UPSC Biology Animal Kingdom The Animal Kingdom

The Animal Kingdom

Category : UPSC

The Animal Kingdom




Of the million or more animal species in the world, more than 98% are invertebrates. Invertebrates don’t have an internal skeleton made of bone. Many invertebrates have a fluid-filled, hydrostatic skeleton, like the jelly fish or worm. Others have a hard outer shell, like insects and crustaceans. There are many types of invertebrates. The most common invertebrates include the protozoa, annelids, echinoderms, mollusks and arthropods. Arthropods include insects, crustaceans and arachnids.


(i) Protozoa

Protozoa are simple, single-celled animals. They are the smallest of all animals. Most protozoa are microscopic in size, and can only be seen under a microscope. However, they do breathe, move and reproduce like multicelled animals.


There are several types of protozoa. The amoebas are dear, shapeless cells. Flagellates have a body shape looking like a hair. Although we can't see them, protozoa do a lot for us. Protozoa play a useful role in the food chain as a source of food for fish and other animals. Some protozoa are helpful to humans by eating dangerous bacteria. Unfortunately, other protozoa are parasites and can be harmful to humans by transmitting disease.


Protozoa eat tiny algae and bacteria. Some protozoa absorb food through their cell membrane. Others surround and engulf their food or have openings to collect food. They digest their food in stomach-like compartments called vacuoles. Protozoa take in oxygen and give off carbon dioxide through the cell membrane. Protozoa reproduces by splitting in half.


(ii) Worms and Leeches

There are about 9,000 species of Annelids known today, including worms and leeches. They can be found almost anywhere in the world. Annelids have existed on Earth for over 120 million years.


Annelids have bodies that are divided into segments. They have very well-developed internal organs. One common characteristic of annelids is that they don't have any limbs.


Some annelids may have long bristles. Others have shorter bristles and seem smooth, like the earthworm.


There are many types of worms. Commonly known worms include earthworms, roundworms and flatworms. Most worms are small, measuring fractions of an inch to several inches long. Other worms, such as the ribbon worm, can grow up to 100 feet in length. Some worms are considered Parasites, in that they live inside the human body.


(iii) Mollusks

Mollusks were among the first inhabitants of the Earth. Fossils of mollusks have been found in rocks and date back over 500 million years. Mollusk fossils are usually well preserved because of their hard shell. Most mollusks have a soft, skin-like organ covered with a hard outside shell. Some mollusks live on land, such as the snail and slug. Other mollusks live in water, such as the oyster, mussel, clam, squid and octopus.


Land living mollusks, like the snail, move slowly on a flat sole called a foot. Ocean living mollusks move or swim by jet propulsion. They propel themselves by ejecting water from their body. For example, the squid ejects water from a cavity within its body, and the scallop ejects water to move by clamping its shell closed. Other ocean living mollusks, like the oyster, attach themselves to rocks or other surfaces, and can’t move. They feed by filtering small food particles from water that flows through them. Snail and Slug the snail family consists of marine snails and land snails all over the world. Land snails live in many habitats from gardens and woodlands, to deserts and mountains. Marine snails are native to all the worlds oceans and seas, and many freshwater rivers and lakes. Along with slug, snails make up the gastropod class of the mollusk phylum. Snails have an external shell, large enough to withdraw their body into it. Gastropods without a shell are known as slugs.



There are about 300 different species of octopus native to many of the world's oceans, especially coral reefs. The octopus doesn’t have an internal or external skeleton, allowing it to squeeze into very small places. The octopus has eight arms or tentacles, that it uses for crawling, exploring things and catching prey. The octopus’ arms have suckers capable of grasping and holding objects, such as their prey. The octopus has a hard beak in the center of its arms that it uses to tear apart its prey for eating. Like the squid, the octopus can suck water into its mantle and expel it out in a fast, strong jet. This jet propulsion provides fast, forward movement. Also like the squid, the octopus can eject a thick cloud of ink to help it escape from predators.


(iv) Squid

There are about 300 species of squid. They are native to most of the world’s oceans. The squid has a distinct head, eight arms and two tentacles. The mouth of the squid has a sharp horny beak used to kill and tear its prey into small pieces. The main body of the squid is enclosed in the mantle, which has a swimming fin along each side. However, the swimming fin is not the squid's main way of moving through the water. The squid can suck water into the mantle and expel it out in a fast, strong jet. This jet propulsion provides fast, forward movement. Although most squid are less than 2 feet in length, the giant squid can grow up to 43 feet in length.


(v) Cuttlefish

Despite their name, the cuttlefish is not a fish, but a mollusk. The cuttlefish is native to all of the oceans of the world, but are more common in shallow coastal temperate and tropical waters. The cuttlefish has an internal shell or bone, called the cuttlebone that helps them to be buoyant. Attached to this body feeding tentacles. The cuttlefish can easily camouflage itself by changing its skin color and pattern to blend in with its background. This helps the cuttlefish to hide from predators, and the sneak up on its prey. Like the squid and octopus, the cuttlefish can eject ink in an effort to escape from predators. This ink, called sepia, was once used as a dye to create ink used by artists.


(vi) Nautilus

The nautilus is native to deep ocean waters. It has a multi-chambered shell. Each chamber is sealed and contains gas which provides the nautilus with buoyancy to float. Like the octopus, squid and cuttlefish, the nautilus uses jet propulsion to move forward. It sucks in water, then expels it in a fast, strong stream to propel itself forward. The nautilus has as many as 90 small tentacles that it uses to catch food, such as shrimp, fish or small crustaceans. It then uses its powerful beak to crush the food. The nautilus is considered a living fossil because its form has remained unchanged for over 400 million years.


(vii) Echinoderms: Starfish, Sea Urchin and Family

Echinoderms are marine animals that live in the ocean. Common echinoderms include the sea star, sea urchin, sand dollar and sea cucumber. Most echinoderms have arms or spines that radiate from the center of their body. The central body contains their organs, and their mouth for feeding.


