The plasma membrane needs lipids, which make a semi-permeable barrier between the cell and its environment. It also needs proteins, which are involved in cross-membrane transport and cell communication, and carbohydrates, which decorate both the proteins and lipids and help cells recognize each other. Hope this helps :)
<span>blastocyst
The outer layers of the blastocyst turn in to the trophoblast after implantation. The trophoblast forms the placenta.</span>
Trophic Levels describe the transfer and different stages of the organisms transferring energy. I just called it Trophic level energy flow in school.
Evolution is when living things go through changes. This occurs through natural selection.
When you swallow food, it doesn't just drop down into your stomach. Muscles contract in a wave-like motion to move the food along through the esophagus. This muscle movement is called, peristalsis, or peristaltic waves. These peristaltic waves contract behind the food bolus pushing it along the digestive tract.
