RBSE Solutions Class 11 Biology Chapter 30 Classification of Nonchordata

RBSE Class 11 Biology Chapter 30 Multiple Choice Objective Questions

 

Question 1. Who first used the term protozoa
(a) Elaeckel
(b) Goldfuss
(c) Lamark
(d) Leeuwenhoek
Answer: (b) Goldfuss
In simple words: The scientist Goldfuss was the first person to use the word "protozoa" to describe a group of very simple, single-celled animals. This term helps classify these tiny living things.

🎯 Exam Tip: Knowing the historical figures who coined scientific terms can be important for general biology knowledge and specific classification questions.

 

Question 2. Bath sponge is
(a) Euspongia
(b) Spongilla
(c) Hippospongia
(d) Pheronema
Answer: (a) Euspongia
In simple words: A bath sponge, which people often use for bathing, is actually a type of sea animal called Euspongia. It's known for its soft, absorbent skeleton.

🎯 Exam Tip: When identifying common names with scientific names, focus on the most representative example unless specified otherwise.

 

Question 4. Connecting link between annelida and mollusca
(a) Peripatus
(b) Neoplina
(c) Limulus
(d) Limax
Answer: (b) Neoplina
In simple words: Neoplina is considered a link between annelids and molluscs because it has features from both groups. It helps scientists understand how these two different animal groups are related in evolution.

🎯 Exam Tip: Understanding connecting links between phyla shows evolutionary relationships. Peripatus is a famous connecting link between Annelida and Arthropoda, while Neopilina connects Annelida and Mollusca.

 

Question 5. Largest invertebrate is
(a) Giant squid
(b) Cuttlefish
(c) Physalia
(d) Balaenoptera
Answer: (a) Giant squid
In simple words: The giant squid is the biggest animal that does not have a backbone. It lives deep in the ocean and can grow to be very large.

🎯 Exam Tip: The giant squid is renowned for its massive size, making it the largest known invertebrate on Earth.

 

Question 6. Aristotle lantern is found in
(a) Starfish
(b) Brittle star
(c) Sea urchin
(d) Sea anemone
Answer: (c) Sea urchin
In simple words: Sea urchins have a special mouth part called Aristotle's lantern. It is a complex set of jaws and muscles that helps them scrape food, like algae, off rocks.

🎯 Exam Tip: The Aristotle's lantern is a unique, complex chewing apparatus found in sea urchins, used for grazing on algae and other food sources.

 

Question 7. Shell of mollusca is secreted by
(a) Foot
(b) Mantle
(c) Ctnidia
(d) Placoid
Answer: (b) Mantle
In simple words: The mantle is a soft layer of tissue in molluscs that covers their internal organs. This special layer makes the material that forms their hard outer shell.

🎯 Exam Tip: The mantle is a key part of molluscs, as it not only secretes the shell but also plays roles in respiration and locomotion.

RBSE Class 11 Biology Chapter 30 Very Short Answer Questions

 

Question 1. On what basis phylum protozoa is classified?
Answer: Phylum Protozoa is classified based on their locomotory organelles. These are the special parts they use to move around. The way they move helps scientists put them into different groups.
In simple words: Protozoa are classified by how they move, using different body parts for locomotion.

🎯 Exam Tip: When asked about classification bases, always identify the primary characteristic used, such as locomotion, body symmetry, or presence of a coelom.

 

Question 2. Which disease is caused by Entamoeba histolytica?
Answer: Entamoeba histolytica causes the disease called Amoebiasis. This is an infection that can affect the intestines, leading to symptoms like stomach pain and diarrhea. This parasite is commonly found in contaminated food or water.
In simple words: Entamoeba histolytica causes Amoebiasis, a disease that affects the gut.

🎯 Exam Tip: Remember important parasitic diseases and the specific organisms that cause them, as this is a common question in medical and biological contexts.

 

Question 3. Write the name of free living platyhelminthese.
Answer: Examples of free-living platyhelminthes include Planaria and catenula. Unlike many other platyhelminthes, these types do not live as parasites inside other animals but rather live independently in water or moist environments. Planarians are well-known for their amazing ability to regenerate lost body parts.
In simple words: Planaria and catenula are flatworms that live freely and are not parasites.

🎯 Exam Tip: Distinguish between free-living and parasitic forms of organisms. Planaria is a classic example of a free-living flatworm, often studied for regeneration.

 

Question 4. Which is the largest phylum of Invertebrates?
Answer: The largest phylum of invertebrates is Arthropoda. This group includes a huge number of species like insects, spiders, and crustaceans, making them the most diverse and abundant animal group on Earth. Their success is partly due to their exoskeleton and jointed legs.
In simple words: Arthropoda is the biggest group of animals without backbones, including insects and spiders.

🎯 Exam Tip: Arthropoda's vast diversity and adaptation to almost all environments make it the largest phylum, a key fact to remember.

