KINGDOM ANIMALIA

 KINGDOM ANIMALIA

Q.1: What are the diploblastic and triploblastic?

Ans: DIPLOBLASTIC AND TRIPLOBLASTIC ORGANIZATION:
Diploblastic are the animals whose body wall is composed of two layers: outer ectoderm and inner endoderm. Between these two layers, a non-cellular gelatinous layer called mesogloea is present.

Fig. 10-1(A): Diploblastic Organization (Hydra - T.S.)

Triploblastic are the animals whose body wall consists of three layers: outer ectoderm, middle mesoderm, and inner endoderm.

Fig. 10-1(B): Triploblastic Organization

Q.2: Write a note on Symmetry?

Ans: Symmetry:
A balanced structure and composition of the body according to the size and shape is called symmetry. It provides the least possible resistance in the movement of the body. There are two types of symmetry:

Bilateral Symmetry:
When the body can be divided into two equal halves by passing through the longitudinal axis, it is called a bilaterally symmetrical body. e.g., man, fish, etc.

Radial Symmetry:
When the body of an animal can be divided into two halves by more than one angle, it is called a radially symmetrical body, e.g., sea anemone. Animals with no plane of symmetry are called asymmetrical, e.g., sponges.

Fig. 10-2(A): Bilateral Symmetry (Man)
Fig. 10-2(B): Radial Symmetry (Sea-anemone)

Q.3: Write a note on Coelom?

Ans:
The internal body cavity of animals is called coelom. According to the coelom, the bilaterally symmetrical animals are divided into three groups.

• Acoelomata:
  These animals do not have a body cavity, e.g., Platyhelminthes (liver fluke, Planaria, etc.).

• Pseudocoelomata:
  These animals contain a primitive body cavity but do not have a true body cavity. It is considered a false cavity, present between the body wall and gut wall, e.g., Nematodes.

• Coelomata:
  These animals contain a true body cavity called coelom. In this cavity, all important organs are present, such as the alimentary canal, excretory organs, and reproductive organs, e.g., Earthworm, Chordate animals (fishes, reptiles, amphibians, birds, and mammals).

Fig.10-3(A): Acoelomate (No body cavity)
Fig.10-3(B): Pseudocoelomate (False Coelom)
Fig.10-3(C): Coelomate

Q.4: What are Protostomes and Deuterostomes?

Ans:
The coelomate animals (containing a true body cavity, coelom) are classified into two groups according to the fate of the blastopore.

• Protostomes: (Proto - First, Stoma - Mouth)
  In these animals, the blastopore is changed into the mouth, e.g., Annelids, Molluscs, Arthropodes.

• Deuterostomes: (Deutero - Second, Stoma - Mouth)
  In these animals, the blastopore is changed into the anus. The mouth is formed from another opening which is developed in the embryo after some time, e.g., Echinoderms, Chordates.

Q.5: Describe the important characters of Phylum Porifera?

Ans: IMPORTANT CHARACTERS PHYLUM PORIFERA:

• They are multicellular organisms. They are flat, cup-shaped, vase-shaped, bell, or fan-like. They have an asymmetrical body, i.e., have no plane of symmetry.
• They are sessile, i.e., do not move. They are attached to any solid object like stone or rock.
• Their body contains pores, called ostia. Through the ostia, water enters the body. The largest pore is known as osculum, through which the water is discharged out.
• Their body skeleton is composed of proteins, calcium carbonate, and silica. The skeleton has spiny structures, called spicules.
• They are diploblastic. Their body wall is composed of two layers, outer ectoderm and inner endoderm. Between these two layers, a middle region is also present, called mesenchyme.
• The cells of ectoderm are called pinacocytes; these are thin, flat, and scale-like. The cells of endoderm are called choanocytes. These cells are oval-shaped and flagellate. The cells which form pores in the body wall are called porocytes.
• The inner body cavity is called spongocoel. It is present with endodermal cells called choanocytes.

Spongocoel may be single or divided into many chambers. There are three types of sponges based on their body cavity:

1. Ascon type:
   Spongocoel consists of a single cavity.

2. Sycon type:
   The spongocoel divides into secondary chambers.

3. Leucon Type:
   The spongocoel divides into secondary and tertiary chambers.

• These animals do not have head, mouth, and alimentary canal. They use bacteria and organic matter as their food by filtration.
• They do not have a nervous system, respiratory system, or excretory system.
• Reproduction is by asexual and sexual methods.
• Asexual reproduction takes place by fragmentation and gemmule formation, and regeneration. Gemmule is a small body produced from amoeboid cells, covered by epithelial cells. During favorable conditions, it develops into new Porifera.
• Sponges are hermaphrodite (bisexual), but some are unisexual. Sperms are transferred into another sponge where fertilization occurs. After fertilization, the zygote develops into a free-swimming Amphiblastula larva. It is attached to the bottom, then develops into a new sponge.
• Examples: Sycon, Euplectella, Euspongia.

