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The answer is (a) Insects 

The answer is (a) Prawn 

Arthropoda is the largest phylum o he kingdom Animalia.

• Vertebrates posses notochord during embryonic stage only. 
• The notochord is replaced by a cartilaginous or bony vertebral column in the adult.

1. On the basis of germ layers all animals will be diploblastic (ectoderm and endoderm) or triploblastic (outer ectoderm, middle mesoderm, and inner endoderm). 

2. Animals show symmetry. They may be radially symmetrical or bilaterally symmetrical. Few animals like sponges lack symmetry.

3. Most animals possess a body cavity between the body wall and alimentary canal and is lined with mesoderm. This is called coelom. Some animals lack coelom (acoelomate) or have false coelom (Pseudocoelomate). 

4. Reproduction is seen in all animals. (asexual/sexual).

The circultory system is of two types, 

1. Open type: The blood remains filled in tissue spaces due to the absence of blood capillaries. 

Eg: Arthropods, Molluscs, Echinoderms, and Urochordates 

2. Closed type: The blood Is circulated through blood vessels of varying diameters (arteries, veins, and capillaries) 

Eg: Annelids, Cephalochordates and Vertebrates

a – viii

b – v

c – iv

d – i

e – ii

f – vii

g – iii

h – vi

The phylum name Platyhelminthes literally means "flatworms."

Have dorsoventrally flattened body. Are endoparasites in animals. 

• Are bilaterally symmetrical, triploblastic, acoelomate. 

• Absorb nutrients through body surface. 

• Parasite forms have hooks and suckers. 

• ‘Flame cells’ help in osmoregulation and excretion. 

• Fertilisation internal. Many larval stages. Planaria has high regeneration capacity. e.g., Taenia, Fasciola.

The organisms belonging to the phylum Cnidaria exhibit the following characters. 

• They are primitive metazoans having tissue grade of organisation.
• They are aquatic both freshwater and marine, solitary or colonial with Radial symmetry.
• The body wall is diploblastic with outer ectroderm and inner endoderm. Ectoderm has specialised stinging cells called Nematocysts
• The body wall encloses a body cavity called coelenteron or Gastrovascular cavity.
• Coelenterates exist in two forms in their life cycle. The asexual reproducing form is called polyp and sexually reproducing form called Medusa. Thus they exhibit polymorphism.
• The polyp stage alternates with the medusa stage in coelectorates and is called Metagenesis.
• Respiratory, circulatory and excretory systern are absent.
• Reproduction occurs both by asexual and sexual methods. Asexual reproduction is by budding arid sexual reproduction is by production of Gametes. 

Phylum Platyhelminthes includes the flatworms which shows the following characters.

• Multicellular organisms with organ grade of organisation. 
• The body is bilaterally symmetrical and dorsoventrally flattened. 
• The body wall is triploblastic with ectoderm, mesoderm and endoderm forming the layers. Coelom is totally absent.
• The body is unsegmented and varies in shape. It may be elongated, flattened, ribbon like or leaf-like. 
• The parasitic forms are protected by a thick cuticle and bears, hooks, spines or suckers for attachment.
• Digestive, circulatory, respiratory and skeletal systems are absent. 
•  Excretion occurs by excretory cells called flame cells which form the protonephridia.
• Nervous system consists of nerve aggregations called ganglia.
• Sexes are mostly united (Hermaphrodites). Reproduction is by asexual and sexual methods. Development is indirect.

Class – Turbellaria Eg. lanaria

Class – Trematoda Eg. Fasciola hepatica

Class – Cestoda Eg. Taenia solium

All chordates possess three fundamental distinct features they are : 

(i) Presence of elongated rod like notochord below the nerve cord and above the alimentary canal. 

• It serves as a primitive internal skeleton. 
• It may persist throughout life in lancelets and lampreys. 
• In adult vertebrates, it may be partially or completely replaced by backbone or vertebral column. 

(ii) A dorsal hollow or tubular fluid filled nerve cord lies above the notochord and below the dorsal body wall. 

• It serves to integrate and co-ordinate the body functions. 
• In higher chordates, the anterior end of the nerve cord gets enlarged to form the brain and the posterior part becomes the spinal cord, protected inside the vertebral column.

(iii) Presence of pharyngeal gill slits or clefts in all chordates at some stage of their life cycle.

• Gill slits or clefts that perforates the walls of pharynx and appears during the development of chordate. 
• In aquatic organisms, pharyngeal gill slits are vascular, lamellar and form the gills for respiration. 
• In terrestrial organisms - traces of non-functional gill clefts appear during embryonic developmental stages and disappear later. 
• Chordates are bilaterally symmetrical, triploblastic, coelomates 
• Organization : organ system level.
• They have post anal tail, closed circulatory system with a ventral myogenic heart except in Amphioxus.

