Class 11 Biology Chapter 4 Animal Kingdom

Key Concept: Evolutionary Significance, Phylogenetic Relationships, Functional Adaptations

c) It provides better support and protects the neural structures

[Solution Description] The vertebral column replaces the notochord in adult vertebrates and provides greater support and protection for the dorsal nerve cord. This structural enhancement allows for improved mobility and stability, facilitating more complex movements and adaptability to different environments, thus offering a significant evolutionary advantage.

Key Concept: Respiratory Structures

c) Gills

[Solution Description] Molluscs typically have gills located within the mantle cavity, which are responsible for gas exchange and thus play a crucial role in respiration. The gills allow oxygen to diffuse into the blood while carbon dioxide diffuses out to be expelled.

Key Concept: Comparative Features

d) Notochord

[Solution Description]

All chordates share four key features at some stage in their life cycle: a notochord, a dorsal hollow nerve cord, pharyngeal gill slits, and a post-anal tail. These features differentiate them from other phyla.

Key Concept: Functional Morphology, Adaptations and Survival

a) Proboscis

[Solution Description] Hemichordates such as acorn worms have a specialized structure called the proboscis, which plays a critical role in burrowing and feeding. The proboscis secretes mucus, capturing food particles from the water, facilitating efficient filter feeding.

Key Concept: Annelids Characteristics

b) Bilateral symmetry

[Solution Description] Annelids are characterized by bilateral symmetry, a segmented body plan, a closed circulatory system, and the presence of nephridia for excretion. Therefore, bilateral symmetry is a characteristic feature of annelids.

Key Concept: Integrated Systems, Real-world Application

c) Assertion is true, but Reason is false.

[Solution Description] The mantle cavity is indeed involved in both respiration and excretion in molluscs; it contains gills for breathing and openings for waste discharge. However, the assertion that the radula, which is a feeding apparatus located in the head region of molluscs, is used for respiratory purposes is incorrect. The radula’s primary function is to scrape or cut food before ingestion. Therefore, while the assertion about the mantle cavity’s role is true, the reason provided is false as the radula does not perform any respiratory functions.

Key Concept: Basic Features

d) Body symmetry

[Solution Description] Fundamental features for classification include arrangement of cells, body symmetry, type of coelom, and pattern of organ systems.

Key Concept: Bioluminescence

b) Bioluminescence

[Solution Description] Ctenophores are known for their well-marked bioluminescence, which is the ability to produce light biologically.

Key Concept: Functional Adaptations, Structural Adaptations

c) The mantle for shell secretion

[Solution Description] In molluscs, one significant adaptation is their ability to secrete calcium carbonate to form shells, providing them with protection against predators and environmental conditions. The shell is produced by the mantle, which is an organ that not only secretes the shell material but provides a space for respiration and excretion. This adaptation showcases how molluscs have evolved to thrive in various environments.

Key Concept: Circulatory System

b) Closed

[Solution Description] Cyclostomata have a closed circulatory system, meaning their blood flows through a series of vessels and does not fill body cavities. This type of system allows more efficient circulation of nutrients and oxygen compared to an open circulatory system.

Key Concept: Germinal Layers Basics

b) Annelids

[Solution Description] Triploblastic animals have three germinal layers: ectoderm, mesoderm, and endoderm. Examples include platyhelminthes to chordates. Among the given options, annelids are triploblastic.

Key Concept: Organisation Levels

c) Organ

[Solution Description] Flatworms, or platyhelminthes, show the organ level of organization, as they have developed structures like a simple digestive system and excretory organs.

Key Concept: Development Type

c) Both A and B

[Solution Description] Aschelminthes may exhibit both direct and indirect development depending on species. This means they can develop directly into adults from the larval stage or undergo a metamorphosis involving intermediate stages.

Key Concept: Levels of Organization

a) Cnidarians

[Solution Description]

The tissue level of organization is characterized by a group of cells working together to perform a specific function, but there are no distinct organs or organ systems. Cnidarians like jellyfish and corals exhibit this type of organization.

Key Concept: Symmetry Type

b) Radial

[Solution Description] Ctenophores exhibit radial symmetry, meaning their body structure can be divided into similar halves by multiple planes passing through the central axis.

