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

Basic structural pattern of limbs, Basic structural pattern of limbs ...

Basic structural pattern of limbs The common structural pattern of tetrapod limbs is extremely clear expressed in their skeletal components and in the manner they are organiz

How sex occurs in bacteria, Q. How sex occurs in bacteria? Occurrence o...

Q. How sex occurs in bacteria? Occurrence of sex in bacteria was first described by Edward Tatum and Joshua Lederberg in 1946 (Nature, volume 158, page 558) who were studying m

Nervous system - brain, BRAI N (ENCEPHELON) Shape - Oval Positio...

BRAI N (ENCEPHELON) Shape - Oval Positio n - Situated in cranial cavity of skull. Medulla oblongeta comes out of foramen magnum in the form of spinal cord. Colou

Explain the term - neurochemical manipulations, Explain the term - Neuroche...

Explain the term - Neurochemical Manipulations Neurochemical and immunological methods have been used to identify groups of neurons in the central nervous system that use speci

Define equilibrium between two solid phases and a gas phase, Define Equilib...

Define Equilibrium between two solid phases and a gas phase? Consider the following reaction equilibrium: 3 CuO(s) + 2NH 3 (g) ↔ 3 Cu(s) + 3H 2 O (g) + N 2 (g) Accordin

Processed chicken products, P r o c esse d Chicken Products Prepar...

P r o c esse d Chicken Products Preparation of comminuted meat products is the best way to salvage meat from spent hens and broiler parent stock. Incorporation of whole eg

Phylum protozoa, What are some examples of organisms belonging to this phyl...

What are some examples of organisms belonging to this phylum? Please name them.

Asexual reproduction and cloning in plants, before stem cuttings are plante...

before stem cuttings are planted the cut end of the stem is often dipped in a hormone powder .what is the point of this?

Define denaturation, Denaturation: With respect to the nucleic acids, refe...

Denaturation: With respect to the nucleic acids, refers to the conversion from the double-stranded to single-stranded state, many times achieved by heating or alkaline conditions.

When does the greatest buffering capacity of weak acids, The greatest buffe...

The greatest buffering capacity of weak acids is when- Select one: a. They are almost completely dissociated b. They are almost completely undissociated c. They are nea

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