What is Considered as an Animal: Understanding the Definition and Characteristics

Animals are a diverse group of organisms that inhabit our planet. From the majestic elephants to the tiny ants, the animal kingdom is full of fascinating creatures. But what exactly is considered an animal? Most people think of mammals, birds, and reptiles when they hear the word animal, but the truth is that the definition is much broader than that. In fact, animals range from sponges in the ocean to insects on the land, and everything in between.

One interesting fact about animals is that they are multicellular organisms, meaning that they are made up of more than one cell. This includes not only the more commonly known animals such as lions and tigers, but also organisms like nematodes and flatworms. All animals are also heterotrophs, meaning that they must consume other organisms for energy. This can involve anything from plants to prey animals. Despite these similarities, animals come in a wide range of shapes, sizes, and forms and have unique adaptations that allow them to survive in their respective habitats.

The question of what is considered an animal is much more complicated than it may seem. In fact, scientists are still discovering new species every year and refining the definition of what qualifies as an animal. From the microscopic to the gigantic, animals come in all shapes and sizes, and their sheer diversity is a testament to the power of evolution. As we continue to learn more about these fascinating creatures, we can gain a deeper appreciation for the incredible biodiversity of our planet.

Classification of Animals

Animals are a diverse group of organisms that share certain characteristics. They are multicellular eukaryotic organisms that are heterotrophic, meaning they obtain their nutrients by consuming other organisms. Scientists have classified animals into various groups over time, based on various criteria, including cell structure, mode of nutrition, and body plan.

Animal Taxonomy

  • Kingdom Animalia: includes all animals, from sponges to mammals.
  • Phylum: the second level of classification, based on body plans, often identified by unique structures like body symmetry, the presence or absence of a skeleton, or the type of body cavity.
  • Class: the third level of classification, which further divides organisms into groups based on their shared characteristics.
  • Order: the fourth level of classification, which includes groups of similar families.
  • Family: more closely related than animals in different families, groups of genera share many characteristics and evolutionary relationships with one another.
  • Genus: more closely related than animals in different genera, groups of species share many characteristics and evolutionary relationships with one another.
  • Species: the most specific level of classification, only animals that can interbreed and produce viable offspring belong to the same species.

Body Plan

Body plan refers to the way an animal’s body is organized, including the basic structural features that determine how an organism interacts with the environment. Animals can be grouped based on their body plan, which includes characteristics such as the number of body layers, symmetry, body cavity type, and segmentation

The basic body plans of animals are:

  • Asymmetrical: animals that lack a definite shape and cannot be divided into equal halves by any plane. Example: Sponges.
  • Radial symmetry: animals that are identical all around a central axis, like the spokes on a wheel. Example: Cnidarians, like jellyfish and sea anemones.
  • Bilateral symmetry: animals that can be divided into two mirror-image halves by a single plane running down the midline of the organism. Example: Mammals, Birds, and Fish.

Classification Table

Kingdom Animalia
Phylum – Porifera
– Cnidaria
– Platyhelminthes
– Annelida
– Arthropoda
-Chordata, etc.
Classes – Mammals
– Birds
– Reptiles
– Fish, etc.

Finally, the classification of animals is continually evolving, as scientists make new discoveries and reanalyze old ones. So, how researchers group or categorize animals today might not be the same tomorrow.

Characteristics of Animals

Animals are fascinating creatures that come in all shapes and sizes. They belong to the kingdom Animalia, which is one of the five kingdoms of living things. Animals share several characteristics that distinguish them from other living organisms.

  • Cellular organization: Animals are made up of one or more cells, which are the basic building blocks of life.
  • Heterotrophic nutrition: Unlike plants, animals cannot make their own food. They must consume other organisms to get the energy and nutrients they need.
  • Movement: Animals are capable of moving on their own due to the presence of muscles and a nervous system.
  • Reproduction: All animals have the ability to reproduce sexually or asexually, depending on the species.
  • Growth and development: Animals go through a series of changes as they grow and develop from a fertilized egg into an adult.

While all animals share these common traits, there is a vast diversity among them in terms of their physical and behavioral characteristics. Some are adapted for life on land, while others thrive underwater. Some are solitary, while others live in large social groups.

