Looking at the onion root tip under the microscope you can see large, rectangular cells with visible distinct cell walls surrounding it (cells have a more regular shape because of the wall). Inside the cells, you can notice darkly stained nucleus, large vacuoles at the center and sometimes small granules within the cytoplasm. Looking the onion root tip under the microscope is often the way to observe mitosis. Usually, you cannot see organelles such as mitochondria, ribosomes, rough and smooth endoplasmic reticulum, centrioles and Golgi body as they appear translucent and because are too small to be seen under the light microscope (electron microscope required). Also, chloroplasts are not present in an onion cell because it is not a photosynthetic cell.
Answer:
All the options are true except option D.
Explanation:
Archaea are a group of prokaryotic organisms i.e. they lack a membrane bound nucleus. They are one of the the three domains of life (the other two being bacteria and eukarya). Archeans possess a cell wall like bacteria but it is not composed of peptidoglycan, like bacteria cell wall.
Archeans are generally known to be found in very severe environmental conditions, hence, they are referred to as extremophiles e.g Some are thermoacidophiles i.e. thrive in very hot and acidic environment while others are extreme halophiles i.e. thrive in salty regions. Archeans known as methanogens produce methane gas as a product of metabolism from carbon dioxide and hydrogen.
However, the domain archeae was only found to be in existence recently after the domain bacteria, hence, they are not considered to evolve before the domain bacteria.
Meiosis occurs in a series of different phases and creates genetically unique reproductive cells. The process which helps make meiotic cells genetically different and occurs during prophase I, but not during prophase II, is crossing over (C). Crossing over is the exchange of genetic material between two homogenous chromosomes. It is one of the final phases of prophase I. This process is called synapsis. It occurs when the matching regions on the matching chromosomes break and then reconnect to the other chromosome