Sea stars, commonly known as the starfish, have 5 or more arms attached to their body.

On the bottom of the Starfish are small tube feet to help with movement and feeding. The starfish’s mouth is underneath, and is capable of eating other sea life such as clams and mussels. Another type of echinoderm is the sea urchin. Sea urchins have many spines connected to their body. These spines help to protect them from predators.


(a) Starfish

The starfish or sea star is native to all of the world’s oceans. There are about 1,800 different species of starfish with the greatest variety living in the tropical Indo-Pacific region. Most starfish have five arms, although some have fewer or more arms. Like other echinoderms, starfish have small tube feet on their underneath body to help with movement and feeding. The starfish's mouth is underneath, and it has two stomachs in the mouth. The stomach sack can come out through the mouth to engulf and digest food, such as clams and mussels.


(b) Crustaceans

Crustaceans are a type of Arthropod. The name may not sound familiar, but you probably know them. You may even have eaten one.


Crustaceans live mostly in the ocean or other waters. Most commonly known crustaceans are the crab, lobster and barnacle.


Crustaceans have a hard, external shell which protects their body. Crustaceans have a head and abdomen. The head has antennae which are part of their sensory system. The abdomen includes the heart, digestive system and reproductive system.


The abdomen also has appendages, such as legs, for crawling and swimming. Many crustaceans also have claws that help with crawling and eating.


(viii) Crab

There are about 10,000 different species of crab. The crab is native to all of the world’s oceans. There are also freshwater crabs, and even some crabs that live on land. Crabs have a large, hard shell. Extending from the front of its shell are the eyes, mouth and two pairs of antennae. The crab has 5 pairs of legs extending from the side of its shell. The first pair of legs have claws or pincers used to catch and hold food. The other pairs of legs are used for walking. Most crabs don’t swim, they use their legs to walk. However, some crabs such as the Blue Crab can use their legs as paddles to swim.


(a) Lobster

Lobsters are native to most oceans of the world. The lobster habitat is rocky, sandy or muddy ocean bottom and they are generally found hiding in crevices or in burrows under rocks. Lobsters have five pairs of legs, the first pair of legs are claws used to catch and hold food. Lobsters have a large exoskeleton. As lobsters grow, the must molt to shed their old exoskeleton as they grow a larger new shell


(b) Shrimp

Shrimp are native to many of the world’s oceans and lakes. They are generally found in shallow water. Their habitat includes both fresh and salt water. Although most shrimp are small, some can grow up to 9 inches in length. The shrimp has a very simple body consisting of the head and thorax, and a muscular abdomen for swimming. They have 8 pairs of legs, 5 for swimming and 3 for feeding. They also have 2 pairs of antennae use for taste and smell to find food. As a crustacean, the shrimp has a thin, almost transparent, exoskeleton. The shrimp is a popular food. In addition to commercial fishing for shrimp, shrimp are also grown in shrimp farms. Shrimp are also commonly found in aquariums.


(ix) Arachnids: Spiders, Ticks and Scorpions

Arachnids are a type of arthropod. You know many of them as spiders. Common arachnids are spiders, scorpions, ticks and mites.


Like other arthropods, the arachnids have a hard exoskeleton and jointed appendages for walking. Most arachnids have. 4 pairs of legs. In some, the first pair of legs may be used for holding their prey and feeding. Unlike other arthropods, arachnids do not have antennae.


Spiders are easily recognized with their 8 legs. All legs are used for walking. The first pair of legs is also used for holding prey and feeding. The second pair of legs may also be used for holding and killing their prey. Most spiders have 8 eyes. Spiders have fangs that are used to inject poison to paralyze or kill their prey. Many spiders can produce silk threads to spin webs for catching prey, and for building an egg sack to hold and protect their eggs.


Scorpions are large arachnids, some reaching over 8 inches in length. They have 4 pairs of legs, and a pair of pincers for catching and holding their prey. Scorpions also have a sharp stinger at the end of their tail that is used to paralyze or kill insects and small animals. Mites and ticks are small arachnids that are parasites living on the blood and tissue fluid of other animals. They can occasionally transmit disease. The abdomen also has appendages, such as legs, for crawling and swimming. Many crustaceans also have claws that help with crawling and eating.


(a) Scorpion

Scorpions are native to many parts of the world. There are about 1,400 different species of scorpion. They prefer warm or hot. climates, but can even be found in cold, snowy areas. Their habitat includes deserts, grasslands and savannahs, forests, intertidal zones, mountains and caves. Scorpions are best known for their long, segmented tail with its venom-injecting barb. The scorpion will use its venomous stinger to capture prey and defend against predators. Scorpions have four pairs of legs and a pair of pincer-like pedipals. These pincers can also be used to catch prey and defend against predators. Scorpions are nocturnal animals. They prefer to find shelter during the day m underground holes or under rocks where it is cool. They come out at night to hunt and reed. Most scorpions prey on insects, spiders, centipedes, and other scorpions. Large scorpions may also prey on small lizards, snakes and mice.


(b) Spider

Spiders are found world-wide on every continent except for Antarctica, There are approximately 40,000 different species of spiders. Spiders vary in size from quite small to relatively large. The Goliath Bird eater can grow up to 10 inches measuring its leg span. Most people can easily recognize a spider by its eight legs. One spider, the Daddy Long Legs, is even named after its eight long legs.


Another recognizable feature related to the spider is its web. Spiders have spinneret glands they use to build webs. These webs provide shelter and help catch food. Spiders also have fangs. Many spiders can inject a venomous liquid through their fangs. This venom is capable of paralyzing or killing predators or prey. Some venom, such as from the Brown Recluse or Black Widow, can even be dangerous or deadly to humans. Although some people are scared of spiders, most spiders will only bite humans in self-defense. Fear of spiders is called arachnophobia. Most spiders have four pairs of eyes. This provides them with very good vision. Some spiders, such as the Tarantula, can be very hairy. While many people are scared of the tarantula, this spider is generally quite harmless. Some people even keep a tarantula as a pet.