1. All chordates possess a notochord. 

2. All chordates possess a dorsal, hollow, nerve cord. 

3. All chordates possess pharyngeal gill clefts in some stage of their life cycle. 

4. Possess a post-anal tail. 

• Polyp and Medusa are two basic body forms found in phylum cnidaria.
• Cnidarians which exist in both forms also exhibit alternation of generations in their life cycle

It is a division of the animal kingdom which includes multicellular organisms whose cells are loosely aggregated and do not form tissues or organs.

The caudal fin has equal lobes, so it is said to be homocercal.

(i) This is the largest phylum of the Kingdom Animalia 

(ii) It includes the largest class called Insecta. 

(iii) They are bilaterally symmetrical, segmented, triploblastic and schizocoelomate animals 

(iv) Organization : organ system level. 

(v) They have jointed appendages - used for locomotion,feeding and are sensory in function. 

(vi) Body is covered by chitinous exoskeleton for protection and to prevent water loss, It is shed o periodically by a process called moulting or ecdysis. 

(vii) The body consists of a head, thorax, and abdomen with a body cavity called haemocoel. 

(viii)Respiratory organs : gills, book gills, book lungs or trachea. 

(ix) Circulatory system : open type.

(x) Sensory organs like antennae, eyes (compound and simple), statocysts (organs of balance equilibrium) are present. 

(xi) Excretion takes place through malpighian tubules, green glands, coxal glands, etc. 

(xii) They are mostly dioecious and oviparous; fertilization is internal. 

(xiii) Life history includes many larval stages followed by metamorphosis. eg. Limulus. 

Coelomic fluid acts as hydrostatic skeleton which helps to maintain the shape of the body.

Compare Schizocoelom with enterocoelom. 

1. Eucoelom or true coelom is a fluid-filled cavity that develops within the mesoderm and is lined by mesodermal epithelium called peritoneum. 

2. Such animals with a true body cavity are called eucoelomates 

3. Based on the mode of formation of coelom, the eucoelomates are classified into two types, 

i. Schizocoelomate animals - In these animals the body cavity is formed by splitting of mesoderm. Eg: Annelids, Arthropods, Molluscs. 

ii. Enterocoelomate animals - In these animals the body cavity is formed from the mesodermal pouches of archenteron. Eg: Echinoderms, hemichordates and chordates.

(i) Annelids are the first segmented animals to evolve. 

(ii) They are aquatic or terrestrial, free living but some are parasitic. 

(iii) They are triploblastic, bilaterally symmetrical, schizocoelomates 

(iv) Organization : organ system level organisation. 

(v) The coelom with coelomic fluid creates a hydrostatic skeleton and aids in locomotion. 

(vi) Body : metamerically segmented and the body surface is divided into segment or metameres. 

(vii) Internally the segments are divided from one another by partitions called septa. This phenomenon is known as metamerism. 

(viii) Nereis have lateral appendages called parapodia, which help in swimming. 

(ix) Circulatory system : closed type and the respiratory pigments are hemoglobin and chlorocruorin. 

(x) Nervous system : paired ganglion connected by the lateral nerves to the double ventral nerve cord. 

(xi) They reproduce sexually. 

(xii) Development is direct or indirect (Larva : trochophore ) eg. Lampito mauritii (Earth worm).

• All Echinoderms are marine animals. 
• These animals have a mesodermal endoskeleton of calcareous ossicles and hence the name Echinodermata.

1, - f, 2 - c, 3 - g, 4 - e, 5- a, 6 - b, 7 – d.

Class Chondrichthyes :

• Have cartilagenous endoskeleton. 

• Mouth ventral. 

• Gill slits without operculum. 

• Skin has placoid scales. 

• Usually oviparous, fertilisation internal. 

• No air bladder, so swim constantly to avoid sinking. 

• Teeth are backwardly directed, modified placoid scales. 

• Notochord is persistent throughout life. Males have claspers on pelvicfins. 

• e.g., Torpedo, Trygon, Scoliodon.

Class Osteichthyes :

• Have bony endoskeleton. 

• Mouth is usually terminal. 

• Four pairs of gill slits covered by operculum. 

• Skin has cycloid/ctenoid scales. 

• Usually viviparous, fertilisation external. 

• Have air bladder which regulates buoyancy. 

• e.g., Hippocampus, Labeo, Catla, Betta.

Protostomia: 

It includes the eumetazoans in which the embryonic blastopore develops into mouth. 

Deuterostomia: 

Eumetazoans in which anus is formed from or near the blastopore and the mouth is formed away from the blastopore. 

They have a true coelom called enterocoel, formed from the archenteron. 