Q.6: Describe the important characters of Phylum Cnidaria?

Ans: Important Characters Of Phylum Cnidaria:

• They are simple aquatic animals. They have a radially symmetrical body.

Body Cavity - Coelenteron:

• Inside the body, a digestive cavity is present, called enteron or coelenteron. It opens to the outside by a single opening mouth.

Diploblastic Organization:

• They are diploblastic, i.e., their body wall consists of two layers, the outer layer is epidermis (ectoderm) and the inner layer is gastrodermis (endoderm), which is present along the body cavity. Between these two layers, a non-cellular gelatinous layer is found, called mesoglea.

Cnidocytes And Nematocytes (Defensive Organs):

• The mouth is surrounded by finger-like structures, called tentacles. The tentacles contain special cells, known as cnidoblasts. These cnidoblasts have capsule-like bodies, the nematocysts. These are the organs of offense and defense.

• Polyp And Medusa: The animals are of two types, one is polyp and the other is medusa. The polyp form is attached to a substrate at one end, e.g., Sea-anemone. The medusa animals are free-swimming, and they are not attached to any object (e.g., Physelia).

  Polymorphism: Many cnidarians live together to form a group or colony. In this colony, many individuals are physically attached together. This group formation is called polymorphism, e.g., Obelia, Physalia (Blue bottle). In polymorphism, polyp and medusa forms live together. In a group, two or more different types of animals are present, called zooids. These zooids collectively form a single species. The zooids perform different functions; such as:

  • Gastro-Zooid: They take food material.
  • Gono-Zooids: They are reproductive zooids.
  • Dactylo-Zooids: They are sensory zooids and they protect the animal.

  Respiratory, Excretory And Circulatory Systems: The cnidarians do not have proper respiratory, excretory, and circulatory systems. All these processes are performed by diffusion through the body surface.

  Nervous System: The nerve cells do not form the brain and spinal cord. They are present in the form of a network, so impulses are conducted in all directions more or less equally.

  Reproductive System: Asexual reproduction is mostly by regeneration and budding. Sexual reproduction also takes place in cnidarians by the fusion of male and female gametes.

Q.7: What are the Corals and Coral reefs?

Ans: CORALS & CORAL REEFS: Some cnidarians secrete a certain chemical substance which forms a protective covering around their body. These are called corals. They are of different shape and size. Underwater near the surface of the sea, coral reefs are formed. These are usually present in warm water. Along the Australian eastern coast, these reefs are found over hundreds of miles, this is called the Great Barrier Reef.

Corals are brightly colored. Red corals are used to make jewelry and other decorative items. In our country, Hakeems prepare an eastern medicine from red coral, commonly called Marjan.

Q.8: Describe the characters of Phylum Platyhelminthes?

Ans: IMPORTANT CHARACTERS:

• They have a flattened body on both sides, so they are called flat-worms. They have a bilaterally symmetrical body.

• They may be free-living, for example, Planaria; some are parasites and live in the body of other animals like Liver-fluke.

• They have a soft body without a skeleton.

• They are triploblastic animals, i.e., their body consists of three layers: outer ectoderm, middle mesoderm, and inner endoderm.

• A true body cavity (coelom) is not found, so they are acoelomate animals (without coelom).

• They have a single gastro-vascular cavity (alimentary canal). In some animals, this cavity is branched and opens to the outside by mouth only (e.g., Planaria). Some animals do not have a gastrovascular cavity, such as Cestodes (Tape worm).

• Blood vascular system is not present. The transportation takes place by diffusion.

• Respiration also takes place by diffusion through the external body surface.

• The nervous system consists of brain ganglia and a pair of connected nerve cords. They also have eye-spots.

• The excretory system takes place by flame cells or proto-nephridia. These cells absorb excretory products, which are discharged out of the body through the pores, called nephridiopores.

• They are hermaphrodite animals, i.e., male and female reproductive organs are present in the same body.

• The parasitic animals are either ectoparasites or endoparasites. They have suckers, which are used to attach them to the host body and to suck food material.

• Some parasitic animals complete their life cycle in the body of one host, and they are called monogenic. Some animals complete their life cycle in the body of two hosts; they are called digenic.

Examples Of Phylum:

• Planaria (Dugesia)
• Live fluke
• Tape worm (Taenia solium)

Q.9: What are the Parasitic adaptations of Flatworms?

Ans:
The parasitic adaptations of flatworms are as follows:

• They have thick body covering, which protects them from host body.
• They have suckers, hooks, and spines for proper attachment and sucking of food material. These are the replacement of locomotory organs.
• Their alimentary canal is reduced or absent in Taenia solium (tapeworm), because they absorb food from host body.
• Reproductive system is much developed and fertility rate is high to increase their number rapidly.

