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.
Alfred Sturtevant and Seymour Benzer's studies of recombination in both Drosophila and bacteriophage demonstrated which of the following? A. The gene is an indivisible unit and
Explain Energy requirement during tuberculosis Energy : The criteria to establish the energy intake is the body weight status coupled with the rise in body temperature. Con
P ARTURITIO N - Gestation period is of 280 days (in rabbit 28 days). Parturition is the expelling of fully mature young ones from the mother's uterus. Oxytocin stimulates
If carbon 1 is the carbonyl group of a 6-carbon aldose (aldohexose), which carbon determines if the sugar is a D- or L- stereoisomer? Select one: a. 1 b. 2 c. 3 d. 4
Neural process occurring in the recovery from brain injury The neural process occurring in the recovery from brain injury are thought to be similar to the processes involved in
Chloroplasts Like mitochondria, chloroplasts are also distinctive organelles of eucaryotic cell. But they are found only in plant cells. Chloroplasts contain membranes forming
Many definitions of species have been offered, but none of them proved to be satisfactory. The definitions did not categorically provide the basis to decide whether two similar gro
What is plant cell walls made of? Explain the function of cell walls? Plant cell walls are made of cellulose embedded in carbohydrates and proteins. Cell walls help su
Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4
Menstrual Cycle- Reproduction Menstrual cycles are characteristic of primates and do not occur in other vertebrate groups. The length of the cycle is highly variable, though 2
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