The Biology of Animals

Have you ever wondered why people keep animals around them? People throughout history have taken an interest in studying animal behavior, psychology, physiology, and intelligence. Today, people all over the world keep animals as pets and companions. In this article, we will learn about why animals are kept by humans.


Humans need animals for a variety of reasons. The majority of us would never care to live alone, let alone rear animals the way that animals are raised in captivity. Animals provide food, companionship, and protection. They allow a person to be near them and experience what it is like to be close to another life form. In fact, many people choose to keep animals simply because they enjoy being around them and having their presence nearby.

The first animals to be kept as pets were probably not very different from the animals we have today. A horse was probably looked upon as a simple beast that could be handled to entertain a visitor or two. As animals evolved into more complex beings, they were able to become capable of running faster and carrying more weight than the simpler animals. As they started to evolve into birds and even insects, they became capable of better movement, flight, and exoskeleton design.

The animals’ ability to grow and reproduce gave rise to new animal cells that occupied different locations in the animal body. In fact, animals are classified as having a single organ or body part – the brain for the most part – while other animals develop many organs and body parts. These new cells are often called organ cells and can form organs such as kidneys, lungs, stomachs, spleen, intestines, and other important organs. The development and organization of these new cells depends on the specific type of animal cell that is found in a particular area of an animal’s body.

One classification of animals that is a bit of a mystery is the unicellular algae that grow in the water of alkaline bodies. They were regarded by early Greeks and Romans as creatures that had no developed brains, since they were not multicellular organisms. It was only with the advent of microscope technologies that unicellular algae began to be viewed as a real living creature, although it was still difficult to see how they were organized and how their structure related to that of other organisms.

The study of animals and how they are related to plants is an extremely important part of the study of nature. This is why animals and plants are classified according to whether they are land animals, aquatic animals, or e.g. invertebrates, reptiles, and birds. It is also possible to classify animals according to their mode of growth, i.e.