(c) Tarantula

The tarantula is a large, hairy spider found in tropical to temperate regions of the southwestern United States, Mexico, Central America, South America, southern Europe, Asia, Africa and Australia. Tarantulas can go up to 4 inches in body size, and have a leg span of up to 12 inches.


Like other arachnids, the tarantula has eight legs, arranged in four pairs. It also has another pair of appendages used for feeling and gripping prey. The tarantula has two fangs used to inject venom into its prey, or in defense against predators. Tarantulas prefer to hunt at night. They will lay a web, but not to catch their prey. They lay strands of web on the ground to act as a trip wire. When an insect, frog, toad or mouse steps on the strand, alerting the tarantula, it will pounce on the unsuspecting victim.


Although many people find the tarantula scary, it is generally harmless to humans. They will not bite unless provoked, and if bitten the pain is usually similar to that of a bee sting. Some tarantulas have even become a popular pet.


(d) Spider Web

Spiders can produce silken thread using spinneret glands on their abdomen. This thread is very strong. It is stronger than a similar size thread of steel. Spiders use this silken thread for many things. A spider will spin a web to protect the entrance of their home from birds or wasps. A web is also used to catch insects or other food. The thread is sticky, and once an insect touches the web, it gets caught. Vibration of the web tells the spider an insect has flown or crawled into the web.


The spider will then wrap its prey in silken thread so it can't escape. The thread is also be used to attach an egg sack to the web. This protects the eggs until the young are born. Sometimes a web is used as a path between places where it is difficult to crawl. There are many different shaped spider webs. Some spiders spin a circular web, or orb web. Other webs look like funnels or tubes. Some webs look like a sheet.


(x) Insects

Insects are the largest group of arthropods. There are over 800,000 different types of insects. Insects are very adaptable, living almost everywhere in the world. Common insects include the fly, beetle, butterfly, moth, dragonfly, bee, wasp and praying mantis.


Insects have an exoskeleton that covers their entire body. An insect’s body consists of 3 parts: the head, thorax and abdomen.


The insect’s head has a pair of antennae, and a pair of compound eyes. Compound eyes are different from human eyes which have a single lens for each eye. Compound eyes have many lenses for each eye. For example, the fly has about 4,000 lenses in a single eye. This provides them with very good eyesight.


The thorax contains the legs for walking, swimming, jumping or digging. The thorax may also have wings for flying. The abdomen contains many body organs, such as the heart, respiratory system, digestive system and reproductive system. The insect’s hard, exoskeleton makes it difficult for the insect to grow and get larger. This is because the exoskeleton can’t grow and get larger. Many insects must molt in order to grow. Molting is the process where an insect sheds it outer skeleton. It wriggles out of this old skin, and a new, larger exoskeleton develops. Invertebrates were the first animals to evolve. The first invertebrates evolved from single-celled, food-eating microorganisms. Invertebrates are often most noted for what they lack: a backbone and a bony skeleton. Invertebrates account for 97 percent of all known species. The simplest invertebrates, in fact the simplest animals, are sponges. Most invertebrates change form as they grow, going through a process known as metamorphosis. Some species of invertebrates form large colonies. Invertebrates will eat almost anything that was or is alive. Many of the world’s parasites are invertebrates.



Animals with an internal skeleton made of bone are called vertebrates. Vertebrates include fish, amphibians, reptiles, birds, mammals, primates, rodents and marsupials.


Although vertebrates represent only a very small percentage of all animals, their size and mobility often allow them to dominate their environment.


(i) Fish

Almost three-fourths of the world’s surface is covered in water. This water is home to over 20,000 different species of fish. The earliest fossils offish date back over 400 million years. There are a wide variety of fish - from the goby which is less than one half an inch long, to the whale shark which can be over 60 feet long. Most fish breathe through gills. Gills perform the gas exchange between the water and the fish’s blood. They allow the fish to breathe oxygen in the water.


Fishes are vertebrates that have a skeleton made of either bone or cartilage. About 95% of fishes have skeletons made of bone. These bony fishes have a swim bladder, a gas-filled sac, that they can inflate or deflate allowing them to float in the water even when not swimming. Fishes with a cartilage skeleton tend to be heavier than water and sink. They must swim to keep afloat. Cartilaginous (cartilage) fish include the ray and the shark.


Most fish swim using a tail fin. Muscles in the tail fin move it from side to side, forcing water backward, and propelling the fish forward. Other fins help the fish change direction and stop. Pectoral fins on their side help them swim up and down. Dorsal and anal fins on the top and bottom keep the fish upright. Pelvic fins on the underside help steer left and right. Many fish eat plants, while others such as the shark, eat other fish. Flying Fish There are about 50 species of flying fish. They are found in all major oceans of the world, particularly in the warm tropical and subtropical waters of the Atlantic, Pacific, and Indian oceans. As their name implies, these fish can fly. They can’t fly as well as a bird, but they can take short flights through the air. Most flying fish use their large pectoral fins as wings. The fish can take short gliding flights above the surface of the water in order to escape from predators.


(a) Paddlefish

There are two different species of paddlefish: the Chinese paddlefish and the American paddlefish. The Chinese paddlefish lives in the Yangtze River in China. The American paddlefish lives in the Mississippi, Missouri, Des Moines, Yellowstone, Ohio and Oklahoma Rivers in the United States. The most recognizable feature of the paddlefish is its large mouth and long snout or bill. The spatula-like snout can be half the length of its body. This is why the paddlefish is sometimes called the spoon fish.


Facts about Fish

Fish are divided into three basic groups which include cartilaginous fish, bony fish, and lobe-tinned fish. Fish were the first animals to evolve backbones.


The ray-finned fish are the largest group of fish.

Fish move by creating a wave motion that moves the length of its body.


Fish are cold-blooded (ectothermic) animals.


Many species of cichlids brood their eggs in their mouth.


After the eggs hatch the parent continues to use their mouth to provide shelter for their young.


Cartilaginous fish include the sea’s largest and most skilled marine predators.


