4.4 Exercise Problems

Q1. What are the difficulties that you would face in the classification of animals if common fundamental features are not taken into account?

Answer: For the classification of living organisms, common fundamental characteristics are considered.
If we consider specific characteristics, then each organism will be placed in a separate group and the entire objective of classification would not be achieved. Classification of animals is also important in comparing different organisms and judging their individual evolutionary significance. If only a single characteristic is considered, then this objective would not be achieved.

Q2. If you are given a specimen, what are the steps that you would follow to classify it?

Answer: There are some fundamental features that help in the classification of living organisms and the features that can be used in classification are as follows:
1. Level of classification: Cellular, tissue, or organ level.
2. Body cavity: Absent or present
3. Type of body symmetry: Radial or bilateral
4. Type of coelom development: Acoelom, Pseudocoelom and true coelom.

Q3. How useful is the study of the nature of body cavity and coelom in the classification of animals?

Answer: Coelom is a fluid-filled space between the body wall and digestive tract. The presence or absence of body cavity or coelom plays a very important role in the classification of animals. Animals that possess a fluid-filled cavity between the body wall and digestive tract are known as coelomates. Annelids, molluscs, arthropods, echinodermates, and chordates are examples of coelomates. On the other hand, the animals in which the body cavity is not lined by mesoderm are known as pseudocoelomates. In such animals, mesoderm is scattered in between ectoderm and endoderm. Aschelminthes is an example of pseudocoelomates. In certain animals, the body cavity is absent. They are known as acoelomates. An example of acoelomates is Platyhelminthes.

Q4. Distinguish between intracellular and extracellular digestion.

Answer: 

\(
\begin{array}{|c|c|}
\hline \begin{array}{l}
\text { Intracellular } \\
\text { digestion }
\end{array} & \begin{array}{l}
\text { Extracellular } \\
\text { digestion }
\end{array} \\
\hline \begin{array}{l}
\text { 1. The } \\
\text { digestion of } \\
\text { food occurs } \\
\text { within the } \\
\text { cell. }
\end{array} & \begin{array}{l}
\text { 1. The } \\
\text { digestion } \\
\text { occurs in the } \\
\text { cavity of } \\
\text { alimentary } \\
\text { canal. }
\end{array} \\
\hline \begin{array}{l}
\text { 2. Digestive } \\
\text { enzymes are } \\
\text { secreted by } \\
\text { the } \\
\text { surrounding } \\
\text { cytoplasm } \\
\text { into the food } \\
\text { vacuole. }
\end{array} & \begin{array}{l}
\text { 2. Digestive } \\
\text { enzymes are } \\
\text { secreted by } \\
\text { special cells } \\
\text { into the } \\
\text { cavity of } \\
\text { alimentary } \\
\text { canal. }
\end{array} \\
\hline \begin{array}{l}
\\
\text { 3. Digestive } \\
\text { products are } \\
\text { diffused into } \\
\text { the } \\
\text { cytoplasm. }
\end{array} & \begin{array}{l}
\text { 3. Digestive } \\
\text { products } \\
\text { diffuse } \\
\text { across the } \\
\text { intestinal } \\
\text { wall into } \\
\text { various parts } \\
\text { of the body. }
\end{array} \\
\hline \begin{array}{l}
\text { 4. It is a less } \\
\text { efficient } \\
\text { method. }
\end{array} & \begin{array}{l}
\text { 4. It is a } \\
\text { more } \\
\text { efficient } \\
\text { method of } \\
\text { digestion. }
\end{array} \\
\hline \begin{array}{l}
\text { 5. It occurs } \\
\text { in unicellular } \\
\text { organisms. }
\end{array} & \begin{array}{l}
\text { 5. It occurs } \\
\text { in } \\
\text { multicellular } \\
\text { organisms. }
\end{array} \\
\hline
\end{array}
\)

Q5. What is the difference between direct and indirect development?