 

Question 5. Which animal show “Tube-within-a tube” arrangement?
Answer: Annelids are animals that show a "tube-within-a-tube" body arrangement. This means their digestive tract, which is one tube, runs through a larger body cavity, which is the outer tube. This structure allows for more complex body functions and movement. Earthworms are a common example of annelids.
In simple words: Annelids, like earthworms, have a "tube-within-a-tube" body plan, meaning a digestive tube inside a body tube.

🎯 Exam Tip: The "tube-within-a-tube" body plan signifies a more advanced body organization, allowing for specialized digestive and body wall functions.

 

Question 6. Which type of coelom is found in annelids?
Answer: Annelids possess a schizocoelom. This type of body cavity forms from the splitting of the mesoderm during embryonic development, creating a true coelom lined by mesodermal tissue. This provides space for organs and allows for efficient movement.
In simple words: Annelids have a schizocoelom, which is a true body cavity that forms from the splitting of the middle cell layer.

🎯 Exam Tip: Differentiating between acoelomate, pseudocoelomate, and eucoelomate (schizocoelom or enterocoelom) is crucial for understanding animal body plans.

 

Question 8. Name the connecting link between annelida & arthropoda.
Answer: The connecting link between annelida and arthropoda is Peripatus. This animal has features from both annelids (like a soft body, simple eyes, and unjointed legs) and arthropods (like a chitinous cuticle and tracheal respiration). Studying such links helps us understand evolution. These unique creatures are often found in humid, tropical forests.
In simple words: Peripatus connects annelids and arthropods because it shares traits from both groups.

🎯 Exam Tip: Connecting links are important evolutionary examples, showing transitional forms between major animal phyla. Peripatus is a classic example.

 

Question 9. Respiratory pigment haemocyanin is found in the animals of which phylum.
Answer: The respiratory pigment haemocyanin is found in animals belonging to the phylum Mollusca. This pigment contains copper and turns blue when it binds with oxygen, unlike hemoglobin which contains iron. It helps in carrying oxygen throughout the body in these invertebrates. It is also found in some arthropods like horseshoe crabs.
In simple words: Molluscs use haemocyanin, a copper-based pigment, to carry oxygen in their blood, which turns blue.

🎯 Exam Tip: Recognize the different types of respiratory pigments and the animal groups they are associated with (e.g., hemoglobin in vertebrates, haemocyanin in molluscs/arthropods).

 

Question 10. The power of regeneration in colelenterates is because of which cells.
Answer: The power of regeneration in coelenterates is due to the presence of interstitial cells. These are undifferentiated stem cells that can develop into various other cell types, allowing coelenterates to repair injuries and regrow lost parts. This ability makes them fascinating subjects for biological studies.
In simple words: Coelenterates can regrow lost parts because they have special cells called interstitial cells.

🎯 Exam Tip: Interstitial cells are pluripotent stem cells vital for regeneration and budding in simple animals like coelenterates, demonstrating remarkable biological plasticity.

 

Question 11. Mesogloea is found in the animals of which phylum.
Answer: Mesogloea is found in animals belonging to the phylum Coelenterata (also known as Cnidaria). It is a jelly-like, non-cellular layer located between the two main tissue layers (ectoderm and endoderm) of their body wall. This layer provides structural support and flexibility to creatures like jellyfish and hydras.
In simple words: Coelenterates have a jelly-like layer called mesogloea between their outer and inner body layers.

🎯 Exam Tip: Mesogloea is a characteristic feature of diploblastic animals like coelenterates, contributing to their body structure and buoyancy.

 

Question 12. Animals of which subphylum of phylum arthropoda are extinct (fossilized).
Answer: Animals of the subphylum Trilobita within the phylum Arthropoda are extinct and are known only from fossils. Trilobites were ancient marine arthropods that lived millions of years ago and are very important for understanding early life forms on Earth. Their fossilized remains are commonly found around the world.
In simple words: Trilobites, an extinct group of arthropods, are only known from fossils found in old rocks.

🎯 Exam Tip: Fossils like trilobites provide crucial evidence for evolution and help reconstruct ancient ecosystems and the history of life.

 

Question 13. Which causes elephantiasis in human beings?
Answer: Elephantiasis in human beings is caused by Filariaworm (specifically Wuchereria bancrofti or Brugia malayi). These parasitic roundworms are transmitted by mosquitoes and block the lymphatic system, leading to severe swelling and thickening of the skin, typically in the legs. Prevention involves controlling mosquito populations and mass drug administration.
In simple words: Elephantiasis is caused by Filariaworms, which are parasites spread by mosquitoes, leading to extreme swelling in parts of the body.

🎯 Exam Tip: Remember the causative agents of major diseases and their mode of transmission, especially for parasitic infections with significant public health impact.

 

Question 14. In which class of protozoa, locomotory orgenelles are absent?
Answer: Locomotory organelles are absent in the class Sporozoa of protozoa. These organisms are typically parasitic and rely on their host for movement, as they do not have structures like flagella, cilia, or pseudopodia for independent locomotion. Plasmodium, the parasite causing malaria, is a well-known example of a sporozoan.
In simple words: Sporozoa are a group of protozoa that do not have special parts for moving, often because they live as parasites inside other living things.

