NCERT Class 11 Biology Animal Kingdom Important Notes

Basis of Classification

Levels of Organisation

1. Cellular Level: In case of cellular level organization, a single cell is responsible for all the metabolic activities. Cellular level organization is present in unicellular animals and some of the muclticellular animals.

2. Tissue Level: In case of tissue level organization, a group of cells is responsible for all the metabolic activities, e.g. coelenterates.

3. Organ Level: In case of organ level organization, some specialized organs are present for some specific functions, e.g. Platyhelminthes.

4. Organ System Level: In organ system level organization, complex organ systems are present for various functions, e.g. mollusca, chordate.

Symmetry

Some of the animals are almost asymmetrical. Their body cannot be divided into two equal halves from any plane, e.g. sponges.

Radial Symmetry: In case of radial symmetry, any plane passing through the central axis divides the body into two identical halves, e.g. coelenterates, ctenophores, echinoderms, etc.

Bilateral Symmetry: In case of bilateral symmetry, the body can be divided into two identical halves only through a single plane, e.g. annelida, arthropoda, etc.

Diploblastic and Triploblastic Organisation

When the cells are arranged in two embryonic layers, the animal is called a diploblastic animal. The two layers are; ectoderm and endoderm. Mesoglea; which is an undifferentiated layer is present between the ectoderm and endoderm. Example: coelenterates.

When the cells are arranged in three embryonic layers, the animal is called triploblastic animal. The three layers are; ectoderm, mesoderm and endoderm. Examples: Platyhelminthes to chordates.

Coelom

The body cavity; which is lined by mesoderm is called coelom.

Coelomates: If coelom is present, the animal is called coelomate, e.g. annelids, molluscs, arthropods, echnioderms, hemichordates and chordates.

Pseudoceolomates: If the body cavity is not lined by mesoderm but the mesoderm is present as scattered pouches in between the ectoderm and endoderm, the animal is called pseudocoelomate, e.g. aschelminthes.

Acoelomates: When the body cavity is absent, the animal is called acoelomate, e.g. platyhelminthes.

Segmentation

The body of some animals is externally and internally divided into segments with serial repetition of at least some organs. For example; the body of the earthworm shows metameric segmentation. This phenomenon is called metamerism.

Notochord

Notochord is a mesodermally derived rod-like structure. It is formed on the dorsal side during embryonic development in some animals. If notochord is present then the animal comes under chordates. An animal without notochord is called non-chordate, e.g. porifera to echinoderms.

CLASSIFICATION OF ANIMALS

PHYLUM – PORIFERA

These are also known as sponges. They are usually found in marine habitat. Most of the poriferans are asymmetrical. Cellular level organization is present in these animals. ‘Pores on the body’ is the main feature of these animals.

Water Transport System in Sponges: Water transport system is a distinguishing feature of sponges. Water enters the body through minute pores on the body wall. Water enters into a central cavity (spongocoel) and then goes out through the osculum. The water transport system helps in gathering food, in exchange of gases and in excretion. The spongocoel and canals are lined by collar cells or choanocytes. Digestion is intracellular. A skeleton made up of spicules or sponging fibres supports the body.

Reproduction: These are hermaphrodite animals, i.e. sexes are not separate. While sexual reproduction is by gamete formation, asexual reproduction is by fragmentation. Fertilization is internal and development is indirect.

PHYLUM – COELENTERATA (CNIDARIA):

These are aquatic animals and most of them live in marine habitat. They can be sessile or free-swimming. The body is radially symmetrical. Body is composed of a cavity which has only one opening. Stinging capsules or nematocytes are present on the tentacles. Cnidoblasts are used for anchorage, defense and for capturing the prey.

Tissue level organization is present in cnidarians. They are diploblastic animals. Digestion is extracellular and intracellular. Some of the cnidarians have a skeleton composed of calcium carbonate, e.g. corals.

There are two basic body forms in the cnidarians, viz. polyp and medusa. Polyp is sessile and cylindrical form, e.g. Hydra, Adamsia, etc. Medussa is umbrella-shaped and free-swimming, e.g. Aurelia (Jelly Fish). Some cnidarians exist in both forms and exhibit alternation of generations, i.e. metagenesis. In this case, the polyp produces the medusa asexually and the medusa produces the polyp sexually.

Common Examples: Physalia (Portuguese man-of-war), Adamsia (Sea anemone), Pennatula (Sea-pen), Gorgonia (Sea-fan) and Meandrina (Brain coral).

