Upload
others
View
1
Download
0
Embed Size (px)
Citation preview
www.gradeup.co
2
Check Phylum Chordata Superclass Tetrapoda notes for NEET 2019 here! Phylum
Chordata is important sections in the Animal Kingdom unit which are mostly asked every
year in NEET, AIIMS, and JIPMER exams. Go through this article to know about Class
Amphibia, Reptilia, Aves, and Mammalia. Let's start with the introduction of Animal
Kingdom and its classification.
Animal Kingdom Superclass Tetrapoda
Introduction
The word “Tetrapoda” was derived from a Greek word which meant “four legs”. Some of
the major groups that fall under Tetrapoda include Amphibians, Reptiles (embraces birds
and dinosaurs also), and mammals. All terrestrial vertebrates, such as lions, hawks,
turtles, and frogs belong to class Tetrapods. Other than terrestrial animals, Tetrapods also
include those animals which have returned their life in water, such as sea snakes, whales,
sea turtles, dolphins, and sea lions. The group also includes extinct animals such as
mosasaurs.
The first vertebrates to truly walk on the land were the early tetrapods. Before the
existence of tetrapods, all vertebrates were confined to aquatic habitats. The conquest of
land by the tetrapods, began in the Paleozoic era which, was around 360 million years
ago. The closest living relatives of tetrapods are the lungfishes.
The key characteristic features of Tetrapods for their classification include the skull and
their four limbs (or if at all they lack four limbs, their ancestors had four limbs. For
example: snakes, caecilians, cetaceans, and so on). The skull is the collection of bones
that surrounds the brain, and it also includes the jaw. The arrangement and the structure
of bones in skull give the name to the major groups of amniote tetrapods. Approximately
30,000 species of tetrapods are reported till date.
Tetrapods may vary greatly in size. The largest living tetrapod reported is the blue whale.
It can grow its length up to 30 meters. Paedophyrine frog is the smallest reported tetrapod,
measuring up to a length of just 8 millimeters.
Habitat of Tetrapods:
Tetrapods inhabit a wide variety of terrestrial habitats which include grasslands,
scrublands, deserts, forests, polar regions, and mountains. While most of the tetrapods
are terrestrial, various groups have evolved to live in aquatic habitats. Tetrapods such as
seals, otters, sea snakes, whales, salamanders, and so on have evolved to depend on
aquatic habitats for some or all phases of their life cycle. Some tetrapods, such as flying
squirrels, bats, and birds have also adopted an aerial or arboreal lifestyle.
Key characteristic features of Tetrapods:
1. They have four limbs (or are descendants of ancestors having four limbs).
2. Their skeleton and muscles are adapted to enable proper support and movement
on land.
3. Cranial bones are adapted to allow their head to stay stable during movement.
4. They possess a layer of dead cells which reduce loss of water across their body
surface.
5. They possess well-developed muscular tongue.
6. They lack internal gills.
7. They possess olfactory organ, which enables them to detect pheromones and play
important role in smell and taste.
8. They possess harderian gland (lubricates eyes) and parathyroid gland (controls
blood calcium level).
www.gradeup.co
3
Characteristic features of the four classes of Tetrapoda
Amphibia Reptilia Aves Mammals
Habitat: Both
aquatic and
terrestrial
Habitat: Mostly
terrestrial
Habitat: Feathers
are present for
flying
Habitat: Mostly
terrestrial, although
some can fly and
some are aquatic
Limbs: Two pairs Limbs: If present,
two pairs
Limbs: Modified
forelimbs as wings Limbs: Two pairs
Skin: Moist without
scales
Skin: Dry, cornified
skin with scale
Skin: Dry without
glands Skin: Hairy skin
Respiration:
Through lungs,
gills, or skin
Respiration:
Through lungs
Respiration:
Through lungs
Respiration:
Through lungs
Heart: Three
chambered and cold
blooded
Heart: Three
chambered with
exception of four
chambered
crocodile
Heart: Four
chambered and
warm blooded
Heart: Four
chambered
Oviparous Oviparous Oviparous Oviparous or
Viviparous
Example:
Salamander, Rana
(frog)
Example:
Chameleon,
Crocodile
Example: Ostrich,
Columba
Example: Dog, Blue
whale, Platypus
(Oviparous)
Class 1: Amphibia (General Characteristics, the difference between Frog, Toad,
ichthyophis, Salamander, Seymouria)
General Characteristics
Amphibians do not have a constant body temperature. They take on the temperature of
their surrounding environment. Hence, they are termed as cold-blooded animals. They
possess moist skin that lacks scales, which allows absorption of oxygen and water and at
the same time makes them vulnerable to loss of bodily fluids.
Approximately 6,200 species of living amphibians have been identified till date.
Amphibians are classified into three orders; Frogs and toads, newts and salamanders, and
caecilians. Frogs and toads are adapted for jumping, newts and salamanders can either
walk or swim, and caecilians only live in water or soil. They are the only amphibians with
no legs.
