Please, can you help to take a note ? ASAP please. Most of this if not all is co
ID: 174925 • Letter: P
Question
Please, can you help to take a note ? ASAP please. Most of this if not all is copied from Biology 3 Edition, by Brooker et al An animal starts its life as a single cell, which will turn into a multicellular organism. There are four essential processes that are needed to make a multicellular organism: Cell Proliferation, which produces more cells, Cell specialization, which produces cells with different characteristics, Cell interactions, which coordinates the behavior of one cell with that of its neighbors and finally cell movement, which rearranges the cells to form structured tissues and organs Embryonic development is the process by which a fertilized egg (that is, a zygote) is transformed into an animal with distinct physiological systems and body parts. The biological information that controls embryonic development resides in both the organism's DNA and in the cytoplasm of the egg. As you have probably observed, the adult forms of animals vary immensely, however, embryonic development follows a similar pattern in most animals. Most modern animals including humans are triploblasts, which means they have three distinct germ layers, and development in these animals can be divided into five general events: fertilization, cleavage, gastrulation, neurulation, and organogenesis. Many species also go through an additional event called metamorphosis, which is a transition from a feeding larval form to an adult. Metamorphosis occurs after organogenesis Read through 3" slide FERTILIZATION The events in fertilization are similar in all triploblasts Fertilization is the union of two gametes, such as an egg cell with a sperm cell, to form a zygote. We will be describing fertilization in sea urchins a well-studied model organism. In our discussion we will talk about the acrosomal reaction and the cortical reaction. The acrosomal reaction is an event in fertilization in which enzymes released from a sperm's acrosome break down the outer layers of an egg cell, which allows the entry of the of the sperm cell's nucleus into the egg cell. The cortical reaction is a n event in fertilization iExplanation / Answer
The information provides insight into fertilization and post fertilization events during embryonic development. The process starts with fertilization i.e. fusion of male and female gametes. Arrival of sperm to the egg makes the acrosome of sperm to release hydrolytic enzymes that dissolve the jelly coat and allows the sperm head to bind to plasma membrane of egg followed by release of sperm nucleus into egg. This acrosomal reaction is followed by cortical reaction to block polyspermy. Fusion of egg and sperm nucleus is followed by cleavage which encompasses rapid cell divisions with no increase in size and resulting in production of blastula with outer epithelial layer and inner cavity. Variation in size and appearance of cleavage stage embryo among the triplobasts is the function of amount of yolk present in egg which in turn determines the pattern of cleavage. The trophactoderm of epithelial layer of blastocyst give rise to placenta and the inner cell mass develops into embryo. In uterus, the embryo is hatched from zona pellucida to facilitate implantation. Implantation is followed by gastrulation which forms a structure with three primary germ layers which in turn eventually give rise to different organs of the embryo. Formation of central nervous system oocurs through the process of neurulation which occurs after gastrulation and involves the formation of neural tube from ectoderm. The neural precursor cells of neural tubes form all neurons and supporting cells. Arrangement of two or more tissue types into specialised structures is called as organogenesis and gives rise to organs of embryo during or just after neurulation but the organs become functional at different stages of development. The processes of cell differentiation and morphogenesis are regulated by autonomous and conditional specifications which in turn are based upon morphogens and cell to cell contact.