Answer:

\(
\begin{array}{|l|l|}
\hline \begin{array}{l}
\text { Direct } \\
\text { development }
\end{array} & \begin{array}{l}
\text { Indirect } \\
\text { development }
\end{array} \\
\hline \begin{array}{l}
\text { 1. It is a type of } \\
\text { development in } \\
\text { which an } \\
\text { embryo } \\
\text { develops into a } \\
\text { mature } \\
\text { individual } \\
\text { without } \\
\text { involving a } \\
\text { larval stage. }
\end{array} & \begin{array}{l}
\text { 1. It is a type of development } \\
\text { that involves a } \\
\text { sexually- } \\
\text { immature larval } \\
\text { stage, having } \\
\text { different food } \\
\text { requirements } \\
\text { than adults. }
\end{array} \\
\hline \begin{array}{l}
\text { 2. } \\
\text { Metamorphosis } \\
\text { is absent. }
\end{array} & \begin{array}{l}
\text { 2. } \\
\text { Metamorphosis } \\
\text { involving the } \\
\text { development of } \\
\text { larva a } \\
\text { sexually mature } \\
\text { adult is } \\
\text { present. }
\end{array} \\
\hline \begin{array}{l}
\text { 3. It occurs in } \\
\text { fishes, reptiles, } \\
\text { birds, and } \\
\text { mammals. }
\end{array} & \begin{array}{l}
\text { 3. It occurs in } \\
\text { most of the } \\
\text { invertebrates } \\
\text { and } \\
\text { amphibians. }
\end{array} \\
\hline
\end{array}
\)

Q6. What are the peculiar features that you find in parasitic Platyhelminthes?

Answer: Taenia (Tapeworm) and Fasciola (liver fluke) are examples of parasitic Platyhelminthes. Peculiar features in parasitic Platyhelminthes are as follows.

• They have dorsiventrally flattened body and bear hooks and suckers to get attached inside the body of the host.
• Their body is covered with thick tegument, which protects them from the action of the digestive juices of the host.
• The tegument also helps in absorbing nutrients from the host’s body.

Q7. What are the reasons that you can think of for the arthropods to constitute the largest group of the animal kingdom?

Answer: The phylum, Arthropoda, consists of more than two-thirds of the animal species on earth. The reasons for the success of arthropods are as follows.

• Jointed legs that allow more mobility on land
• Hard exoskeleton made of chitin that protects the body
• The hard exoskeleton also reduces water loss from the body of arthropods making them more adapted to terrestrial conditions.

Q8. The water vascular system is the characteristic of which group of the following:
(a) Porifera
(b) Ctenophora
(c) Echinodermata
(d) Chordata

Answer: The water vascular system is a characteristic feature of the phylum, Echinodermata. It consists of an array of radiating channels, tube feet, and madreporite. The water vascular system helps in locomotion, food capturing, and respiration.

Q9. “All vertebrates are chordates but all chordates are not vertebrates”. Justify the statement.

Answer: The characteristic features of the phylum, Chordata, include the presence of a notochord and paired pharyngeal gill slits. In sub-phylum Vertebrata, the notochord present in embryos gets replaced by a cartilaginous or bony vertebral column in adults. Thus, it can be said that all vertebrates are chordates but all chordates are not vertebrates.

Q10. How important is the presence of atr bladder in Pisces? 

Answer: Gas bladder or air bladder is a gas-filled sac present in fishes. It helps in maintaining buoyancy. Thus, it helps fishes to ascend or descend and stay in the water current.

Q11. What are the modifications that are observed in birds that help them fly?

Answer: Birds have undergone many structural adaptations to suit their aerial life. Some of these adaptations are as follows.

• Streamlined body for rapid and smooth movement
• Covering of feathers for insulation
• Forelimbs modified into wings and hind limbs used for walking, perching, and swimming
• Presence of pneumatic bones to reduce weight
• Presence of additional air sacs to supplement respiration

Q12. Could the number of eggs or young ones produced by an oviparous and viviparous mother be equal? Why?

