Hydra – metazoa, Biology

Assignment Help:

Hydra – Metazoa

The animals of phyla Cnidaria and Ctenophora are made up of only two germ layers: ectoderm which forms the outer covering of the animal and endoderm which is the inner layer and is also known as the gastroderm. However, a non-cellular jelly like substance mesoglea is present between ectoderm and endoderm which acts as a cement to bind the two layers. This layer should not be confused with the third germ layer i.e. mesoderm. Since animals of these two phyla do not have mesoderm, they are said to be diploblastic.

2474_Hydra – Metazoa.png

Figure: L.S. Hydra

If we cut a longitudinal section through 'Hydra we see two distinct layers bound together by a non-cellular mesoglea. The two germ layers give rise to many different cell types - as evident from figure. Rest of the animals (platyhelminths to mammals) are all made up of three germ layers viz. ectoderm, endoderm and mesoderm. These animals are triploblastic. If we cut a section say through a horse (a mammal and triploblastic) can we expect to see three layers like you see two layers in diploblastic Hydra? No we will net, because these three germ layers do not .remain as such, they differentiate and modify to give rise to different structures and organs in the body of the horse. The three layers will be distinct only during early embryology. Hence we call them the embryonic layers or the germ layers.


Related Discussions:- Hydra – metazoa

Best relates the severity and frequency of natural events, In general, whic...

In general, which of the following best relates the severity and frequency of natural events, such as storms or droughts? A) Nothing is known about this relationship. B) The severi

Striped muscles, STRIPED MUSCLES - These muscles are found in the li...

STRIPED MUSCLES - These muscles are found in the limbs, body walls, tongue, pharynx and beginning of oesophagus and are under the control of animal's will. These muscle f

Deficiency diseases-predisposing factors, Predisposing factors The inc...

Predisposing factors The incidence of metabolic diseases in cows and buffaloes increases as the milk production increases and the herd size becomes larger. The highest inciden

What is the essential condition for protein to be identical, What is the es...

What is the essential condition for a protein to be identical to another protein? For a protein to be identical to another protein it is essential for the sequence of amino aci

Explain subphylum vertebrata, Subphylum  Vertebrata : (41,700 species, th...

Subphylum  Vertebrata : (41,700 species, the vertebrates) Vertebral column of bone or cartilage, head is well developed, heart is ventrally situated dorsal aorta, two pairs of

Life cycle of filarial worm, Life cycle of Filarial worm Filariasis : ...

Life cycle of Filarial worm Filariasis : It is popularly known as elephantiasis. It is caused by a nematode parasite, wuchereria bancrofti, and W.Malayi. Parasite : Wucher

Define end and the beginning of the first interphase period, Q. What are th...

Q. What are the events that mark the end and the beginning of the first interphase period? What happens inside the cell in this period? The initial interphase period is the G1.

Cholesterol, CHOLESTEROL Other name is parental steroid. It is ...

CHOLESTEROL Other name is parental steroid. It is present all over the body but absent in cerebrospinal fluid. Cholesterol is found exclusively in animal food. It

What are the bacteriophages, Q What are the bacteriophages? Bacteriopha...

Q What are the bacteriophages? Bacteriophages are viruses specialized in parasitism of bacteria. They are used in genetic engineering as molecular cloning vehicles to include r

Importance of the brain evolved from fishes to reptiles, Q. How has the imp...

Q. How has the importance of the brain evolved from fishes to reptiles? From the least to the most complex brain structure, it is evident that the brain, from fishes to beings

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

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!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd