bzyct-133-solved-assignment-2024-ss-10cd7422-4b11-4531-9171-a6445826d855
BZYCT-133 Solved Assignment 2024
- a) Write two important differences between scales of reptiles and fishes.
Answer:
Scales in reptiles and fishes serve as protective coverings, but they differ significantly in their structure and composition. Here are two important differences:
-
Material and Structure:
- Reptile Scales: Reptile scales are made of keratin, the same protein that forms human hair and nails. They are part of the epidermis (outer skin layer) and do not overlap each other significantly.
- Fish Scales: Fish scales are usually made of bone-like material and are a part of the dermis (inner skin layer). They overlap like shingles on a roof, providing a flexible armor.
-
Growth Pattern:
- Reptile Scales: As reptiles grow, their scales do not increase in size; instead, reptiles shed their skin periodically to accommodate body growth.
- Fish Scales: Fish scales grow with the fish, enlarging as the fish grows. They do not shed their scales in the same way reptiles shed their skin.
These differences reflect the adaptation of each group to their respective environments and lifestyles. Reptile scales are adapted for life on land, providing protection against abrasion and dehydration, while fish scales are designed for an aquatic environment, offering streamlined protection and flexibility.
b) Explain keratinization in terrestrial vertebrates.
Answer:
Keratinization is a vital process in terrestrial vertebrates that helps them adapt to life on land. It involves the production of keratin, a tough, fibrous protein, which forms part of the skin and its appendages (like hair, nails, feathers, and scales). Here’s an explanation of how keratinization works and its significance:
Process of Keratinization
- Cellular Production: Keratinization begins in the basal layer of the epidermis, where new skin cells (keratinocytes) are produced.
- Keratin Synthesis: As these cells mature and move towards the skin’s surface, they start producing and filling up with keratin.
- Cell Transformation: Gradually, the cells become flatter, their nuclei and organelles disintegrate, and they transform into tough, non-living keratin-filled structures.
- Formation of Protective Layer: These keratin-rich cells form the outermost layer of the skin, creating a barrier that is resistant to mechanical damage, water loss, and pathogen entry.
- Shedding: Eventually, these cells are shed from the surface of the skin as part of the natural renewal process.
Significance in Terrestrial Vertebrates
- Protection Against Dehydration: Keratinization is crucial for preventing water loss, a significant challenge for terrestrial life. The keratinized skin acts as a barrier to water, reducing evaporation.
- Physical Barrier: The tough nature of keratin provides a physical shield against abrasion, injury, and environmental factors like UV radiation.
- Adaptation to Diverse Environments: Different types of keratinization allow terrestrial vertebrates to adapt to a wide range of habitats, from deserts to forests.
- Formation of Appendages: Keratin is also essential in forming various appendages like hair in mammals, feathers in birds, and scales in reptiles, each serving specific functions like insulation, flight, and protection.
In summary, keratinization is a key evolutionary adaptation that has enabled terrestrial vertebrates to survive and thrive in diverse and often challenging terrestrial environments. It provides both a physical and physiological defense mechanism, contributing significantly to the