Detailed Notes :3-Chapter4-Animal Kingdom

4.2.7 Phylum – Arthropod

1. Huge Diversity:

   • Arthropods constitute the largest phylum in the animal kingdom, comprising over two-thirds of all named species on Earth.
   • They exhibit remarkable diversity in terms of morphology, habitat, and behavior.

2. Organ-System Level of Organization:

   • Arthropods have organ-system level of organization, with distinct organ systems performing specific functions.

3. Bilateral Symmetry:

   • They display bilateral symmetry, with a distinct left and right side.

4. Triploblastic and Coelomate:

   • Arthropods are triploblastic organisms, consisting of three embryonic germ layers: ectoderm, mesoderm, and endoderm.
   • They are coelomate animals, possessing a true body cavity (coelom) that is completely lined with mesoderm.

5. Chitinous Exoskeleton:

   • The body of arthropods is covered by a tough, chitinous exoskeleton, providing support and protection.
   • This exoskeleton is molted periodically to accommodate growth.

6. Body Segmentation:

   • Arthropods typically have a body divided into distinct regions: head, thorax, and abdomen.

7. Jointed Appendages:

   • Arthropods are characterized by jointed appendages (arthros-jointed, poda-appendages), which are used for locomotion, feeding, and sensory perception.

8. Respiratory Organs:

   • Arthropods may have various respiratory organs, including gills, book gills, book lungs, or a tracheal system, depending on the species.

9. Circulatory System:

   • The circulatory system of arthropods is of the open type, where blood is pumped into the body cavity and bathes the organs directly.

10. Sensory Organs:

    • Arthropods possess sensory organs such as antennae, compound eyes, simple eyes, statocysts (balancing organs), and tactile hairs.

11. Excretory System:

    • Excretion in arthropods occurs through specialized structures called Malpighian tubules.

12. Reproductive System:

    • Arthropods are mostly dioecious (separate sexes), with males and females being distinct individuals.
    • Fertilization is typically internal.
    • They are mostly oviparous (reproducing by laying eggs).

13. Development:

    • Development in arthropods may be direct (young ones resemble the adult) or indirect (involving larval stages).

14. Examples:

    • Examples of economically important insects include Apis (Honey Bee), Bombyx (Silkworm), and Laccifer (Lac Insect).
    • Examples of vectors include Anopheles, Culex, and Aedes (Mosquitoes).
    • Examples of gregarious pests include Locusta (Locust).
    • Limulus (King Crab) is considered a living fossil.

4.2.8 Phylum – Mollusca

1. Huge Diversity:

   • Mollusca is the second largest animal phylum, comprising a wide variety of species found in terrestrial or aquatic (marine or freshwater) habitats.

2. Organ-System Level of Organization:

   • Molluscs have organ-system level of organization, with distinct organ systems performing specific functions.

3. Bilateral Symmetry:

   • They display bilateral symmetry, with a distinct left and right side.

4. Triploblastic and Coelomate:

   • Molluscs are triploblastic organisms, consisting of three embryonic germ layers: ectoderm, mesoderm, and endoderm.
   • They are coelomate animals, possessing a true body cavity (coelom) that is completely lined with mesoderm.

5. Calcareous Shell:

   • The body of molluscs is often covered by a calcareous shell, providing protection and support.
   • However, not all molluscs have shells.

6. Body Structure:

   • The body of molluscs is unsegmented and typically consists of three main parts: a distinct head, a muscular foot for locomotion, and a visceral hump containing internal organs.
   • A soft and spongy layer of skin called the mantle covers the visceral hump.

7. Mantle Cavity and Gills:

   • The space between the visceral hump and the mantle is called the mantle cavity, which contains feather-like gills.
   • The gills serve both respiratory and excretory functions.

8. Sensory Tentacles:

   • Molluscs often have sensory tentacles located on the anterior head region, which aid in detecting food and other environmental stimuli.

9. Radula:

   • The mouth of molluscs contains a file-like rasping organ called the radula, which is used for feeding.
   • The radula is unique to molluscs and is adapted for scraping food particles.

10. Reproductive System:

    • Molluscs are usually dioecious (separate sexes) and oviparous (reproducing by laying eggs).
    • They often exhibit indirect development, involving larval stages before reaching adulthood.

11. Examples:

    • Examples of molluscs include Pila (Apple Snail), Pinctada (Pearl Oyster), Sepia (Cuttlefish), Loligo (Squid), Octopus (Devil Fish), Aplysia (Seahare), Dentalium (Tusk Shell), and Chaetopleura (Chiton).

4.2.9 Phylum – Echinodermata

1. Endoskeleton of Calcareous Ossicles:

   • Echinoderms have an endoskeleton composed of calcareous ossicles, giving them their characteristic spiny appearance.

2. Marine Habitat:

   • All echinoderms are exclusively marine organisms.

3. Organ-System Level of Organization:

   • Echinoderms exhibit organ-system level of organization, with distinct organ systems performing specific functions.

4. Radial Symmetry (Adults) and Bilateral Symmetry (Larvae):

   • Adult echinoderms typically display radial symmetry, with body parts arranged symmetrically around a central axis.
   • However, echinoderm larvae are bilaterally symmetrical.

