Samacheer Class 9 Science - Animal Kingdom

• (a) Mollusca
• (b) Coelenterata
• (c) Echinodermata
• (d) Porifera

Answer:
(c) Echinodermata

• (a) Porifera
• (b) Coelenterata
• (c) Annelida
• (d) Arthropoda

Answer:
(b) Coelenterata

• (a) Fishes and Amphibians
• (b) Amphibians and Aves
• (c) Aves and Mammals
• (d) Reptiles and Mammals

Answer:
(c) Aves and Mammals

Birds and mammals are warm-blooded (homeothermic).

• (a) Lizard
• (b) Snake
• (c) Crocodile
• (d) Calotes

Answer:
(c) Crocodile

• (a) Acrania
• (b) Acephalia
• (c) Apteria
• (d) Acoelomate

Answer:
(a) Acrania

• (a) Hydra, Tapeworm, Earthworm, Amphioxus
• (b) Hydra, Tapeworm, Earthworm, Ascidian
• (c) Hydra, Tapeworm, Earthworm, Balanoglossus
• (d) Hydra, Ascaris, Earthworm

Answer:
(b) Hydra, Tapeworm, Earthworm, Ascidian

• (a) Fish, Frog, Lizard, Man
• (b) Fish, Frog, Lizard, Crow
• (c) Fish, Frog, Lizard, Snake
• (d) Fish, Frog, Lizard, Crow

Answer:
(c) Fish, Frog, Lizard, Snake

• (a) Fish
• (b) Frog
• (c) Bird
• (d) Bat

Answer:
(c) Bird

• (a) flame cells
• (b) nephridia
• (c) body surface
• (d) solenocytes

Answer:
(a) Flame cells

The statement that canal system is seen in coelenterates is False. The correct statement is that the canal system is seen in Porifera, which are sponges. Porifera have a system of canals and chambers that allow water to flow through their bodies, enabling them to filter feed and obtain oxygen. Coelenterates, also known as Cnidarians, have a different body structure with a gastrovascular cavity but do not possess a canal system like that found in sponges.

The statement that hermaphrodites possess both male and female reproductive organs is True. Hermaphrodites are organisms that have both male and female reproductive organs in the same individual. This allows them to produce both sperm and eggs, giving them the ability to reproduce either through self-fertilization or through cross-fertilization with another individual of the same species.

Answer: False. Correct Statement: Trachea is the respiratory organ of arthropods, not annelids. Arthropods such as insects, spiders, and centipedes possess a system of branching tubes called tracheae that deliver oxygen directly to their body tissues. Annelids, on the other hand, respire through their moist skin (cutaneous respiration) or through specialized respiratory structures like gills in aquatic forms. This is an important distinction when classifying the respiratory adaptations of different invertebrate groups.

Answer: False. Correct Statement: Bipinnaria is the larval form of starfish, which belongs to the phylum Echinodermata, not Mollusca. The bipinnaria larva is a free-swimming, planktonic stage characterized by a ciliated body with two prominent ciliated bands that resemble feathered structures. This larva eventually develops into a more advanced larval stage called the brachiolaria before metamorphosing into the adult starfish. Mollusca have different larval forms such as the trochophore or veliger larvae, depending on the specific molluscan class.

Answer: True. Balanoglossus is indeed a ciliary feeder. This hemichordate organism uses cilia present on its proboscis and collar regions to create water currents that draw in small food particles, organic debris, and plankton from the surrounding water. The cilia trap these particles and direct them toward the mouth, where they are ingested. This ciliary feeding mechanism is an important adaptation that allows Balanoglossus to obtain nutrition from its marine environment efficiently.

Answer: True. Fishes possess a two-chambered heart consisting of one atrium and one ventricle. In this simple circulatory system, deoxygenated blood from the body returns to the atrium, then flows into the ventricle, which pumps it to the gills for oxygenation. After the blood is oxygenated in the gills, it travels directly to the body tissues. This two-chambered heart is characteristic of all fish species and represents a basic vertebrate circulatory design that is less complex than the three or four-chambered hearts found in amphibians, reptiles, and mammals.

Answer: False. Correct Statement: The skin of amphibians is smooth and moist, not reptiles. Amphibians such as frogs, toads, and salamanders have smooth, permeable skin that must remain moist to facilitate cutaneous respiration and prevent desiccation. In contrast, reptiles have dry, scaly skin covered with keratin that provides protection against water loss and is adapted for life primarily on land. This fundamental difference in skin structure reflects the different habitats and physiological requirements of these two vertebrate classes.

