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

Water to flow within the xylem from the roots to the leaves, What are the f...

What are the forces that facilitate to make water to flow within the xylem from the roots to the leaves? Water enters the roots because of the root pressure and a water column

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

Biochemical, Explain the salient features biochemical origin of life.

Explain the salient features biochemical origin of life.

Distribution of Nitrate Reductase and Nitrite Reductase, Distribution of Ni...

Distribution of Nitrate Reductase and Nitrite Reductase Let us see whether nitrate assimilation depends upon the reductants produced in photosynthesis or in oxidative metaboli

Double fertilization, Double fertilization  It carries two sperm cells to t...

Double fertilization  It carries two sperm cells to the female. A characteristic of angiosperms in which the pollen tube gametophyte in the ovule. The one sperm cell fuses with the

Population dispersal, Population Dispersal Population dispersal i...

Population Dispersal Population dispersal is the movement of individuals into or out of the population or the population area. It occurs in three following ways in a popu

Pennetula, identifying characters of pennetula

identifying characters of pennetula

Importance of counselling for diabetic patient, Q. Importance of counsellin...

Q. Importance of counselling for diabetic patient? Diabetes is a life-long illness. Life style modification and precautions taken by the patient can prevent complications and i

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