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

What is meant by the arch reflex, What is meant by the arch reflex? In ...

What is meant by the arch reflex? In some situations the movement of the skeletal striated muscles does not depend upon commands of the superior motor neurons, i.e., it is not

Describe phosphorylated for atp formation, Q. What is compound that is phos...

Q. What is compound that is phosphorylated for ATP formation? What is resulting compound when ATP liberates energy? adenosine triphosphate or ATP is formed after the binding of

Special situations of pulmonary embolism, Q. Special situations of Pulmonar...

Q. Special situations of Pulmonary Embolism? The CXR is often abnormal in pulmonary embolism. Atelectasis and other focal pulmonary parenchymal abnormalities are the most commo

What is the gel electrophoresis, Which of the following is a false stateme...

Which of the following is a false statement regarding gel electrophoresis? A. An electric current is used in order move DNA fragments by a semi-porous gel. B. Fragments of n

What are the main characteristics of the bryophytes, What are the main char...

What are the main characteristics of the bryophytes? Bryophytes are nonvascular plants, i.e., they do not have conductive tissues and they perform transport of water and nutrie

Dietary fibre requirement during diabetes, Q. Dietary Fibre requirement dur...

Q. Dietary Fibre requirement during diabetes? Dietary fibre is that part of food which is not digested by the intestines. High fibre meals have shown to give the best glycemic

Explain requirements and recommended dietary intake, Explain Requirements a...

Explain Requirements and Recommended Dietary Intake? A very small daily intake of vitamin C (10-15 mg/day for an adult) is required to avoid deficiency and stave off scurvy. Ho

Explain chemically defined or synthetic media-culture media, Explain Chemic...

Explain Chemically Defined or Synthetic Media - Culture Media? Synthetic media are those media where detailed composition of the medium is known in terms of the chemical nature

Explain the sporangiophores features of rhizopus, Explain the Sporangiophor...

Explain the Sporangiophores features of Rhizopus? 1. Sporangiophores swell at the tip into a spherical knob like structure called sporangium. It has two zones. - Central dom

Human evolution, In the last unit we traced the human evolutionary history ...

In the last unit we traced the human evolutionary history mostly from a palaeontological viewpoint. Although still fragmentary, the available fossil evidence makes it possible to c

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