🎯 Exam Tip: The absence of locomotory organelles is a key characteristic of parasitic protozoa like sporozoans, reflecting their adapted lifestyle within a host.

RBSE Class 11 Biology Chapter 30 Short Answer Questions

 

Question 1. On what basis of locomotory orgenelles, phylum protozoa is classified into how many classes?
Answer: On the basis of locomotory organelles, the phylum Protozoa is divided into 4 classes. These classes are:
1. Class - Flagellata or Mastigophora: These protozoans move using flagella, which are long, whip-like structures. Examples include Euglena, Noctiluca, Leishmania, Trichomonas, and Trypanosoma. Trypanosoma causes sleeping sickness.
2. Class - Sarcodina or Rhizopoda: These protozoans move using pseudopodia, which are temporary extensions of their cytoplasm. Examples include Amoeba, Entamoeba, and Pelomyxa. Amoeba are often studied for their unique movement.
3. Class - Ciliata: These protozoans move using cilia, which are short, hair-like structures that beat in coordinated waves. Examples include Paramecium, Vorticella, Didineum, Balantidium, Opalina, Nyctotherus, and Spirostomum. Paramecium is a common pond organism.
4. Class - Sporozoa: In this class, locomotory organelles are absent. All members are parasitic and rely on their hosts for movement. Examples include Plasmodium, Monocystes, and Nosema. Plasmodium causes malaria, a widespread disease.
In simple words: Protozoa are grouped into four classes based on how they move: Flagellata uses flagella, Sarcodina uses false feet, Ciliata uses tiny hairs, and Sporozoa do not move on their own because they are parasites.

🎯 Exam Tip: Clearly list each class with its specific locomotory structure and at least one representative example to score full marks in classification questions.

 

Question 2. Write four features of pseudocoelomates.
Answer: Here are four features of pseudocoelomates:

• The body is generally round, elongated, and tapers to a point at both ends. It is covered by a thick outer protective layer called a cuticle.
• They possess a pseudocoelom, which is a body cavity not fully lined by mesoderm, allowing organs to float freely within it.
• Respiratory and blood vascular systems are not present in these animals. They typically rely on diffusion for gas exchange and nutrient transport.
• The body wall consists of a syncytial epidermis and a muscular layer made up of longitudinal muscle cells, which are often found arranged in four distinct sections or quadrants. This gives them a characteristic wriggling movement.

In simple words: Pseudocoelomates have a round, pointed body with a thick skin, a body cavity not fully lined with a special tissue, no breathing or blood systems, and muscles arranged in four parts.

🎯 Exam Tip: Focus on the definition of pseudocoelom (false coelom) and how it affects the presence or absence of other organ systems compared to true coelomates.

 

Question 4. What is "living fossil"? Give example.
Answer: A "living fossil" refers to an animal species that has remained largely unchanged over millions of years and closely resembles its ancient fossilized ancestors. These species are often on the verge of extinction, representing a lineage that has survived significant evolutionary changes around them. Examples include Limulus (horseshoe crab) and Peripatus. The Coelacanth fish is another famous living fossil.
In simple words: A living fossil is an animal that has barely changed over millions of years and looks like its old fossil relatives. Limulus and Peripatus are examples.

🎯 Exam Tip: When defining "living fossil," emphasize both morphological stasis over geological time and their close resemblance to ancient fossil forms.

 

Question 5. Write the functions of nematoblasts in coelenterates.
Answer: In coelenterates, nematoblasts (also called cnidoblasts) have several important functions. They help in offense by stinging prey, defense by deterring predators, locomotion through their ability to anchor to surfaces, and ingestion of food by paralyzing and capturing prey. These specialized stinging cells are a hallmark feature of the phylum Cnidaria. They contain a stinging capsule called a nematocyst.
In simple words: Nematoblasts in coelenterates are stinging cells that help them attack, defend, move, and catch food.

🎯 Exam Tip: Highlight the multi-functional role of nematoblasts (cnidoblasts) beyond just stinging, including their importance in feeding and defense.

 

Question 6. Name four phyla exhibiting indirect development.
Answer: The four phyla exhibiting indirect development are Echinodermata, Porifera, Coelenterata, and Nematoda. Indirect development means that the young organism (larva) looks very different from the adult form and goes through a metamorphosis stage. This often involves a free-swimming larval stage before becoming a sessile or adult form. Many aquatic invertebrates follow this pattern.
In simple words: Echinodermata, Porifera, Coelenterata, and Nematoda are four phyla where babies look different from adults and change shape as they grow.

🎯 Exam Tip: Understand that indirect development involves a larval stage and metamorphosis, which can aid in dispersal and reduce competition with adults.

