Explore topic-wise InterviewSolutions in .

1. The larval stage of the tunicate possesses all the features characteristic of chordates, a notochord, a dorsal hollow nerve cord, pharyngeal slits and a post-anal tail. 

2. In the adult stage the notochord, nerve cord, and tail disappear.

Phylum: Echinodermata.

(c)   Annelid

1. These pore bearing animals are commonly called sponges. 

2. They are aquatic, mostly marine, asymmetrical. 

3. They are primitive, multicellular, sessile animals with cellular level of organization. 

4. They are either radially symmetrical or asymmetrical animals. 

5. They possess a water transport system or canal system (water enters through minute pores called ostia the water enters into a central cavity (spongocoel) and goes out through the osculum. 

6. This water transport system is helpful in food gathering, circulation, respiration and removal of waste. 

7. Choanocytes or collar cells are special flagellated cells lining the spongocoel and the canals. 

8. Nutrition is holozoic and intracellular. 

9. All sponges are hermaphrodites. 

10.Asexually reproduction by fragmentation or gemmule formation 

11.Sexually by the formation of gametes. 

12.Development is indirect with different types of larval stages (Larvae: parenchymula and amphiblastula) eg. Sycon (Scypha), Spongilla (fresh water sponge).

Choanocytes / Collar cells.

Organisms bearing microscopic ‘pores’ on their body are called poriferans and belong to phylum porifera.

• They possess a water transport system or canal system
• (water enters through minute pores called ostia the water enters into a central cavity (spongocoel) and goes out through the osculum.
• This water transport system is helpful in food gathering, circulation, respiration and removal of waste. 

1. If the body cavity is not fully lined by the mesodermal epithelium, but the mesoderm is formed as scattered pouches between the ectoderm and endoderm. 

2. Such a body cavity is called a pseudocoel and is filled with pseudocoelomic fluid. 

3. Animals that possess a pseudocoel are called pseudocoelomates Eg: Round worms. 

Aschelminthes.

(c) Arthropoda 

1. Protozoa :

• Single-celled eukaryotes.
• Locomotion is done by pseudopodia.
• The nutrition is either autotrophic or heterotrophic.

2. Platyhelminthes:

• This Phylum includes flatworms.
• Excretion and osmoregulation occur through flame cells.
• These worms are hermaphrodites having both male and female reproductive organs in a single individual.

3. Mollusca:

• Soft-bodied animals without segmentation.
• The body is covered by a mantle and a shell.
• Respiration is carried through gills or lungs or both.

4. Class Reptilia:

• The body is covered by an exoskeleton of homy epidermal scales.
• The respiration is by lungs.
• The heart is three-chambered, except crocodile, which has four chambers.-

5. Class Mammalia:

• They have epidermal hairs, sweat, sebaceous and scent glands.
• The mammary glands are the modified integumentary glands.
• The external ear or pinna is present in most of the mammals.

1. False.

Correct Statement: Amoebic dysentery is caused by protozoa entamoeba histolytica.

2. True

3. True

4. True

5. False.

Correct Statement: In phylum Mollusca the body of organisms is divided into head, muscular foot and the visceral mass.

Phylum Porifera.

• Absence of nervous and muscular tissue indicates that sponges must have been one of the earliest forms in the course of evolution.
• Absence of tissues indicate that the body organisation would have been at cellular level only without cells forming compact tissues.
• Further this also indicates that sponges do not show locomotion since they have no means of evaluating the surrounding because they lack muscular tissue. 
• They are sedentary since they lack muscular tissue 

• In sponges, the outer layer is formed of pinacocytes (plate like cells that maintain the size and structure of the sponge), which does the function of muscular tissue
• Nerve cells and sensory cells perform the function of nervous tissue. 

(i) Cellular level- loose cell aggregates, small division of labour e.g. Sponges. 

(ii) Tissue level- Groups of cells performing same functions. e.g. Coelenterate. 

(iii) Organ level- Tissues grouped into organs e.g. Higher animals. 

• All members of Kingdom Animalia are metazoans (multicellular animals) and exhibit different patterns of cellular organisation. 
• The cells of the metazoans are not capable of independent existence and exhibit division of labour. 
• Among the metazoans, cells may be functionally isolated or similar kinds of cells may be grouped together to form tissues, organ and organ systems. 

Cellular level: Here cells are arranged as loose cell aggregates.

Tissue level: Here the cells performing the same function are arranged into tissues

eg: Hydra, Pleurobrachia

Organ level: Here tissues are grouped together to form organs, each specialised for a particular function.

eg: members of Platyhelminthes

Organ system: Organs have associated to form functional systems each system concerned with a specific physiological function.

Eg: Arthropoda, Mollusca, Mammalia.

Viviparous are animals which give birth to young ones of their own kind. e.g., Mammals. Oviparous are animals which lay eggs e.g., Reptiles, birds etc.

Compacted pellets of faeces of earthworm laid as heaps are called worm castings.