5. Triploblastic and Coelomate:

   • Echinoderms are triploblastic organisms, consisting of three embryonic germ layers: ectoderm, mesoderm, and endoderm.
   • They are coelomate animals, possessing a true body cavity (coelom) completely lined with mesoderm.

6. Complete Digestive System:

   • The digestive system of echinoderms is complete, with a mouth located on the lower (ventral) side and an anus on the upper (dorsal) side.

7. Water Vascular System:

   • The most distinctive feature of echinoderms is the presence of a water vascular system.
   • This system consists of a network of fluid-filled canals and tube feet, which are used for locomotion, capturing and transporting food, and respiration.

8. Absence of Excretory System:

   • Echinoderms lack a specialized excretory system.

9. Separate Sexes and Sexual Reproduction:

   • Echinoderms have separate sexes (dioecious), with males and females being distinct individuals.
   • Reproduction is typically sexual, with external fertilization.

10. Indirect Development with Free-Swimming Larvae:

    • Development in echinoderms is indirect, involving larval stages before reaching adulthood.
    • These larvae are free-swimming and undergo metamorphosis into the adult form.

11. Examples:

    • Examples of echinoderms include Asterias (Starfish), Echinus (Sea Urchin), Antedon (Sea Lily), Cucumaria (Sea Cucumber), and Ophiura (Brittle Star).

4.2.11 Phylum – Chordata

1. Notochord:

   • Presence of a notochord, a flexible rod-like structure derived from mesoderm, providing skeletal support and acting as a precursor to the vertebral column in vertebrates.
   • In protochordates, such as Urochordata (Tunicates) and Cephalochordata (Lancelets), the notochord persists throughout life or is present only in the larval stage.

2. Dorsal Hollow Nerve Cord:

   • Presence of a dorsal hollow nerve cord, derived from ectoderm, running along the dorsal side of the body.
   • This nerve cord serves as the central nervous system and is a defining feature of chordates.

3. Paired Pharyngeal Gill Slits:

   • Presence of paired pharyngeal gill slits or pouches, which are openings in the pharynx that may function in filter-feeding, respiration, or excretion.

4. Bilateral Symmetry:

   • Chordates exhibit bilateral symmetry, with a distinct left and right side.

5. Triploblastic and Coelomate:

   • Chordates are triploblastic organisms, consisting of three embryonic germ layers: ectoderm, mesoderm, and endoderm.
   • They are coelomate animals, possessing a true body cavity (coelom) completely lined with mesoderm.

6. Post-Anal Tail:

   • Presence of a post-anal tail, an extension of the body past the anus, which may be present during embryonic development or persist into adulthood in some species.

7. Closed Circulatory System:

   • Chordates typically have a closed circulatory system, with blood enclosed within vessels and pumped by a heart.

• Subphylum Urochordata (Tunicates) and Cephalochordata (Lancelets) are often referred to as protochordates and are exclusively marine. They exhibit characteristics typical of chordates, such as a notochord, dorsal hollow nerve cord, and pharyngeal gill slits.

• Subphylum Vertebrata encompasses animals with a vertebral column, replacing the notochord during embryonic development. Vertebrates possess additional features such as a ventral muscular heart with chambers, kidneys for excretion and osmoregulation, and paired appendages, which may be fins or limbs.

Examples of chordates include:

• Urochordata: Ascidia, Salpa, Doliolum
• Cephalochordata: Branchiostoma (Amphioxus or Lancelet).

The subphylum Vertebrata is further divided as follows:

1.

Class Agnatha (Jawless Fishes):

1. • Agnathans are characterized by the absence of jaws.
   • They possess a cartilaginous skeleton and typically have a round, eel-like body shape.
   • Examples include lampreys and hagfishes.

2. Class Chondrichthyes (Cartilaginous Fishes):

   • Chondrichthyans are characterized by a skeleton made of cartilage instead of bone.
   • They typically have paired fins, a streamlined body, and placoid scales.
   • Examples include sharks, rays, and skates.

3. Class Osteichthyes (Bony Fishes):

   • Osteichthyans are characterized by a skeleton made of bone.
   • They have gills covered by a bony operculum and typically possess swim bladders for buoyancy control.
   • Examples include ray-finned fishes (Actinopterygii) and lobe-finned fishes (Sarcopterygii).

4. Class Amphibia (Amphibians):

   • Amphibians are tetrapod vertebrates that typically undergo metamorphosis from an aquatic larval stage to a terrestrial adult stage.
   • They have moist skin, lay eggs in water or damp environments, and often have a biphasic life cycle.
   • Examples include frogs, toads, salamanders, and caecilians.

5. Class Reptilia (Reptiles):

   • Reptiles are tetrapod vertebrates that are characterized by scales or scutes covering their body.
   • They are ectothermic (cold-blooded) and lay shelled eggs on land.
   • Examples include snakes, lizards, turtles, crocodilians, and tuatara.

6. Class Aves (Birds):

   • Birds are characterized by feathers, a beak without teeth, and a lightweight skeleton with pneumatic bones.
   • They are endothermic (warm-blooded) and possess adaptations for flight.
   • Examples include eagles, sparrows, penguins, and ostriches.

7. Class Mammalia (Mammals):

   • Mammals are characterized by mammary glands, hair or fur, and a neocortex region in the brain.
   • They are endothermic (warm-blooded) and typically give birth to live young.
   • Examples include humans, dogs, cats, whales, and elephant.