7 Most SAQ’s of Animal Diversity – II Chapter in Inter 1st Year Zoology (TS/AP)

4 Marks

SAQ-1 : Name the four ‘hallmarks’ of chordates and explain the principal function of each of them.

Introduction

Chordates, a diverse group of animals, are characterized by four distinctive ‘hallmarks’ that are crucial in defining their biology and evolutionary relationships. These features are present at some stage of their development and serve specific principal functions.

Four Hallmarks of Chordates

1. Notochord: The notochord is a flexible, rod-shaped structure that runs along the back of the animal. Its primary function is to provide support and structural rigidity to the body. In most vertebrates, it is replaced by the vertebral column during development.
2. Dorsal Hollow Nerve Cord: Unlike the solid nerve cords found in other animal groups, chordates possess a dorsal hollow nerve cord. This structure differentiates into the central nervous system, including the brain and spinal cord, and is crucial for nerve signal transmission and processing.
3. Pharyngeal Slits: Pharyngeal slits are openings in the throat area, or pharynx. In aquatic chordates, they develop into gills for respiration, while in terrestrial vertebrates, they play various roles in ear and neck development and do not always remain as functional structures in the adult form.
4. Post-Anal Tail: The post-anal tail extends beyond the anus and is a key feature in chordates. It provides locomotive benefits, aiding in movement and balance, especially in aquatic environments. In many species, the tail may reduce in size or change its function during the course of development.

Summary

The four hallmarks of chordates – notochord, dorsal hollow nerve cord, pharyngeal slits, and post-anal tail – play critical roles in their structural support, nervous system development, respiration (or developmental roles in the case of pharyngeal slits), and locomotion. These features are fundamental in distinguishing chordates from other animal groups and are key to understanding their evolution and development.

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SAQ-2 : Compare and contrast cartilaginous and bony fishes.

Introduction

Cartilaginous and bony fishes represent two distinct classes of fishes, each exhibiting unique characteristics. This comparison will highlight the similarities and differences between them, focusing on their skeletal structure, buoyancy mechanisms, gill covers, and reproductive strategies.

Comparison of Cartilaginous and Bony Fishes

1. Skeletal Structure:
   • Cartilaginous Fishes: Have skeletons made entirely of cartilage, which is lighter and more flexible than bone. Examples include sharks and rays.
   • Bony Fishes: Possess skeletons primarily composed of bone, making them heavier but more robust. This group includes the majority of fish species.
2. Buoyancy Mechanisms:
   • Cartilaginous Fishes: Rely on their large liver filled with oils, such as squalene, for buoyancy. They lack swim bladders.
   • Bony Fishes: Often use a swim bladder, a gas-filled organ, to control their buoyancy.
3. Gill Covers (Operculum):
   • Cartilaginous Fishes: Do not have an operculum (gill cover). Instead, they have separate gill slits.
   • Bony Fishes: Have a bony operculum that covers and protects the gills.
4. Reproductive Strategies:
   • Cartilaginous Fishes: Many species are ovoviviparous or viviparous, where the young develop inside the mother’s body.
   • Bony Fishes: Typically oviparous, laying eggs which are fertilized and develop outside the mother’s body.

Contrast between Cartilaginous and Bony Fishes

1. Skeletal Composition: Cartilaginous fishes have cartilaginous skeletons, whereas bony fishes have calcified bone skeletons.
2. Buoyancy Control: Cartilaginous fishes use liver oils for buoyancy, unlike the swim bladders in bony fishes.
3. Gill Structure: The absence of an operculum in cartilaginous fishes contrasts with the operculum present in bony fishes.
4. Reproduction: Differences in reproductive strategies, with many cartilaginous fishes having live births compared to the egg-laying nature of most bony fishes.

Summary

Cartilaginous and bony fishes differ significantly in their skeletal structures, buoyancy mechanisms, gill coverings, and reproductive strategies. Cartilaginous fishes have a lighter, more flexible cartilage-based skeleton, use liver oils for buoyancy, lack an operculum, and often give live birth. In contrast, bony fishes have a robust bony skeleton, control buoyancy with a swim bladder, have a protective operculum over their gills, and generally lay eggs. Understanding these differences is crucial in the study of fish biology and ecology.

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SAQ-3 : What are the modifications that are observed in birds that help them in flight?

Introduction

Birds have evolved various anatomical and physiological adaptations that enable them to fly. These modifications are specialized to enhance flight efficiency and maneuverability, distinguishing them from other vertebrates.