The animals differ greatly in their shape and size. Their body shows different levels of organisation and body plan. 

(i) Protoplasmic Level – e.g. protozoans 

(ii) Cellular Level - e.g. sponges 

(iii) Tissue Level - e-g. coelenterates 

(iv) Organ system Level – e.g. all metazoans.

The sponges have pores all over the body, cellular level of organisation, a canal system for the passage of water current, choanocytes lining the main cavity (spongocoel) or certain canal (radial canal), skeleton made up of spicules and spongin fibres and absence of mouth and digestive cavity.

Cobra and Krait.

(i) Agatha 

(ii) Gnathostomata

Notochord is a solid, cylindrical, rod like structure formed of vacuolated cells present in the mid dorsal body axis of the chordates.

Segmentation of external and internal body into linear sequence of segments (repetition of atleast some organ) is called metamerism.

Metameric Segmentation: External segmentation correspond to internal segmentation, e.g., Earthworm. 

Non-metameric Segmentation : External segmentation do not correspond internal segmentation, e.g. Platyhelminthes.

Bilateral symmetry. 

In bilateral type of symmetry, the body can be divided into two equal halves by a single plane only because the important body organs are paired and occur on the two sides of a central axis.

(i) Kangaroo is a herbivorous marsupial. 

(ii) The females are smaller than the males. The former has the marsupial pouch in which the immature young ones are fed by the mother. 

(iii) The young one at the time of birth is very small but can crawl to the pouch of the mother. 

(iv) The long thick stout tails makes a tripod with hind limbs.

(i) Germinal or germ layers are primary layers of cell which differentiate in developing embryo and from which various tissues and organs of the animal body develop. 

(ii) A maximum of three germinal layers are found in embryo. They are ectoderm, mesoderm and endoderm. Out of these, mesoderm is the last to develop in between ectoderm and endoderm.

(i) Sexes are separate with no sexual dimorphism. 

(ii) Fertilization is generally external. 

(iii) Development includes ciliated, bilaterally symmetrical larva, which is usually free swimming and undergoes conspicuous metamorphosis. 

(iv) A few forms reproduce asexually by division. 

(v) Autotomy and regeneration are very common.

(d) Colloblasts

Sub-phylum Urochordata are known as sea-squirts, adults are mostly marine and fixed, body is covered by test/tunic, notochord & nerve cord are found in the larvae and are lost and reduced to a ganglion in the adult. 

Example: Herdmania.

Sub -phylum cephalochordata have fish like body, notochord and nerve cord are present throughout, eyes, nose, ears and jaws are absent, butarimal represents the fundamental plan of the chordate body in a simple form. Example: Amphioxus.

• Have tissue level organisation, are diploblastic. 

• Digestion both extra and intracellular. 

• Body has eight external rows of ciliated comb plates for locomotion. 

• Show Bioluminescence (living organism emit light). 

• Only sexual reproduction occurs. External fertilisation. Indirect develop ment. e.g., Ctenoplana.

The Aschelminthes is also called ‘round worms’. The phylum are bilaterally symmetrical, triploblastic, pseudocoelomate.

• Alimentary canal complete (has muscular pharynx), wastes removed through excretory pore. 

• Sexes separate. Shows dimophism. 

• Females longer than males. 

• Fertilisation internal. Development direct or indirect. e.g., Ascaris, Wuchereria.

1. Bioluminescence (the ability of a living organism to emit light) is well marked in Ctenophores. 

2. They lack nematocyte but possess special cells called lasso cells or colloblasts to capture food. 

3. They show indirect development and the larva is called cydippid. Eg: Pleurobrachia.

• Body is bilaterally symmetrical and triplo blastic. Body wall shows syncytial nature. 
• Body is vermiform, cylindrical without a definite head.
• Cuticle is tough and resistant. 
• The body cavity is a false coelom, (pseudocoelomate) and lies between body wall and the digestive tract.
• Digestive system is complete with mouth and anus.
• Circulatory & respiratory systems are absent.
• Sexes are always separate, exhibit sexual dimorphism and show Simple or complex life cycle. 
• Excretory system shows a pair of longitudinal excretory canals with an excretory pore.

Examples 

• Ascaris lumbricoides (roundworm)
• Ancylostoma duodenale (hookworm)

(c) Tongue worms 

• The Ctenophores have eight external rows of ciliated comb plates (comb jellies) in the mesoglea which help in locomotion. 
• Hence they are commonly called as comb jellies or sea walnuts.

Have skeleton composed of calcium carbonate which gets deposited and can lead to formation of land forms. e.g., Lakshadweep (a coral island).

• In closed circulatory system, the circulation is controlled by contraction of the heart. 
• Blood flows faster and at high pressure. 

• Limulus or the King crab continues to remain unchanged for past 190 million years. 
• Hence it is called living fossil.

Radula is a file like a rasping organ which helps feeding in molluscans.