PHYLUM – CTENOPHORA

These are commonly known as sea walnuts or comb jellies. These are exclusively marine animals. The body is radially symmetrical and diploblastic. Tissue level organization is present. There are eight eternal rows of ciliated comb plates on the body. These rows help in locomotion. Digestion is both extracellular and intracellular. Bioluminescence is well-developed in ctenophores.

Reproduction: These are hermaphrodite animals. Reproduction is only through sexual means. Fertilisation is external and development is indirect.

Common Examples: Pleurobrachia and Ctenoplana.

PHYLUM – PLATYHELMINTHES

Habit and Habitat: These are also called flatworms because of dorso-ventrally flattened body. Most of the flatworms live as endoparasites in animals; including human bodies. They are bilaterally symmetrical, triploblastic and acoelomate animals. Organ level organization is present in them.

Hooks and suckers are present in the parasitic forms. Some of the flatworms absorb nutrients from the host directly through their body surface. Osmoregulation and excretion are carried on by specialized cells called flame cells.

Reproduction: Flatworms are hermaphrodite animals. Fertilization is internal and development is indirect. Some members have the ability for regeneration, e.g. planaria.

Common Examples: Taenia solium (Tapeworm), Fasciola (Liverfluke)

PHYLUM – ASCHELMINTHES

Habit and Habitat: These are also called roundworms because their body appears circular in cross-section. They can be free living, aquatic and terrestrial. Some of them are parasitic in plants and animals. Organ system level of organization is present. The roundworms are bilaterally symmetrical, triploblastic and pseudocoelomate.

Digestive System: Alimentary canal is complete. Well developed muscular pharynx is present. There is an excretory tube to remove wastes through excretory pore.

Reproduction: The roundworms are dioecious, i.e. sexes are separate. Females are usually longer than males. Fertilization is internal and development can be direct or indirect.

Common Examples:- Ascaris (Round Worm), Wuchereria (Filaria worm), Ancylostoma (Hookworm).

PHYLUM – ANNELIDA

Habit and Habitat: The annelids are aquatic or terrestrial. The aquatic annelids are found in marine and freshwater habitats. Most of them are free-living, while some can be parasitic. Organ system level organization is present. Body is bilaterally symmetrical, coelomate and triploblastic. The body is metamerically symmetrical. The body is distinctly divided into segments or metameres.

Longitudinal and circular muscles are present to help in locomotion. Aquatic annelida possess lateral appendages (parapodia) which facilitates swimming, e.g. Nereis. Closed circulatory system is present.

Nephridia are present for excretion and osmoregulation. The neural system is composed of paired ganglia which are connected by lateral nerves to a double ventral nerve cord.

Reproduction: Earthworms and leeches are hermaphrodite, while nereis is dioecious.

Common Examples:- Nereis, Pheretima (Earthworm) and Hirudinaria (Blood sucking leech).

PHYLUM – ARTHROPODA

The presence of joint appendages is the reason for name arthropoda. This is the largest phylum of Animalia and over two-thirds of all known species on the earth are arthropods.

Organ system level of organization is present. Body is bilaterally symmetrical, triploblastic, segmented and coelomate.

Structure: The body consists of head, thorax and abdomen. Body is covered with exoskeleton made up of chitin. Respiration is carried out by gills, book gills, book lungs or tracheal system. Open circulatory system is present. Sensory organs; like antennae, eyes, statocysts (balance organs) are present. Eyes can be compound or simple. Malpighian tubules are the excretory organs.

Reproduction: Most of the arthropods are dioecious. Fertilisation is usually internal and development can be direct or indirect. Most of them are oviparous.

Common Examples:- Economically important insects – Apis (Honey bee), Bombyx (Silkworm), Laccifer (Lac insect) Vectors – Anopheles, Culex and Aedes (Mosquitoes) Gregarious pest – Locusta (Locust) Living fossil – Limulus (King crab).

PHYLUM – MOLLUSCA

Mollusca is the second largest phylum of Animalia. They are terrestrial or aquatic. The aquatic molluscs live in marine or freshwater habitats. Organ system level organization is present. Body is bilaterally symmetrical, triploblastic and coelomate.

The body is covered by a shell which is made up of calcium carbonate. Body is unsegmented with a distinct head, muscular foot and visceral hump. A mantle is formed over the visceral hump by a soft and spongy layer of skin. The space between the hump and the mantle is called mantle cavity. Feather-like gills are present in the mantle cavity. The gills facilitate respiration and excretion. Sensory tentacles are present in the anterior head region. File-like rasping organ; called radula is present in the mouth for feeding.

