It measures the total rate at which photosynthesis or chemosynthesis happens in a system.
Viruses are at the heart of this century-old debate. Viruses<span> are parasites that infect plants, animals, fungi and bacteria. They consist of genetic material surrounded by a protein coat and are unable to grow or reproduce without a host. The classification of viruses has confused scientists for nearly 100 years. Originally they were viewed as poisons. In fact, the word ''virus'' is Latin for ''poison.'' They have since been viewed as living creatures, then mere bio-chemical compounds, and, most recently, somewhere in between chemical compounds and lifeforms.</span>Non-cellular life<span> refers to organisms, such as viruses, that exist without any cells, and it is a very controversial topic. The cell theory, which is one of the fundamental tenets of biology, states that all living things are composed of cells and that cells are the basic units of life. So the idea that something can be considered alive without having cells is an issue that is up for debate.
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Answer:
C - Contains the embryonic disk
Explanation:
After an egg is fertilized, it begins to divide into smaller cells, from the 1 cell stage, to 2, to 4 and so on. Then, on the third day, the cells fall within 16-200 cells and it is then called a <em>morula</em>.
On the fifth day, the morula becomes a ball of calls which is now differentiated into an <em>inner cell mass and a trophectoderm</em>. The inner cell mass becomes the <em>embryo</em> as development goes on and the trophectoderm, becomes the <em>placenta</em>.
As development goes on further, the floor of the amniotic cavity is formed by the embryonic disk, a layer of prismatic cells derived from the inner cell mass.
The embryonic disc develops into 3 layers:
There is a major differentiation of cells which gives a template for the origin of development of specific organs of the embryo.