These include sharks, skates, rays, and chimeras. These fish have skeletons made from cartilage, not bone. The cartilaginous skeletons are more flexible than bone.


The lateral line system on some fish detects variations in water pressure.


This helps fish detect prey and avoid predators.


(ii) Amphibians

Amphibians lay their eggs in water, and young amphibians tend to resemble small fish.


The tadpole, or newborn frog, is born and lives in water, it has a tail that allows it to swim like a fish. It also has gills so that it can breathe under water. As the tadpole grow into a frog, it loses its gills and tail, and develops legs for moving on land. Most amphibians can both walk and swim in water.


Depending on the species of amphibian, breathing can take place in gills, lungs, the lining of the mouth, the skin, or some combination of these.


Amphibian’s body temperature changes with its environment. In cold climates, amphibians hibernate during the winter. There are over 6,400 species of amphibians found worldwide, except in Antarctica and Greenland. Amphibians are vertebrates and include animals such as frogs, toads, salamanders, newts and worm-like caecilians. They can be found on land, and in fresh water. They live in a variety of habitats from deserts to rain forests, permanent ponds or high mountain meadows. Most amphibians have four limbs, but some amphibians don’t have any limbs. Amphibians are cold-blooded meaning they use the environment to regulate their body temperature. Amphibians spend part of their life in water, and part of their life on land.


(iii) Reptiles: African Clawed Frog

The African Clawed Frog is native to South Africa, the sub-Saharan in east and southern Africa, and Namibia and Angola in western Africa, Their habitat includes warm stagnant pools and quiet streams. Their name comes from the three short claws on each of its hind feet. It spends most of its time underwater, only coming to the surface to breathe. African clawed frogs don’t have tongues. The frog's uses its front limbs and unwebbed fingers to push food into its mouth.


(a) Poison Dart Frog

The poison dart frog is a family of frogs native to Central and South America. Their habitat is humid, tropical areas such as tropical rainforests. They may live on the ground as well as in trees. Most poison dart frogs are brightly colored, which makes them easily recognizable and warns potential predators to stay away. Why do the predators stay away? As their name implies, this frog is highly poisonous. They secrete a toxin through their skin that is capable of killing a predator. Many species are critically endangered


(b) Frog

There are over 5,000 species of frogs. They are native to most of the world, except Antarctica. Generally, we think of frogs as having a short, stout body with long hind legs ideal for jumping. Most of us can recognize a frog’s call as the familiar croaking or ribbit sound. Another common characteristics is that frogs don’t have tails. The various species also have a wide range of different characteristics. Some frogs are small, such as the Coqui. Other frogs can be quite large, some frogs are even poisonous, such as the Poison Dart Frog.


(c) Reptiles: lizards, Snakes, Others

Reptiles have been around for 300 million years, even during the dinosaur age. The most common reptiles include alligators, crocodiles, lizards, snakes, tortoises and turtles. Reptiles are air-breathing animals, although many live not only on land but in water. The most noticeable feature of reptiles are the scales that cover their body. The majority of reptiles lay eggs to give birth to their young. Although reptiles breathe through lungs, some reptiles can also absorb oxygen in water through membranes in their mouth.


Reptiles are often called cold-blooded because they can’t regulate their own body temperature. Their body temperature depends on the external temperature. They will lay in the sun to heat their body, or hide in the ground, under a rock or in water to cool their body.

Crocodiles and alligators are large reptiles that spend much of their time on land and in water. They can walk on land using their webbed feet. They can also use their long tail to swim in water Crocodiles feed on large animals they catch on land or in water. They have powerful jaws and teeth to tear apart their prey. Lizards and snakes are the largest group of reptiles. Lizards are four legged animals with a long tail. Many lizards can shed their tail to escape from predators. They can then grow a new tail. Some lizards, such as the chameleon, can change colors to blend into their environment. This camouflage helps to protect them from predators.


Snakes don’t have limbs. They move by slithering along the ground. Some snakes are poisonous, or venomous, such as the rattle snake, cobra, and eastern green mamba. They have fangs which bite into their prey and inject poison into the victim. Other snakes, such as the boa constrictor and the python kill their prey by crushing it.


Most snakes can dislocate their jaw, allowing them to swallow prey much larger than themselves.


(d) Alligator

The alligator is native to the United States and China. Alligators are covered with scales, head to toe. They can grow up to fifteen feet long and weigh over one thousand pounds. Based on fossils, the alligator has been on earth for 200 million years. They have a very strong jaw, capable of crushing their prey. Alligators are cold-blooded. They lay eggs to produce their young.


(e) Anaconda Snake

The anaconda is a large, non-venomous snake native to tropical South America and Northern Africa. They mostly live in swamps or watery The green anaconda is the biggest snake in the world, with the largest measuring up to 37.5 feet in length. The anaconda is related to the boa constrictor snake. They kill their prey by constriction or squeezing. They wrap themselves around their prey and squeeze to prevent the prey from breathing. They then swallow the animal whole.


(f) Chameleon

The chameleon is a member of the lizard family native to Africa, Madagascar, southern Europe, and Asia. There are about 135 different species of chameleon. Their habitat includes rain forest, savanna, semi-desert, and steppe land. Chameleons are best known for their ability to change color. However, they don’t really change color to match their surroundings, but based on mood, such as fear or anger, and based on temperature and humidity. They are also known for their ability to move each eye separately, and for their long, sticky tongue. Their eye can rotate 360 degrees to view its prey, they its fast, sticky tongue can catch its prey.


(g) Cobra Snake

The cobra is a venomous snake native to Africa and Asia. There are about 30 different species of cobra, with the King Cobra being the world’s largest venomous shake. The cobra’s habitat ranges from tropical rain forests and swamps to savannas and deserts. The name cobra is Portuguese for “snake with hood.” Cobra’s are most famous for this hood, which is created by elongated ribs that extend the loose skin of the neck behind the snake’s head. Cobras will raise the front part of their bodies

and display their hood when threatened or disturbed. They will also make a hissing sound.