Q.10: What are the Precautions against diseases?

Ans: Precautions Against Diseases: Flatworms are mostly parasites and cause many diseases. The precautions and control measures are as follows:

• Hygienic life should be maintained.
• Sanitary conditions should be properly maintained.
• Careful inspection of edible items is necessary.
• Meat should be cooked properly to kill the parasites.

Q.11: Describe the important characters of Phylum Aschelminthes?

Ans: Important Characters:

• The Nematodes are also called roundworms. They have elongated and round bodies. The anterior and posterior ends are thin and pointed. They have bilaterally symmetrical body.
• The body is without segments. It is covered with a tough cuticle.
• They are triploblastic. Their body wall is composed of three layers, ectoderm, mesoderm, and endoderm.
• The nematodes have only longitudinal muscles. Circular muscles are not present. So they can only bend or swim poorly.
• The body cavity is a primitive cavity, called pseudo-coelom. It lies between the body-wall and gut-wall. The pseudo-coelom is considered as a false cavity.
• They have a complete digestive system.
• They have a circulatory system.
• The nervous system is composed of brain and nerve cords.
• The roundworms contain the essential and established characters of higher animals like digestive system, circulatory system, and nervous system.

Q.12: Describe the different diseases caused by Nematodes?

Ans: Diseases by Nematodes:

Elephantiasis or Filariasis (Thread Worm Disease)
It is caused by thread worm, Wuchereria. It is transferred into the body of man from blood sucking mosquitoes. When this mosquito bites a healthy person, this worm enters his body. It lives in lymphatic vessels and prevents the proper flow of lymph through the lymphatic vessels. As a result of this, hands, feet, and legs become extremely swollen; therefore, the disease is known as Elephantiasis.

This disease is very common in poor tropical countries. The main reason for spreading the disease is improper sanitary system in the area.

Hookworm Disease:
The hookworm, Ancylostoma enters the body of man in the form of larvae through the skin of man and finally enters the intestine. It lives there as a parasite and sucks the blood.

Ascaris Disease:
Ascaris lives in the intestine of children, lives as a parasite and uses the food of host body. It disturbs the growth and development of the children.

Q.13: Describe the important characters of Phylum Annelida?

Ans: Important Characters of Phylum Annelida:

• They have elongated and segmented body. Their segments are externally ring-like. These rings or external segments are called metameres.
• Their segmentation is called metameric segmentation, because the segmentation is both externally as well as internally.
• They have bilaterally symmetrical body.
• They are triploblastic animals i.e., the body consists of three layers, outer ectoderm, middle mesoderm, and inner endoderm.
• The alimentary canal is elongated and tube-like. It extends from mouth to the anus.
• These animals possess a true-coelom (true body cavity). It lies between the layers of mesoderm. Due to the presence of a true coelom they are called coelomates. There is development of coelomic compartments in their body.
• They have closed-type of circulatory system i.e., the blood flows in blood vessels. The blood is red due to the presence of hemoglobin of the major blood vessels are dorsal and ventral blood vessels. The number of hearts is two or more.
• There is no special respiratory organs. The respiration takes place through external surface of the body.
• The excretion is by convoluted tube-like organs, called nephridia. In each segment a pair or more nephridia are present.
• The locomotion of the body is by small hair-like structures, called setae. They are found along the segments in pairs: The setae or chaetae are with or without parapodia.

Q.14: Describe the important characters of Phylum Mollusca?

Ans: Important Characters:

• They have soft, unsegmented body with bilateral symmetry with organ system organization.
• They are triploblastic i.e. body consists of three layers, ectoderm, mesoderm, and endoderm.
• Alimentary canal is in the form of a straight or coiled tube with mouth and anus at the opposite side.
• Coelom is reduced, consists of few fluid-filled cavities, and makes a part of hydrostatic skeleton.
• Appendages are not produced from their body.
• From the lower side of their body, a special structure foot is developed, which helps in locomotion, sensation, and feeding.
• The upper layer of the body is called mantle. It produces shell for the protection of the body.
• The head is distinct. Mouth, eyes, and tentacles are present on the head.
• They have a dorsal visceral mass that includes major organs.
• In some animals, a special structure is produced in their mouth, called radula. It is used for scraping, tearing, and pulling of food.
• Respiration takes place by gills or lungs. In aquatic animals, gills are present, and in terrestrial animals, poorly-developed lungs are present.
• Excretion is by kidneys.
• Circulatory system is of open type, but the cephalopoda have closed type of circulatory system. Heart is present.
• Nervous system consists of a cerebral-ganglion, a pair of pedal nerves up to the foot and a pair of visceral body.
• Reproductive organs are found either in the same body or in separate bodies. Fertilization is in water.
• After fertilization, the egg develops into a larva, which is changed into an adult.
• The larva is of trochophore type.

