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The body of these worms is circular (round) in cross section and hence are called round worms.

• In phylum Mollusca the digestive system is complete and mouth contains a rasping organ called radula with transverse rows of chitinous teeth for feeding.

• In Arthropods the body is covered by chitinous exoskeleton for protection and to prevent water loss, It is shed off periodically by a process called moulting or ecdysis.

The exoskeleton Arthropods is dead and cannot grow. Therefore the old exoskeleton is thrown off and new one is developed periodically which is known as Moulting / Ecdysis. 

The body cavity of coelenterates is called the coelenteron or gastrovascular cavity.

In Arthropods blood fills in the body cavity (coelom) called Haemocoel. 

Coral reefs are limestone formations, formed of the exoskeleton of stony corals. Example Madreporia.

The term platyhelminthes refers to flatworms.

Organisms having jointed appendages are grouped in phylum Arthropoda. 

Flame cells are the excretory organs of the phylum platyhelminthes. They are found in excretory ducts/protonephridia.

Flame cells are the excretory organs of flatworms.

Liver fluke – Fasciola hepatica Tapeworm – Taenia solium

(a) Cockroach - Chitinous outer covering exoskeleton 

(b) Human being - Epidermal hair, nails 

(c) Garden lizard - Epidermal scales 

(d) Snail - Calcareous Shell 

(e) Dog - Epidermal hair, nails, hoofs.

Holozoic  nutrition.

(b) Comb jelly fish 

(a) Physalia - Portugese man of war

(b) p - (iii), q - (iv), r - (ii), s - (i) 

Undifferentiated layer present between ectoderm and endoderm. It is found in Coelenterates.

Organisms having a false coelom which is not derived from the mesoderm are called Psecudococlomates

Example: Ascaris. 

• Arthropods-gills or gill books in aquatic forms and tracheae or book lungs in terrestrial forms.
• Amphibians -Skin, gills and lungs in the larvae & skin and lungs in adults.

Male ascaris has the presence of penial setae.

1. Flatworms are called acoelomate animals. 

2. They do not possess a body cavity or coelom. 

3. Since there is nobody cavity in these animals their body is solid without a perivisceral cavity. 

4. This restricts the free movement of internal organs. Eg. Flatworms.

(b) Flame cells 

(c) Earthworm

Planaria have a great capacity of regeneration. 

Comb plates is not associated with platyhelminthes.

(b) Flame cells

The answer is (c) Ostia 

The answer is :-

(c) Ostia✅

(b) Lamelliform gills 

• Widely distributed. Warm-blooded (endothermous) or homeothermous vertebrates.
• The body is fusiform covered with feathers. Scales cover the hind limbs.
• Forelimbs are modified into wings. Whereas hind limbs consist of usually 4 toes and adapted for perching, walking or swimming.
• Adapted for aerial life. Lungs are the respiratory organs, they are connected to thin walled air sacs.
• Skeleton is light and bones contain air cavities (pneumatized) skull is monocondylar as in reptiles.
• Voicebox is called syrinx which is situated at the base of the trachea.
• Heart is perfectly 4 chambered. There is a single aortic arch on the right side only. RBC are nucleated and biconvex. 
• Kidneys are advanced type that is metanephric. Uric acid is the nitrogenous waste. Sexes are separate. Ovary is single in female. Fertilization is internal. Oviparous laying eggs. Eggs contain much yolk. Eggs are covered by shell. Eggs hatch after a period of incubation by parents. Birds show high degree of parental care.
• Jaws are modified into beak. No living bird possesses teeth. Class Aves divided into sub class Archaeornithes and Neornithes. Living Birds are included under Neornithes which are classified into Ratitae and carinatae. Ratitae are flight less birds whereas carinatae are flying birds.

Examples – snakes, lizards

• Eucoelom or true coelom is a fluidfilled cavity that develops within the mesoderm and is lined by mesodermal epithelium called peritoneum. 
• Such animals with a true body cavity are called coelomates or eucoeloniates. 

• In Phylum Annelida, the body is metamerically segmented. 
• The body surface is divided into segment or metameres. 
• Internally the segments are divided from one another by partitions called septa. 
• This phenomenon is known as metamerism. 

• Animals which do not possess a body cavity are called acoelomates. 
• Since there is no body cavity in these animals their body is solid without a perivisceral cavity, this restricts the free movement of internal organs eg. Flatworms. 

If body is externally and internally divided into segments with serial repetition of atleast some organs then phenomenon is called metamerism. 

Example: Earthworm.

• The simplest body plan is seen in sponges. 
• They do not display symmetry and are asymmetryical. 
• Such animals lack a definite body plan or are irregular shaped and any plane passing through the centre of the body does not divide them into two equal halves (Sponges).

Two embryonic layers – Ectoderm and Endoderm – Diploblastic. 

Three embryonic layers- Ectoderm, Mesoderm and endoderm- Triploblastic. 

