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

Nutrition intervention, Nutrition intervention Nutrition intervention, ...

Nutrition intervention Nutrition intervention, the third step of  the nutrition care process, is a specific set of activities and associated materials used  to address the prob

Explain founder effect, Founder effect The difference in gene pools amongs...

Founder effect The difference in gene pools amongs an original population and a new population founded by one or a few individuals randomly separated from the original population,

Prevent vitamin a deficiency, Vitamin a deficiency leads to a variety of di...

Vitamin a deficiency leads to a variety of disorders of the eyes and this effects the vision. Some of the disorders due to vitamin A deficiency are given below. 1) Night Blindne

Explain about hypothalamus, Explain about Hypothalamus Another importan...

Explain about Hypothalamus Another important part of brain is hypothalamus. It is very small in sie. It controls many important functions which are as follows:  Blood pre

Characteristic features of phylum cnidaria, Characteristic features of Phyl...

Characteristic features of Phylum Cnidaria All are aquatic animals. Radial or biradial symmetry around an oro-aboral axis, but no head. Diploblastic, with an epidermi

Define the factors causing underweight - etiology, Define the Factors Causi...

Define the Factors Causing Underweight - Etiology? There are a number of factors causing underweight. These are: Poor selection of food Physical activity Mothe

What is tuberculosis, What is tuberculosis? How is the disease transmitted?...

What is tuberculosis? How is the disease transmitted? Is there treatment for tuberculosis? Tuberculosis is a disease caused by the Mycobacterium tuberculosis, bacteria which at

What is iris coloboma, What is Iris Coloboma Coloboma is a congenital a...

What is Iris Coloboma Coloboma is a congenital abnormality due to non-fusion of the embryonic choroidal fissure. It can affect any part of the eye and may involve the optic ner

What are the body fat measurements, What are the Body Fat Measurements? ...

What are the Body Fat Measurements? Obesity is best classified in adults based on Body Mass Index (BMI) classification. BMI, you already know, is a measure of body jut based on

What are the two divisions of the angiosperms, What are the two divisions o...

What are the two divisions of the angiosperms? The angiosperms are separated into monocotyledonous and dicotyledonous. (These categories are defined later in this text.) Pla

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