Reproduction: These are usually dioecious and oviparous. Development is indirect.

Common Examples:- Pila (Apple snail), Pinctada (Pearl oyster), Sepia (Cuttlefish), Loligo (Squid), Octopus (Devil fish), Aplysia (Seahare), Dentalium (Tusk shell) and Chaetopleura (Chiton).

PHYLUM – ECHINODERMATA

Ehinodermates have an endoskeleton made up of calcareous ossicles. Due to this, the body is covered with spines. These are marine animals. Organ system level organization is present. Adults are radially symmetrical but larvae are bilaterally symmetrical. Body is triploblastic and coelomate. Digesive system is complete. Mouth is present on the ventral side and anus is present on the dorsal side.

Water canal system is the most distinctive feature of echinoderms. The water canal system helps in locomotion, capture and transport of food and respiration. Excretory system is absent.

Reproduction: These are dioecious animals. Fertilisation is usually external. Development is indirect. Larvae are free-swimming.

Common Examples:- Asterias (Star fish), Echinus (Sea urchin), Antedon (Sea lily), Cucumaria (Sea cucumber) and Ophiura (Brittle star).

PHYLUM – HEMICHORDATA

This phylum has a small group of animals which look like worms. Organ system level organization is present. Body is bilaterally symmetrical, triploblastic and coelomate. The body is cylindrical and consists and anterior proboscis, a collar and a long trunk.

Open circulatory system is present. Gills are present for respiration. Proboscis gland is the excretory organ.

Reproduction: These are dioecious animals. Fertilisation is external and development is indirect.

Common Examples:- Balanoglossus and Saccoglossus.

PHYLUM – CHORDATA

The main features of chordates are the presence of notochord, a dorsal hollow nerve cord and paired pharyngeal gill slits. The body is bilaterally symmetrical, triploblastic, coelomate. Organ system level of organization is present. Closed circulatory system is present. A post anal tail is present.

Phylum Chordata is divided into three subphyla which are as follows:

1. Urochordata or Tunicata,

2. Cephalochordata and

3. Vertebrata.

Subphyla Urochordata and Cephalochordata are usually referred to as protochordates. These are exclusively marine animals. In Urochordata, notochord is present only in larval tail. In Cephalochordata, the notochord extends from head to tail region and is persistent throughout the life.

Common Examples:- Urochordata – Ascidia, Salpa, Doliolum; Cephalochordata – Branchiostoma (Amphioxus or Lancelet).

VERTEBARATA

Notochord is present during the embryonic period only. After that, the notochord is replaced by a cartilaginous or bony vertebral column in the adult.

A ventral muscular heart is present as the main organ of the circulatory system. The heart can have two, three or four chambers. Kidneys are present for excretion and osmoregulation. Paired appendages are present for locomotion.

Phylum chordata can be divided into two sub-phyla, viz. agnatha and gnathostomata.

Sub-phylum Agnatha: Jaws are absent.

Sub-Phylum Gnathostomata: Jaws are present.

There is only one class; Cyclostomata in the sub-phylum Agnatha. Gnathostomata is divided into two super-classes, viz. pisces and tetrapoda. Fins are present in pisces for locomotion. Four limbs are present in tetrapoda for locomotion. Super-class tetrapoda is further divided into four classes, viz. amphibia, reptilia, aves and mammalia.

CLASS – CYCLOSTOMATA

All the existing members of the class Cyclostomata are ectoparasites on some fishes. The body is elongated. There are 6 -15 pairs of gill slits for respiration. A sucking and circular mouth is present. The body is devoid of scales and paired fins.

Cranium and vertebral column are composed of cartilage. Closed circulatory system is present.

Reproduction: They are marine animals but migrate to freshwater for spawning. They die within a few days of spawning. The larvae return to the ocean after metamorphosis.

Common Examples: Petromyzon (Lamprey) and Myxine (Hagfish).

CLASS – CHONDRICHTHYES

These are also known as cartilaginous fish because of cartilaginous endoskeleton. These are marine animals. Mouth is ventrally located. Notochord is present throughout the life. Gill slits are separate and operculum (gill cover) is absent. Skin is tough and has minute placoid scales. Teeth are modified placoid scales and are backwardly directed. Jaws are very powerful. These are predaceous animals. Air bladder is absent and hence the animal has to swim constantly to avoid sinking.