(h) Crocodile

The crocodile is native to tropical areas in Africa, Asia, the Americas and Australia. The crocodile is an ancient, prehistoric creature, believed to have inhabited earth for over 200 million years. The name crocodile comes from an Ancient Greek word meaning “lizard of the river.” Crocodiles prefer freshwater habitats like rivers, lakes and wetlands. Crocodiles are similar to alligators and caiman. They are very fast over short distances, even out of water. They catch their prey by waiting for fish or land animals to come close, then rushing out to attack.


(i) Coral Snake

The coral snake is a venomous snake native to southern United States including Arizona and from Louisiana to North Carolina, including all of Florida. Coral snakes are small in size, averaging 3 feet in length. They are a very beautiful snake with their red, yellow, white, and black colored banding. They are the second most venomous snake in the United States, behind the rattlesnake.



The iguana is a family of lizards native to tropical areas of Central and South America and the Caribbean. The green iguana, which is a popular pet, lives in tropical rainforest areas near water, such as rivers or streams. Other iguanas live in the dry, hot desert. Like other reptiles, the iguana is cold blooded meaning they do not produce their own body heat. If an iguana is cold, it will lie on warm rocks to soak up the sun's heat. Green iguanas are omnivorous meaning they eat both plants, and meat, but they mostly eat plants.


(j) Komodo Dragon

The komodo dragon is a lizard native to islands in Indonesia. They are a member of the monitor lizard family. They are the largest of the lizards, growing up to 10 feet in length and weight over 200 pounds. It is carnivorous, eating animals such as pig and deer. It is also cannibalistic, eating other komodo dragons. The komodo dragon has even been known to attack and kill humans. They are now an endangered species.


(k) Lizard

There are over 5,000 different types of lizards in the world. They are native to every continent, except Antarctica. Most lizards are small and harmless to humans. But, the large Komodo Dragon has been known to attack and kill humans. Lizards have some of the strangest characteristics. Some lizards can walk on water. Others can lose their tail to escape a predator Others can squirt blood from their eyes. The Chameleon can change colors to match its surroundings. The Chinese Water Dragon can not only swim to escape predators, but it can remain under water for up to 25 minutes. Some lizards are small, but others such as the Monitor Lizard can grow up to 6 feet in length. Lizards such as the Gila Monster are venomous. And, some lizards such as the Gecko and the Iguana are common pets.


(l) Mamba Snake

The black mamba is native to Africa. Their habitat is open grasslands, savannahs and woodlands. It is the largest venomous snake in Africa and the second largest venomous snake in the world. They are considered the deadliest snake in Africa. They are also considered fastest land snake in the world, able to reach speeds of 12 miles per hour. Although they are called the black mamba, they are generally gray, gray brown, or olive green in color. The name black mamba comes from the black color inside their mouth.


(m) Viper Snake

The viper is a family of venomous snakes found all over the world, except in Australia and Madagascar. Vipers range in size from the small dwarf viper which is 10 inches in length, to the large bushmaster at 10 feet in length. Vipers have a pair of fangs that are used to inject venom from glands in the rear of the upper jaws. These fangs are hinged, and when not in use fold back against the roof of the mouth.


(n) Turtle

Turtles are a reptile found in most parts of the world. Some turtles live on land, while others live in the sea. They are easily recognized by their shell. The turtle’s shell is covered with scales made keratin, the same material as human fingernails. Many turtles can retract their head and limbs into their shell for protection. The largest turtle, the leatherback sea turtle, can have a shell length of 80 inches. A small turtle may be only 3 inches long. Turtles have a beak, not teeth. Female turtles lay eggs to reproduce their young.


(o) Tortoise

The tortoise is a reptile, closely related to the turtle. The tortoise is often described as a land turtle. Turtles usually live in water and have large blade-shaped flippers for swimming. Therefore, turtles find it hard to walk on land. Whereas, the tortoise has legs rather than flippers and can walk quiet well on land. Like the turtle, the tortoise has a large protective shell. Tortoises can have longer life span that humans, sometimes living to be over 150 years old.


(p) Sea Turtle

Sea turtles are native to all the world’s ocean, except the Arctic Ocean. The largest sea turtles are seven feet in length and five feet in width, weighing up to 1300 pounds. Some sea turtles are believed to live to be 80 to 100 years old. Sea turtles spend much of their time under water, but must return to the surface to breathe air. All species of sea turtles are listed as threatened or endangered.


(q) Sea Snake

Sea snakes are found in warm, tropical, coastal waters of the Indian Ocean and Pacific Ocean. A few species are also found in Oceania. Sea snakes are venomous snakes, and have fangs. Sea snakes are highly adapted to living in the water. For example, they have a paddle-like tail for swimming. Although these snakes spend most of their time in the water, they must come to the surface to breathe air.


(r) Pitviper Snake

The pitviper is a family of venomous snakes found in Eastern Europe, Asia and the Americas. Their habitat ranges from desert to rainforests. Pitvipers have a deep pit between the eye and the nostril on either side of the head. This is an organ that detects heat from warm-blooded prey. Common pitvipers include the bushmaster, copperhead and rattlesnake


(s) Python Snake

The python snake is native to Africa, Asia and Australia. Burmese pythons were introduce to the Florida Everglades National Park in the 1990s. The python is one of the largest snakes in the world. The reticulated python may grow to over 30 feet long and weight over 300 pounds. The python generally feeds on small reptiles and mammals, but has been know to eat deer and other large animals. The python kills its prey by constriction. It wraps itself, or coils around its prey suffocating the animal by preventing it from breathing.


(t) Rattlesnake

Rattlesnakes are venomous snakes native to North America and a few other parts of the Northern Hemisphere. They get their name from the rattle located at the tip of their tails that is used as a warning device when threatened. The rattle is a set of rings on the tip of their tail. When vibrated, the rattle creates a hissing sound that warns off predators. Rattlesnakes use their

venomous bite to catch and kill prey such as mice, rats, small birds and other small animals.