Q.15: Describe the characters of class Bivalvia of Phylum Mollusca and Pearl formation?

Ans: Important Characters of Class Bivalvia:

• The head is not distinct.
• The shell consists of two pieces. It can be opened or closed. It has a hinge joint.
• The foot is large. It comes out from the opened shell and is used for locomotion or burrowing in sand.
• Respiration takes place by gills, which are thin and plate-like.
• Pearl formation: In Pearl Oyster Molluscs, pearl-formation takes place.

Q16: Describe the characters of Phylum Arthropoda?

Ans: Important Characters of Phylum Arthropoda:

• They have metamerically segmented and bilaterally symmetrical body.
• The body is covered by an outer covering, called exoskeleton. It is made up of proteins and chitin.
• Their body is triploblastic i.e. consists of three layers, outer ectoderm, middle mesoderm, and inner endoderm.
• The body of these animals is divided into head, thorax, and abdomen. In some animals, head and thorax are fused together to form Cephalothorax.
• From the body jointed legs or appendages are produced. The antennae, jaws, legs, and swimming organs are in pairs.
• Circulatory system is of open type i.e. blood vessels are absent, and the blood flows freely throughout the body.
• The body cavity is known as haemocoel, because the blood flows through it.
• The true body cavity coelom is very small and contains reproductive organs.
• The digestive system consists of a tube-like structure, which extends from mouth to the anus. Jaws are present.
• In terrestrial animals respiration is by trachea or book lungs. In aquatic animals, it is by gills.
• Nervous system consists of a brain in the anterior region (head) and a double nerve cord in the lower region of the body.
• They have compound eyes with mosaic vision.
• In insects and other animals, excretion takes place by malpighian tubules. In some animals, green antennary glands are the excretory organs.
• Sexes are found in separate bodies. Fertilization is internal. Development takes place by metamorphosis.

Q.17: What is Metamorphosis and describe its types?

Ans: Metamorphosis: The process of development from egg to the adult stage is called metamorphosis. It is of two types:

1. Incomplete Metamorphosis:

   • In this process, the egg is directly changed into a new individual which is similar to the adult, called nymph.
   • The nymph passes many stages of development. It becomes larger and mature, then finally changes into an adult, e.g., Cockroach, Grasshopper.

2. Complete Metamorphosis:

   • In this process, different stages are present, (i) egg, (ii) Larva, (iii) Pupa, (iv) Imago.
   • The egg produces larva. The larva may be of different types, maggot, grub, caterpillar, or worm-like.
   • The larva is an active form and takes its food from outside.
   • After many molts, the larva is changed into pupa. It covers itself by a protective coat and becomes inactive, using its internal stored food.
   • In pupa, internal major changes occur, and after a certain period, imago comes out.
   • The complete metamorphosis occurs in mosquito, butterfly, honey bee, etc.

Q.18: What are the advantages of Exoskeleton jointed appendages and wings?

Ans: Advantages of Exoskeleton Jointed Appendages and Wings:

• In arthropods, jointed appendages with exoskeleton are present. The jointed appendages help in walking, swimming, food capture, copulation, and sensory mechanism.
• The exoskeleton has the following advantages:
  • It is a protective covering around their body and appendages.
  • It makes them waterproof.
  • Exoskeleton is nonliving, after a particular period, it is shed down and new exoskeleton is formed. This process is called molting or ecdysis.
  • It also provides sites of muscle attachment. The muscles and jointed appendages work together and perform many functions, such as walking, swimming, flying, and other activities.
• Wings are the flying organs, helping in fast and easy movement of insects to other places.

Q.19: Name the classes of Phylum Arthropoda?

Ans: Phylum Arthropoda is divided into five classes:

• Class – Merostomata (with mouth plates) e.g., King crab (Limulus).
• Class – Arachnida (Spider-like animals) e.g., Scorpions, Spiders.
• Class – Crustaceae (with carapace) e.g., Prawn, Crab.
• Class – Myriapoda (with many legs) e.g., Centipedes, Millipedes.
• Class – Insecta or Hexapoda (with six legs) e.g., Butterflies, Mosquitoes, etc.

Q.20: Describe the characters of Class Insecta of Phylum Arthropoda?