There are two chambers in the heart. Some animals of this class have electric organs, e.g. torpedo. Some animals, on the other hand, possess poison sting, e.g. Trygon. They are cold-blooded (poikilothermous) animals.

Reproduction: These are dioecious animals. The pelvic fins in males bear claspers. Fertilization is internal and many of them are viviparous.

Common Examples: Scoliodon (Dog fish), Pristis (Saw fish), Carcharodon (Great white shark), Trygon (Sting ray).

CLASS – OSTEICHTHYES

These are also called bony fishes because of bony endoskeleton. The body is streamlined. Mouth is usually terminal. There are four pairs of gills which are covered by operculum on each side. The skin is covered with cycloid/ctenoid scales. Air bladder is present which helps in buoyancy. The heart is two-chambered. They are cold-blooded animals.

Reproduction: These are dioecious animals. Fertilization is usually external and development is direct. Most of the bony fishes are oviparous.

Common Examples:- Marine – Exocoetus (Flying fish), Hippocampus (Sea horse); Freshwater – Labeo (Rohu), Catla (Katla), Clarias (Magur); Aquarium – Betta (Fighting fish), Pterophyllum (Angel fish).

CLASS – AMPHIBIA

The amphibians can live both in aquatic and terrestrial habitats. They need water for fertilization. Two pairs of limbs are present in most of the amphibians. Body is divided into head and trunk. Tail can be present in some of them. The skin is moist and scales are absent. Eyelids are present on the eyes. A tympanum represents the ear. There is a common chamber; called cloaca; in which the alimentary canal, urinary tract and reproductive tract open. Respiration is by gills, lungs and through skin.

There are three chambers in the heart (two auricles and one ventricle). These are cold-blooded animals.

Reproduction: These are dioecious animals. Fertilization is external and development can be direct or indirect. These are oviparous animals.

Common Examples:- Bufo (Toad), Rana (Frog), Hyla (Tree frog), Salamandra (Salamander), Ichthyophis (Limbless amphibia).

CLASS – REPTILIA

These animals show creeping or crawling mode of locomotion. Most of them are terrestrial animals. The body is covered by dry and cornified skin, epidermal scales (scutes). Tympanum represents ear. Limbs are in two pairs; when present.

Three-chambered heart is present in most of the reptiles. Crocodiles have four-chambered heart. These are cold-blooded animals.

Reproduction: These are dioecious animals. Fertilization is internal and development is direct. These are oviparous animals.

Common Examples:- Chelone (Turtle), Testudo (Tortoise), Chameleon (Tree lizard), Calotes (Garden lizard), Crocodilus (Crocodile), Alligator (Alligator). Hemidactylus (Wall lizard), Poisonous snakes – Naja (Cobra), Bangarus (Krait), Vipera (Viper).

CLASS – AVES

Presence of feathers and wings are the characteristic features of Aves. The forelimbs are modified into wings. The hind limbs usually have scales and are modified for walking, swimming or clasping the tree branches. Skin is dry without glands, but oil gland is present at the base of the tail. Beaks are present.

The endoskeleton is composed of bones. Long bones are pneumatic, i.e. are hollow with air cavities. Air cavities in the long bones help in weight reduction and this is an important flight adaptation. Crop and gizzard are the additional chambers in the digestive tract.

There are four chambers in the heart. They are warm-blooded (homoiothermous) animals. Respiration is by lungs, and air sacs; connected to lungs; supplement respiration.

Reproduction: These are dioecious animals. Fertilization is internal and development is direct. They are oviparous animals.

Common Examples:- Corvus (Crow), Columba (Pigeon), Psittacula (Parrot), Struthio (Ostrich), Pavo (Peacock), Aptenodytes (Penguin), Neophron (Vulture).

CLASS – MAMMALIA

Presence of mammary glands is the most unique feature of these animals. The young ones are nourished by the mammary glands. Hairs are present on the skin and external ears are present. Different types of teeth are present in the jaw. The two pairs of limbs are adapted for walking, running, climbing, burrowing, swimming or flying.

There are four chambers in the heart. They are warm-blooded animals. Respiration is by lungs.

Reproduction: They are dioecious animals. Fertilization is internal and development is direct. Most of them are viviparous.

Common Examples:- Oviparous - Ornithorhynchus (Platypus);

Viviparous - Macropus (Kangaroo), Pteropus (Flying fox), Camelus (Camel), Macaca(Monkey), Rattus (Rat), Canis (Dog), Felis (Cat), Elephas (Elephant), Equus (Horse), Delphinus (Common dolphin), Balaenoptera (Blue whale), Panthera tigris (Tiger), Panthera leo (Lion).

