Migration is the cyclic movement of all or large portion of an animal population from own habitat to another place (one or more) for getting favorable environment, feeding, breeding, etc. The word migration is formed from Latin word migratus (past
Arrector pili
Arrector pili (plural: arrectores pilorum) is a small fan-shaped smooth muscle attached to each hair follicle in mammals. The hair stands on end when the muscle contracts. অ্যারেক্টর পিলি: স্তন্যপায়ীদের প্রতিটি লোম একটি লোমকূপের (Hair follicle) মধ্যে অবস্থান
Acoelomate
Acoelomate (plural acoelomates) means an animal that lacks a fluid filled body cavity named coelom. Body cavity (the space between outer side of alimentary canal and inner side of body wall) of acoelomates is filled with mesodermal cell as well
Zygote
Zygote is a diploid cell (fertilized egg) resulting from the fusion of haploid female gamete (Ovum, female reproductive/sex cell) and male gamete (sperm, male reproductive/sex cell). It is also known as Zygocyte. On the other word, zygote is a fertilized
Yolk sac
A sac (bag or pouch) like membranous extension of the gut containing nutritive materials (yolk) found in the larvae of bony fishes and the embryos of reptiles, birds and primitive mammals. It is situated at the ventral side of sac
Xanthophyll
Xanthophyll is a yellow coloured carotenoid pigment (natural colouring matter) found in animal as well as plant cells. The word Xanthophyll is created from ancient Greek word “xanthos” means “yellow” and from “phyllo” or “phyllon” means “leaf”. The chemical structure
Weberian ossicles
Weberian ossicles (Weberian apparatus) is a chain of four small bones that connect the labyrinth of internal ear (auditory system) to the air bladder of fishes belonging to the superorder Ostariophysi (orders Cypriniformes, Gonorynchiformes, and Siluriformes). This chain comprises four
Ventral
Generally ventral means near the lower or under side of an animal. It is an opposite end of dorsal. In fishes, ventral side always stays in the bottom/floor of water-bodies during locomotion. In human, it is on the front side
Unicellular
Unicellular means having of only one cell. An organism consisting of single cell called unicellular organism. Most of all are microscopic but some are visible to the naked eye. All Prokaryotes, most Protists, and some kinds of Fungi are unicellular.
Tooth
Tooth (plural: teeth) is a small, hard and whitish outgrowth on the jaw or skin of mouth as well as pharynx of most vertebrates. It is not made of bone. A typical vertebrate’s tooth consists of pulp, dentine, cementum and
Scale
Scale is a skin derived thin bony or horny small plate that protecting the skin of most fishes and reptiles and usually overlapping one another. In fishes, scales are bony, derived from dermis (inner layer of skin). There are five
Respiration
Respiration is a physiological process by which organisms exchange gases (especially intake of oxygen and release of carbon dioxide), with the environment. This process is also known as external respiration. On the other hand, internal or cellular respiration means the
Quadrate bone
Quadrate bone (in brief, quadrate) is a cartilaginous bone at the posterior-ventral edge of the upper jaw (skull) in most vertebrates. Quadrate forms an articulation with the lower jaw in bony fishes, amphibians, reptiles and birds. It is very much