Answer: The number of eggs produced by an oviparous mother will be more than the young ones produced by a viviparous mother. This is because in oviparous animals, the development of young ones takes place outside the mother’s body. Their eggs are more prone to environmental conditions and predators. Therefore, to overcome the loss, more eggs are produced by mothers so that even under harsh environmental conditions, some eggs might be able to survive and produce young ones. On the other hand, in viviparous organisms, the development of young ones takes place in safe conditions inside the body of the mother. They are less exposed to environmental conditions and predators. Therefore, there are more chances of their survival and hence, less number of young ones is produced compared to the number of eggs.

Q13. Segmentation in the body is first observed in which of the following:
(a) Platyhelminthes
(b) Aschelminthes
(c) Annelida
(d) Arthropoda

Answer: The body segmentation first appeared in the phylum, Annelida (annulus meaning little ring).

Q14. Match the following.

\(
\begin{array}{|l|l|}
\hline \text { (a) Operculum } & \text { (i) Ctenophora } \\
\hline \text { (b) Parapodia } & \text { (ii) Mollusca } \\
\hline \text { (c) Scales } & \text { (iii) Porifera } \\
\hline \text { (d) Comb plates } & \text { (iv) Reptilia } \\
\hline \text { (e)Radula } & \text { (v) Annelida } \\
\hline \text { (f)Hairs } & \text { (vi) Cyclostomata and Chondrichthyes } \\
\hline \text { (g) Choanocytes } & \text { (vii) Mammalia } \\
\hline \text { (h) Gill slits } & \text { (viii)Osteichthyes } \\
\hline
\end{array}
\)

Answer: 

\(
\begin{array}{|l|l|}
\hline \text { (a) Operculum } & \text { (viii) Osteichthyes } \\
\hline \text { (b) Parapodia } & \text { (v) Annelida } \\
\hline \text { (c) Scales } & \text { (iv) Reptilia } \\
\hline \text { (d) Comb plates } & \text { (i) Ctenophora } \\
\hline \text { (e)Radula } & \text { (ii) Mollusca } \\
\hline \text { (f)Hairs } & \text { (vii) Mammalia } \\
\hline \text { (g) Choanocytes } & \text { (iii) Porifera } \\
\hline \text { (h) Gill slits } & \text { (vi) Cyclostomata and Chondrichthyes } \\
\hline
\end{array}
\)

Q15. Prepare a list of some animals that are found parasitic on human beings.

Answer: 

\(
\begin{array}{|l|l|l|}
\hline \text { S.No. } & \begin{array}{l}
\text { Name of } \\
\text { organism }
\end{array} & \text { Phylum } \\
\hline 1 & \begin{array}{l}
\text { Taenia } \\
\text { solium }
\end{array} & \text { Platyhelminthes } \\
\hline 2 & \begin{array}{l}
\text { Fasciola } \\
\text { hepatica }
\end{array} & \text { Platyhelminthes } \\
\hline 3 & \begin{array}{l}
\text { Ascaris } \\
\text { lumbricoides }
\end{array} & \text { Aschelminthes } \\
\hline 4 & \begin{array}{l}
\text { Wucheria } \\
\text { Bancrofti }
\end{array} & \text { Aschelminthes } \\
\hline 5 & \text { Ancylostoma } & \text { Aschelminthes } \\
\hline
\end{array}
\)

Exemplar Section

VERY SHORT ANSWER TYPE QUESTIONS

Q1. Identify the phylum in which adults exhibit radial symmetry and larva exhibit bilateral symmetry.

Answer: In phylum echinodermata, adults show radial symmetry whereas larva show bilateral symmetry.

Q2. What is the importance of pneumatic bones and air sacs in Aves?

Answer: Pneumatic bones in Aves keep the body light and thus help in flight. Air sacs help in respiration and buoyancy.

Q3. What is metagenesis? Mention an example which exhibits this phenomenon.

Answer: Alternation of generation is known as metagenesis. Obelia exhibits this phenomenon.

Q4. What is the role of feathers?