Distinct Characters of 4 classes of the Superclass Tetrapoda:

1. Amphibia: Capable of living on both land and water but need water for some stages of the life cycle. Respiration is through lungs, skin and gills. These are cold-blooded animals.

2. Reptilia: Creeping or crawling mode of locomotion. The skin is hard with scale like structures. These are cold-blooded animals.

3. Aves: Pneumatic bones, feathers and wings are the important flight adaptations. Forelimbs are modified into wings. These are warm-blooded animals.

4. Mammal: Milk is produced by the mammary glands in females and is utilised for nourishing the young ones. Hairs are present on the skin. External ears are present. These are warm-blooded animals.

NCERT Solution for Class 11 Biology Animal Kingdom 

Question 1. What are the difficulties that you would face in classification of animals, if common fundamental features are not taken into account?

Answer: 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.

Question 2:- If you are given a specimen, what are the steps that you would follow to classify it?

Answer: Steps to Follow for Classification:

• The first step should be look for the presence or absence of vertebral column.

• The next step would be to identify the level of organization.

• The next step should be to look for symmetry, i.e. radial or bilateral or asymmetrical.

• The next step would be to look for presence or absence of body cavity.

Question 3:- How useful is the study of the nature of body cavity and coelom in the classification of animals?

Answer: 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.

Question 4. Distinguish between intracellular and extracellular digestion?

Answer: In case of intracellular digestion, digestion takes place inside the cell. Digestive enzymes are secreted in the food vacuole where food is digested. Absorption and assimilation are also intracellular in this case. Food is simple in this case.

In case of extracellular digestion, digestion takes place outside the cell. A rudimentary or developed alimentary canal may be present for facilitating extracellular digestion. Extracellular digestion is more evolved than intracellular digestion. Complex food can be utilised in this case.

Question 5. What is the difference between direct and indirect development?

Answer: When the young one resembles the adult animal, then it is the case of direct development. But when the young one looks entirely different than the adult animal, it is the case of indirect development. An animal may pass through several forms during indirect development, e.g. frog and silk moth.

Question 6. What are the peculiar features that you find in parasitic platyhelminthes?

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

Question 7. What are the reasons that you can think of for the arthropods to constitute the largest group of the animal kingdom?

Answer: Arthropoda is the first phylum in which animals have properly developed organ systems. Elaborate organ system helped the arthropods in surviving in diverse conditions. Moreover, the arthropods are the earliest among the animals with well developed organ system. These are the reasons that arthropoda is the largest phylum in the animal kingdom.

Question 8. Water vascular system is the characteristic of which group of the following:

(a) Porifera (b) Ctenophora (c) Echinodermata (d) Chordata

Answer: (a) Porifera and (c) Echinodermata

Question 9. “All vertebrates are chordates but all chordates are not vertebrates”. Justify the statement.

Answer: 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.

Question 10. How important is the presence of air bladder in Pisces?

Answer: Air blassed helps the bony fishes in buoyancy.

Question 11. What are the modifications that are observed in birds that help them fly?

Answer: 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.

Question 12. Could the number of eggs or young ones produced by an oviparous and viviparous mother be equal? Why?

Answer: In case of oviparous animals, eggs are exposed to the vagaries of nature and also face the danger of predators. Hence, a larger number of eggs needs to be laid to ensure survival of the species.

In case of viviparous animals, the foetus develops to a size that it can have better chances of survival after birth. Moreover, development of foetus requires more resources from the female’s body. Hence, a smaller number of offsprings are produced by viviparous animals.

Question 13. Segmentation in the body is first observed in which of the following:

(a) Platyhelminthes (b) Aschelminthes (c) Annelida (d) Arthropoda

Answer: (c) Annelida

Question14. Match the following:

Question 15. Prepare a list of some animals that are found parasitic on human beings

Answer: Ascaris, Wucheraria, Acylostoma, Taenia, Fasciola

Important Questions for NCERT Class 11 Biology Animal Kingdom

Ques. In which of the following animals nerve cell is present but brain is absent?
(a) Sponge        (b) Earthworm
(c) Cockroach    (d) Hydra

Answer: D

Ques. In which of the following, notochord is present in embryonic stage?
(a) All chordates    (b) Some chordates
(c) Vertebrates       (d) Non chordates 

Answer: A

Ques. In which of the following animals, haemocyanin pigment is found?
(a) Annelida     (b) Echinodermata
(c) Insecta       (d) Mollusca 

Answer: D

Ques. In which of the following animals post anal tail is found?
(a) Earthworm    (b) Lower invertebrates
(c) Scorpion       (d) Snake 

Answer: D

Ques. In Hydra, waste material of food digestion and nitrogenous waste material are removed respectively from
(a) mouth and mouth
(b) body wall and body wall
(c) mouth and body wall
(d) mouth and tentacles. 