 

Question 7. Write salient features of phylum hemichordata.
Answer: Here are the salient features of phylum Hemichordata:

• They can be solitary or colonial, mostly live in marine environments, and are tubicolous (living in tubes), free-living, or free-swimming.
• Their bodies are bilaterally symmetrical, triploblastic (having three germ layers), and possess an enterocoelic true coelom.
• The body is clearly divided into three regions: a proboscis, a collar, and a trunk.
• The proboscis contains an endoskeleton called the buccal diverticulum, which is similar to, but not the same as, the notochord found in chordates.
• They have a straight or U-shaped alimentary canal for digestion.
• Excretion occurs through a specialized structure called the glomerulus, which is located in the proboscis.
• Gill slits are present, allowing for respiration.
• They are unisexual (separate sexes), reproduce through external fertilization, and undergo indirect development with a larval stage called tornaria.
• The phylum is further divided into two classes.

In simple words: Hemichordates are marine animals, symmetrical with three body layers and a true body cavity. They have a proboscis, collar, and trunk, a simple gut, and breathe through gill slits. They reproduce with separate sexes and have a larval stage.

🎯 Exam Tip: When listing features of a phylum, ensure a comprehensive description covering body plan, habitat, major systems (digestive, excretory, respiratory), and reproductive characteristics.

 

Question 8. What is sexual dimorphism? Give example.
Answer: Sexual dimorphism is a condition where male and female individuals of the same species can be identified by distinct external features other than their reproductive organs. These differences can include size, color, markings, or secondary sexual characteristics. For example, in humans, men and women often differ in height, body hair, and voice pitch. The peacock's elaborate tail feathers compared to the peahen's duller plumage is another clear example. It helps in mate recognition and selection.
In simple words: Sexual dimorphism means males and females of a species look different on the outside. A common example is men and women, or peacocks and peahens.

🎯 Exam Tip: When explaining sexual dimorphism, ensure you highlight that the differences are *external* and *non-reproductive*, and provide clear, recognizable examples.

 

Question 9. Give the reason why the hemichordates are kept under invertebrates.
Answer: Hemichordates are classified as invertebrates primarily because their proboscis contains an endoskeleton called the buccal diverticulum, which is not considered homologous to the notochord found in true chordates. Although they share some features with chordates (like pharyngeal gill slits), the absence of a true notochord and other key chordate characteristics places them within the invertebrate group. They are often seen as an evolutionary link but ultimately lack the definitive chordate defining traits. Additionally, their nervous system is more diffuse than a typical chordate nerve cord.
In simple words: Hemichordates are invertebrates because their supporting rod (buccal diverticulum) is not the same as the notochord found in backboned animals.

🎯 Exam Tip: The distinction between chordates and invertebrates hinges on key features like the notochord. A thorough understanding of these defining characteristics is essential.

 

Question 10. Give the names of classes of phylum Porifera and their respective examples.
Answer: The phylum Porifera (sponges) is divided into the following classes:
1. Class - Calcarea (Calcisponqiae): The skeleton of these sponges is made up of spicules composed of calcium carbonate (CaCO3). Examples include Leucosolenia, Sycon, Grantia, and Leucilla. They are generally small and marine.
2. Class - Hexactinillida (Hyalospongiae): These sponges have a skeleton made of silica spicules, which are six-pointed and give them a glassy appearance. Examples include Hyalonema, Euplectella, and Pheronema. They are typically deep-sea sponges.
3. Class Demospongiae: The skeleton of these sponges consists of spongin fibers, silica spicules, or both. This is the largest class of sponges. Examples include Euspongia (bath sponge), Spongilla (freshwater sponge), Chalina, and Cliona Spheceospongia. They display a wide range of forms and colors.
In simple words: Porifera has three main classes: Calcarea (calcium skeleton), Hexactinellida (silica skeleton), and Demospongiae (spongin fibers or silica). Each class has different types of sponges as examples.

🎯 Exam Tip: When classifying sponges, remember to link each class to its specific skeletal composition, as this is the primary distinguishing feature.

 

Question 11. Write four features of phylum Echinodermata.
Answer: Here are four features of phylum Echinodermata:
1. They possess specialized tube feet, which are small, muscular appendages that help in locomotion (movement) and respiration (breathing). These are part of their unique water vascular system. Many tube feet work together like tiny suction cups.
2. They have a distinctive "Water vascular system" where water enters through a madriporite (a sieve plate) and circulates through a network of canals, operating the tube feet. This system is unique to echinoderms.
3. Blood vascular, respiratory, and excretory systems are absent in these animals. They use their water vascular system and dermal branchiae for these functions.
4. Most echinoderms exhibit radial symmetry in their adult stage, typically pentamerous radial symmetry, meaning their body parts are arranged in fives around a central axis. However, their larval forms show bilateral symmetry. Their skin is spiny due to an endoskeleton of calcareous ossicles.
In simple words: Echinoderms have tube feet for moving and breathing, a special water system for their feet, no separate blood or breathing systems, and adult bodies shaped like a star with five parts.

🎯 Exam Tip: The water vascular system and tube feet are the most distinctive features of echinoderms; ensure you describe their function accurately.