• Symmetry is the body arrangement in which parts that lie on opposite side of an axis are identical. 
• An animal's body plan results from the animal's pattern of development. 

On the basis of the origin and development, animals are classified into two categories: Diploblastic and Triploblastic. 

• Animals in which the developing embryo has three germinal layers are called triploblastic animals and consists of outer ectoderm (skin, hair, neuron, nail, teeth, etc), inner endoderm (gut, lung, liver) and middle mesoderm (muscle, bone, heart). 
• Most of the triploblastic animals show organ system level of organisation Eg.,Flat worms to Chordates.

• Animals in which the cells are arranged in two embryonic layers the external ectoderm and internal endoderm are called diploblastic animals. 
• In these animals the ectoderm gives rise to the epidermis (the outer layer of the body wall) 
• Endoderm gives rise to gastrodermis (tissue lining the gut cavity). 
• An undifferentiated layer present between the ectoderm and endoderm is the mesoglea Eg. Corals, Jellyfish, Sea anemone.

• Symmetrical animals have paired body parts that are arranged on either side of a plane passing through the central axis. 
• When any plane passing through the central axis of the body divides an organism into two identical parts, it is called radial symmetry. 
• Such radially symmetrical animals have a top and bottom side but no dorsal (back) and ventral (abdomen) side, no right and left side. 
• They have a body plan in which the body parts are organised in a circle around an axis. 
• It is the principal symmetry in diploblastic animals. 
• Cnidarians such as sea anemone and corals are radially symmetrical. 
• However, triploblastic animals like echinoderms,Starfish have five planes of symmetry and show Pentamerous radial symmetry.

(i) Unique feature 

• Their body is covered by hair 
• Presence of mammary glands is the most unique feature of mammals. 

(ii) Some of them are adapted to fly or live in water. 

(iii) They have two pairs of limbs adapted for walking, running, climbing, burrowing, swimming and flying. 

(iv) Their skin is glandular in nature, consisting of sweat glands, scent glands and sebaceous glands. 

(v) Exoskeleton includes horny epidermal horns, spines, scales, claws, nails, hooves and bony dermal plates. 

(vi) Teeth are thecodont, heterodont and diphyodont. 

(vii) External ears or pinnae are present. 

(viii) The heart is four chambered and possess a left systematic arch. 

(ix) Mature RBCs are circular, biconcave and non nucleated. 

(x) Mammals have a large brain when compared to other animals. 

(xi) They show greatest intelligence among all animals. 

(xii) Their kidneys are metanephric and are ureotelic. 

(xiii) All are homeothermic, 

(xiv) Sexes are separate and fertilization is internal. 

eg. Platypus, Kangaroo, Monkey, Elephant.

1. They are mostly terrestrial animals and their body is covered by dry, and cornified skin with epidermal scales or scutes. 

2. Reptiles have three chambered heart but four chambered in crocodiles. 

3. All are cold blooded amniotes. 

4. Most reptiles lay cleidoic eggs with extraembryonic membranes like amnion, allantois, chorion and yolk sac. 

5. Excretion : metanephric kidneys and are uricotelic. 

6. They are monoecious. 

7. Internal fertilization takes place and all are oviparous. eg. Calotes (Garden Lizard), Draco (Flying Lizard), Crocodilus (Crocodile).

• Amphibians are the first vertebrates and tetrapods to live both in aquatic as well as terrestrial habitats. 

They are poikilothermic. 

• Body : divided into head and trunk and most of them have two pairs of limbs; 
• Tail may or may not be present. 
• Skin : smooth or rough, moist, pigmented and glandular. 
• Eyes have eyelids and the tympanum represents the ear. 
• Respiration is by gills, lungs and through the skin. 
• Heart is three chambered. 
• Kidneys are mesonephric. 
• Sexes are separate and fertilization is external. 
• They are oviparous and development is indirect. 
• They show hibernation and aestivation. Eg. Bufo (Toad), Rana (Frog).

1. Subphylum Vertebrata is divided into two divisions, Agnatha and Gnathostomata. Agnatha 

Agnatha includes jawless fish-like aquatic. 

Vertebrates without paired appendages.

Notochord persists in the adult. 

Agnatha includes class-Cyclostomata.

Gnathostomata 

It includes jawed vertebrates with paired appendages. 

Notochord is replaced partly or wholly by the vertebral column. 

It includes jawed fishes (Pisces) and Tetrapoda (amphibia, reptilia, aves and mammals). 

Pisces includes all fishes which are essentially aquatic forms with paired fins for swimming and gills for respiration. 

Pisces includes cartilaginous fishes (Chondrichthyes) and bony fishes (Osteicthyes).

Gills are the respiratory organs of fishes. 

Haemocoel is name given to fluid filled body of Arthropod.

Arthropoda is  largest phylum In kingdom Animals.