It is considered that the origin of chordates is deeply associated with the deuterostome lineage, where the early ancestors are sharing characters with hemichordates and echinoderms. In this group, the basic features such as a notochord, dorsal hollow nerve cord (DHNC), pharyngeal gill slits, post-anal tail and endostyle are present at some stage of development. … Read more
Domain Eukaryota Kingdom Animalia Phylum Chordata Subphylum Tunicata Class Ascidiacea Order Stolidobranchia Family Pyuridae Genus Herdmania Authority Lahille, 1888 What is Herdmania? Herdmania is a solitary ascidian which is included under the Subphylum Tunicata of the Phylum Chordata. It is a sessile marine animal and the adult remains attached to hard substratum like rocks or … Read more
A fish is an aquatic vertebrate which is mostly characterized by the presence of gills throughout life, a streamlined body, and paired as well as unpaired fins which helps in swimming. It is the group that comprises jawless forms like hagfish and lampreys, cartilaginous fishes like sharks and rays, and the bony fishes which is … Read more
Agnatha is the superclass of vertebrates in which true jaws are absent. It is the group that represent the most primitive and earliest craniates, and in this group the mouth parts are simple without any jaw elements. It is the condition where the animals show a very old vertebrate body plan which is already present … Read more
What Is Induced Breeding (hypophysation)? Induced breeding is the process in which fishes are stimulated to reproduce under controlled conditions when natural spawning does not occur in captivity. It is the technique where hormonal preparations are used to activate the maturation of gonads and to release the gametes. This is referred to as hypophysation because … Read more
What is Biological Clocks? Biological clocks are the internal timing system present in living organisms, and it is the process by which rhythmic changes occur in a regular pattern. It is an endogenous mechanism that runs for about 24 hours, and this rhythmic behaviour is referred to as circadian rhythm. The rhythm continues even in … Read more
What is Sphenodon? Sphenodon is the reptile that is commonly known as the tuatara, and it is the only living representative of the order Rhynchocephalia. It is the reptile that is found naturally in New Zealand, and it is considered a very old lineage that diverged from other reptiles in ancient geological time. The body … Read more
What Is Trochophore Larva? Trochophore larva refers as an early free-swimming stage found by many marine invertebrates like annelids, mollusks, etc. It can define as – a small, spherical or pear-shape larva having a ring of cilia (called prototroch) around its middle part. This larva usually formed after fertilization → from the zygote → and … Read more
What is Biogeny (Formation of Primitive Life)? 1. Formation of nucleic acids and nucleoproteins The formation of nucleic acids and nucleoproteins considered as one of the key transition in Biogeny where information molecules begin to store and transmit life instructions. It started after Chemogeny produced small organic monomers like nucleobases, sugars, phosphates, etc. Prebiotic synthesis … Read more
What is cleavage? Characteristics of cleavage Step by step process of Cleavage Types of cleavages The cleavage pattern in embryos mainly determined by yolk quantity and how that yolk is distributed by the cytoplasm.Also, timing and direction of mitotic spindle (inside egg) play important role. Yolk usually slow / restrict the process of complete division. … Read more