Furthermore, animals can be classified into different groups based on their evolutionary history, physical features, and genetic makeup. This system of classification, known as taxonomy, helps scientists organize and study the vast array of animal life on Earth.

Types of Animals

There are several different types of animals, each with its own unique characteristics. These include:

  • Vertebrates: Animals with a backbone, including mammals, birds, reptiles, amphibians, and fish.
  • Invertebrates: Animals without a backbone, such as insects, spiders, worms, and mollusks.
  • Mammals: Animals that nurse their young with milk, have hair or fur, and are warm-blooded.
  • Birds: Animals that have feathers, a beak, and lay eggs.
  • Reptiles: Animals that have scales, are cold-blooded, and lay eggs.
  • Amphibians: Animals that can live both in water and on land, have smooth skin, and lay eggs in water.
  • Fish: Animals that live in water, have scales and gills, and lay eggs.

Diversity of Animals

The diversity of animals is truly staggering, with over 1 million known species and many more yet to be discovered. From tiny insects to massive whales, animals come in a variety of shapes, sizes, and colors.

Group Examples
Mammals Dogs, cats, elephants, whales, bats, humans
Birds Eagles, penguins, parrots, ostriches, ducks
Reptiles Snakes, turtles, alligators, lizards, crocodiles
Amphibians Frogs, toads, salamanders
Fish Salmon, tuna, sharks, clownfish, seahorses
Invertebrates Spiders, insects, crustaceans, jellyfish, starfish, worms

Each species has its own unique adaptations that have allowed it to survive and thrive in its particular environment. Studying these adaptations can help us learn more about the incredible diversity of life on our planet.

Animal Kingdom

The animal kingdom, also known as Animalia, is one of the five kingdoms in biology. This kingdom is composed of multicellular organisms that are heterotrophic, meaning they consume other organisms to obtain their nutrients and energy. The animal kingdom is diverse and can be divided into different subcategories based on various characteristics.

What is Considered as an Animal?

  • Animals are eukaryotic, meaning they have cells with a nucleus and membrane-bound organelles
  • They lack a cell wall
  • Animals are motile, meaning they can move independently
  • They exhibit symmetry, which can either be radial or bilateral
  • Animals have specialized sensory organs and nervous systems for sensing the environment and responding to stimuli

Subcategories of the Animal Kingdom

The animal kingdom can be classified further into subcategories based on different characteristics such as body plan, embryonic development, and genetic makeup. Some of the major subcategories include:

  • Vertebrates – animals with a backbone or spinal column. These include mammals, birds, reptiles, amphibians, and fish.
  • Invertebrates – animals without a backbone or spinal column. These include insects, crustaceans, arachnids, mollusks, and echinoderms.
  • Chordates – animals with a notochord, which is a flexible rod that supports the body. These include vertebrates as well as some invertebrates such as tunicates and lancelets.
  • Arthropods – animals with jointed legs and exoskeletons. These include insects, spiders, and crustaceans.

Diversity in the Animal Kingdom

The animal kingdom is incredibly diverse, with over 1 million known species and likely many more still undiscovered. Animals come in all shapes and sizes, from microscopic organisms to the largest animals on the planet such as the blue whale. They live in a variety of environments, from the depths of the ocean to the land and air.

Class Examples
Mammals Humans, elephants, dogs, whales
Birds Eagles, penguins, ostriches, parrots
Reptiles Turtles, snakes, lizards, crocodiles
Amphibians Frogs, salamanders, newts
Fish Sharks, salmon, clownfish
Insects Butterflies, ants, bees, beetles
Mollusks Snails, octopuses, squid

The animal kingdom is a fascinating and complex group of organisms. From tiny insects to massive whales, animals come in all shapes and sizes and play important roles in ecosystems around the world.