Key Concept: Comparative Analysis, Functional Adaptations

b) The presence of nematocysts for direct toxin delivery

[Solution Description] Cnidocytes contain specialized organelles called nematocysts that can eject a harpoon-like filament to deliver toxins into prey or predators. This mechanism provides a unique and effective approach to prey capture and defense, distinguishing cnidocytes from similar cells in other organisms.

Key Concept: Physiological Processes, Functional Adaptations

d) Utilizes an excretory pore system for osmoregulation and waste removal.

[Solution Description] The excretory system of Aschelminthes, which consists of an excretory tube with pores, assists in osmoregulation and removal of metabolic wastes effectively. This differs from flame cells in flatworms and allows Aschelminthes to maintain internal balance in diverse habitats, contributing to their adaptability and success across various environments.

Key Concept: Regeneration Mechanism, Functional Morphology

c) Stem cell proliferation facilitates new tissue formation.

[Solution Description] Planaria exhibits remarkable regenerative capabilities primarily due to stem cell proliferation. These stem cells, also known as neoblasts, can differentiate into various cell types needed for replacing lost or damaged tissues. Such a mechanism reflects its simple body structure without complex specialization, allowing easy replacement and repair of cells across its dorsoventrally flattened body.

Key Concept: Tissue Organisation Impact, Symmetry and Function

c) It organizes specialized light-emitting tissues.

[Solution Description] The tissue-level organisation in ctenophores allows for specialized tissues that can perform specific functions such as bioluminescence. In cellular-level organisms, cells are more generalized, leading to less complex functionalities. This organization facilitates the integration of various cells into light-producing structures capable of synchronizing light emission. Radial symmetry ensures these light-emitting organs are evenly distributed, enhancing visibility from all directions.

Key Concept: Skeleton Composition

b) Spicules or spongin fibers

[Solution Description] The skeletons of sponges are typically composed of spicules, which can be made of silica or calcium carbonate, or of fibrous protein structures known as spongin fibers.

Key Concept: Symmetry Type

b) Bilateral

[Solution Description] Pseudocoelomates are bilaterally symmetrical, meaning their bodies can be divided into mirror-image halves along one plane.

Key Concept: Reproductive System

c) Monoecious nature

[Solution Description]

Earthworms are monoecious, meaning they have both male and female reproductive organs within the same individual. This allows them to reproduce by exchanging sperm with another worm.

Key Concept: Developmental Process

c) Both direct and indirect

[Solution Description] The development process in arthropods can be either direct or indirect. Direct development involves offspring resembling small adults, while indirect development involves metamorphosis stages like larvae and pupae before reaching adulthood.

Key Concept: Basic Definition

b) Excretion

[Solution Description] Flame cells play a crucial role in maintaining water balance and excreting waste products. They are part of the osmoregulatory system, aiding in the removal of excess water and waste substances.

Key Concept: Pseudocoelomate Identification

b) Aschelminthes

[Solution Description] Pseudocoelomates are animals that possess a pseudocoel, a false body cavity not completely lined by mesoderm. The phylum Aschelminthes (modern term Nematoda) includes such organisms.

Key Concept: Function of Cnidoblasts

c) Defense and prey capture

[Solution Description] Cnidoblasts are specialized cells found in cnidarians containing nematocysts, which are primarily used for defense and prey capture by delivering toxins through a stinging mechanism.

Key Concept: Real-World Application, Advanced Reasoning

c) Enhances oxygen delivery efficiency

[Solution Description] A closed circulatory system, where blood is contained within vessels, allows precise regulation of circulation and gas exchange. For annelids in variable oxygen environments, this system enables efficient transport of oxygen to tissues even when ambient levels fluctuate, ensuring survival and maintaining metabolic activities despite environmental challenges.

Key Concept: Structural Component

c) Collar cells

[Solution Description] Choanocytes are commonly known as collar cells because they possess a distinctive collar-like ring of microvilli surrounding their flagellum, essential for their role in filtering water and capturing food particles.

Key Concept: Classification Application

c) Frog

[Solution Description]

A chordate is characterized by the presence of a notochord at some stage in its life cycle. The frog is an example of a chordate since it belongs to the class Amphibia within the phylum Chordata, and it possesses a notochord during its embryonic development.

Key Concept: Locomotion

c) Assertion is true, but Reason is false.

[Solution Description] Assertion is true as Ctenophores utilize their eight external rows of ciliated comb plates for movement through water. However, the reason provided is false because the ciliated comb plates are not responsible for bioluminescence. Bioluminescence is a separate feature found in these organisms but is not attributed to the function of the comb plates.