Answer: Feathers keep the body light and thus help in flight.

Q5. Which group of chordates possess sucking and circular mouth without jaws?

Answer: Cyclostomes have a sucking and circular mouth without jaws.

Q6. Give one example each for an animal possessing placoid scales and that with cycloid scales.

Answer: Placoid scales—Pristis, Trygon, Torpedo. Cycloid scales—Labeo Catla, Clarias

Q7. Mention two modifications in reptiles required for terrestrial mode of life.

Answer: 1. Their body is covered by dry and comified skin, epidermal scales or scutes.
2. Cleidoic eggs

Q8. Mention one example each for animals with chitinous exoskeleton and those covered by a calcareous shell.

Answer: The body of arthropods (like cockroach) is covered by chitinous exoskeleton and molluscan (like Pila) body is covered by a calcareous shell.

Q9. What is the role of radula in molluscs?

Answer: Radula is a file-like rasping organ help in feeding.

Q10. Name the animal, which exhibits the phenomenon of bioluminescence. Mention the phylum to which it belongs.

Answer: Bioluminescence (the property of a living organism to emit light) is well- marked in ctenophores. Examples: Pleurobrachia, and Ctenoplana.

Q11. Write one example each of the following in the space provided.
a. Cold blooded animal ________________________
b. Warm blooded animal ________________________
c. Animal possessing dry and cornified skin _______________
d. Dioecious animal _____________________ 

Answer: a. Cold blooded animal: amphibians (Frog)
b. Warm blooded animal: mammals (Human)
c. Animal possessing dry and cornified skin: reptiles (Lizard)
d. Dioecious animal: aschelminthes (Ascaris)

Q12. Differentiate between a diploblastic and a triploblastic animal.

Answer: (i) Diploblastic: Animals in which the cells are arranged in two embryonic layers, an external ectoderm and an internal endoderm, are called diploblastic animals, e.g. Poriferas, coelenterates and ctenophores.
(ii) Triploblastic: Those animals in which the developing embryo has a third germinal layer, mesoderm, in between the ectoderm and endoderm, are called triploblastic animals. E.g.: Platyhelminthes to Chordates.

Q13. Give an example of the following
a. Round worm
b. Fish possessing poison sting
c. A limbless reptile/ amphibian
d. An oviparous mammal

Answer: Examples:
a. Roundworm: Ascaris
b. Fish possessing poison sting: Trygon
c. A limbless reptile/ amphibian: Snakelfcthyophis
d. An oviparous mammal: Ornithorynchus (Duck-billed platypus)

Q14. Provide appropriate technical term in the space provided.
a. Blood-filled cavity in arthropods __________________________.
b. Free-floating form of cnidaria _____________________________.
c. Stinging organ of jelly fishes ______________________________.
d. Lateral appendages in aquatic annelids ___________________.

Answer: Provide appropriate technical term in the space provided.
a. Blood-filled cavity in arthropods: Haemocoel
b. Free-floating form of cnidaria: Medusa
c. Stinging organ of jelly fishes: Nematocyst
d. Lateral appendages in aquatic annelids: Parapodia

Q15. Match the following:
\(
\begin{array}{rlrl}
& \text { Animals } & & \text { Locomotory Organ } \\
\text { a. } & \text { Octopus } & \text { i. } & \text { Limbs } \\
\text { b. } & \text { Crocodile } & \text { ii. } & \text { Comb plates } \\
\text { c. } & \text { Catla } & \text { iii. } & \text { Tentacles } \\
\text { d. } & \text { Ctenoplana } & \text { iv. } & \text { Fins }
\end{array}
\)

Answer: 

\(
\begin{array}{|l|l|l|l|}
\hline & \text { Animals } & & \text { Locomotory organ } \\
\hline \text { a. } & \text { Octopus } & \text { (iii) } & \text { Tentacles } \\
\hline \text { b. } & \text { Crocodile } & \text { (i) } & \text { Limbs } \\
\hline \text { c. } & \text { Catla } & \text { (iv) } & \text { Fins } \\
\hline \text { d. } & \text { Ctenoplana } & \text { (ii) } & \text { Comb plates } \\
\hline
\end{array}
\)