• Cyclostomes are marine but migrate to fresh waters for spawning. 
• This is called anadromous migration. 
• After reproducing they die within a few days. 
• The larva after metamorphosis returns to the ocean.

(b) Ospharidiam 

(a) Annelids 

Presence of a copper-containing respiratory pigment is seen in Phylum Mollusca. 

(c) Echinodermata 

(a) Porifera and (c) Echinodermata

Presence of notochord at some stage of life is the key feature of chordates. Notochord is present in vertebrates in the embryonic stage and hence all vertebrates are chordates. But in some of the chordates, notochord may persist throughout the life. Hence, all chordates are not vertebrates.

All chordates consists of notochord present in some stage of life. Only invertebrates this notochord present in embryonic stage is replaced by the vertebral column during adult stage.

Air blassed helps the bony fishes in buoyancy.

The following modification helps birds to fly

• presence of feathers
• presence of pneumatic bones; pneumatic bones are long hollow bones (have air cavities)
• Fore limbs are modified into wings to help in flight
• hind limbs generally have scales helping them to clasp the prey in flight or a tree branch
• Excretion of urine and faeces is through single opening and excretion has very less amount of water this is to reduce body weight
• Aerodynamically built body helps in flying.

 Following are the modifications in birds that help them fly:

 • Pneumatic or hollow bones reduce weight. 

• Forelimbs are modified into wings. 

• Streamlined body helps in flying. 

• Uricotelic excretion helps in minimizing the need for carrying water and thus helps in weight reduction.

Advantages : 

1. The larval forms are much different from the adult and thrive on different food resources 

2. They also grow in a different ecological habitat. 

3. Hence in case of calamities, they may continue to exist even if the adults die.

4. Indirect development is a better means for the species to survive. 

Disadvantages: 

1. Chances of all larvae developing into adult cannot be assumed. 

2. Eggs have very little yolk. 

3. Parental care is not seen.

Direct Development: In this case the young or offsprings resembles the adult i.e., no intermediate stage

ex: Humans, Birds, etc.,

Indirect Development: In this case the young ones when hatched or born doesn’t resemble adult but undergoes through many intermediate stages to become adult,

e.g.: frogs have tadpole stage before becoming adult frogs. Butterfly have larvae, cocoon stage before becomes butterfly, etc.,

Hooks and Suckers are present in parasitic Platyhelminthes. Some of them absorb nutrients from host directly through their body surface, e.g.: Taenia (Tapeworm), Fasciola/liver fluke). 

Hooks and suckers are present in parasitic platyhelminthes. Suckers facilitate the sucking of blood from the host.

The body cavity present between the body wall and the midgut in triploblastic animals is called Coelom. Or It is the cavity present be¬tween mesoderm and endoderm in triploblastic animals. 

The nature of coelom gives important clue for classification of animals. The absence of coelom means that the animal has not developed a division of labour for various biological activities. On the other hand, the presence of coelom shows further evolution from simple to more complex organism. 

(b) Pheretima 

Using the common fundamental features helps in segregating the animals in different groups. Let us take the example of presence or absence of notochord. This feature helps us in grouping the animals among chordates and non-chordates. Similarly, two or three embryonic layers are taken for grouping the animals under diploblastic and triploblastic categories. Use of fundamental features in classification paves the way for further segregation of animals among different sub-groups. 

The following features are used as the basis of animal classification.

Level of Organization:- Identify the level of organization like cellular, tissue or a still higher level of Organization organ level of organization.

Body symmetry: Identify if the animals are asymmetrical, radially or have bilateral symmetry.

Diploblastic of triploblastic:- based on the presence of a number of embryonic layers.

Diploblastic: two embryonic layers as external ectoderm and as internal

Endoderm triploblastic: three embryonic layers as external ectoderm, middle mesoderm and inner endoderm.

Body cavity: The presence or absence of body cavity animals possessing coelom are called coelomates. Animals in which body cavity absent are called acoelomates

Segmentation: some animals show segmentation of body externally or internally

Presence of Notochord: chordates are animals with notochord and non-chordates which don’t form notochord during embryonic development.

In spite of differences in the structure of different animals, there are common fundamental features for various types of animals in relation to the arrangement of cells, body symmetry, nature of coeloms, patterns of digestive, circulatory or reproductive systems.

These features are necessary because they help in grouping organisms with more similar traits, arrangement and classification of animals as primitive or highly developed. It provides a basis for classification, helps in researching closely related species, etc.,

• Taenia (Tapeworn)
• Fasciola (liver fluke)
• Ascaris (round worm)
• wachereia (filaria worm)
• Ancylostoma (Hook worm)
• Hirudinaria (blood sucking leech)

 Ascaris, Wucheraria, Acylostoma, Taenia, Fasciola