GSEB Class 11 Biology Solutions Chapter 4 Animal Kingdom

Question 1. What are the difficulties that you would face in the classification of animals if common fundamental features are not taken into account?
Answer: Despite differences in animal structures, there are shared basic traits among various animal types. These include how cells are arranged, body symmetry, the nature of coeloms, and the patterns of digestive, circulatory, or reproductive systems.
These characteristics are vital because they help group organisms with more similar attributes, arrangements, and categorize animals as primitive or highly developed. They provide a foundation for classifying animals and assist in researching closely related species.
In simple words: It would be very hard to sort animals without looking at their basic body features like cell arrangement or body symmetry. These shared traits are essential for grouping animals and understanding how they are related or developed.

Exam Tip: When classifying, always consider fundamental features like cellular organization, body symmetry, coelom type, and system patterns as they reveal evolutionary relationships.

Question 2. If you are given a specimen, what are the steps that you would follow to classify it?
Answer: We would take these steps to classify a specimen:
1. Levels or grades of organization
2. Patterns in the organ system
3. Symmetry
4. Diploblastic and triploblastic organization.
5. Body cavity and coelom
6. Segmentation.
In simple words: To classify an animal, we would check its organization level, how its organs are set up, its body symmetry, if it has two or three cell layers, the type of body cavity, and if its body is segmented.

Exam Tip: Remember these six key criteria for animal classification as they are universally applied to group organisms systematically.

Question 3. How useful is the study of the nature of the body cavity and coelom in the classification of animals?
Answer: The type of space (body cavity) between the body wall and the digestive tube is very important for classification. Besides these basic features of the body cavity, there are many other specific characteristics for each phylum or class. A body cavity that is lined by mesoderm is known as a coelom. Animals that have a coelom are called coelomates. Animals without a body cavity are called acoelomates. In some animals, the body cavity is not lined by mesoderm. Instead, the mesoderm appears as scattered pouches between the ectoderm and endoderm. Such a body cavity is known as a pseudocoelom, and animals that have it are called pseudocoelomates.
In simple words: Knowing about an animal's body cavity or coelom is very helpful for classifying it. Animals are grouped based on whether they have a true coelom (coelomates), no coelom (acoelomates), or a false coelom (pseudocoelomates).

Exam Tip: Understanding coelom development (acoelomate, pseudocoelomate, coelomate) is crucial as it signifies major evolutionary advancements and helps distinguish broad animal groups.

Question 4. Distinguish between intracellular and extracellular digestion?
Answer: Intracellular digestion happens partly inside cells, specifically within the gastrodermis cells. The coelenteron also distributes food while partly digesting it. Because it performs both roles, the coelenteron is referred to as the gastrovascular cavity.
Extracellular digestion happens partly outside cells, occurring in the coelenteron through digestive enzymes released by the gastrodermis cells.
In simple words: Intracellular digestion happens inside cells, like in gastrodermis cells, while extracellular digestion occurs outside cells in areas like the coelenteron, using secreted enzymes.

Exam Tip: Remember that intracellular digestion typically involves phagocytosis within cells, while extracellular digestion uses enzymes released into a cavity or outside the body.

Question 5. What is the difference between direct and indirect development?
Answer: Direct development means the young or offspring look similar to the adult, without any intermediate stages. Examples include humans and birds. Indirect development means the young, when hatched or born, do not look like the adult but go through many intermediate stages to become an adult. For example, frogs have a tadpole stage before becoming adult frogs. Butterflies have larvae and a cocoon stage before they become butterflies.
In simple words: Direct development means baby animals look like small adults, while indirect development means they go through different forms, like a caterpillar turning into a butterfly, before becoming an adult.

Exam Tip: Focus on the presence or absence of a larval stage to differentiate between direct and indirect development. Common examples like insects and amphibians are good for illustration.