SHORT ANSWER TYPE QUESTIONS

Q1. Differentiate between:
a. Open circulatory system and closed circulatory system
b. Oviparous and viviparous characteristic
c. Direct development and Indirect development

Answer: (a) Blood is pumped out the heart and the cells and tissues are directly bathed in the open circulatory system whereas the closed circulatory system is circulated throughout the body with the help of series of vessels
(b) Laying of fertilized and unfertilized eggs are known as oviparous whereas giving birth to young ones is viviparous
(c) When a larval stage is absent in the development of the organism, it is direct development whereas the larval stage is present in the development of the organism which does not resemble the adult is called indirect development.

Q2. Sort out the animals on the basis of their symmetry (radial or bilateral) coelenterates, ctenophores, annelids, arthropods, and echinoderms.

Answer: Coelenterates: Radial Ctenophores: Radial Annelids: Bilateral Arthropods: Bilateral Echinoderms: Radial

Q3. There has been an increase in the number of chambers in heart during evolution of vertebrates. Give the names of the class of vertebrates having two, three or four-chambered heart.

Answer: Two chambered heart: chondrichthyes and osteichthyes
Three chambered heart: Amphibia and Reptilia
Four chambered heart: Aves and mammalia

Q4. Fill up the blank spaces appropriately
\(
\begin{array}{l|c|c|c}
\text { Phylum/Class } & \text { Excretory Organ } & \text { Circulatory Organ } & \text { Respiratory Organ } \\
\hline \text { Arthropoda } & A & B & \begin{array}{l}
\text { Lungs/ Gills/ } \\
\text { Tracheal System }
\end{array} \\
\hline C & \text { Nephridia } & \text { Closed } & \text { Skin/parapodia } \\
\hline D & \text { Metanephridia } & \text { Open } & E \\
\hline \text { Amphibia } & F & \text { Closed } & \text { Lung }
\end{array}
\)

Answer: A = Malpighian Tubule/ coxal glands/ antemary glands/ green glands
B = Open
C = Annelida
D = Mollusca
E = Feather like gills
F = Kidney

Q5. Match the following:
\(
\begin{array}{|l|l|l|l|}
\hline \text { a. } & \text { Amphibia } & \text { (i) } & \text { Air bladder } \\
\hline \text { b. } & \text { Mammals } & \text { (ii) } & \text { Cartilagenous notochord } \\
\hline \text { c. } & \text { Chondrichthyes } & \text { (hi) } & \text { Mammary glands } \\
\hline \text { d. } & \text { Osteichthyes } & \text { (iv) } & \text { Pneumatic bones } \\
\hline \text { e. } & \text { Cyclostomata } & \text { (v) } & \text { Dual habitat } \\
\hline \text { f. } & \text { Aves } & \text { (vi) } & \text { Sucking and circular mouth without jaws } \\
\hline
\end{array}
\)

Answer:

\(
\begin{array}{llll}
\hline \text { a. } & \text { Amphibia } & \text { (v) } & \text { Dual habitat } \\
\hline \text { b. } & \text { Mammals } & \text { (iii) } & \text { Mammary glands } \\
\hline \text { c. } & \text { Chondrichthyes } & \text { (ii) } & \text { Cartilagenous notochord } \\
\hline \text { d. } & \text { Osteichthyes } & \text { (i) } & \text { Air bladder } \\
\hline \text { e. } & \text { Cyclostomata } & \text { (vi) } & \text { Sucking and circular mouth without jaws } \\
\hline \text { f. } & \text { Aves } & \text { (iv) } & \text { Pneumatic bones } \\
\hline
\end{array}
\)

Q6. Endoparasites are found inside the host body. Mention the special structure, possessed by these and which enables them to survive in those conditions.