 

Question. Write the salient features, names of classes with examples of phylum mollusca.
Answer:
**Phylum - Mollusca**
(Gr. Mollis = Soft bodied)

**General:**
The animals of this phylum have soft bodies and are typically unsegmented. Snails, mussels, cowries, and other shelled creatures found near rivers, ponds, and lakes all belong to molluscs. The term "mollusca" was introduced by John Johnstone in 1605. According to Mayer (1953), this phylum includes approximately 80,000 species, making it one of the largest animal phyla. Molluscs are known for their diverse forms and habitats, ranging from tiny snails to large squids.

**Salient Features:**

• Their body is bilaterally symmetrical (though some may become asymmetrical), triploblastic (three germ layers), unsegmented, and soft.
• They live in aquatic environments, with some forms adapted to amphibious (land and water) life; they can be solitary or free-living.
• A reduced coelom, known as a schizocoelom, is present.
• The body is covered by a soft mental layer, the mantle.
• They possess an exoskeleton, usually a shell made of calcium carbonate (CaCO3), which may be internal or absent in some species. The nacreous layer of the mantle secretes this shell.
• The body is typically divided into three main parts: a head, a visceral mass (containing organs), and a muscular foot.
• A toothed, ribbon-like structure called a radula is present in the mouth, used for scraping or cutting food, though it is absent in bivalves.
• Respiration primarily occurs through gills (ctenidia), while amphibious forms may also have lung-like structures.
• Their blood is typically blue due to the presence of haemocyanin, a copper-containing respiratory pigment. The blood vascular system can be partly open and partly closed.
• Excretion is carried out by metanephridia or specialized organs like Bojanus' organ or Keber's organ.
• Simple eyes and statocysts (for balance) may be present, though they can be absent in some species.
• They can be unisexual (separate sexes) or bisexual (hermaphroditic). Fertilization can be external or internal, and development can be direct or indirect.

**Classification of Phylum Mollusca:**
Based on their general characteristics, molluscs are divided into 7 classes (Hyman, 1961).
1. Class - Monoplacophora:
* They are considered a connecting link between annelids and arthropods due to shared characteristics.
* The shell consists of only one valve (plate).
* Example - Neoplina. These are small, deep-sea molluscs that were once thought to be extinct.
2. Class - Polyplacophora (Amphineura):
* Their shell is made of multiple (usually eight) overlapping plates.
* Examples - Chiton, Lepidopleurus. These are commonly known as chitons, found clinging to rocks in intertidal zones.
3. Class - Scaphopoda:
* The shell is tusk-shaped and open at both ends, resembling an elephant's tusk.
* Example - Dentalium. These are marine molluscs that burrow into sand.
4. Class - Gastropoda:
* Many are amphibious, capable of living both in water and on land.
* Their body exhibits torsion, meaning their internal organs twist during development, leading to an asymmetrical adult form.
* The foot is broad and muscular, used for crawling.
* The larval stage is called a veliger.
* Examples - Pila (apple snail), Cypraea (cowrie), Doris (sea lemon), Aplysia (sea hare), Limax (slug), Helix (garden snail). This is the largest and most diverse class of molluscs.
5. Class - Pelecypoda or Bivalvia:
* The shell consists of two valves (halves) that are hinged together on one side.
* The foot is shaped like a plough, used for burrowing.
* The larval stage is called a glochidium.
* Examples - Unio (freshwater mussel), Solen (razor clam), Mytilus (mussel), Teredo (shipworm), Pinctada (pearl oyster). These filter feeders are important in aquatic ecosystems.
6. Class - Cephalopoda:
* The shell can be external, internal, or completely absent.
* The foot is divided to form oral arms (tentacles) and a funnel, which are used for movement and capturing prey.
* Examples - Sepia (cuttlefish), Octopus, Loligo (squid), Nautilus. These are highly intelligent marine predators.

*(Figure 30.7: Members of phylum Mollusca, showing Unio, Pila, Sepia, and Octopus. This image illustrates the diversity of forms within the phylum Mollusca.)*

**Economic Importance of Phylum Mollusca:**
* **As Food:** The fleshy bodies of many molluscs, especially bivalves and gastropods, are consumed as food by humans worldwide. Mussels, clams, and oysters are popular seafood items. They are a good source of protein.
* **Pearliculture:** Natural pearls are valuable animal products obtained from various species of pearl oysters, such as Pinctada radiata, Pinctada vulgaris, and Pinctada margaritifera. In India, the Lingha pearl is particularly well-known. The pearl is formed by the nacreous layer of the mantle secreting layers around an irritant. Chemically, natural pearl is composed of 88-90% Argonite (calcium carbonate), 3.5-6% Conchiolin (a scleroprotein), and a small percentage of water and residue. The first human-made pearl was produced by Japanese scientist Tokichi Nishikawa. The beauty of a pearl comes from its many layers.

*(Figure 30.7: Showing pearl formation. This image would illustrate the process of pearl formation within a bivalve mollusc.)*
In simple words: Molluscs are soft-bodied animals with a shell (often). They have a symmetrical, segmented body with a head, foot, and organ mass. They breathe with gills, have blue blood, and can live in water or on land. They are split into many classes, like Monoplacophora, which connects them to other worm-like and insect-like creatures. They are important because many types are eaten as food, and pearl oysters make valuable pearls.

