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

Describe asd closure and vsd closure in heart dieases, Describe ASD closure...

Describe ASD closure and VSD closure in heart dieases? ASD Closures : Small ASD's can be closed directly. Others will need a pericardial patch. Piimum ASD and Sinus Venosus A

Explain monomeric enzymes, Monomeric enzymes Monomeric enzymes are thos...

Monomeric enzymes Monomeric enzymes are those which consist of only a single polypeptide chain, so they cannot be dissociated into smaller units. Very few monomeric enzymes are

Floating stage - hydrarch, Floating Stage - Hydrarch The pond is now c...

Floating Stage - Hydrarch The pond is now colonised by plant species which are rooted in mud but their leaves reach water surface and float. These are species of Nelumbo, Nymp

Collibacillosis, C o l l i ba c i ll o si s It is commonly s...

C o l l i ba c i ll o si s It is commonly seen in newly born farm animals and occurs in septicaemic and enteric collibacillosis forms. E tiology: The disea

Define reagents-nelson somogyi method for glucose estimation, Define Reagen...

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

Determine the medical history - assessment, Determine the Medical History -...

Determine the Medical History - Assessment  A child's medical history often contains predictors of neuropsychological functioning. Perhaps the most obvious predictor is the pre

Germ layers - metazoa, Germ Layers - Metazoa The infolding of the blas...

Germ Layers - Metazoa The infolding of the blastoderm of the blastula forms a gastrula with two or more layers. The outer layer is the ectoderm' and the endoderm lines the inn

Define some food related problems in parkinson''s disease, Define Some Food...

Define Some Food Related Problems in parkinson's disease? As the disease progresses some food related difficulties appear. These are: 1. Difficulty in food preparation

Structures in a vertebrate with a four-chambered heart, Which of the follow...

Which of the following structures in a vertebrate with a four-chambered heart would have blood with the highest oxygen concentration? And why?

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