Domestic Animals

Domestic animals are those that are commonly kept and raised by humans for various purposes, such as companionship, food, transportation, and labor. The following are some of the most well-known domestic animals:

  • Dogs: Known as man’s best friend, dogs are kept as companions, guard dogs, therapy animals, and police dogs.
  • Cats: Domesticated for thousands of years, cats are popular household pets that also help control rodent populations.
  • Cattle: Raised for their milk, meat, and leather, cattle are domesticated bovines that have been bred for centuries to increase their productivity.
  • Chickens: The most common type of poultry, chickens are kept primarily for their eggs and meat.
  • Horses: Known for their strength and speed, horses have been domesticated for transportation, racing, and work purposes for thousands of years.
  • Pigs: Domesticated pigs are raised for their meat and also for scientific research.
  • Sheep: Domesticated for their wool, milk, and meat, sheep have been selectively bred for their desirable traits for thousands of years.
  • Rabbits: Often kept as pets, rabbits are also raised for their meat and fur.
  • Goats: Domesticated goats are raised for their milk, meat, and wool, and are also used for weed control and as pack animals.


The domestication of animals is a process that has occurred over centuries, where animals are selectively bred to enhance desired traits and remove undesirable ones. In many cases, domesticated animals have evolved from wild ancestors and have adapted to living in close proximity to humans. Selective breeding has allowed for domesticated animals to have more predictable behaviors, better physical attributes, and increased productivity for human use.

Animal Welfare

As domestic animals are often kept in captivity and used for human purposes, their welfare is an important consideration. Many animal welfare organizations work to ensure that domesticated animals are treated humanely and have their basic needs met, such as access to appropriate food, shelter, water, and veterinary care. Responsible pet ownership and farm animal husbandry practices also play a role in ensuring animal welfare standards are met.

Comparison of Domestic Animals

Animal Main Use Lifespan Breeding Cycle Distinctive Feature
Dog Companionship, Protection, Work 8-16 years 2 cycles per year Variety of breeds and sizes
Cat Companionship, Rodent Control 12-20 years 3 cycles per year Flexible bodies and sharp claws
Cattle Milk, Meat, Leather 18-22 years 1 cycle per year Large size and docile demeanor
Chicken Eggs, Meat 5-10 years 1 cycle per month Varied feather colors and patterns
Horse Transportation, Racing, Work 25-30 years 1 cycle per year Powerful muscles and swift speed
Pig Meat, Research 9-15 years 1 cycle per year Omnivorous and intelligent
Sheep Wool, Milk, Meat 7-12 years 1 cycle per year Placid temperament and soft wool
Rabbit Meat, Fur, Pets 8-12 years 4 cycles per year Long ears and soft fur
Goat Milk, Meat, Wool, Weed Control, Packing 10-15 years 1 cycle per year Curved horns and surefootedness

While all domestic animals have their unique qualities and uses, they all play an important role in human society. Responsible ownership, breeding, and welfare practices can ensure that these animals have a good quality of life, while also meeting human needs and demands.

Wild animals

Wild animals are those that are not domesticated or tamed and live in their natural habitat. These animals generally have a high level of adaptation to their surroundings and a predator-prey relationship with other species.

  • Lion – Known as the king of the jungle, lions are fierce predators that can be found in sub-Saharan Africa and parts of Asia. With their muscular build, sharp teeth and claws, lions are at the top of the food chain in their habitat.
  • Tiger – Tigers are the largest of the big cats and can be found in parts of Asia. They are solitary animals that occupy large territories and are known for their exceptional hunting skills.
  • Brown bear – Brown bears are found in parts of North America, Europe, and Asia. The brown bear is a large and powerful predator that can weigh up to 1,500 pounds. They are omnivores and will eat anything from grass and berries to fish and small mammals.

Wild animals are an important part of the ecosystem and play a vital role in maintaining the balance of nature. However, many species are threatened by habitat loss, poaching, and other human activities.

Many conservation efforts have been put in place to protect wild animals and their habitats. Initiatives such as national parks and reserves, anti-poaching laws, and public education campaigns have helped to raise awareness about the importance of preserving these species and their habitats.

Species Conservation Status
African Elephant Vulnerable
Giant Panda Endangered
Siberian Tiger Endangered

It’s important for us to do our part in protecting these magnificent animals and their habitats so that future generations can enjoy the natural beauty and diversity of our planet.