Question 6. What are the peculiar features that you find in parasitic Platyhelminthes?
Answer: Parasitic forms of Platyhelminthes have hooks and suckers. They are parasitic flatworms, often called flukes. Their body is unsegmented and leaf-like, covered by a thick living tegument without an epidermis. The mouth is at the front and has suckers for attaching to the host. Their life cycle includes a larval stage and requires more than one host. Examples include Fasciola (the liver fluke) and Schistosoma (the blood fluke).
In simple words: Parasitic flatworms have special features like hooks and suckers to attach to their host. Their body is covered by a tough skin and they often need more than one host to complete their life cycle, which includes a larval stage.

Exam Tip: Key features of parasitic adaptations in Platyhelminthes include structures for attachment (hooks/suckers), a protective tegument, and complex life cycles often involving multiple hosts.

Question 7. What are the reasons that you can think of the arthropods to constitute the largest group of the animal kingdom?
Answer: The following might be the reasons why arthropods form the largest group in the animal kingdom:

• They are the first phylum to have well-developed digestive, circulatory, and respiratory systems.
• Their body is covered by a chitinous exoskeleton, which helps them survive even extreme conditions.
• They are usually small and reproduce rapidly compared to all other phyla, so they have higher numbers.
• They possess highly developed sensory organs such as antennae, compound and simple eyes, and statocysts, which help them stay safe from predators.
• Arthropods can be found everywhere, even in volcanic springs where survival is difficult. They live in water, air, and on land, having evolved to suit all conditions.

Exam Tip: When explaining arthropod success, emphasize their adaptable exoskeleton, efficient organ systems, high reproductive rates, advanced sensory capabilities, and broad ecological distribution.

Question 8. Water vascular system is characteristic of which group of the following:
(a) Porifera
(b) Ctenophora
(c) Echinodermata
(d) Chordata
Answer: (c) Echinodermata
The water vascular system is the most distinguishing feature of echinoderms. It aids in locomotion, food capture, food transport, and respiration.
In simple words: The water vascular system is a special network of canals and tube feet found only in echinoderms, helping them move, eat, and breathe.

Exam Tip: Associate the water vascular system exclusively with Echinodermata (e.g., starfish, sea urchins) as it is their unique defining characteristic for movement and feeding.

Question 9. "All vertebrates are chordates but all chordates are not vertebrates.” Justify the statement.
Answer: All chordates have a notochord at some stage of their life. However, only in vertebrates is this notochord replaced by a vertebral column during the adult stage. In other chordates (like Urochordata and Cephalochordata), the notochord persists throughout life or is present only in the larval stage, and they do not develop a vertebral column.
In simple words: Every animal with a backbone (vertebrate) started as a chordate with a notochord. But not all chordates (like tunicates or lancelets) develop a backbone; some keep their notochord instead.

Exam Tip: To justify this statement, clearly define "chordate" (presence of notochord, dorsal hollow nerve cord, pharyngeal slits, post-anal tail) and "vertebrate" (notochord replaced by vertebral column) and provide examples of non-vertebrate chordates.

Question 10. How important is the presence of an air bladder in Pisces?
Answer: The air bladder in Pisces helps regulate buoyancy. Sharks, for example, do not have an air bladder like bony fishes. Because of this, they must swim constantly; otherwise, they will sink to the bottom. Bony fishes do not experience such a problem as their air bladder helps them stay at a certain depth without continuous swimming.
In simple words: The air bladder in bony fish helps them float or sink in water without needing to constantly swim. Sharks, without an air bladder, have to keep moving to avoid sinking.

Exam Tip: Highlight that the air bladder's primary function is buoyancy regulation, allowing fish to maintain depth, and use the contrast between bony fish and cartilaginous fish (sharks) to illustrate its importance.

Question 11. What are the modifications that are observed in birds that help them fly?
Answer: The following modifications help birds fly:

• They have feathers.
• They possess pneumatic bones; these long, hollow bones contain air cavities, making them lighter.
• Their forelimbs are modified into wings, which assist in flight.
• Hind limbs generally have scales and help them grasp prey during flight or perch on a tree branch.
• Urine and feces are excreted through a single opening, and very little water is lost, which helps reduce body weight.
• An aerodynamically built body helps in flying.