Modifications in Birds for Flight

1. Lightweight Skeleton:
   • Hollow Bones: Birds have a lightweight skeleton with hollow, air-filled bones, reducing the overall body weight without compromising structural strength.
2. Powerful Muscles:
   • Pectoral Muscles: The pectoral muscles, particularly the pectoralis major and supracoracoideus, are well-developed and powerful, providing the necessary force for wing flapping.
3. Wings for Flight:
   • Wing Shape and Structure: Bird wings are adapted for flight with a shape that creates lift. The wing bones, such as the humerus, radius, and ulna, are modified for flight.
   • Feathers: Feathers play a crucial role in flight. Flight feathers on the wings and tail are particularly important for air control and lift.
4. Respiratory Efficiency:
   • Air Sacs: Birds possess a unique respiratory system with air sacs that provide continuous oxygen flow during both inhalation and exhalation, ensuring high metabolic demands during flight are met.
5. Streamlined Body:
   • Body Shape: The body of a bird is streamlined, minimizing air resistance during flight. This shape facilitates more efficient and faster movement through the air.
6. Efficient Circulatory System:
   • High Metabolic Rate: Birds have a high metabolic rate and an efficient heart and circulatory system to supply muscles with nutrients and oxygen rapidly.
7. Reduced Weight:
   • Lack of Urinary Bladder: Most birds lack a urinary bladder, reducing weight. They excrete uric acid instead of liquid urine.
   • Single Ovary: Female birds often have only a single ovary, further reducing body weight.
8. Keen Vision:
   • Eyesight: Excellent eyesight is critical for navigation, foraging, and avoiding predators while flying.

Summary

Birds exhibit various modifications that aid in flight, including a lightweight skeleton with hollow bones, powerful pectoral muscles, specialized wings with flight feathers, an efficient respiratory system with air sacs, a streamlined body, an efficient circulatory system, weight-reducing features like the lack of a urinary bladder and a single ovary, and keen vision. These adaptations collectively enable birds to master the skies with remarkable agility and efficiency.

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SAQ-4 : Describe the structure of the heart of frog.

Introduction

The heart of a frog is a crucial organ in its circulatory system, exhibiting a structure that is somewhat different from that of mammals. Understanding the heart’s structure is essential for comprehending how amphibians circulate blood throughout their body.

Structure of the Frog’s Heart

1. Chamber Composition:
   • Three Chambers: The frog’s heart consists of three chambers: two atria (the right and left atrium) and one ventricle.
2. Atria:
   • Right Atrium: Receives deoxygenated blood from the body.
   • Left Atrium: Receives oxygenated blood from the lungs and skin.
   • Separation: Although the atria are separate, they open into a common ventricle.
3. Ventricle:
   • Single Ventricle: The single ventricle pumps both oxygenated and deoxygenated blood. This mix occurs because of the incomplete separation of the ventricle.
4. Conus Arteriosus:
   • Valved Structure: A valved structure, the conus arteriosus, extends from the ventricle and leads to the truncus arteriosus, which then divides into arteries.
   • Function: It helps in preventing the backflow of blood and directs blood flow from the ventricle to the arteries.
5. Blood Flow Regulation:
   • Spiral Valve: The presence of a spiral valve in the conus arteriosus ensures that the mixing of oxygenated and deoxygenated blood is minimized.
   • Pathways: Blood from the ventricle is directed either to the lungs and skin for oxygenation or to the rest of the body.
6. Sinus Venosus:
   • Receiving Chamber: The sinus venosus is a thin-walled sac and acts as a receiving chamber for deoxygenated blood from the body before it enters the right atrium.

Summary

The heart of a frog is a complex organ with a three-chambered structure, including two atria and one ventricle. This configuration results in the mixing of oxygenated and deoxygenated blood to some degree. The heart features a conus arteriosus with a spiral valve that aids in regulating blood flow and minimizing blood mixing. Additionally, the sinus venosus plays a crucial role as a preliminary gathering point for deoxygenated blood. Understanding this structure provides insight into the amphibian circulatory system and how it differs from that of mammals.

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SAQ-5 : List out the extant orders of the class reptilian. Give two examples for each order.

Introduction

The class Reptilia comprises several extant orders, each characterized by unique features and adaptations. This list will provide an overview of these orders along with two examples for each, offering insights into the diversity within the class Reptilia.

