NCERT Summary: Gist of Biology - 10 - Notes | Study Science & Technology for UPSC CSE - UPSC

(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 know 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 lithographica, 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 under ground. 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. Orca’s 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 dophins 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 Cenezoic 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 Agnatha)
The first vertebrates were the jawless fish (Class Agnatha). 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 lived 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 (such as lampreys, and hagfish). These modern day jawless fish are not direct survivors of the Class Agnatha but are instead distant cousins of 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 bladders 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-finned 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 during 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).