BIOLOGY Paper - Amphibian Development - Human Development Essay

BIOLOGY Paper - Amphibian Development - Human Development - Essay Example s belong to Tetrapods or four-legged vertebrates and are considered as ectothermic vertebrates.3 Physically, frogs’ skin is smooth, has three-chambered heart, and does not have claws on their toes. Frogs usually lay their eggs in water until it hatches to into tadpole or larva. Tadpoles has to be on the water since they breathes with their gills. Chicks are classified as endothermic vertebrates. 3 Their physiological appearance includes skin covered with feathers, has four-chambered heart, lightweight bones that are hollow, and with wings. Similar to frogs, chicks also lay eggs. In comparison between the eggs produced by chicks and frogs, the egg that comes from chicks has more yolk than the frogs. Since human fertilized egg or the zygote does not contain any yolk, we will take into consideration the frog’s reproduction and development as the best choice in comparison with the human reproduction and development process. There is a huge difference between a frog egg (mesolecithal egg) and human ova (egg cells). Mesolecithal egg has a moderate amount of yolk being distributed throughout the cytoplasm of the egg with more concentration towards the ‘vegetal pole.’ On the other hand, the human ova do not show traces of yolk. Also, the external portion of the frog egg has a smooth surface while the human ova has an uneven surface. Frog egg is divided into a dark pigmented hemisphere called the animal hemisphere while the lightly pigmented hemisphere is known as the vegetal hemisphere. The gray crescent is the dorsal surface of the embryo that plays a role in establishing the embryonic axis. See figure 1. Human ova, measures around 0.2 mm. in diameter, are enclosed within the egg follicles of the ovaries.5 The cell substance of the ovum i is called oà ¶plasm.10 (in amphibians, oà ¶plasm is equivalent to the yolk) The nucleus is known as the germinal vesicle while the nucleolus is the germinal spot. The ovum is enclosed by a thick transparent envelope called the