Ans: Class – Insecta:

• The body of insects is divided into three parts, head, thorax, and abdomen.
• From the head, a pair of antennae is produced.
• Mouth parts are modified according to their function, such as:
  • Biting and chewing type e.g., Cockroach.
  • Piercing and sucking type e.g., Mosquito.
  • Chewing and lapping type e.g., Honey bee.
  • Sponging type e.g., Housefly.
  • Siphoning type e.g., Butterfly.
• Thorax is made up of three segments, prothorax, mesothorax, and metathorax.
• From the lower side of the thorax, three pairs of legs are developed for walking.
• From the upper side of the thorax, two pairs of wings are produced for flying.
• Respiration takes place by trachea. In aquatic insects, gills are present.
• Excretion occurs by malpighian tubules.
• Usually, sexual reproduction takes place, but in some insects parthenogenesis is also common, in which eggs are changed into adults without fertilization.
• In some insects, complete metamorphosis occurs, e.g., butterfly, and in some insects, incomplete metamorphosis takes place, e.g., cockroach, grasshopper.
• They have an open type of circulatory system.

Insects are of two types:

1. Pterigota: These insects have wings, e.g., Butterfly.

Apterigota:
These insects are without wings. e.g. Ants.

Q.21: Write down the successful characters of insects?

Ans: Insects - Successful Group:
Insects are considered a successful group of animals on the basis of many characters, such as:

• They are found everywhere, from lower regions up to the tops of the Himalayas, because they can tolerate temperatures up to 65°C. They can be found in hot springs, Antarctic low temperatures, and even in oil wells.
• They have developed mouth parts according to their need.
• They have a protective exoskeleton.
• They have wings for flying and jointed appendages.
• They have well-developed brain and sense organs.

Physiological Adaptations:

• They have proper digestion with digestive enzymes.
• They have a high reproductive rate and metamorphosis.

Q.22: Describe the characters of Phylum Echinodermata?

Ans: Important Characters of Phylum Echinodermata:

• They are all marine animals.
• Their larvae have bilaterally symmetrical bodies, but adults have radially symmetrical bodies.
• These animals usually have five parts or arms, so they are considered as pentaradial or pentamerous animals.
• Their body is unsegmented without a head and brain.
• They have a calcareous skeleton. The calcareous plates also bear spines, called spicules, so the phylum is called Echinodermata. The spines may be short in sand dollars or long as in sea urchins.
• They are triploblastic, i.e., the body has three layers: outer ectoderm, middle mesoderm, and inner endoderm.
• They contain a true body cavity, the Coelom. It is divided into five parts.

Q.23: Describe the characters of Hemichordata?

Ans: Important Characters:

• They have a soft, unsegmented body.
• Their body consists of three parts: proboscis, collar, and trunk.
• Sexes are separate. Fertilization is external. The zygote forms a larva, termed as tornaria larva. It develops into an adult animal.
  Example: Balanoglossus.

Q.24: Write down the important characters of Phylum Chordata?

Ans: Important Characters: The important characters of phylum Chordata which are different from other animals are as follows:

• Notochord:
  It is a solid rod-like structure present in the dorsal region of the body. In protochordata, it persists in adult animals, but in vertebrates, it is changed into a vertebral column.

• Pharyngeal Pouches And Gill Slits:
  They have pouches in the pharyngeal region, called pharyngeal pouches. These pouches open to the outside by gill slits.

Q.25: What is the brief classification of Phylum Chordata?

Ans: Classification of Phylum Chordata: Phylum Chordata is divided into two groups:

• Acraniata or Protochordata
• Craniata or Vertebrata

Group - Acraniata or Protochordata:

• They are simple chordates without a brain box or cranium, so the brain is not prominent.
• The notochord does not change into a vertebral column.

Group Acraniata is divided into two subphyla:

• Sub-phylum - Urochordata
• Sub-phylum - Cephalochordata

The two phyla Urochordata and Cephalochordata include soft-bodied marine animals. They are connecting links between vertebrates and invertebrates.

Q.26: Describe the important characters of Urochordata?

Ans: Sub-Phylum – Urochordata: (Notochord in the Tail) The animals of this phylum are called Tunicates or Sea-squirts.

• The characters of Chordata are only found in their larva but not in the adult stage. The larva has a nerve cord and notochord in its tail. In the pharynx, gill slits are present. When the larva is changed into an adult, the tail degenerates, therefore, the nerve cord and notochord disappear. Only gill slits are present in the adult stage. Due to the presence of notochord in the tail, they are called Urochordates.
• Their body is covered by a covering called tunic, so they are called tunicates.

Q.27: Describe the important Characters of Cephalochordata?

Ans: Important Characters of Sub-Phylum – Cephalochordata: (Notochord From Head to Tail)

• They are small fish-like animals. Their body is segmented and pointed at both ends. The segments are called myomeres. They are about 60 in number.
• The notochord is present from the anterior region to the tip of the tail.
• The pharyngeal region is large and contains many pairs of gill slits.
• The nerve cord is stretched through the entire region of the body.
• The sexes are found in separate animals, e.g., Amphioxus.

Q.28: Describe the important characteristics of Agnatha?

