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1.1 Animal size/mass. 1.2 The level of development at birth. 1.3 Environmental factor. 2 See also. 3 References. ... The gestation figures given here are shown in ...
In animals, the process involves a sperm fusing with an ovum, which eventually leads to the development of an embryo. Depending on the animal species, the process can occur within the body of the female in internal fertilization, or outside in the case of external fertilization. The fertilized egg cell is known as the zygote. [2] [5]
Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million in total. Animals range in size from 8.5 millionths of a metre to 33.6 metres (110 ft) long and have complex interactions with each other and their environments, forming intricate food webs.
Blood cells begin to form on the sac in the center of the embryo, as well as cells which begin to differentiate into blood vessels. Endocardial cells begin to form the myocardium. At about 24 days past fertilization, there is a primitive S-shaped tubule heart which begins beating. The flow of fluids throughout the embryo begins at this stage.
2. Acorn Woodpecker. These birds get their name from their unique habit of storing acorns in trees, which they use as a food source. Sometimes, they can store tens of thousands of them.
2. Xeme. Also known as Sabine's Gull, these animals are graceful seabirds that live in a variety of habitats depending on the season. In the summer, they can be found across the Arctic and ...
2. Swan. These elegant birds are graceful swimmers and recognized for their long necks and beautiful movements when in lakes and ponds. They are also known as one of the largest flying birds in ...
Lists of individual animals (2 C, 22 P) Lists of invertebrates (7 C, 14 P) L. Lists of largest animals (20 P) M. Lists of molluscs (4 C, 8 P)