Endangered species

Endangered species are animals that are at risk of becoming extinct due to a variety of factors such as loss of habitat, climate change, pollution, and competition with non-native species. The World Wildlife Fund estimates that there are currently over 17,000 animal species at risk of becoming extinct.

Causes of endangerment

  • Habitat destruction: Deforestation, agricultural expansion and urbanisation cause habitat degradation and fragmentation that can lead to loss of biodiversity and consequential extinction of species
  • Climate change: Changes in temperature, precipitation, sea level, and ocean acidity are already affecting species’ behaviour, geographic range, and reproduction, leading to species extinction
  • Pollution: Landfills, pesticides, fertilisers and toxic waste can have detrimental effects on animal health, leading to a decrease in population

Efforts to conserve endangered species

Governments, organisations and individuals have made efforts to prevent extinction of endangered species by using methods such as:

  • Legal protection through laws and regulations banning hunting, trading, or exploitation of these animals
  • Research on their habitat, population, and behaviour to develop conservation strategies
  • Reintroduction programs aimed at breeding and releasing animals back into the wild after regaining stable populations in captivity
  • Preserving genetic diversity through cryopreservation of animal tissues and seeds for future use in breeding programs

Examples of endangered species

Some of the most iconic endangered animals include:

Animal Reason for endangerment
Panda Habitat loss due to deforestation
Tiger Poaching and habitat loss
Rhino Poaching for horn and habitat loss
Orangutan Habitat loss due to deforestation

Efforts to conserve and rebuild populations of these species continue to be important in preserving biodiversity and ensuring the survival of endangered animals.

Animal Behavior

Animal behavior refers to the actions and reactions of animals to different stimuli in their environment. It encompasses a wide range of activities, including how animals communicate, interact with each other, find food, and defend themselves against predators. Studying animal behavior is important because it provides insights into how animals survive and adapt to their environment.

  • Social behavior: This refers to how animals interact with each other. Social behavior can involve cooperation, aggression, and competition. Some animals form complex social structures, such as packs or herds.
  • Mating behavior: Animals have evolved different ways of attracting and selecting mates. Some use elaborate displays, while others rely on chemical signals or vocalizations.
  • Foraging behavior: This refers to how animals find food. Some animals are solitary hunters, while others hunt in packs. Still, others rely on scavenging or grazing.

Animals also exhibit a range of instinctual behaviors, which are programmed into their DNA. These can include migration, hibernation, and nesting. Instinctual behaviors are crucial to an animal’s survival, and they often occur without the need for learning or experience.

Scientists use a variety of research methods to study animal behavior, including observation, experimentation, and modeling. They also use technologies such as GPS tracking and bioacoustics to gain insights into animal behavior that were previously impossible to obtain.

Example: Animal Behavior:
Birds flying in a V-formation Social Behavior
Peacocks displaying their feathers to attract mates Mating Behavior
Lions hunting in packs Foraging Behavior

Overall, animal behavior is a complex and fascinating field of study. By understanding how animals behave in their natural habitats, scientists can gain valuable insights into the workings of the natural world.

What is Considered as an Animal: FAQs

1. What is considered as an animal?

Animals are living organisms that are classified under the kingdom Animalia. They are multicellular, eukaryotic, and have specialized tissues. They vary in size, shape, and behavior.

2. Are insects considered as animals?

Yes, insects fall under the animal classification. They are part of the arthropod group, which includes crustaceans, spiders, and centipedes.

3. Are fish considered as animals?

Yes, fish are also considered as animals. They are part of the aquatic vertebrates group, along with amphibians, reptiles, birds, and mammals.

4. Are bacteria considered as animals?

No, bacteria are not part of the animal kingdom. They belong to a separate classification called Monera, which includes all prokaryotic organisms.

5. Are humans considered animals?

Yes, humans are classified as animals under the kingdom Animalia. They are part of the mammalian group and share similarities with other primates.

6. Do animals have emotions?

There is ongoing debate and research about whether animals have emotions. Some studies suggest that animals can experience and express emotions, while others argue that their behaviors are based on instincts.

7. Why is it important to understand what is considered as an animal?

Understanding what is classified as an animal is important for several reasons. It helps in scientific research and classification, conservation efforts, animal welfare, and our understanding of the natural world.


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