Secondary egg envelopes, Biology

Assignment Help:

Secondary Egg Envelopes

These are secreted by oviducts and other accessory parts of genital organs while the egg is passing through them from ovary to the exterior.

a) In ovoviviparous sharks the egg is surrounded by a hard shell secreted by shell glands of the oviduct. The shell is drawn out as twisted horns which serve to entangle the egg among sea weeds.

b) In amphibians, the eggs are surrounded by a layer of jelly which protects the egg from adverse effects of sun rays, abrasion as well as from predators (because of its bad taste). The jelly absorbs water and swells.

 c) In birds, reptiles and monotremes, the secondary envelopes include the white of egg surrounding the yolky ovum, followed by inner and outer shell membranes (which are in close contact with one another) and the outermost calcareous shell which is 'porous. The shell is elastic and compressible when the egg is laid but it hardens on exposure to atmosphere.


Related Discussions:- Secondary egg envelopes

What is cuticle, What is Cuticle? The nonliving, and noncellular outer ...

What is Cuticle? The nonliving, and noncellular outer layer of an organism secreted by underlying epidermis. Cuticles are common in a range of animals including nematodes, anne

Phases of ovarian cycle, Phases of Ovarian Cycle In non-mammalian vert...

Phases of Ovarian Cycle In non-mammalian vertebrates the ovarian cycle consists of the following phase; Pre breeding phase Breeding phase and Post breedin

Tracheae - respiratory organs, Tracheae - Respiratory Organs Tracheal ...

Tracheae - Respiratory Organs Tracheal respiration is characteristic of insects. Onychophorans, diplopods, arachnids, and chilopods as well use tracheal system for respiration

Evolution of dental implants, The first evidence of implants dates back to ...

The first evidence of implants dates back to 600 A.D. in the Mayan population. There are reports that the ancient Egyptians attempted intra-osseous implantation of animal teeth or

Biosynthesis of cholesterol, Animals are able to synthesize cholesterol de ...

Animals are able to synthesize cholesterol de novo by an elegant series of reactions in that all 27 carbon atoms of cholesterol are derived from acetyl CoA. The  acetate  units  ar

Determinants of vascular tone, The vascular tone increases as the arterial ...

The vascular tone increases as the arterial size decreases. The tone at any time reflects the effects of excitory and inhibitory pathways. Neurotransmitters, physical forces like s

Show common contraindications of the contraceptive pills, Q. What are the c...

Q. What are the common contraindications of the contraceptive pills? There are medical reports associating the use of contraceptive pills with vomiting, headaches, vertigo, nau

Aschelminthes, in what part of the human body aschelminthes found?

in what part of the human body aschelminthes found?

Explain inhibition of cancer cell proliferation and growth, Explain Inhibit...

Explain Inhibition of cancer cell proliferation and growth? Vitamin D diminishes proliferation of abnormal intestinal, lymphatic, mammary and skeletal cells and provides a pote

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