Anas Zoology

  (Image Source:  https://scopeblog.stanford.edu/2013/08/04/image-of-the-week-botryllus-organism/ ) The Urochordata also known as Tunicata is a part of Phylum Chordata. General Characteristics of Urochordates: They are marine and sedentary. Their body is enclosed in a test/tunica. Notochord is present in the tail region in larvae (hence urochordate) and disappears in adults. Alimentary canal is complete and are ciliary feeders. Respiration is through numerous gill slits (Stigmata) which opens into the ectoderm lined cavity, the atrium. They show open circulation. They have special corpuscles, vanadocytes (except in Herdmania ) to extract vanadium from sea water and store it in blood vessels. Dorsal tubular nerve chord appears only in larval stage, which in adults is replaced by a single dorsal ganglia. Sense organs are in the form of receptors. Excretion is by nephrocytes, pyloric gland or neural gland. Asexual reproduction is by budding. Mostly hermaphrodite. Their developmen...

INTEGUMENT: Vertebrate body is covered by a tough, three layered body wall consisting of outer integument, middle muscular layer, and inner coelomic epithelium. It displays important morphological and physiological variations between different vertebrate groups depending on their adaptations for various habitats and mode of life. However, being a protective covering the integument is basically similar in structure in all vertebrates. Histologically skin is made up of two distinct layers. Epidermis: Ectodermal, stratified squamous epithelium, made up of few to several layers of cells. These layers include: Stratum germinativum/stratum malpighi/ stratum cyclindricum: It is the the innermost layer, firmly attached with the dermis and is settled on the basement membrane . It is continuously growing layer which push the new cell layers towards surface. It gets nourishment from dermis. Stratum corneum: It is the outermost partially cornified layer consisting of dead cells. It is made up of p...

  Amoeba Amoeba always reproduce asexually. There are different ways of asexual reproduction in Amoeba and they are as follows: 1) Binary Fission: Parent Amoeba divides into two daughter amoebae in favorable conditions. This is known as binary fission. Different phases of mitosis are accompanied with changes in the shape of body. In prophase, body becomes spherical with numerous pseudopodia and nucleus show intranuclear spindle. Chromatids appear as duplicated chromosomes in the nucleus. In metaphase chromosome arrange at the equator. In anaphase daughter chromosomes move towards opposite poles. In telophase. pseudopodia assume normal shape, constriction appear in the middle. One of the daughter retain contractile vacuole and the other acquires new vacuole. Now the parent after binary fission starts living as two individuals which later on grow in size.  Binary Fission in Amoeba 2) Sporulation: Some species of Amoeba reproduce by sporulation. Sporulation begins with breakdown ...