Answer: True. The wings of birds are indeed modified forelimbs. During the course of evolution, the forelimbs of birds have undergone significant structural modifications to form wings capable of flight. The bones of the bird wing correspond to the bones found in the forelimbs of other vertebrates, including the humerus, radius, and ulna, along with modified carpal and metacarpal bones. These wings are covered with feathers that provide the surface area and aerodynamic properties necessary for flight. This evolutionary adaptation represents one of the most significant modifications of the vertebrate limb structure.

Answer: True. Female mammals possess mammary glands, which are specialized glands that produce milk to nourish their offspring. These glands are a defining characteristic of the class Mammalia and represent a unique adaptation for parental care. The mammary glands develop during pregnancy and begin lactation after birth, allowing female mammals to provide complete nutrition to their young during the early stages of life. This feature distinguishes mammals from all other vertebrate classes and is one of the key characteristics used to define the class.

Answer: Taxonomy is the branch of biology that deals with the identification, naming, and classification of organisms. It involves the systematic arrangement of living organisms into hierarchical categories based on their structural, functional, and evolutionary characteristics. Taxonomists use various methods including morphological analysis, genetic studies, and evolutionary relationships to organize organisms into groups such as kingdom, phylum, class, order, family, genus, and species. The primary goal of taxonomy is to create a comprehensive and organized system that reflects the diversity of life and the evolutionary relationships among different organisms.

Answer: A nematocyst is a specialized stinging capsule present within cnidocytes, which are specialized cells found in coelenterates such as hydra, jellyfish, and sea anemones. Each nematocyst contains a coiled, hollow thread that can be rapidly discharged when triggered by contact with prey or threats. The nematocyst serves two primary functions: it helps in the defense of the organism against predators and parasites, and it aids in the capture and immobilization of prey organisms. When discharged, the nematocyst injects toxins that can paralyze or kill small organisms, making it an effective hunting and defensive tool for these aquatic animals.

Answer:

Their body wall consists of two germ layers:

• Ectoderm
• Endoderm

These are separated by mesoglea.

Hence they are called diploblastic animals.

Answer: Amphibians exhibit different respiratory mechanisms depending on their life stage. Larval amphibians such as tadpoles respire through gills, which extract dissolved oxygen from water. Adult amphibians, however, undergo metamorphosis and develop lungs as their primary respiratory organ. In addition to lungs, adult amphibians also respire through their moist skin, a process called cutaneous respiration, and through the mucous membrane lining the buccopharyngeal cavity. This combination of respiratory organs allows adult amphibians to survive both in aquatic and terrestrial environments, making them truly adapted to their dual lifestyle.

Answer: Locomotion in starfish occurs through the coordinated action of tube feet, which are small, sucker-like structures distributed across the arms and body surface. These tube feet are part of the water vascular system, a unique hydraulic system found only in echinoderms. The water vascular system contains fluid-filled canals that connect to each tube foot, allowing them to extend and contract. When the tube feet extend and attach to the substrate using their suckers, they pull the starfish forward in a slow, gliding motion. This mechanism enables starfish to move across the ocean floor and climb vertical surfaces with remarkable efficiency.

Answer:

No.

• Jellyfish belongs to Coelenterata.
• Starfish belongs to Echinodermata.

Both are invertebrates.

True fishes are vertebrates.

Correction made:
Jellyfish body is not made of calcium carbonate.

Answer: Frogs are called amphibians because they live both in water and on land during different stages of their life cycle. The term amphibian literally means living a double life. Frogs begin their life cycle as aquatic tadpoles that breathe through gills and live entirely in water. As they undergo metamorphosis, they develop lungs and limbs, transforming into terrestrial or semi-aquatic adults that can breathe air and move on land. This ability to thrive in both aquatic and terrestrial environments, combined with their dependence on water for reproduction, makes frogs characteristic representatives of the class Amphibia.

Answer:

Features:

• Bilaterally symmetrical
• Triploblastic
• True coelomates
• Body divided into segments
• Covered by moist cuticle
• Setae/parapodia used for locomotion
• Sexes may be separate or united

Examples:

• Earthworm
• Leech
• Nereis

# Chordata

(i) Protochordata

• Urochordata
• Cephalochordata

(ii) Vertebrata

• Pisces
• Amphibia
• Reptilia
• Aves
• Mammalia

Answer:

• Aquatic vertebrates
• Cold-blooded
• Body streamlined
• Respiration by gills
• Locomotion by fins
• Heart is two-chambered

Types of Fishes

Cartilaginous fishes

Example:

• Shark
• Skate

Bony fishes

Example:

• Carp
• Mullet