurs, but later became the dominant animals on earth. Man is one of the last mammals to have evolved, our ancestors having appeared on Earth only 2 million years ago.
The giant crow is a giant invertebrate that can measure up to 18 meters long.
Invertebrates have no common characteristics, except for a few, and they are related to each other in different ways.
Some invertebrates, like hydra, look more like plants than animals, and it is easy to confuse them with algae.