🎯 Exam Tip: When detailing a phylum, structure your response with general characteristics, salient features (with bullet points), classification with examples for each class, and economic importance for clarity and completeness.

 

Question 2. Explain how arthropods are economically beneficial and harmful?
Answer:
**Economic Importance of Phylum Arthropoda:**
**(A) Beneficial Importance**
Insects, which are part of the phylum Arthropoda, hold significant importance, and many are reared for occupational purposes.
(i) Apiculture: This is the practice of rearing honey bees to obtain honey and wax. Honey is used as food and medicine, effective for conditions like coughs, colds, fevers, and ulcers. Two notable Indian honey bee species are Apis indica and Apis dorsata. Bees play a vital role in plant pollination.
(ii) Lac Culture: Lac insects are reared to produce lac, a resinous substance used as a coating around the female insect and the twig it lives on. Jharkhand, Chhattisgarh, and West Bengal are leading producers of lac in India. Lac is used in shellac, dyes, and cosmetics.
(iii) Sericulture: This involves rearing silkworms to produce silk. Different species of silkworms produce various types of silk. For instance, Bombyx mori produces mulberry silk and is reared on mulberry leaves. Antheraea paphia produces tussar silk, Antheraea assama produces muga silk, Antheraea ricini produces eri silk, and Antheraea proylei produces oak silk. Silk thread is composed of fibroin and sericin proteins, known for its strength and luster.
(iv) Prawn Farming (Shrimp Fish Farming): Prawns (e.g., Palaemon, also known as Jhinga machhali) are popular seafood and are cultivated on a large scale, especially in South India. Many species of prawns, such as Fenneropenaeus indicus, are farmed commercially. Prawn farming provides food and economic opportunities.
(v) Pollination of flowers: Many plants rely on insects for pollination. Honey bees, bumble bees, and other insects perform most of the pollination, which is crucial for fruit and seed production. This biological service is essential for ecosystems and agriculture.
(vi) Edible insects: Insects serve as food for many animals, including birds, lizards, and fish, which are in turn consumed by humans. In many cultures, certain insects are directly eaten by humans as a source of protein and nutrients. They are a sustainable food source.
(vii) Destruction of harmful insects: Some arthropods are beneficial because they prey on other harmful insects. For example, dragonflies feed on mosquitoes and other insect pests, helping to control their populations naturally. This is a form of biological pest control.
(viii) Medicine synthesis: Certain insects are used in medicine. The blister beetle (genus Lytta) produces cantharidin, a substance historically used for hair growth. Cochineal bugs (Dactylopius coccus) produce carminic acid, used as a natural dye and in some medical preparations. These insects offer compounds with medicinal properties.

**(B) Harmful Importance**
Many species of arthropods cause various diseases in human beings and destroy stored food and household items. Here are some examples:
* **Disease Vectors:** Anopheles quadrimaculatus spreads malaria fever. Culex pipiens causes elephantiasis. Aedes aegypti transmits yellow fever. Phlebotomus argentipes transmits kala-azar fever. Musca domestica (house fly) spreads cholera, typhoid, and diarrhea. Cimex lectularius (bed bug) carries typhus fever and TB. Pediculus humanus capitis (human lice) also transmit typhus fever and itching. Glossina palpalis (tsetse fly) causes African sleeping sickness. Xenopsylla cheopis (oriental rat flea) transmits plague. These insects act as carriers for many serious illnesses.
*(Figure 30.6: Members of phylum Arthropoda, showing Spider, Scorpion, Crab, Centipede, Silk moth, Millipede, Prawn, House fly. This image illustrates the diversity of forms within the phylum Arthropoda.)*
In simple words: Arthropods are helpful because honey bees give us honey and wax, lac insects make lac for coatings, silkworms give us silk, and prawns are farmed for food. They also help pollinate flowers, serve as food for other animals, and some even eat harmful insects or are used to make medicines. However, some arthropods like mosquitoes and flies spread diseases to humans, and others are pests that spoil stored food and damage household items.

🎯 Exam Tip: When discussing economic importance, categorize effects into beneficial and harmful aspects, providing specific arthropod examples and the associated product, service, or impact for each.

 

Question 3. Write the salient features, classes and economic importance of phylum platyhelminthese.
Answer:
**Phylum - Platyhelminthes**
[Gr. Platy = Flat & helminthes = Worm]

**General:**
Platyhelminthes are commonly known as flatworms. They are simple animals, generally bilateral and unsegmented. They are the most primitive and simplest animals to exhibit bilateral symmetry. They can be free-living or parasitic. Their bodies are flattened dorsoventrally, meaning they are flat from top to bottom. Flatworms are an important group for studying early animal evolution and the development of organ systems.