Ans: Important Characters of Sub-Phylum – Agnatha: (Mouth Without Jaws)

• Their body is elongated. They have a cartilaginous skeleton. They are cold-blooded animals.
• Their skin is soft, smooth, and without scales.
• They have a round mouth, so they are called cyclostomes. The mouth is without jaws.
• The tongue is spiny. In the mouth, many rings of teeth are present.
• The notochord does not change into a vertebral column. It remains in its original condition.
• Fertilization is external. Their larva is called ammocoete larva, which develops into an adult animal.

Q.29: Describe the characters of Chondrichthyes?

Ans: Class - Chondrichthyes or Elasmobranchii: (Cartilaginous Fishes)

In this class, Dog fish, Sharks, Skates, and Rays are included. Most of them are found in sea water. Their characters are as follows:

• They have a cartilaginous skeleton.
• Their body is covered by placoid scales i.e. denticle-like or enamel-covered scales.
• They have fins, a pair of pectoral fins, a pair of posterior fins, two median dorsal fins and caudal fin. They help in the movement. Their caudal (Tail) fin is hetero-cercal.
• Five pairs of gills are present which are not covered by any covering or operculum. The water passes outside through the gill slits. Gills are the respiratory organs.
• The heart consists of two chambers, one atrium and one ventricle. The circulatory system is of closed type.
• Eyes are without eyelids.
• Excretion takes place by kidneys.
• The sexes are separate and fertilization is internal. In some sharks ovo-viviparous reproduction takes place in which the female sharks retain eggs within their bodies until the partial development of young sharks.

E.g. Sharks, Skates, Electric ray (Torpedo), Dog fish (scoliodon or small shark). These are commonly found on our coasts.

Q.30: Describe the characters of Osteichthyes?

Ans: Class - Osteichthyes: (Bony Fishes)

The characters of these fishes are as follows:

• Their body consists of three parts: head, trunk, and tail.
• Their body is covered by scales, called cycloid or ctenoid. These plates form exoskeleton.
• Their skeleton is made up of bones (Bony skeleton).
• Respiration takes place by four pairs of gills. The gill slits are covered by a hard covering, the operculum.
• They contain an air bladder which is not used for respiration. It regulates buoyancy i.e., helps in swimming.

Q.31: Write a note on Dipnoi (Lung Fish)?

Ans: Lung Fishes: Lung fishes belong to the order Dipnoi of class osteichthyes. These fishes contain lungs which are the modified organs of air bladders. These fishes respire by gills or the modified lungs. They can live without water for several months. These fishes are found in South America, Africa and Australia.

Q.32: Describe the important characters of Class Amphibians?

Ans: Characters of Amphibians:

• The amphibians can live both in water and on dry land.
• They are cold-blooded animals (poikilotherms), i.e. their body temperature can change according to the environment.
• They have bony skeleton with strong back bone (vertebral column) and pairs of limbs. Notochord is replaced by vertebral column.
• Their skin is soft, thin and moist. It takes part in respiration. Respiration also occurs by lungs and buccal cavity. In larva the respiration is by gills.
• The heart is advance than fishes. It is three chambered, two atria (auricles) and one ventricle.
• Eyelids are present. The eyes contain tear-glands to keep them moist during dry season.
• External ear is absent, only internal ear is present.
• During winter they take rest in mud, it is called hibernation. During this period they become inactive and use their internal reserve food. Some animals also take rest during summer, it is called aestivation.
• They lay their eggs in water, Fertilization is external. The zygote develops from the yolk of egg and changes into tadpole larva. It respires by gills and feeds on aquatic plants. The larva develops into an adult animal by metamorphosis.

Q.33: Write a note on Amphibia on unsuccessful land vertebrates?

Ans: Amphibia as Unsuccessful Land Vertebrates: Amphibians are considered as unsuccessful land vertebrates, because:

• Amphibians are cold-blooded animals. They face the problem of change in temperature.
• Their skin is smooth without scales or any exoskeleton, so they cannot be protected from extreme temperature, so they live close to water places.
• There is quick loss of water in air which is dangerous for the animal.
• Their eggs are small and without any shell, so their development occurs in water, it indicates unsuccessful land adaptation.
• Their eggs do not contain sufficient yolk for complete development, the larva comes out earlier in water and respires by gills.

All these points indicate that amphibians need water during different conditions of their life, so they are the unsuccessful land vertebrates.

Q.34: Describe the important Characters of Reptiles?