Facts About Reptiles

There are about 8,000 species of known reptiles alive today.

The first reptiles appeared approximately 340 million years ago during the Carboniferous Period.

Reptiles are cold-blooded.

Reptiles have scales.

The Mesozoic Era is the ‘Age of Reptiles’.

In many reptiles, the sex of the young is determined by the temperature the embryos are exposed to during incubation.

Some of the largest reptiles alive today include the leatherback turtle, the Komodo dragon, and the saltwater crocodile.


(iv) Birds

There are over 8,000 species of birds. Birds have 3 major differentiating characteristics: wings for flight, feathers, and a beak rather than teeth. Birds have adapted their vertebrate skeleton for flight. Their bones and skull are very thin, making their bodies extremely light. To support flight also required other changes to their skeleton. Obvious changes are the addition of wings. Other changes are less obvious. The claws and muscles of a bird’s foot are designed to lock and hold onto a perch even while the bird is sleeping. A bird’s respiratory system is also adapted to make it easier to breathe at high elevations, where air is thinner

More information on birds


(a) Albatross

The Albatross is a large sea bird found near the Southern Ocean and North Pacific. The albatross is among the largest flying birds, and has the largest wing span. Its large wings are excellent for flying, but can make taking off and landing quite difficult.


(b) Swan

Swans are a family of birds native to many parts of the world including the Americas, Europe, Asia, Africa and Australia. Swans are the largest of the waterfowl compared to ducks and geese. The largest swan in the world is the trumpeter swan of North America whose wingspan can reach 10 feet. The habitat of the swan is ponds, lakes, coastal bays and rivers. They are easily recognized by their very long necks which are often held in a graceful curve. Their long necks allow them to feed underwater without diving.


(c) Vulture

Vultures are native to the Americas, Africa, Asia, and Europe. They are scavenging birds feeding mostly on carrion, that is carcasses of dead animals. Vultures have a good sense of smell, and can smell a dead animal from great heights. One recognizable characteristic of many vultures is their bald head with no feathers


(d) Ruby-Throated Hummingbird

The ruby-throated hummingbird is native to: the Canadian prairies; eastern Canada, United States and Mexico; Central America; and, parts of South America. Its habitat is deciduous and pine forests and forest edges, orchards, and gardens. The hummingbird has strong flight muscles and blade-like wings allowing it to fly not only forward, but also straight up and down, sideways, and backwards, and to hover in front of flowers as it feeds on nectar and insects.


(e) Parrot

Parrots are native to most warm and tropical parts of the world including Australia and the islands of the Pacific Ocean, India, Southeast Asia, southern regions of North America, South America and Africa. There are about 372 different species of parrot. Parrots are one of the smartest birds. Not only can they mimic human speech, studies have shown they can associate words with their meanings and form simple sentences


(f) Ostrich

The ostrich is a large flightless bird native to Africa. It is easily recognized by its long neck and legs. The ostrich is a fast runner, capable of reaching speeds up to 45 miles per hour. A large male ostrich can weight up to 350 pounds. Matching its size, ostrich eggs are the largest of all eggs. Penguins are a group of aquatic, flightless birds mostly living in the Southern Hemisphere, particularly the Antarctica. However, the Galapagos Penguin prefers a more temperate climate living near the equator. Penguins are easily recognizable by their black and white coloring, and their unusually upright, waddling gait. The penguin looks like it is formally dressed in a man's tuxedo. These birds have adapted for life in the water. Their wings have become flippers allowing them to swim fast in the water.


(g) Peacock

Peacocks are large colorful pheasants. Although most people know this bird by the name peacock, this name specifically refers to the male bird. The female is called a peahen. Collectively they are referred to as peafowl. There are three species of peafowl. The blue peacock lives in India and Sri Lanka, the green peacock lives in Java and Myanmar, and the Congo peacock lives in African rain forests. The peacock is best known for its known and valued for its brilliant tail feathers. This iridescent blue-green or green colored tail plumage, also called the train, has bright spots on it called “eyes”.


(h) Kiwi

The kiwi is a flightless birds native to New Zealand. It is an endangered species. They are an interesting looking bird with a plump body and a long bill. Kiwi are shy and usually nocturnal. The kiwi is a national symbol of New Zealand. They are so well known to the world, and representative of New Zealand, that all New Zealanders are called “Kiwis”.


(i) Hornbill

Hornbills are a family of birds native to tropical and sub-tropical Africa and Asia. They can be found in open country as well as forested areas. The most distinctive feature of the hornbill is their heavy bill. It is long and down- curved, and often brightly-colored. Hornbills are omnivorous birds meaning they will eat fruit, insects and small animals. They cannot swallow food from the tip of the beak because their tongue is too short. They must toss it to the back of their throat.


(j) Great Blue Heron

The great blue heron is a large wading bird common over most of North and Central America, as well as the West Indies and the Galapagos Islands. They live near bodies of water such as fresh and saltwater marshes, mangrove swamps, flooded meadows, lake edges, or shorelines. They build their nest in trees or bushes near the water. They are often seen standing in shallow water or at the water’s edge. They use their long legs to wade through the water, and they spear fish or frogs with their long, sharp bill.


(k) Golden Eagle

The Golden Eagle is a large bird of prey living in North American and other parts of the northern hemisphere. It is one of the best known birds of prey in the Northern Hemisphere. It is powerful and strong with a wingspan of over 7 feet.


The golden eagle’s eyesight is about 8 times more powerful than a human, and can spot prey from a long distance. Their talons are well designed for killing and carrying their prey. They also have a powerful beak for tearing into its food.


(l) Flamingo

The flamingo can be found in many parts of the world including Africa, Asia, North America, Central America, South America, and Europe. They live near large, shallow lakes or lagoons. They are best known for their pink color. They also have distinctive long legs and neck, and a curved, pink bill colored black on the end.