**Salient Features:**
1. They can be solitary, free-living, or parasitic. They are bilaterally symmetrical, triploblastic (have three germ layers), and acoelomate (lack a body cavity).
2. Their body can be unsegmented or pseudosegmented (appearing segmented but not truly so).
3. The body cavity, if any, is filled with special mesenchyma or parenchyma tissues, which is why they are called acoelomates.
4. The alimentary canal (digestive tract) is either absent or incomplete, often having only one opening.
5. They may possess cilia for movement, or suckers and hooks for attachment, especially in parasitic forms.
6. Excretion is carried out by specialized cells called flame cells, which function like primitive kidneys.
7. Respiration is usually anaerobic, meaning it occurs without oxygen, especially in parasitic forms living inside hosts.
8. They lack respiratory, blood vascular, and sensory systems. Gas exchange and nutrient transport occur mainly by diffusion.
9. They can be unisexual (separate sexes) or bisexual (hermaphroditic), exhibit internal fertilization, and development can be direct or indirect. Some have complex life cycles involving multiple hosts.
10. Most flatworms show polyembryony (formation of multiple embryos from a single zygote) and embryogenesis.
11. They have special vitelline glands that secrete yolk, providing nourishment for developing embryos.

**(ii) Pests of stored grains:** Many insects destroy stored food materials, leading to significant economic losses. Examples include:
* Sitophilus oryzae (rice weevil) damages rice grains.
* Sitotroga cerealella (Angoumois grain moth) affects many cereals.
* Tribolium confusum (confused flour beetle) or red flour beetle contaminates all types of flour and whole cereals.
* Podia interpunctella (Indian meal moth) infests wheat.
* Tragoderma granarium (khapra beetle) damages wheat and other grains. These pests spoil large quantities of food if not controlled.

**(iii) Household pests:** Many insects cause damage to various household items. Such as:
* Lepisma saccharina (silverfish) eats old books and clothes.
* Liposcelis transvaalensis (book louse) damages books.
* Monomorium indicum (white ant) destroys wooden articles.
* Mastotermes obesi (termite) also damages wooden articles. These pests can cause structural damage and destroy personal belongings.

**Classification of Platyhelminthes:**
Platyhelminthes are classified into three classes based on their general features:
1. Class - Turbellaria:
* These are mostly free-living, aquatic worms found in both marine and freshwater environments, and are typically free-swimming. They undergo direct development and have an incomplete alimentary canal; their body is unsegmented.
* Examples - Planaria, Gunda, Aphronta, Catenula, Convoluta. Planaria is famous for its regenerative abilities.
2. Class - Trematoda:
* These are both ectoparasites (living outside the host) and endoparasites (living inside the host). They have an unsegmented body and possess suckers, usually two, on their body for attachment. Their alimentary canal is incomplete, and they exhibit polyembryony and embryogenesis.
* Examples - Fasciola (liver fluke), Schistosoma (blood fluke), Paragonimus (lung fluke). These parasites often have complex life cycles.
3. Class - Cestoda:
* All members of this class are endoparasites. They completely lack an alimentary canal and absorb nutrients directly through their body surface.
* They have a pseudosegmented body, consisting of segments called proglottids, and possess both hooks and suckers for attachment to the host's intestine. Each proglottid contains reproductive organs.
* Examples - Taenia (tapeworm), Echinococcus (hydatid worm), Diphyllobothrium (fish tapeworm), Hymenolepis (dwarf tapeworm). These are well-known intestinal parasites.

**Economic Importance of Platyhelminthes:**
This phylum is significant because many of its members are pathogens (disease-causing organisms) in human beings and other animals. They can cause a range of health issues. Their parasitic nature makes them medically and economically important to understand and control. Some free-living forms are important in ecological food chains, but their pathogenic role is more prominent. Here is a table detailing some important pathogens:

In simple words: Platyhelminthes are flatworms, either free-living or parasites, with a flat body and no true body cavity. They are classified into three classes: Turbellaria (free-living), Trematoda (flukes), and Cestoda (tapeworms). Many flatworms cause diseases in humans and animals, making them important to study. They can also be pests that destroy stored grains and household items.

🎯 Exam Tip: When detailing a phylum, ensure you cover its general characteristics, classification (with examples for each class), and any notable economic or medical importance, using tables for clear data presentation.

 

Question 4. Classify the phylum protozoa on the basis of locomotory orgenelles and explain its economic importance with examples.
Answer:
**Phylum - Protozoa**
[Gr. Protos \( \implies \) First and Zoon \( \implies \) Animal]

**General:**
Protozoa are the most primitive and simplest animals. Structurally, they are acellular (meaning unicellular) and eukaryotic organisms. There are approximately 15,000 known protozoan species in the world, inhabiting diverse environments. They are microscopic organisms, typically ranging in size from 0.001 to 3.0 mm. Some are parasitic or commensal, while others are symbiotic. Many are solitary, but some live in colonies. They exhibit a protoplasmic grade of organization, meaning all vital activities are performed within a single cell. Their body can be naked or covered by a thin protective layer called a pellicle. Most are uninucleated (one nucleus), but some can be binucleated or multinucleated. Nutrition is mostly holozoic (animal-like), but some are holophytic (plant-like) or saprozoic (absorbing dissolved nutrients), or parasitic. Respiration and excretion occur by diffusion through the body surface. Contractile vacuoles are present for osmoregulation (water balance). Asexual reproduction occurs through binary fission, multiple fission, or budding, while some also undergo a simple type of sexual reproduction called conjugation. Some protozoa can form cysts, and many have the power of regeneration. Their unicellular body cannot be divided into somatoplasm and germplasm, and they are considered immortal under ideal conditions.