Difference between Frogs, Toads, Ichthyophis, Salamander, Seymouria
Frogs and toads lack tail in their adulthood, which is a distinguishing feature from other
amphibians. Frogs and toads also have longer back legs (modified for jumping) as
compared to other amphibians. Although they are closely related, they differ in various
ways. Frogs spend more time in water while toads spend more time on land. Frogs have
moister, smoother skin than toads and longer hind legs. On the other hand, salamanders
and newts possess tails even in adulthood. They possess long body with shorter legs with
same length adapted for swimming and walking. They possess an unusual characteristic
of regenerating legs after having been lost to predators. Caecilians are closely related to
salamanders. They possess a long, worm-like body with no legs. They evolved from a
tetrapod ancestor, but during the course of evolution they lost their legs. Ichthyophis is
a genus of caecilians. Seymouria is an extinct genus of terrestrial tetrapod found as fossils
in Permian rocks.
www.gradeup.co
4
Class 2: Reptilia (General characteristics, Difference between Tortoise, chelone,
chameleon, Hemidactlylus, Hydrophis, Phrynosoma)
General Characteristics
All reptiles are vertebrates (have a backbone) and most of the reptiles lay hard shelled
eggs, while a few give birth to young ones. Reptiles are also cold blooded and they possess
scutes or scales. They are mostly terrestrial and inhabit the warmer region of the world.
They respire through lungs.
Difference between Tortoise, chelone, chameleon, Hemidactlylus, Hydrophis,
Phrynosoma
Tortoise is half terrestrial inhabiting mainly in fresh water and is larger in size. Chelone,
also known as turtles, are aquatic inhabiting mainly in marine and are comparatively
smaller in size. Tortoise does not have paddles and their head show many movements
while turtles have paddles and their head cannot move. Hemidactylus is found in all the
tropical regions of the world. It is a genus of the gecko family. Approximately 90 species
of Hemidactylus has been described. Hydrophis is also known as sea snake. Their tail is
compressed laterally and is adapted to swim in water. It is deadly poisonous.
Phrynosoma are also known as “Horned lizards”. Phrynosoma means toad-bodied and
are characterized by rounded, flattened body with blunt snout. Chameleons are
distinguished by their highly modified, extrudable tongues, and horns on their bows. 203
species of Chameleons are identified till date. They have independently mobile eyes with
stereoscopic vision.
Class 3: Aves (General Characteristics), kiwi, Hummingbird, Short note on birds
are glorified reptiles.
General Characteristics
Aves possess a spindle shaped body having four divisions: head, neck, trunk, and tail.
Their forelimbs are modified to fly. They have an epidermal covering of feathers and leg
scales and possess either beak or bill. They have a well-developed nervous system and a
four-chambered heart. They are warm blooded and sexes are separated.
Kiwi is the only bird that has nostrils at the tip of their beaks. While other birds hunt their
prey by hearing or by sight, Kiwis use their beaky nostrils to sniff food at night. Although
it has wings, it cannot fly. Humming birds are the smallest birds known, belonging to
family Trochilidae. They have the ability to fly.
Birds are often given the title as “Glorified reptiles”. They are given the title as they are
structurally similar to reptiles, although they have features that are adapted to flying, an
advanced feature. Characteristic features of birds are their beaks and feathers. Feathers
have the function of flight, regulation of body temperature, and attraction of their mates.
Class 4: Mammalia (General characteristics), Differences between Prototheria,
Metatheria and Eutheria
General Characteristics
Mammalia are warm blooded, hairy animals that possess mammary glands. They give
birth to young ones and nourish them with milk. Approximately 4,000 species of mammals
have been identified till date. Their skin possesses both sebaceous (oil) glands and
sudoriferous (sweat) glands. Teeth are heterodont (different types) and are developed
twice in their life-time (milk and permanent). All mammals, except a few, possess seven
neck (cervical) vertebrae. They respire through lungs.
www.gradeup.co
5
Differences between Prototheria, Metatheria, and Eutheria
Prototheria Metatheria Eutheria
They are also called ‘Egg
laying mammals’.
They are also called as
‘Pouched mammals or
marsupials’.
They are also called as
‘Placental mammals’.
They possess ear without
pinna.
They possess ear with
pinna.
They possess ear with
pinna.
They are oviparous. They are viviparous. They are viviparous.
They lack placenta. They possess small
placenta.
They possess very large
placenta.
Ornithorhynchus, Macropus, Pteropus, and Balaenoptera.
Ornithorhynchus are also called as duck-billed platypus. They inhabit in both aquatic
and terrestrial habitat. They are endothermic and their physical feature shows bilateral
symmetry. They are oviparous and produce young ones in more than one group
(Iteroparous).
Macropus is a marsupial genus belonging to family Macropodidae. They inhabit terrestrial
habitat. They are endothermic and their physical feature shows bilateral symmetry. They
are viviparous and undergo seasonal breeding.
Pteropus is a genus of bats. They are among one of the largest bats in the world. They
are arboreal. They are endothermic and their physical feature shows bilateral symmetry.
They are viviparous and produce young ones in more than one group (Iteroparous).
Balaenoptera is a genus of Balaenopteridae. It consists of eight extant species. It is also
commonly known as blue whales. They inhabit in aquatic environment. They are
endothermic and their physical feature shows bilateral symmetry. They are viviparous and
produce young ones in more than one group (Iteroparous).
All about NEET examination: https://gradeup.co/medical-entrance-exams/neet
All the best!
Team Gradeup