A fertilized egg usually implants itself and develops in the uterus.
<span>During the prenatal development, fertilized egg adheres to the wall of the uterus. Zygote (fertilized egg) at this stage forms blastocyst. The blastocyst consists of an inner cell mass and the outer layer -the trophoblast. Trophoblast surrounds the inner cell mass and a fluid-filled cavity - blastocoele. Inner cell mass will form embryo and trophoblast gives rise to the placenta.</span>
Tha Water Cycle The "first" step in the water cycle is when water in oceans, lakes, or other bodies/collections of water is warmed up by the Sun. Heat adds energy to matter. This causes the molecules in the water to move faster and farther apart, until they move so far apart that they become a gas instead of a liquid - the water becomes water vapor. Eventually the water vapour condenses into clouds. This means that the particles in the water vapour slow down and cool off, resulting in them becoming water droplets. These water droplets group together to form clouds. This is why a parachutist unfortunate enough to fall through a cloud would end up covered in water droplets. When enough water droplets (remember, these are usually very small to begin with) form 'inside' clouds, they become heavy enough to fall towards the Earth. This is usually observed as rain, but Precipitation can also occur as snow, hail, sleet, etc., depending on temperatures and humidity. Runoff is when water travels across land. Rain will land in the ground, streets, oceans, and in streams and rivers. Eventually it makes its way to a body of water. After a while, the water is evaporated and the water cycle repeats. The Carbon Cycle Starts with Carbon in the atmosphere, plants pull the Carbon dioxide out of the air through photosynthesis. Consumers eat plants, and digest parts of the carbon. through respiration, consumers release them back into the atmosphere. When the animal dies off, it eventually evolves into fossil fuels, which is made up largely of carbon. Humans use the fossil fuels and release the carbon into the air. The Nitrogen Cycle Starts with Nitrogen in the atmosphere. The nitrogen gets into the ground through nitrogen fixation (Lightning & Bacteria. Consumers consume plants that absorb the nitrogen from the soil, and when the animal dies and decays, the nitrogen is released from its body and is absorbed back in the soil. We use the nitrogen in fossil fuels to make fertilizers. When it rains, the Nitrogen is washed away (runoff) into surface water, or be absorbed into the ground (Ground Water). The runoff of the nitrogen into the surface water is that it destroys all the oxygen build up in the water, called Eutrophication. The Phosphorus Cycle The Phosphorus Cycle starts with the weathering of rocks. This releases phosphorus into the ecosystem. The phosphorus is absorbed by plants, which are consumed by animals. When the plants or animals die, they release the phosphorus back into the soil through decomposition. Through mining, we use the phosphorus and put it into fertilizers, which is once again consumed by the ground, and released into surface water. Which causes Eutrophication.<span>Full transcript</span>
photosynthesis
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If the sperm cell fertilises the ovum, and implantation does not occur, then the corpus luteum degenerates and it turns into corpus albicans, stopping progesterone secretion. If fertilisation occurs and implantation also, the syncytiotrophoblast, the "root part" of the blastocyst (one of the early structures originated from the zygote), produces a hormone that is called <span>human chorionic gonadotropin (hCG). The hCG is what makes the corpus luteum keep secreting progesterone and maintain itself. The progesterone will then help keep the endometrium and, therefore, allow the development of the embryo to happen.</span>