Answer: The life cycles of endoparasities are more complex because of their extreme specialisation. Their morphological and anatomical features are greatly simplified while emphasizing their reproductive potential.
In accordance with their life style parasites evolve special adaptations such as:
1. Loss of unnecessary sense organs.
2. Loss of digestive system.
3. High reproductive capacity.
4. Presence of adhesive organs or suckers to cling on to the host.

Q7. Match the following and write correct choice in space provided
\(
\begin{array}{llll}
\hline & \text { Animal } & & \text { Characteristics } \\
\hline \text { a. } & \text { Pila } & \text { (i) } & \text { Jointed appendages } \\
\hline \text { b. } & \text { Cockroach } & \text { (ii) } & \text { Perching } \\
\hline \text { c. } & \text { Asterias } & \text { (iii) } & \text { Water vascular system } \\
\hline \text { d. } & \text { Torpedo } & \text { (iv) } & \text { Electric organ } \\
\hline \text { e. } & \text { Parrot } & \text { (v) } & \text { Presence of shell } \\
\hline \text { f. } & \text { Dog fish } & \text { (vi) } & \text { Placoid scales } \\
\hline
\end{array}
\)
a. ____________________, b. ____________________, c. ____________________
d. ____________________, e. ____________________, f. ____________________

Answer: 

\(
\begin{array}{llll}
\hline & \text { Animal } & & \text { Characteristics } \\
\hline \text { a. } & \text { Pila } & \text { (v) } & \text { Presence of shell } \\
\hline \text { b. } & \text { Cockroach } & \text { (i) } & \text { Jointed appendages } \\
\hline \text { c. } & \text { Asterias } & \text { (iii) } & \text { Water vascular system } \\
\hline \text { d. } & \text { Torpedo } & \text { (iv) } & \text { Electric organ } \\
\hline \text { e. } & \text { Parrot } & \text { (ii) } & \text { Perching } \\
\hline \text { f. } & \text { Dog fish } & \text { (vi) } & \text { Placoid scales } \\
\hline
\end{array}
\)

Q8. Differentiate between:
a. Open and closed circulatory system
b. Oviparity and viviparity
c. Direct and indirect development
d. Aceolomate and pseudocoelomate
e. Notochord and nerve cord
f. Polyp and medusa

Answer: a. The circulatory system may be of two types:
1. Open type in which the blood is pumped out of the heart and the cells and tissues are directly bathed in it. E.g.: Arthropoda, Mollusca and Hemichordata.
2. Closed type in which the blood is circulated through a series of vessels of varying diameters (arteries, veins and capillaries). E.g.: Annelida and Chordata.

b. Oviparous animals give birth to an egg while viviparous animals are those that give birth to the live young ones.
c. Direct development: It is a type of development in which an embryo develops into a mature individual without involving a larval stage. Indirect development: It is a type of development that involves a sexuallyimmature larval stage.
d. Acoelomate: The animals in which the body cavity is absent are called acoelomates, e.g.: Porifers, Coelentrates, Ctenophores and Platyhelminthes. ,
Pseudocoelomate: In some animals, the body cavity is not lined by mesoderm, instead, the mesoderm is present as scattered pouches in between the ectodenp and endoderm. E.g., aschelminthes
e. Notochord is a mesodermally derived rod-like-structure formed on the dorsal side during embryonic development in some animals and it is the part of skeletal system. .
Nerve cord is the part of nervous system.
f. The polyp is a sessile and cylindrical fonn like Hydra, Adamsia, etc., whereas, the medusa is umbrellashaped and free-swimming like Aurelia or jelly fish.