Extant Orders of Reptilia and Their Examples

1. Order Squamata:
   • Characteristics: Largest order of reptiles, characterized by their scaled skin and the presence of movable quadrate bones.
   • Examples:
     • Python regius (Ball Python)
     • Varanus komodoensis (Komodo Dragon)
2. Order Testudines (or Chelonia):
   • Characteristics: Known for their bony or cartilaginous shell developed from their ribs.
   • Examples:
     • Chelonia mydas (Green Sea Turtle)
     • Terrapene carolina (Eastern Box Turtle)
3. Order Crocodilia:
   • Characteristics: Includes large, predatory, semi-aquatic reptiles with a long snout and a strong tail.
   • Examples:
     • Crocodylus niloticus (Nile Crocodile)
     • Alligator mississippiensis (American Alligator)
4. Order Rhynchocephalia:
   • Characteristics: Known for their unique beak-like structure and a special type of joint in the skull.
   • Examples:
     • Sphenodon punctatus (Tuatara)
     • There is only one extant genus (Sphenodon) in this order, so the second example is not applicable.

Summary

The class Reptilia is diverse and includes several orders: Squamata (snakes and lizards), Testudines (turtles and tortoises), Crocodilia (crocodiles and alligators), and Rhynchocephalia (tuatara). Each order showcases unique physical characteristics and adaptations that have enabled these reptilian species to thrive in various environments. This diversity highlights the evolutionary success of the class Reptilia.

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SAQ-6 : List out eight characteristics that help distinguish a fish from the other vertebrates.

Introduction

Fish, a diverse group of aquatic organisms, exhibit specific characteristics that set them apart from other vertebrates. Understanding these distinguishing features is crucial for recognizing fish and differentiating them from other vertebrate classes.

Characteristics Distinguishing Fish from Other Vertebrates

1. Aquatic Habitat:
   • Water Dwelling: Fish are primarily aquatic, living in either freshwater or marine environments.
2. Body Shape:
   • Streamlined Body: Most fish have a streamlined body shape, which aids in efficient movement through water.
3. Respiratory System:
   • Gills for Breathing: Fish respire using gills, which extract oxygen from water.
4. Scales:
   • Presence of Scales: Fish are covered in scales, providing protection and aiding in movement.
5. Fins:
   • Fins for Locomotion: They have fins of various shapes and sizes that aid in swimming, balance, and direction.
6. Cold-Blooded (Poikilothermic):
   • Temperature Regulation: Fish are cold-blooded or poikilothermic, meaning their body temperature changes with the environment.
7. Swim Bladder:
   • Buoyancy Control: Many fish possess a swim bladder for buoyancy control, allowing them to maintain their depth in the water without expending energy.
8. Lateral Line System:
   • Sensory System: The lateral line system is a unique sensory organ in fish that detects movements and vibrations in the surrounding water.

Summary

Fish can be distinguished from other vertebrates by their aquatic habitat, streamlined body shape, gills for respiration, presence of scales, various types of fins for locomotion, cold-blooded nature, swim bladder for buoyancy, and lateral line system for sensing their environment. These characteristics are key to the survival and adaptation of fish in aquatic environments.

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SAQ-7 : Write eight salient features of the class amphibian.

Introduction

Amphibians, belonging to the class Amphibia, are intriguing creatures known for their distinct characteristics and adaptations. This diverse group includes frogs, toads, salamanders, and caecilians.

Salient Features of the Class Amphibian

1. Distinct Head and Trunk: Amphibians have a body structure divided into a distinct head and trunk, with some species having a tail.
2. Soft and Moist Skin: A key characteristic is their soft, moist, and glandular skin, lacking scales except in some Apoda members.
3. Limbs: Most amphibians have two pairs of limbs, varying in size. Caecilians, a subgroup, are limbless.
4. Skull and Vertebrae: Amphibians have a dicondylic skull structure. Anurans have procoelous vertebrae, caecilians have amphicoelous vertebrae, and urodeles typically have opisthocoelous vertebrae. The presence of a sternum is noted.
5. Buccal Respiration: Some species utilize buccal respiration, breathing through their mouth lining, especially when submerged.
6. Aquatic Larval Stage: Many undergo a metamorphosis process, starting as aquatic larvae like tadpoles and transforming into adult terrestrial forms.
7. Moist Habitat Dependence: Their soft and permeable skin requires them to live in moist habitats to avoid dehydration.
8. Unique Diversity: Amphibians represent a diverse group with over 7,000 species, showcasing a range of adaptations and behaviors.

Summary

The class Amphibia is marked by distinctive features such as soft and moist skin, presence of limbs (or absence in caecilians), unique skull and vertebrae structures, and the ability for buccal respiration. Their dependence on moist habitats, the process of metamorphosis, and their remarkable diversity are key aspects of their biology. These characteristics set amphibians apart from other vertebrate classes.