In this article we will discuss about the embryonic development of egg and yolk in insects and birds. Egg: The eggs are generally spherical but eggs of insects are elongated and cylindrical. The eggs of some polychaetes, fishes and birds are oval in shape. The egg cells are covered by plasma membrane which is secreted by egg cytoplasm (ooplasm). The [...]
The following points highlight the six kingdoms of all organisms. The kingdoms are: 1. Monera 2. Protista 3. Fungi 4. Plantae 5. Animalia 6. Chromista. Kingdom # 1. Monera: (i) Most organisms are very simple and prokaryotic (the nucleus is incipient type in which nuclear membrane and nucleolus are absent). (ii) Generally one-celled microscopic organism. (iii) Mostly phototrophs and chemotrophs; [...]
The upcoming discussion will update you about the difference between embryological characteristics of Protostomes and Deuterostomes. Difference # Protostomes: 1. Cleavage of Protostomes are spiral, determinate or mosaic. Bilateral-mosaic cleavage of some protostomes (e.g., nematodes). 2. In Protostomes, the blastopore either becomes the mouth, the anus forms a new structure (e.g., most of molluscs) or the blastopore gives rise to [...]