Exam Tip: When discussing flight adaptations in birds, emphasize weight reduction (pneumatic bones, efficient excretion) and power generation/aerodynamics (feathers, wings, body shape).

Question 12. Could the number of eggs or young ones produced by an oviparous and viviparous mother be equal? Why?
Answer: In oviparous animals, the newly hatched young may look like the adult. This kind of development is called direct development. In some cases, young hatched from eggs do not resemble the adult; these young are called larvae, nymphs, or naiads. They live independently for some time and then undergo a major change to become adults. This change from larvae to adults is known as metamorphosis, and such development is called indirect development. Viviparous animals create tiny eggs, and the developing embryo gets its food from the mother's reproductive tract through the placenta, as seen in mammals.
In simple words: No, the number of eggs or young ones produced by oviparous (egg-laying) and viviparous (live-bearing) mothers is usually not equal. Oviparous animals often lay many eggs because the young develop outside the mother and face more dangers, requiring a higher quantity for survival. Viviparous animals, however, typically produce fewer young because the embryos develop inside the mother, receiving protection and nourishment, which increases their chances of survival.

Exam Tip: The key difference in offspring number relates to parental investment and survival rates. Oviparous species compensate for external risks with high egg numbers, while viviparous species prioritize internal protection and nourishment for fewer, more viable offspring.

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
(a) Platyhelminthes have a blind sac body plan. Flatworms have a head at the front end. They have a brain, sense organs, and move forward during locomotion. There are no appendages. The body surface is ciliated. They have an organ-system level of body organization and are dorso-ventrally flattened, commonly known as flatworms.
(b) Aschelminthes: The body of aschelminths appears circular in cross-section, hence the name roundworm. They can be free-living, aquatic, terrestrial, or parasitic in plants and animals. Roundworms have an organ-system level of body organization.
(c) Annelida: Annelids were the first segmented animals. Their body surface is clearly marked out into segments or metameres, like rings, giving them the phylum name Annelida. A cuticle covers the body. Muscles in the body wall help in locomotion on the ground.
(d) Arthropods are bilaterally symmetrical, triploblastic, segmented, and acoelomate animals. The body of arthropods is covered by a cuticle that forms the exoskeleton. The body segments are fused to form the head, thorax, and abdomen. They have jointed appendages. These appendages are variously modified to form antennae, mouthparts, pincers (chelicerae), or walking legs.
In simple words: Segmentation, where the body is divided into repeating units, first appeared in Annelida, like earthworms. While other groups have different body plans, Annelids were the first to show this distinct segmentation.

Exam Tip: Remember that true segmentation (metamerism) first evolved in the Annelida, marking a significant step in animal body plan complexity. Arthropods also show segmentation, but Annelids precede them in this evolutionary trait.

Question 14. Match the following:
(i) Operculum (a) Ctenophora
(ii) Parapodia (b) Mollusca
(iii) Scales (c) Porifera
(iv) Comb plates (d) Reptilia
(v) Radula (e) Annelida
(vi) Hairs (f) Cyclostomata & Chondrichthyes
(vii) Choanocytes (g) Mammalia
(viii) Gill slits (h) Osteichthyes
Answer:
(i) h
(ii) e
(iii) d
(iv) a
(v) b
(vi) g
(vii) c
(viii) f
In simple words: Match the unique body parts with the correct animal groups. For example, operculum belongs to bony fish, parapodia to annelids, scales to reptiles, comb plates to ctenophores, a radula to mollusks, hairs to mammals, choanocytes to sponges, and gill slits to jawless fish and cartilaginous fish.

Exam Tip: For matching questions, focus on unique identifying features of each phylum or class. Create a mental checklist of characteristic structures for each group.

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

• Taenia (Tapeworm)
• Fasciola (liver fluke)
• Ascaris (roundworm)
• Wuchereria (filaria worm)
• Ancylostoma (Hookworm)
• Hirudinaria (bloodsucking leech)

Exam Tip: When listing human parasites, try to include a variety from different phyla (e.g., Platyhelminthes, Aschelminthes, Annelida) to show a broader understanding.