Key Concept: Basic Definition

a) Metamerism

[Solution Description] The division of an animal’s body into segments is known as metamerism.

Key Concept: Comparative Anatomy

b) Possession of a stomochord

[Solution Description] Hemichordates possess a structure called the stomochord, which is unique to them and distinguishes them from true chordates. True chordates have a notochord, a more complex structure that plays a significant role in their physiology.

Key Concept: Development Types

b) Indirect development only

[Solution Description]

In arthropods, indirect development involves a life cycle with distinct larval stages that eventually metamorphose into adulthood. This contrasts direct development, where offspring resemble miniature adults at birth.

Key Concept: Respiratory System

d) Alveoli

[Solution Description] The respiratory structures observed in arthropods include gills, book gills, book lungs, and tracheal systems. Alveoli are characteristic of mammals and are not found in arthropods.

Key Concept: Germ Layer Concept

c) Three

[Solution Description]

Coelomates have three germ layers, making them triploblastic organisms. These germ layers are ectoderm, mesoderm, and endoderm, which give rise to various tissues and organs during development.

Key Concept: Amphibian Features

c) Amphibians have moist skin without scales.

[Solution Description] Amphibians are known to have a moist skin, which helps them in respiration along with lungs and gills. This feature is crucial for their survival both in water and on land. Additionally, amphibia do not have scales; this differentiates them from reptiles.

Key Concept: Developmental Stages

b) Larval stage

[Solution Description] Echinoderms show different types of symmetry at various stages of their life cycle. As larvae, they exhibit bilateral symmetry, allowing them to swim freely in the water. This is distinct from the radial symmetry seen in their adult form.

Key Concept: Basic Definition

d) Dorsoventrally flattened body

[Solution Description]

The defining characteristic of the phylum Platyhelminthes is their dorsoventrally flattened body. This means that their bodies are flat from top to bottom. This feature distinguishes them from many other animal phyla.

Key Concept: Symmetry Transition

d) Bilateral to radial

[Solution Description] Echinoderms exhibit bilateral symmetry in their larval stage which aids in mobility and development. As they grow into adults, they undergo a transition to radial symmetry, allowing them to interact with the environment from all sides.

Key Concept: Parasitic Nature

b) Animals

[Solution Description] Wuchereria, also known as the filarial worm, is a parasite primarily affecting animals, including humans, where it can cause diseases such as lymphatic filariasis.

Key Concept: Symmetry Types

b) Radial

[Solution Description] Coelenterates exhibit radial symmetry where body parts are arranged around a central axis.

Key Concept: Water Vascular System

b) Locomotion

[Solution Description] The water vascular system in echinoderms plays multiple roles, including locomotion, food transport, and respiration. It is a distinctive feature of these organisms that helps them move using tube feet.

Key Concept: Definition Recall

b) Animals with separate sexes

[Solution Description] The term ‘dioecious’ refers to animals that have separate male and female individuals. This characteristic is key for sexual reproduction, allowing distinct sexes to produce offspring through genetic recombination.

Key Concept: Excretory Organ

c) Proboscis gland

[Solution Description] The proboscis gland serves as the excretory organ in Hemichordata, responsible for removing waste products from the body.

Key Concept: Basic Structure

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.

[Solution Description] The assertion states that sponges possess a skeleton composed of spicules, which is a true statement as per the syllabus. The reason provided is also true; spicules indeed play a role in providing structural support to the sponge body. Moreover, this support function explains why spicules are considered part of the sponge’s skeleton, making the reason a correct explanation for the assertion.

Key Concept: Basic Identification

b) Parapodia

[Solution Description] Nereis uses parapodia for locomotion, which are lateral appendages that aid in swimming.

Key Concept: Gills Structure

c) Four

[Solution Description] Class Osteichthyes fishes generally have four pairs of gills. Each pair is covered by a bony plate known as an operculum on each side of the head. This structure facilitates breathing by protecting the delicate gill tissues and assisting in water flow over the gills.

Key Concept: Basic Definition

b) Respiration

[Solution Description] The water vascular system in echinoderms serves multiple crucial functions including locomotion, capturing and transporting food, and aiding in respiration.