(m) Falcon

The falcon is a species of raptor found on every continent, except Antarctica. They live in a wide variety of habitats from tropics, deserts, and maritime to the tundra. They have excellent vision allowing them to see prey from high in the sky. Once spotting its prey, the falcon dives down after it. Falcons have thin tapered wings enabling them to fly at high speed and to change direction rapidly. Peregrine Falcons can dive at speeds over 200 miles per hour (322 km/hr.), making them the fastest-moving animal on Earth.

Facts About Birds

The earliest known bird, Archaeopteryx lithographic, lived about 150 million years ago during the Jurassic Period.

Birds are not the only animals that are capable of flight.

Flight is not a characteristic restricted to birds. Bats, which are mammals, fly with great agility and insects, which are arthropods, were fluttering through the air several million years before birds

Birds do not have teeth.

The largest of all birds is the ostrich.


(v) Mammals

Mammals have several unique characteristics that differentiate them from other animals. Most mammals have hair, or fur, covering their body. They are also capable of regulating their body temperature. The mammals metabolism controls heat production, and the sweat glands help cool the body. These allow the mammal to maintain a constant body temperature, regardless of the environmental temperature. One other difference is that mammals give birth to fully formed babies, and the female mammals produce milk to feed their young. Most mammals walk on 4 legs, with only the humans walking upright on 2 legs. Aquatic mammals have flippers, or fins, for swimming rather than legs. Common mammals include: primates, such humans and monkeys; marsupials; rodents; whales; dolphins; and, seals.


(a) Marsupials

Marsupials are best known for the Australian members of the family, the kangaroo, wallaby and the koala. The only marsupial native to North America is the Virginia opossum. There are also some marsupials native to Central America and South America.

Marsupials are members of the mammal family. However, they are different from other mammals because they have an abdominal pouch to carry their young. The marsupial female gives birth very early and the baby animal climbs from the mother’s birth canal to her pouch. Here the baby marsupial continues to develop for weeks, or even months, depending on the species.


At birth, marsupial babies are not fully developed. The baby’s hind legs are just nubs. The baby lives and continues to develop in the mother’s pouch. The pouch, or marsupium, also has the mother’s mammary glands for feeding the baby. A baby kangaroo may live in its mother's pouch for 6 months. Koalas and wombats are a little different from Kangaroos. The kangaroo's pouch is on the front, while the koala and wombat pouches are on the back.


(b) Kangaroo

The kangaroo is native to Australia. It is the largest of the marsupials, and a national symbol of Australia. As a marsupial the kangaroo differs from other mammals in having a pouch on its stomach for carrying its young. Early European explorers in Australia said the kangaroo had a head like a deer (without antlers), stood upright like a man, and hopped like a frog, Kangaroos have large, powerful hind legs, and large feet, well adapted for jumping. They can hop along at 25 miles per hour, and are capable of reaching speeds up to 45 miles per hour for short distances.


(c) Primates

Humans are part of the primate family. Other common primates include the monkey, baboon, orangutan, chimpanzee and gorilla. While humans inhabit much of the world, most other primates live in tropical or subtropical regions of the Americas, Africa and Asia.

Primates have several distinctive features that separate them from other mammals. Primates have well developed hands and feet, with fingers and toes. Their opposable thumb makes it easy for them to grab things.


Primate eyes are forward in the head giving them stereoscopic vision. This allows them to judge distance. Primates also have large, highly developed brains. Their intelligence allows them to control and manipulate their environment. The highly developed visual center of the brain helps primates distinguish colors. Their large brain also allows them to develop complex language and communication skills. Monkeys and apes walk on all four limbs, but they may run upright using only their hind legs.

Although primates are born fully formed, they tend to have a long gestation period in their mother’s womb. Parents also care for and educate their young much longer than other animals. This results in a strong bond between a baby and the mother. Primates are very social animals, and tend to form strong bonds with family and friends.


While humans are similar to monkeys in many ways, there are also several significant differences. The human brain is more than twice the size of other primates. This makes humans the most intelligent primate, with the most developed communication, language and reasoning skills. Humans are able to make and use complex tools to help control their environment. Humans also walk upright on two legs. Although primates are born fully formed, they tend to have a long gestation period in their mother’s womb.


(d) Rodents: Squirrels, Mice, Porcupines and Others

The largest family of mammals are the rodents. These mammals are named rodent, which means “gnawing animal,” because of their large incisor teeth and the way they eat. The two long pairs of incisors are used like chisels to gnaw on hard foods like nuts and wood. These incisors must grow continuously since they are worn down by gnawing. There are 3 major types of rodents, represented by squirrels, mice and porcupines.


Squirrel-like rodents such as the squirrel and gopher, have bushy long tails and large eyes. They can live in trees or underground in tunnels. They may hibernate during the winter Mouse-like rodents include the mouse, rat and hamster. Some have a long, thin tail with short legs. Others have a short tail. They mostly live above ground, although some burrow underground. They may also hibernate during the winter Rats and mice often live near humans, sometimes in their buildings, so they can live off human food and garbage. Porcupines differ from other mammals because they have long, sharp quills on their backs for protection.


(e) Whales and Dolphins

Although they live in the water — whales, dolphins and porpoises are mammals. Since whales and dolphins are mammals, they cannot breathe under water. They must come to the surface to breathe air. They breathe through a blowhole, or nostrils, on the top of their head. Babies are born under water and must be pushed to the surface, by the mother, so that they can take a breath. Whales and dolphins also look different from many other mammals because they don’t have fur. Although, they do have a sparse covering of hair. The circulatory and respiratory systems have adapted to living in water. Whales and dolphins can dive deep in the water on a single breath. Whales and dolphins also have a highly developed brain. They are consider to be very intelligent. Dolphins, and some whales, can use echolocation to find food and identify objects around them. They make loud clicking and squeaking sounds that bounce off objects and echo back to the dolphin. This echo tells the dolphin about the nearby object.


