Fish are aquatic animals with streamlined bodies, fins instead of limbs, and gills. Gills are organs that extract oxygen from the water and excrete carbon dioxide. Vertebrata is home to all fish, amphibians, reptiles, mammals and birds. They are also studied by scientists for clues as to how vertebrates (animals with backbones) evolved.

In contrast, invertebrates lack a backbone and are immensely diverse, making up about 97% of all known animal species. This group encompasses several phyla, including Arthropoda (insects, spiders, crustaceans), Mollusca (snails, clams, octopuses), Annelida (earthworms, leeches), and many others. Vertebrates, belonging to the phylum Chordata, have a backbone or spinal column, which forms the main support structure for the body and houses the spinal cord. This group includes mammals, birds, reptiles, amphibians, and fish.

• Only after their small movements were noticed in 1765 did the animal nature of sponges slowly come to be recognized.
• Animals originated in the ocean; all extant animal phyla, except for Micrognathozoa and Onychophora, feature at least some marine species.
• Although seemingly more like plants than animals, sponges are nevertheless members of Animalia.
• Diversity of form, in contrast to size, only impinges peripherally on human awareness of life and thus is less noticed.

Animals differ from members of the two other kingdoms of multicellular eukaryotes, the plants (Plantae) and the fungi (Mycota), in fundamental variations in morphology and physiology. This is largely because animals have developed muscles and hence mobility, a characteristic that has stimulated the further development of tissues and organ systems. Lizards, dinosaurs, crocodiles, turtles, and snakes – all belong to that ancient and stout class of animals known as the reptiles. This is a diverse group with more than 10,000 different species and a huge representation in the fossil record.

• They can be found in nearly every environment on the planet, and they currently account for over half of all known living organisms in the world.
• In 1874, Ernst Haeckel divided the animal kingdom into the multicellular Metazoa (now synonymous with Animalia) and the Protozoa, single-celled organisms no longer considered animals.
• Click on the images and links below to explore different aspects of the animal kingdom.

What are the basic functional systems of animals?

More than half are passerines, or “perching birds”, members of the order Passeriformes. Passerine feet have three forward-facing toes and one backward-facing toe, an arrangement favorable to perching. Most mollusks live in the sea, but some, such as snails and slugs, are also found on land. In order to be placed in the animal kingdom, rather than another kingdom, an organism must have certain characteristics, which are listed in the following section.

The animal kingdom

Other than out of simple curiosity, humans study animals to learn about themselves, who are a very recent product of the evolution of animals. Animals differ from plants and fungi in fundamental variations in morphology and physiology, notably in regard to animals’ development of muscles and mobility. The two major groups of animals are vertebrates and invertebrates. They usually have gills, paired fins, a long body covered with scales, and tend to be cold-blooded. “Fish” is a term used to refer to lampreys, sharks, coelacanths and ray-finned fishes, but is not a taxonomic group, which is a clade or group containing a common ancestor and all its descendants. Our comprehensive animal database serves educators, researchers, students, and nature lovers across educational institutions, wildlife organizations, and conservation groups globally.

Types Of Invertebrates

Carl Linnaeus created the first hierarchical biological classification for animals in 1758 with his Systema Naturae, which Jean-Baptiste Lamarck expanded into 14 phyla by 1809. In 1874, Ernst Haeckel divided the animal kingdom into the multicellular Metazoa (now synonymous with Animalia) and the Protozoa, single-celled organisms no longer considered animals. Explore the fascinating world of reptiles through scientific knowledge and comprehensive research. From savage crocodiles to exotic snakes, discover how they have evolved unique characteristics, behaviors, and adaptations that help them thrive in diverse ecosystems.

Invertebrates

The most common pets include dogs, cats, fish, and birds, but there are also many amazing exotic pets like reptiles, lizards, and more! Unlike invertebrates, vertebrates (members of the subphylum Vertebrata) form a scientific group in animal classification. Animal Pedia is a growing digital encyclopedia that brings the animal kingdom to life, currently featuring an extensive collection of reptiles species. We offer comprehensive species profiles and clear scientific insights into biodiversity, and ecology. Perfect for wildlife enthusiasts, students, researchers or even casual learners, Animal Pedia makes learning about animals engaging and accessible.

Animals That Can Survive the Harsh Vacuum of Space

In animal classification, each animal is grouped based on various features, such as physical characteristics, genetic relationships, and evolutionary history. Animal classification provides a structured way to name, rank, and classify the millions of animal species discovered. Although all animals share the above characteristics, animals exhibit diverse body plans, life cycles, and forms of behavior. The kingdom Animalia is one of the most diverse groups of organisms on the planet, containing millions of species spread across various habitats around the globe. To have the classification of an amphibian, an animal must be a vertebrate, require water to survive, be cold-blooded, and spend time both on land and in water.

Joeys undergo further development within a special pouch in the mother’s body. The majority of the world’s marsupials are found in Australia (including New Guinea and nearby islands); the rest are found in the Americas. Last but not least we come to the mammals, members of the class Mammalia. Mammals have hair, are warm-blooded, breathe air, and all but five species give birth to animal spirits live young. Amphibians have moist skin, and lack the protective scales found in reptiles.

Terms such as “kingdom”, “order” and “family” are explained in the “Animal Classification” section, below. Discover how zoologists classify animals into groups such as classes, orders, and families. Click on the images and links below to explore different aspects of the animal kingdom. The National Geographic Photo Ark is a multiyear project creating intimate portraits of every species in captivity to inspire people to help ensure their survival in the wild.

You might think of coral as the rocky substance that makes coral reefs. In fact, corals are invertebrate animals that, in their larval form, are able to swim. Most corals remain in their larval form for just a few days before settling in a suitable position. Vertebrates and invertebrates are two major divisions within the kingdom Animalia, differentiated primarily by the presence or absence of a backbone.

History of classification

Lancelets are small fish-like animals with translucent bodies. Although they don’t have a backbone – and are therefore not vertebrates – they do possess a flexible central nerve cord called a notochord. Animal classification is the scientific system used to categorize and organize the vast diversity of animals on Earth. Animals have evolved to live in a wide variety of habitats. On the pages below, you can explore various habitats and the animals found in each. See lists of animals that start with every letter of the alphabet, from A to Z.

The presence of muscles and mobility is one of the primary characteristics of the animal kingdom. Animals that are considered mammals include warm-blooded vertebrates that have hair or fur and whose babies drink milk. Unlike other animal types like birds and insects, all mammal babies drink milk that comes from their mother’s bodies.