Key Concept: Complex Classification, Advanced Comparative Analysis

b) Only Chordata have a dorsal hollow nerve cord

[Solution Description] Hemichordates, like chordates, possess a structure that somewhat resembles a notochord – called a stomochord, but it is not homologous to the notochord. A significant difference lies in the dorsal hollow nerve cord, which is present in chordates but absent in hemichordates. This nerve cord is fundamental in the development of more sophisticated nervous systems in chordates.

Key Concept: Organ System Function

a) Open

[Solution Description] Arthropods possess an open circulatory system. In this system, the blood is not confined to vessels and instead flows freely within body cavities where the organs are bathed directly in the blood or hemolymph. This helps distribute nutrients and remove waste products efficiently despite being less complex than closed systems.

Key Concept: Development Type

a) Direct

[Solution Description] Sepia (Cuttlefish) undergoes direct development, meaning it develops into a form that resembles the adult without undergoing metamorphosis or larval stages. This is typical for many cephalopods.

Key Concept: Functional Anatomy

d) Proboscis gland

[Solution Description] In Hemichordata, the excretory organ is known as the proboscis gland. It plays a vital role in the excretion process.

Key Concept: Basic Definition

c) Blood is pumped out of the heart and directly bathes the cells and tissues

[Solution Description] An open circulatory system is one in which blood is pumped out of the heart and directly bathes the cells and tissues instead of circulating within closed vessels.

Key Concept: Shell Function

d) Provides protection from predators

[Solution Description] The calcareous shell provides protection to the soft body of molluscs from predators and environmental damage. It acts as a hard barrier that shields the internal organs and soft tissues.

Key Concept: Parasitic Features

b) Presence of hooks and suckers

[Solution Description]

Parasitic forms of the phylum Platyhelminthes often have specialized structures such as hooks and suckers. These structures help them attach to the host organism’s tissues effectively.

Key Concept: Body Opening

a) One

[Solution Description]

Cnidarians have a central gastro-vascular cavity with a single opening serving as both mouth and anus.

Key Concept: Insect Examples

c) Laccifer (Lac Insect)

[Solution Description] The economically important insects mentioned in the syllabus are Apis (Honeybee), Bombyx (Silkworm), and Laccifer (Lac Insect). These insects contribute significantly to industries like honey production, silk manufacturing, and lac processing.

Key Concept: Basic Function

b) Defense and capturing prey

[Solution Description] The primary functions of cnidoblasts in cnidarians are anchorage, defense, and prey capture. Among these, the most commonly recognized function is for defense and capturing prey.

Key Concept: Real-world Application, Evolutionary Adaptations

b) Replacement of the notochord by intervertebral discs and vertebrae

[Solution Description] The transformation of the notochord into intervertebral discs and the vertebral column in vertebrates provides insights into spinal flexibility and structural integrity, thereby aiding research into regenerative treatments for spinal injuries.

Key Concept: Examples Identification

b) Fasciola

[Solution Description] Among the given options, Taenia and Fasciola are examples of parasitic acoelomates. They belong to the class Platyhelminthes, which are characterized by being acoelomate and having no body cavity.

Key Concept: Reproduction Method

b) Sexually

[Solution Description] Ctenophores reproduce sexually with external fertilization, where gametes are released into the water and fertilization occurs outside the organism’s body.

Key Concept: Concept Understanding

c) By allowing independent segment movement

[Solution Description] Metameric segmentation allows for more controlled and flexible movement since each segment can move independently, providing structural benefits.

Key Concept: Bone Structure

c) Hollow bones with air cavities

[Solution Description]

Birds possess hollow bones with air cavities known as pneumatic bones. This adaptation reduces overall body weight, making it easier to maintain flight.

Key Concept: Reproduction

b) Fragmentation

[Solution Description] Sponges reproduce asexually through fragmentation, where pieces of sponge break off and develop into new individuals.

Key Concept: Basic Definition

c) The division of the body into segments

[Solution Description] Metamerism is the division of the body into segments, also known as metameres, which is a key characteristic seen in organisms like earthworms.

Key Concept: Radial Symmetry

c) Echinoderms

[Solution Description] Animals with radial symmetry can be divided into similar halves by any longitudinal plane passing through the central axis. Coelenterates, ctenophores, and echinoderms exhibit this type of symmetry.