**Classification of Protozoa:**
On the basis of locomotory organelles, the phylum Protozoa is divided into 4 classes:
1. Class - Flagellata or Mastigophora:
* Locomotion is by flagella.
* Examples: Euglena, Noctiluca, Leishmania, Trichomonas, Trypanosoma etc.
2. Class - Sarcodina or Rhizopoda:
* Locomotion is by pseudopodia (false feet).
* Examples: Amoeba, Entamoeba, Pelomyxa etc.
3. Class - Ciliata:
* Locomotion is by cilia (short hair-like structures).
* Examples: Paramecium, Vorticella, Didineum, Balantidium, Opalina, Nyctotherus, Spirostomum etc.
4. Class - Sporozoa:
* Locomotory organelles are absent.
* They are parasitic.
* Examples: Plasmodium, Monocystis, Nosema etc. Plasmodium is responsible for malaria.

**Economic Importance of Protozoa:**
**Beneficial Importance**
1. Protozoans serve as a primary food source for many smaller animals in aquatic ecosystems, helping to sustain the food chain. They are crucial for maintaining ecological balance and nutrient cycling.
2. Many protozoans inhabit ponds and other freshwater bodies. They feed on organic material, helping to clean the water and making it suitable for drinking and supporting other aquatic life.
3. Being unicellular, protozoans are extensively used in laboratories for educational purposes. Students study them to observe biological variations, understand the origins and evolution of animals, and learn about heredity. They are excellent model organisms for cell biology research.

**Harmful Importance**
Many species of protozoans cause various diseases in human beings, as listed in the table below. These diseases can range from mild infections to severe, life-threatening conditions.

In simple words: Protozoa are tiny, single-celled animals. They are grouped into four classes based on how they move: Flagellata, Sarcodina, Ciliata, and Sporozoa. Some protozoa are useful as food for other creatures and help clean water. However, many protozoa are harmful because they cause diseases in humans, like amoebiasis and malaria, as shown in the table.

🎯 Exam Tip: For questions asking for both classification and economic importance, ensure you cover both beneficial and harmful aspects with specific examples and, if appropriate, organize information in tables for clarity.

 

Question 3. Write the salient features, classes and economic importance of phylum platyhelminthese.
Answer: (This part of the answer details the harmful economic importance, as presented in the table below.)

In simple words: This table shows different types of flatworms (Platyhelminthes) that cause diseases in humans and other animals. It lists where they infect, what illness they cause, and how they spread.

🎯 Exam Tip: When asked about economic importance, always discuss both beneficial and harmful aspects with specific examples of pathogens and diseases.

 

Question 4. Classify the phylum protozoa on the basis of locomotory orgenelles and explain its economic importance with examples.
Answer: Protozoa are the simplest and most basic animals. They are single-celled (acellular) organisms with a true nucleus (eukaryotic). There are about 15,000 known types of protozoa around the world. These tiny organisms were among the first forms of animal life to evolve, playing a crucial role in early ecosystems.

Classification of Protozoa:
Protozoa are grouped into four main classes based on how they move:
1. Class - Flagellata (or Mastigophora): These move using long, whip-like structures called flagella. Examples include Euglena, Noctiluca, Leishmania, Trichomonas, and Trypanosoma.
2. Class - Sarcodina (or Rhizopoda): These move by forming temporary extensions of their cell body, called pseudopodia. Amoeba, Entamoeba, and Pelomyxa are common examples.
3. Class - Ciliata: These use tiny, hair-like structures called cilia for movement. Paramecium, Vorticella, Didineum, Balantidium, Opalina, Nyctotherus, and Spirostomum are well-known members of this group.
4. Class - Sporozoa: These protozoa do not have special moving parts. They are all parasites, meaning they live inside other organisms. Plasmodium, Monocystis, and Nosema are examples.

Economic Importance:
Protozoa have both beneficial and harmful impacts.

(A) Beneficial Importance:
1. Protozoa are very important for the environment and for science. Some help clean water by eating tiny organic bits, thus maintaining ecological balance.
2. They also serve as a food source for other small organisms in aquatic environments.
3. Because they are single-celled, scientists often study protozoa in laboratories to understand biological processes like variation, evolution, and heredity.

(B) Harmful Importance:
Many protozoan species cause various diseases in humans and animals. These are listed in the table below:

In simple words: Protozoa are single-celled animals grouped by how they move. They are important because some clean water and help science, but many others cause serious diseases in humans and animals, like malaria and amoebiasis.

🎯 Exam Tip: When classifying organisms, always mention the basis of classification. For economic importance, always provide specific examples for both beneficial and harmful aspects, detailing the species and their impact.