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

Population, Population You must be familiar with the term 'population'. I...

Population You must be familiar with the term 'population'. It is one of the most talked about issues of this century. It is feared that the rapid growth of the world population

Quick transient responses - behaviour of plants, Quick transient responses ...

Quick transient responses - Behaviour of Plants Such responses are stimulated by factors showing significant variations over relatively small time period e.g., those showing w

Key skills for healthy coping, Key skills for healthy coping are: - Pr...

Key skills for healthy coping are: - Problem-solving and goal setting skills: Finding a problem and challenges, thinking of alternatives for dealing with them, testing those

What are the diagnostic models, Diagnostic Models Study models made fro...

Diagnostic Models Study models made from impressions of the arches are invaluable for diagnosis and treatment planning. The model must be mounted on an adjustable or semi adjus

Criteria for identifying biodiversity hot spots, A simple method used to id...

A simple method used to identify areas of high conservation priority is the selection of countries according to highest species richness. Among the top 12 countries identified this

Cutin, CUTIN It is a lipid formed by polymerization and cross-esterific...

CUTIN It is a lipid formed by polymerization and cross-esterification of hydroxy fatty acids. Cutin occurs inside outer epidermal walls of plant surfaces as bringing agent t

Why overwatering a potted tomato plant will kill it, Consistently overwater...

Consistently overwatering a potted tomato pla nt will eventually kill it. Using the map, suggest why waterlogged soil results in plant death. O2 cannot reach respiring root cells.

Visualize patient ductus arteriosus, Q. Visualize Patient Ductus Arteriosus...

Q. Visualize Patient Ductus Arteriosus? Best view to visualize a patient ductus arteriosus is high parasternal or ductal view. A patient ductus arteriosus in this view is see

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