Q9. Give the characteristic features of the following citing one example of each
a. Chondrichthyes and ostichthyes
b. Urochordata and cephalochordata

Answer: a. Chondrichthyes-. They are marine animals with streamlined body and have cartilaginous endoskeleton. Mouth is located ventrally. Notochord is persistent throughout life. Gill slits are separate and without operculum (gill cover). The skin is tough, containing minute placoid scales. Teeth are modified placoid scales which are backwardly directed. Their jaws are very powerful. These animals are predaceous. Due to the absence of air bladder, they have to swim constantly to avoid sinking. Scoliodon (Dog fish), Pristis (Saw fish), Carcharodon (Great white shark), Trygon (Sting ray).
Osteichthyes: It includes both marine and fresh water fishes with bony endoskeleton. Their body is streamlined. Mouth is mostly terminal. They have four pairs of gills which are covered by an operculum on each side. Skin is covered with cycloid/ctenoid scales. Air bladder is present which regulates buoyancy.
Examples: Marine—Exocoetus (Flying fish), Hippocampus (Sea horse); Freshwater—Labeo (Rohu), Catla (Katla), Clarias (Magur); Aquarium—Betta (Fighting fish), Pterophyllum (Angel fish),
b. Subphyla Urochordata and Cephalochordata are often referred to as protochordates and are exclusively marine. In Urochordata, notochord is present only in larval tail, while in Cephalochordata, it extends from head to tail region and is persistent throughout their life.
Examples: Urochordata—Ascidia, Salpa, Doliolum; Cephalochordata— Branchiostoma (Amphioxus or Lancelet).

Q10. Mention two similarities between
a. Aves and mammals
b. A frog and crocodile
c. A turtle and pila

Answer: a. Similarities between aves and mammalian
(i) Both are homeothermic animals (warm blooded)
(ii) Both have four chambered heart
b. Similarities between frog and crocodile
(i) Both are poikilothermic animals (cold blooded)
(ii) Both are oviparous animals
c. Similarities between turtle and Pila
(i) Both are poikilothermic animals (cold blooded)
(ii) Both are oviparous animals

Q11. Name
a. A limbless animal
b. A cold blooded animal
c. A warm blooded animal
d. An animal possessing dry and cornified skin
e. An animal having canal system and spicules
f. An animal with cnidoblasts

Answer: a. A limbless animal: Icthyophis
b. A cold blooded animal: Trygon (sting ray)
c. A warm blooded animal: Macaca (monkey)
d. An animal possessing dry and comifiedskin: Naja (Cobra)
e. An animal having canal system and spicules: Euspongia (bath sponge)
f. An animal with cnidoblasts: Hydra.

Q12. Give an example for each of the following
a. A viviparous animal
b. A fish possessing a poison sting
c. A fish possessing an electric organ
d. An organ, which regulates buoyancy
e. Animal, which exhibits alternation of generation
f. Oviparous animal with mammary gland

Answer: a. A viviparous animal: Panthera leo (lion)
b. A fish possessing a poison sting: Trygon (sting ray)
c. A fish possessing an electric organ: Torpedo
d. An organ, which regulates buoyancy: Air bladder
e. Animal, which exhibits alternation of generation: Obelia (Sea-fur)
f. Oviparous animal with mammary gland: Ornithorhynchus (Platypus).

Q13. Excretory organs of different animals are given below. Choose correctly and write in the space provided.
\(
\begin{array}{llll}
\hline & \text { Animal } & & \text { Excetory Organ/Unit } \\
\hline \text { a. } & \text { Balanoglossus } & \text { (i) } & \text { Metanephridia } \\
\hline \text { b. } & \text { Leech } & \text { (ii) } & \text { Nephridia } \\
\hline \text { c. } & \text { Locust } & \text { (iii) } & \text { Flame cells } \\
\hline \text { d. } & \text { Liver fluke } & \text { (iv) } & \text { Absent } \\
\hline \text { e. } & \text { Sea urchin } & \text { (v) } & \text { Malpighian tubule } \\
\hline \text { f. } & \text { Pila } & \text { (vi) } & \text { Proboscis gland } \\
\end{array}
\)

Answer:

\(
\begin{array}{|l|l|l|l|}
\hline \text { a. } & \text { Balanoglossus } & \text { (vi) } & \text { Proboscis gland } \\
\hline \text { b. } & \text { Leech } & \text { (ii) } & \text { Nephridia } \\
\hline \text { c. } & \text { Locust } & \text { (v) } & \text { Malpighian tubule } \\
\hline \text { d. } & \text { Liver fluke } & \text { (iii) } & \text { Flame cells } \\
\hline \text { e. } & \text { Sea urchin } & \text { (iv) } & \text { Absent } \\
\hline \text { f. } & \text { Pila } & \text { (i) } & \text { Metanephridia } \\
\hline
\end{array}
\)

LONG ANSWER TYPE QUESTIONS

Q1. Give three major differences between chordates and non-chordates and draw a schematic sketch of a chordate showing those features.