Ans: Important Characters of Reptiles:

• They are poikilotherms, i.e., cold-blooded animals. They also take rest during winter like amphibians, called hibernation.
• Their skin is dry and covered by scales.
• Their body has bony skeleton.
• They have two pairs of legs, each with five claws. They are used for rapid locomotion. Snakes have no limbs.
• The heart consists of two atria (auricles) and one incompletely divided ventricle and thus separation of oxygenated and deoxygenated blood is not complete. In crocodile the heart has completely divided into two ventricles.
• Respiration takes place by lungs.
• Excretion is by kidneys.
• Fertilization is internal. They lay eggs which are large and surrounded by outer shell.
• The development of embryo takes place inside the shell, the yolk of egg provides energy. In the egg a protective membrane is present, called amnion, so they are called amniotes. This membrane is also found in birds and mammals.

Q.35: Write a note on Reptiles as successful land vertebrates?

Ans: Reptiles as Successful Land Vertebrates: Reptiles are the first successful animals on land. Their adaptations on dry places are as follows:

• They have exoskeleton of horny scales and plates on their skin, so they can sustain the frequent change in the temperature. There is also less water loss from the body.
• They have developed kidneys to retain sufficient water and excretion of urine.
• They have developed limbs with claws. These are used in proper movement, digging and climbing. These are also used for their defence against their enemies.

Q.36: What are the common reptiles of World and Pakistan?

Ans: Common Reptiles: The common reptiles are tortoise, turtles, lizards, snakes, crocodiles, alligators. A living fossil Sphenodon is found in New Zealand only.

Reptiles of Pakistan: In Pakistan, many species of tortoise and turtles are found, e.g., Chelone mydas (Green turtles). Wall lizard, Garden lizard, Uromestic, Crocodiles, and Snakes are common. Cobra, Viper, Krait, Python, and other snakes are common in Pakistan.

Q.37: Write a note on snakes?

Ans: Snakes: The snakes are limb-less lizards. They live in burrows. Their eyes are without eye-lids. Some snakes are terrestrial and some are water-living. Certain kinds of snakes are poisonous. The poison is produced in specially modified salivary glands which is transferred into the body of prey through their teeth (Fangs). This venom (poison) is the mixture of certain substances which attacks the nerves and blood thus it usually causes death of the prey.

Q.38: Describe the important characters of Class Aves?

Ans: Important Characters of Class Aves (Birds):

• They are warm-blooded animals (Homeotherms). They can regulate their internal body temperature.
• The body is covered by feathers which trap air and prevent the loss of body heat.
• They have a bony skeleton. Bones are hollow, thin, and light.
• Fore limbs are modified into wings for flying.
• Eyes are large with eyelids.
• External ear is absent, but sense of hearing is well developed.
• The neck has great mobility which helps in feeding, nest building, preening and defence.
• Mouth parts are modified into beak. Teeth are absent. The shape of beak is modified according to the function in different animals.
• Hind limbs have claws.
• Respiration takes place by lungs. The lungs also contain air sacs for the storage of air.

Q.39: Describe the different classes of birds or non-flying and flying birds?

Ans: Classification of Birds: The birds are classified into two sub-classes:

• Sub Class - Ratitae (Sternum raft like): These are heavy non-flying birds.
• Sub Class - Carinatae (Sternum with keel): They are small flying birds.

Sub Class — Ratitae: (Non-Flying Birds)

• They are big-sized, flightless heavy birds.
• They cannot fly due to their heavy weight. The weight of Ostrich is 150 kg.
• Their wings are vestigial or rudiments i.e., very much reduced and functionless.
• Their sternum is flat without keel.
• Their flight muscles are poorly developed.

Sub Class — Carinatae: (Flying Birds)

• They are all modern flying birds.
• They are small, with light weight.
• Their wings are highly developed.
• Feathers of wings have interlocking mechanism.
• Their sternum has a crest like keel to support the flight muscles.

Q.40: What are the common birds of Pakistan?

Ans: Common Birds of Pakistan: Sparrow, Pigeons, Myna, Bulbul, Hoopoes, Crow, Doves, Parrots, Fowls, Cuckoo, Ducks, Kites, Falcons and Owls are common prey birds. Ducks, Sea gull Terns and Granes are migratory birds. Peacock and Houbara are the most beautiful birds.

Q.41: Describe the flight adaptations in birds?

Ans: Flight Adaptations in Birds:

• Wings: They have special organs for flying, called wings. These are the modified form of fore-limbs.
• Feathers: Their body is covered by feathers which help to maintain the body temperature and prevent the loss of body heat.
• Sternum with Strong Muscles: The body structure is modified for flying. The sternum, central part of pectoral girdle is larger and strong for the attachment of wing-muscles and better support.
• Light & Hollow Bones: Their bones are hollow and light for easy flight.
• Blood Circulation: Their heart consists of four chambers and circulatory system is very fast. It helps to maintain the blood pressure and to control the amount of oxygen.
• Energy Requirement: The metabolism of the body is very rapid and fast, so great amount of energy is produced which is used in flying and maintains the body temperature. It is due to rich supply of O₂ from heart and by extra ordinary respiratory system. The lungs are supplemented by a number of air-sacs. They store air which is used during flight.
• Maintenance of Body Temperature: They are warm-blooded animals. The muscular activity rises temperature but it is maintained by the ventilating action (exchange of warm and cold air) of air sacs.