Answer: C

Ques. Cleavage in mammals is
(a) holoblastic equal    (b) holoblastic unequal
(c) superficial              (d) discoidal. 

Answer: B

Ques. Similarity in Ascaris lumbricoides and Anopheles stephensi is
(a) sexual dimorphism
(b) metamerism
(c) anaerobic respiration
(d) endoparasitism. 

Answer: A

Ques. Which of the following characters is absent in all chordates?
(a) Diaphragm                     (b) Coelom
(c) Pharyngeal gill clefts       (d) Dorsal nerve cord

Answer: A

Ques. What is true for mammalia?
(a) Platypus is oviparous.
(b) Bats have feather.
(c) Elephant is ovoviviparous.
(d) Diaphragm is absent in them. 

Answer: A

Ques. Aquatic reptiles are
(a) ureotelic          (b) ureotelic in water
(c) ammonotelic    (d) ureotelic over land.

Answer: B

Ques. Temperature changes, in the environment, affect most of the animals which are
(a) poikilothermic     (b) homoiothermic
(c) aquatic               (d) desert living.

Answer: A

Ques. The canal system is a characteristic feature of
(a) echinoderms        (b) sponges
(c) helminthes           (d) coelenterates. 

Answer: B

Ques. Which of the following is not found in birds?
(a) Pelvic girdle           (b) Pectoral girdle
(c) Hindlimb               (d) Forelimb 

Answer: D

Ques. The long bones are hollow and connected by air passages. They are the characteristics of
(a) reptilia         (b) land vertebrates
(c) aves            (d) mammals. 

Answer: C

Ques. Solenocytes are the main excretory structures in
(a) echinodermates       (b) platyhelminthes
(c) annelids                  (d) molluscs. 

Answer: B

Ques. Most appropriate term to describe the life cycle of Obelia is
(a) metamorphosis     (b) neoteny
(c) metagenesis         (d) all of these.

Answer: C

Ques. The lower jaw in mammals is made up of
(a) dentary           (b) maxilla
(c) angulars          (d) mandible. 

Answer: A

Ques. Which one of the following cells, found in testes of rabbit, secretes male hormone?
(a) Epithelial cells    (b) Spermatocytes
(c) Leydig’s cell       (d) Sertoli cells 

Answer: C

Ques. What is common among silverfish, scorpion, crab and honey bee?
(a) Jointed legs              (b) Metamorphosis
(c) Compound eyes        (d) Poison glands 

Answer: C

Ques. The embryonated egg of Ascaris represents
(a) an egg with blastula
(b) an egg with a juvenile
(c) an egg with an egg
(d) an egg with gastrula. 

Answer: B

Ques. Which of the following statements is without exception for sponges?
(a) They all have calcareous spicules.
(b) They have high regenerative power.
(c) They are found only in marine water.
(d) They are all radially symmetrical. 

Answer: B

Ques. Pneumatic bone is found in
(a) shark            (b) Rana
(c) pigeon          (d) whale. 

Answer: C

Ques. The nephridia in earthworm are analogous to
(a) nematoblasts of Hydra
(b) flame cells of Planaria
(c) gills of prawn
(d) trachea of insects. 

Answer: B

Ques. Which of the following is common among mammals?
(a) They undergo no moulting.
(b) They have seven cervical vertebrae.
(c) They are carnivores.
(d) They have ventral nerve cord. 

Answer: A

Ques. The formation of canal system in sponges is due to
(a) folding of inner walls
(b) gastro-vascular system
(c) reproduction
(d) porous walls.

Answer: D

Ques. The organisms attached to the substratum, generally, possess
(a) one single opening of the digestive canal
(b) cilia on the surface to create water current
(c) radial symmetry
(d) asymmetrical body. 

Answer: C

Ques. A common characteristic of all vertebrates without exception is
(a) the division of body into head, neck, trunk and tail
(b) their body covered with an exoskeleton
(c) the possession of two pairs of functional appendages
(d) the presence of well-developed skull.

Answer: D