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

Define measuring direct aerobic fitness, Define Measuring Direct Aerobic Fi...

Define Measuring Direct Aerobic Fitness (VO 2 max) For direct measurement of VO, max, the subject is asked to perform exercise for 12 to 15 minutes. A stationary bicycle or a

Digestive System, When a piece of thread is tied tightly around an animal p...

When a piece of thread is tied tightly around an animal pancreatic duct the animal experiences difficult in digestion but does not suffer from diabetes mellitus.Explain why?

Moss stage - xerarch, Moss Stage - Xerarch The accumulation of soil, p...

Moss Stage - Xerarch The accumulation of soil, particularly in the crevices and depressions of rock favours the growth of certain xerophytic mosses, e.g., species of Polytrich

Conduction in myelinated axons, Conduction in Myelinated Axons The mye...

Conduction in Myelinated Axons The myelin sheath provides insulation for the axon preventing movements of Na + and K + through the membrane. Therefore, if this myelin sheath

Define regulation of water balance, Define Regulation of Water Balance? ...

Define Regulation of Water Balance? The input of water, as well as, its loss can be highly variable due to individual habits and environmental factors; in spite of this, the to

Telophase of karyokinesis, - The chromosomes at each pole uncoil and elonga...

- The chromosomes at each pole uncoil and elongate to form the chromatin. - A nucleolus reappears at each pole. - Spindle fibers and asters disappear and centrioles split. - A nu

Introduction to transgenic animals, Transgenic Animal Over the centurie...

Transgenic Animal Over the centuries, animals with new combinations of genes have been produced using conventional breeding methods by means of careful selection of particular

What main idea, What key idea, contained in Malthus's essay on populations,...

What key idea, contained in Malthus's essay on populations, helped Darwin formulates his theory of natural selection?

How the allele frequencies in a population, A dominant allele will always i...

A dominant allele will always increase in frequency over time. Yes No Q44. When a gene has two alleles, the allele frequencies in a population automatically move toward an equilibr

What is osteogenesis, Osteogenesis The term osteogenesis describes esse...

Osteogenesis The term osteogenesis describes essentially two distinctly different phenomena by which bone can become juxtaposed to an implant surface.

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