Q.42: Describe the important characters of Class Mammalia?

Ans: Important Characters:

• They are warm-blooded animals (Homoiotherms). They have constant body temperature which remains between 37°C–40°C.

Q.43: What are the different classes of Class Mammalia?

Ans: Classification of Mammalia: The class mammalia is divided into three sub-classes.

• Sub-class - Prototheria (Egg laying mammals)
• Sub-class - Metatheria (Pouched mammals)
• Sub-class - Eutheria (Placental mammals)

Sub-Class – Prototheria:

• It is a very primitive class. The animals of this class are egg-laying (oviparous).
• They do not have ear pinna like reptiles.
• They have cloaca i.e. the common opening of rectum and urogenital system, so they are considered as connecting link between reptiles and mammals.
• Their body is covered by hairs.
• They have mammary glands to provide nourishment to their young ones. e.g. Platypus (Duck bill), Spiny ant eater.
• This sub-class has single order, Monotremata, so they are also called monotremes.

Sub-Class – Metatheria:

• These animals have pouch along their abdomen, so they are called pouched mammals.
• Their immature young ones are migrated into the pouch, called Marsupium.
• In the pouch mammary glands are present. The young ones get their food from these mammary glands.
• They are viviparous i.e. they produce young ones.
• Their eggs are not laid. Fertilization is internal.
• Their eggs do not contain sufficient yolk, so immature young ones are produced in the pouch.
  • E.g. Kangaroo, Koala bear, Wombats, Opossums.

Sub-Class – Eutheria: These are the placental mammals. The development of their embryo takes place in the uterus. There is a cord between mother and the embryo, called placenta, through which food and oxygen are supplied. The mother takes care of her young after birth and feeds from mammary glands.

• E.g. Cow, Monkey, Elephant, Dog, Cat, Rat, and Man.

• Small Eutherian Mammals:

  • Squirrels, Rabbits, Hedgehogs, Rats, Scaly ant eaters.

• Ungulates (Hoofed Mammals):

  • Sheep, Goats, Cows, Deers, Camels, Giraffes, Horses, Donkeys, Zebras, Rhinoceros etc.

• Carnivores:

  • Cats, Dogs, Lions, Tigers.

• Omnivores:

  • Bear, Man. Large placental mammals are Elephants and Whales.

• Flying Mammal:

• Bat.

Q.44: Distinguish between the following:

Chondrichthyes & Osteichthyes:

Chondrichthyes	Osteichthyes
These are cartilaginous fishes i.e. they have cartilaginous skeleton.	These are bony fishes i.e. they have bony skeleton.
Their skin is covered by placoid scales, which are sharp enamel-coated scales.	Their skin is covered by cycloid scales, which are thin bony plate-like scales.
They contain 5 exposed gill slits on each side, without operculum.	Their gills are covered by operculum.
Their tail fin is heterocercal. E.g. Sharks, Skates, Dog-fish.	Their tail fin is homocercal. E.g. Sea horse, Eal fish, Globe Fish, Flying fish

Poikilotherms & Homeotherms:

Poikilotherms	Homeiotherms
These are cold-blooded animals i.e. their body temperature is changed according to their environment.	They are warm-blooded animals i.e. their body temperature remains constant.
Show hibernation during winter season.	They do not show hibernation during winter season.
Show aestivation during summer season.	They do not show aestivation during summer season.
Their body is either smooth or covered by scales. E.g. Fishes, Amphibians, Reptiles	Their body is covered by feathers or hairs. E.g. Birds, Mammals

Incomplete Metamorphosis & Complete Metamorphosis:

Incomplete Metamorphosis	Complete Metamorphosis
In this metamorphosis there are only two stages, egg stage and Nymph Stage (young insect).	In this process there are four stages, egg stage, larva stage, pupa stage and imago stage.
In this process complete development occurs in the egg.	In this process initial development occurs in the egg, then larva comes out.
Larva and pupa stages are absent. E.g. Cockroach, Grasshopper	Larva and pupa stages are present. E.g. Butterfly, Mosquito

Class Ratitae & Class Carinatae:

Class Ratitae	Class Carinatae
These are non-flying birds.	These are flying birds.
They are big-sized, heavy birds.	They are small-sized with light weight.
Their wings are vestigial or reduced and functionless.	Their wings are highly-developed.
Their sternum is flat without keel.	Their sternum has a crest-like keel to support the flight muscles.
Their flight muscles are poorly developed.	Their flight muscles are well-developed.