Zoology - Biology Notes Online

Origin of Tetrapods (Amphibia)

By Sourav Pan Published on October 3, 2024 14 min readby Sourav Pan

Tetrapod phylogeny from The Tangled Bank, used with permission of the author, Carl Zimmer, and publisher, Roberts & Company, Greenwood Village, Colorado.

Tetrapoda: Evolution from Fish to Land-Dwelling Vertebrates Tetrapods are a group of vertebrates that includes amphibians, reptiles, birds, and mammals. The first tetrapods evolved during the Devonian period from crossopterygian fishes, which were adapted to shallow, marshy environments. These fishes already possessed some features that made their transition to land possible. The transition from aquatic … Read more

Amphibian – Characteristics, Origin, Morphology, Classification

By Sourav Pan Published on October 3, 2024 25 min readby Sourav Pan

Amphibian - Characteristics, Origin, Morphology, Classification

What is Amphibian? Scientific Classification of Amphibian Category Classification Kingdom Animalia Phylum Chordata Clade Batrachomorpha Class Amphibia Order Anura, Caudata, Gymnophiona Amphibians are believed to have evolved from a population of osteolepid fishes during the later part of the Devonian period. These fishes began spending more time on land, moving from one pool to another. … Read more

Sphenodon – Morphology, Habitat, Affinities

By Sourav Pan Published on October 3, 2024 26 min readby Sourav Pan

Sphenodon - Morphology, Habitat, Affinities

What is Sphenodon? Habits and Habitat of Sphenodon Sphenodon, commonly known as the tuatara, exhibits a range of distinct behaviors and occupies specific habitats that have enabled it to survive as a relic of ancient reptilian lineages. These habits and habitat preferences are vital to understanding the unique biology and conservation needs of this species. … Read more

Protochordata – Characteristics and Classification

By Sourav Pan Published on October 3, 2024 24 min readby Sourav Pan

Protochordata - Characteristics and Classification

What is Protochordata? Characteristics of Protochordata Protochordata, often referred to as primitive chordates, exhibit several defining features that differentiate them from more advanced vertebrates. These organisms are primarily marine and show a blend of both invertebrate and vertebrate characteristics. Below is a detailed overview of the key characteristics of protochordates: Classification of Protochordata Protochordate is … Read more

Phylum Chordata – Characteristics and Classification

By Sourav Pan Published on October 2, 2024 26 min readby Sourav Pan

Phylum Chordata - Characteristics and Classification

What is Chordata? Characteristics of Chordates Below are the main characteristics of chordates: In addition to the primary characteristics listed above, chordates share several other notable features: Anatomy of Chordates The anatomy of chordates encompasses a unique set of features that distinguishes them from other animal phyla. These anatomical characteristics manifest at various life stages … Read more

Phylum Echinodermata – Definition, Classification, Characteristics, Examples

By Sourav Pan Published on October 2, 2024 36 min readby Sourav Pan

Phylum Echinodermata - Definition, Classification, Characteristics, Examples

What is Phylum Echinodermata? Phylum Echinodermata Definition Phylum Echinodermata encompasses marine organisms characterized by a calcareous endoskeleton, pentamerous radial symmetry in adulthood, and a specialized water vascular system, with notable members including starfish, sea urchins, and sea cucumbers. Characteristics of Phylum Echinodermata In essence, Phylum Echinodermata represents a diverse group of marine organisms, distinguished by … Read more

Larval Forms of Echinodermata

By Sourav Pan Published on October 2, 2024 15 min readby Sourav Pan

The development of echinoderms is characterized by a unique and intricate process of metamorphosis, which is unlike any other group of animals. Echinoderms exhibit two primary modes of development: direct and indirect. In direct development, there are no distinct larval stages, and the organism proceeds directly from egg to adult. In contrast, indirect development involves … Read more

Pearl formation in bivalves

By Sourav Pan Published on October 2, 2024 18 min readby Sourav Pan

Pearls are organic gemstones produced by certain bivalve mollusks, such as oysters and mussels. These remarkable structures form in response to irritants that enter the mollusk’s shell. When an irritant, such as a parasite or grain of sand, enters the mollusk, it triggers a defensive mechanism. The mollusk secretes layers of aragonite and conchiolin, substances … Read more

Torsion and Detorsion in Gastropoda

By Sourav Pan Published on October 2, 2024 18 min readby Sourav Pan

What is Torsion? Conditions before Torsion The following points outline the key features and conditions that are present in the veliger larva prior to the onset of torsion: How Torsion Occurs Torsion in gastropods is a complex, stepwise process that leads to the twisting of visceral organs in a counterclockwise direction, resulting in a significant … Read more

Respiration in Mollusca

By Sourav Pan Published on October 2, 2024 20 min readby Sourav Pan

A “generalized mollusk”: An anatomical diagram of a hypothetical ancestral mollusk, showing features common to many mollusk types.

Types of Respiration in Mollusca Mollusca exhibit various types of respiration, depending on their habitat and morphology. Their respiratory systems are adapted to meet the specific demands of their environments. The three primary types of respiration in mollusks are cutaneous, branchial, and pulmonary respiration. Aquatic Respiration in Mollusca Aquatic respiration in mollusks involves the extraction … Read more