Key Concept: Water Vascular System

b) Locomotion

[Solution Description] The water vascular system in echinoderms primarily aids in locomotion by allowing the organisms to move through hydraulic pressure. It also assists with feeding and respiration, but its main role in movement should be highlighted. Therefore, the primary function is locomotion.

Key Concept: Subphyla Characteristics

c) Assertion is true, but Reason is false.

[Solution Description]

In Urochordata, which is one of the subphyla within Chordates, the notochord is present only during the larval stage and disappears as the organism matures into an adult. In adults, the body is supported by a structure called the tunic, composed mainly of a cellulose-like substance. The assertion that Urochordates have a notochord during the larval stage is true, but the reason that it provides skeletal support for adults is false. The notochord’s function is primarily relevant in the larval stage where it aids in mobility, not providing skeletal support in adulthood.

Key Concept: Development Stages

b) Indirect development with larval stages

[Solution Description] Taenia employs an indirect type of development characterized by multiple larval stages. During its lifecycle, it undergoes several transformations before reaching its adult form, indicative of complex life cycles in parasites.

Key Concept: Reproductive Features

b) Dioecious with external fertilization

[Solution Description] Echinoderms commonly reproduce via external fertilization and have indirect development. This means that fertilization occurs outside the organism, followed by a larval stage. Thus, the correct answer is dioecious with external fertilization.

Key Concept: Real-World Application, Structural Adaptations

c) Calcium carbonate skeleton

[Solution Description] Ocean acidification leads to a decrease in the concentration of carbonate ions in seawater. Corals, being cnidarians with calcium carbonate skeletons, rely on these ions for building their exoskeleton. As acidification progresses, it becomes more challenging for corals to maintain and build their structures due to the reduced availability of necessary carbonate compounds.

Key Concept: Skeleton Composition

d) Calcium carbonate

[Solution Description] Corals have a hard external skeleton made up of calcium carbonate. This composition not only provides structural support but also contributes to the formation of coral reefs.

Key Concept: Basic Definition

c) It has two distinct openings, mouth and anus.

[Solution Description] A complete alimentary canal is a digestive system with two separate openings: a mouth for ingestion and an anus for egestion.

Key Concept:

c) Both exhibit a closed circulatory system.

Both have an open circulatory system.

Key Concept: Tissue Layers

b) Triploblastic

[Solution Description] Platyhelminthes are triploblastic, meaning they develop from three primary germ layers: ectoderm, mesoderm, and endoderm.

Key Concept: Structural Adaptation, Ecological Role

c) They enhance structural integrity and deter potential predators.

[Solution Description]

Spicules provide critical structural support for sponges like Euspongia, enabling them to maintain form and create a defensive mechanism against predators. This adaptation is important ecologically as it allows the sponges to occupy specific niches such as filtering water efficiently in their marine environment. The correct choice should reflect how these structures contribute to the ecological balance or survival strategies.

Key Concept: Definition Recall

b) Division of an organism into parts that regenerate into new individuals

[Solution Description] In asexual reproduction by fragmentation, an organism divides into parts that regenerate into new individuals. This process does not involve the fusion of gametes, resulting in offspring genetically identical to the parent.

Key Concept: Basic Definition

a) A type of symmetry where an organism can be divided into similar halves by multiple planes passing through one main central axis.

[Solution Description] Radial symmetry is a body plan where any plane passing through the central axis divides the organism into two identical halves.

Key Concept: Evolutionary Adaptation, Thermoregulation

c) Producing metabolic heat internally

[Solution Description] Mammals are homoiothermous, meaning they can regulate their body temperature independently of the environment through metabolic heat production. This is crucial for survival in extreme climates such as polar regions.

Key Concept: Water System

d) It expels water from the sponge

[Solution Description] In the water transport or canal system of sponges, the osculum is responsible for expelling water out of the body after it has passed through the spongocoel.

Key Concept: Basic Definition

a) Heart

[Solution Description] In a closed circulatory system, the heart is crucial as it pumps blood through vessels, ensuring circulation throughout the body.

Key Concept: Excretion Mechanism

b) Flame cells

[Solution Description] Flatworms possess a simple excretory system that includes specialized cells known as flame cells. These flame cells operate similar to a primitive kidney, aiding in both osmoregulation and waste removal from the body by filtering fluids.

Key Concept: Heart Structure

c) Four

[Solution Description] Crocodiles are an exception among reptiles as they possess a four-chambered heart, unlike most reptiles which have a three-chambered heart.