Animal Kingdom

Without taking common fundamental features into account, classification becomes extremely difficult because:

• Confusion: Every organism would be treated as distinct, making it impossible to study their relationships.
• No Grouping: We cannot group animals based on similarities (like cell arrangement, symmetry, or coelom), leading to a chaotic list of millions of species.
• Evolutionary Link: It becomes impossible to trace the evolutionary history or phylogeny of animals.
• Comparison: Comparing different organisms to find similarities and dissimilarities would be unscientific and arbitrary.

To classify a specimen, I would examine features in the following hierarchical order:

1. Level of Organization: Cellular, Tissue, Organ, or Organ-system level.
2. Symmetry: Asymmetrical, Radial, or Bilateral.
3. Germ Layers: Diploblastic (two layers) or Triploblastic (three layers).
4. Coelom (Body Cavity): Acoelomate, Pseudocoelomate, or Coelomate.
5. Segmentation: Presence or absence of true segmentation (metamerism).
6. Notochord: Presence (Chordate) or absence (Non-chordate).

The nature of the body cavity is a primary criterion for classification, dividing animals into three major groups:

• Acoelomates: No body cavity (e.g., Platyhelminthes). The space is filled with parenchyma.
• Pseudocoelomates: Body cavity is not lined by mesoderm; mesoderm is present as scattered pouches (e.g., Aschelminthes).
• Coelomates: True body cavity lined by mesoderm (e.g., Annelida to Chordata). This allows for complex organ systems and greater body flexibility.

Parasitic flatworms (e.g., Tapeworms, Liver flukes) exhibit specific adaptations:

• Hooks and Suckers: Present for firm attachment to the host’s internal organs.
• Direct Absorption: Some absorb nutrients directly from the host through their body surface.
• Thick Tegument: A protective covering to resist the host’s digestive enzymes.
• High Reproductive Capacity: They produce enormous numbers of eggs to ensure species survival.

Arthropoda is the largest phylum due to:

• Chitinous Exoskeleton: Provides protection and prevents water loss, allowing survival on land.
• Jointed Appendages: Enable efficient mobility for walking, flying, or swimming.
• Diverse Habitats: They can survive in air, water, and soil.
• Reproductive Strategy: High reproductive rate and short life cycles.
• Sensory Organs: Well-developed antennae, eyes, and statocysts.

(c) Echinodermata

The water vascular system helps in locomotion, capture and transport of food, and respiration.

Justification:

• Chordates are defined by the presence of a Notochord at some stage of life.
• Vertebrates are a sub-phylum of Chordata where the notochord is replaced by a cartilaginous or bony vertebral column in the adult.
• However, other chordates like Protochordates (Urochordata and Cephalochordata) possess a notochord but lack a vertebral column. Thus, they are chordates but not vertebrates.

The air bladder (found in Class Osteichthyes or Bony fishes) regulates buoyancy. It allows the fish to float or stay at a particular depth without constantly swimming, thereby conserving energy.

• Forelimbs modified into wings: Provides surface area for lift.
• Pneumatic Bones: Hollow bones make the skeleton lightweight.
• Streamlined Body: Reduces air resistance.
• Feathers: Provide insulation and flight surface.
• Absence of Urinary Bladder: Reduces body weight.

No, they are generally not equal.

• Oviparous animals: Lay a large number of eggs because the eggs develop outside the body and are exposed to predators and environmental risks. High numbers ensure some survival.
• Viviparous animals: Give birth to fewer young ones because the embryo develops inside the mother’s body, receiving protection and nutrition. Survival chances are much higher, so fewer offspring are needed.

(c) Annelida

Annelids exhibit true metameric segmentation (both external and internal).

• Tapeworm (Taenia solium) – Platyhelminthes
• Liver Fluke (Fasciola) – Platyhelminthes
• Roundworm (Ascaris) – Aschelminthes
• Hookworm (Ancylostoma) – Aschelminthes
• Filarial Worm (Wuchereria) – Aschelminthes
• Head Louse (Pediculus humanus) – Arthropoda (Ectoparasite)