(f) Whale

The whale is a marine mammal found many ocean areas from arctic and sub-arctic to warmer waters. Whales are best known for their size, which can be up to 110 feet long. The Blue Whale is the largest known mammal to ever live, up to 110 feet long and weighing 150 tons. The whale breathes air into its lungs through a blowhole on the top if its head.


(g) Orca

The Orca, also known as the Killer Whale, is the largest of the dolphin family. It can be found in most of the world’s oceans. Orcas have very distinction coloring with a black back, white chest and sides, and a white patch above and behind the eye. The orca is considered very intelligent and trainable. The orca's playfulness and sheer size make them a popular exhibit at aquariums and aquatic theme parks.


(h) Dolphin

Although dolphins live in the water, they are a mammal. They are related to the whale and porpoise. They breathe air through a blow hole on the top of their head. They must routinely return to the surface for air. Dolphins are very friendly to humans, and are considered to be very intelligent.


(i) Seals, Seal Lions and Walrus

The seals are marine mammals. The seal family includes the seal, sea lion and the walrus. A seal’s respiratory system is adapted for water. A seal can go for 40 minutes without a breath. This allows them to dive to a depth of over 2,000 feet. Seals are well designed to swim in water. Their bodies are very streamlined and their flippers propel them quickly through the water. Seals also spend considerable time lying around on rocky islands and beaches. But they are clumsy and move slowly on land using their flippers. Baby seals are born on land after a long, 12 month gestation period.


The pups develop rapidly, with some able to swim within a few hours of birth. Walruses differ from seals in that they are larger and have large tusks. They can be over 10 feet long and over 3,000 pounds.


Facts About Mammals

The first Mammals are tetrapods. Mammals have four limbs, a characteristic that places them among the group of animals known as tetrapods. It should be noted that although some mammals such as whales, dugongs, and manatees have lost their hind limbs during the course of evolution, they are tetrapods by descent, mammals appeared approximately 200 million years ago during the Jurassic Period. Mammals are warm-blooded. All mammals have hair. The Cenozoic Era is the ‘Age of Mammals’. The largest mammal is the blue whale. The smallest mammal is the bumblebee bat.


The Basics of Vertebrate Evolution from Jawless Fish to Mammals

  • Evolution
  • Vertebrates


Vertebrates are a well-known group of animals that includes mammals, birds, reptiles, amphibians, and fish. The defining characteristic of vertebrates is their backbone, an anatomical feature that first appeared in the fossil record about 500 million years ago, during the Ordovician period.


Jawless Fish (Class Agatha)

The first vertebrates were the jawless fish (Class Agatha). These fish-like animals had hard bony plates that covered their bodies and as their name implies, they did not have jaws. Additionally, these early fish did not have paired fins. The jawless fish are thought to have relied on filter feeding to capture their food, and most likely would have sucked water and debris from the seafloor into their mouth, releasing water and waste out of their gills. The jawless fish that Jived during the Ordovician period all went extinct by the end of the Devonian period. Yet today there are some species of fish that lack jaws. These modern day jawless fish are not direct survivors of the Class Agatha but are instead distant cousins d the cartilaginous fish.


Armored Fish (Class Placodermi)

The armored fish evolved during the Silurian period. Like their predecessors, they too lacked jaw bones but possessed paired fins. The armored fish diversified during the Devonian period but declined and fell into extinction by the end of the Permian period.


Cartilaginous Fish (Class Chondrichthyes)

Cartilaginous fish, better known as sharks, skates, and rays evolved during the Silurian period. Cartilaginous fish have skeletons composed of cartilage, not bone. They also differ from other fish in that they lack swim bidders and lungs.


Bony Fish (Class Osteichthyes)

Members of the Class Osteichthyes first arose during the late Silurian. The majority of modern fish belong to this group. Bony fish diverged into two groups, one that evolved into modern fish, the other that evolved into lungfish, lobe-finned fish, and fleshy-tinned fish. The fleshy finned fish gave rise to the amphibians.


Amphibians (Class Amphibia)

Amphibians were the first vertebrates to venture out into land. Early amphibians retained many fish-like characteristics but

coring the Carboniferous period amphibians diversified. They retained close ties to water though, producing fish-like eggs that lacked a hard protective coating and requiring moist environments to keep their skin damp, Additionally, amphibians underwent larval phases that were entirely aquatic and only the adult animals were able to tackle land habitats.


Reptiles (Class Reptilia)

Reptiles arose during the Carboniferous period and quickly took over as the dominant vertebrate of the land. Reptiles freed themselves from aquatic habitats where amphibians had not. Reptiles developed hard-shelled eggs that could be laid on dry land. They had dry skin made of scales that served as protection and helped retain moisture. Reptiles developed larger and more powerful legs than those of amphibians. The placement of the reptilian legs beneath the body (instead of at the side as in amphibians) enabled them greater mobility.


Birds (Class Aves)

Sometime during the early Jurassic, two groups of reptiles gained the ability to fly and one of these groups later gave rise to the birds. Birds developed a range of adaptations that enabled flight such as feathers, hollow bones, and warm-bloodedness.


Mammals (Class Mammalia)

Mammals, like birds, evolved from a reptilian ancestor. Mammals developed a four-chambered Heart, hair covering, and most do not lay eggs and instead give birth to live young (the exception is the monotremes).


Progression of Vertebrate Evolution

The following table shows the progression of vertebrate evolution (organisms listed at the top of the table evolved earlier than those lower in the table).

Animal Group


Key Feature

Jawless Fish


no jaws- no paired fins- gave rise to placoderms, cartilaginous and bony fish



no jaws- armored fish

Cartilaginous fish


cartilage skeletons- no swim bladder- no lungs internal fertilization

Bony fish


gills- lungs- swim bladder- some developed fleshy fins (gave rise to amphibians)



first vertebrates to venture out onto land- remained quite tied to aquatic habitats- external fertilization- eggs had no amnion or shell- moist skin



scales- hard- shelled eggs- stronger legs positioned directly beneath body



feathers- hollow bones



fur- mammary glands- warmblooded


Other Topics

NCERT Summary - The Animal Kingdom

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