Animal cells lack the rigid cell walls that characterize plant cells. The bodies of most animals (all except sponges) are made up of cells organized into tissues; each tissue specialized to some degree to perform specific functions. In most, tissues are organized into even more specialized organs. Most animals are capable of complex and relatively rapid movement compared to plants and other organisms. Most reproduce sexually, by means of differentiated eggs and sperm. Most animals are diploid, meaning that the cells of adults contain two copies of the genetic material. The development of most animals is characterized by distinctive stages, including a zygote, formed by the product of the first few division of cells following fertilization; a blastula, which is a hollow ball of cells formed by the developing zygote; and a gastrula, which is formed when the blastula folds in on itself to form a double-walled structure with an opening to the outside, the blastopore. Open access journal articles are essentially peer-reviewed and available for access through the directory of Open Access journals. OMICS Group International supports this system and provides access to 700+ peer-reviewed journals with no restrictions and thus promotes the Open Access movement with a view to promote scientific advancements. The research articles published in OMICS Group journals are immediately and permanently available online without charge.
Last date updated on September, 2024
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