Answer: Animals belonging to phylum Chordata are fundamentally characterised by the presence of a notochord, a dorsal hollow nerve cord and paired
pharyngeal gill slits. These are bilaterally symmetrical, triploblastic, coelomate with organ-system level of organisation. They possess a post anal tail and a closed circulatory system.
\(
\begin{array}{|l|l|l|}
\hline \text { S. No. } & \text { Chordates } & \text { Non-chordates } \\
\hline \text { 1. } & \text { Notochord present. } & \text { Notochord absent. } \\
\hline 2 . & \begin{array}{l}
\text { Central nervous system is dorsal, hollow and } \\
\text { single. }
\end{array} & \begin{array}{l}
\text { Central nervous system is ventral, solid and } \\
\text { double. }
\end{array} \\
\hline \text { 3. } & \text { Pharynx perforated by gill slits. } & \text { Gill slits are absent. } \\
\hline \text { 4. } & \text { Heart is ventral. } & \text { Heart is dorsal (if present). } \\
\hline \text { 5. } & \text { A post-anal part (tail) is present. } & \text { Post-anal tail is absent. } \\
\hline
\end{array}
\)

Q2. What is the relationship between germinal layers and the formation of body cavity in case of coelomate, acoelomates and pseudocoelomates? 

Answer: Presence or absence of a cavity between the body wall and the gut wall is very important in classification. The body cavity, which is lined by mesoderm is called coelom. Animals possessing coelom are called coelomates, e.g., annelids, molluscs, arthropods, echinoderms, hemichordates and chordates. In some animals, the body cavity is not lined by mesoderm, instead, the mesoderm is present as scattered pouches in between the ectoderm and endoderm. Such a body cavity is called pseudocoelom and the animals possessing them are called pseudocoelomates, e.g., aschelminthes. The animals in which the body cavity is absent are called acoelomates, e.g., platyhelminthes

Q3. Comment upon the habitats and external features of animals belonging to class, amphibia and reptilia.

Answer: Class—Amphibia As the name indicates (Gr., Amphi: dual, bios, life), amphibians can live in aquatic as well as terrestrial habitats. Most of them have two pairs of limbs. Body is divisible into head and trunk. Tail may be present in some. The amphibian skin is moist (without scales). The eyes have eyelids. A tympanum represents the ear.
Examples: Bufo (Toad), Rana (Frog), Hyla (Tree frog), Salamandra (Salamander), Ichthyophis (Limbless amphibia).
Class-Reptilia :The class name refers to their creeping or crawling mode of locomotion (Latin, repere or reptum, to creep or crawl). They are mostly terrestrial animals and their body is covered by dry and comified skin, epidermal scales or scutes. They do not have external ear openings. Tympanum represents ear. Limbs, when present, are two pairs.
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).

Q4. Mammals are most adapted among the vertebrates. Elaborate.

Answer: Mammals are most adapted among the vertebrates as they are found in a variety of habitats – polar ice caps, deserts, mountains, forests, grasslands and*dark caves. Some of them have adapted to fly or live in water.
They have two pairs of limbs, adapted for walking, running, climbing,. burrowing, swimming or flying. The skin of mammals is unique in possessing hair. External ears or pinnae are present. Different types of teeth are present in the jaw. Heart is four chambered.
They are ‘homoiot’hermous. Respiration is by lungs. Sexes are separate and fertilisation is internal. They are viviparous with few exceptions and development is direct.