Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
Colonial Theory - Metazoa
This is the most popular theory on the origin of Metazoa. The idea was conceived by Haeckel (1874) modified by Metschnikoff (1886) and revived by Hyman (1940). This theory considers the flagellates to be the most probable ancestral group of metazoans. For support of this theory the following evidences are cited:
1) Flagellated spermatazoa occur throughout the metazoan series.
2) Monoflagellated cells (with a single flagellum) are also common in lower metazoans (especially among sponges and coelenterates).
3) True sperms and eggs (feature of metazoans) are present in phytoflagellates.
4) Phytoflagellates also display a type of colonial organization that could have led to a multicellular construction. In fact, differentiation between somatic and reproductive cells has been attained in Volvox. Although Volvox is often used as a model for the flagellated colonial ancestor, it is not the likely ancestor of metazoans. Ultrastructural evidence points to the choanoflagellates (a small group of animal like flagellates) as the probable ancestor. Choanoflagellates have mitochondria and flagellar structures very similar to those in metazoan cells. Also choanocytes i.e. cells with a collar of microvilli are found in a number of groups of metazoans notably the sponges.
SPERM A T OGENESIS The process of maturation of reproductive cells in the testes of male to form spermatozoa (sperm) is known as spermatogenesis. The testes are formed
The gene is a distinct portion of a cell's DNA. Genes are coded instructions for making all the body needs, mainly proteins. Human beings have about 25,000 genes. Researchers have
Solubility You are aware that gases are soluble in liquid. Solubility of a gas in a liquid depends on the partial pressure, temperature and presence of other solutes. Table
Diarrhoeas disease: Diarrhoeas disease rank among th most leading causes of children's death in developing countries. We shall discuss two main problems in this section i.e.
Evolutionary Herbicide tolerant crops (HTC) Increased use of herbicide can result in increase in development of weed resistance to that herbicide either through
Q. Can you explain Likar System with Electrodes? The 12 lead Mason - Likar system with electrodes is used. The plastic adhesive electrodes has self contained electrode jelly in
For an individual having a genotype formed of two different alleles that condition different varieties of the same phenotypical trait, upon what will the phenotypical feature actua
SURGERY FOR CORONARY ARTERY DISEASE : Stenotic coronary artery disease (CAD) is caused by the thickening and narrowing of the coronary arteries (Atherosclerosis). Initially it cau
The PCR (polymerase chain reaction) is an extremely simple as immensely powerful methods. It permits enormous amplification of any particular sequence of DNA
Define Reagents - Nelson Somogyi Method for Glucose Estimation? 1. Alkaline copper reagent Alkaline A- Buy commercial from SDS chemicals etc Alkaline B- Weigh 6.25 g anhy
Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!
whatsapp: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd