Answer: Option B
Explanation: The thin layer that forms the outer covering of the cell is known as the cell membrane. It is composed of the lipid bilayer which as embedded proteins.
This membrane is selectively permeable which means it allows only specific molecules to pass through them.
The main function of cell membrane is to protect the cell from the outer environment and by the invasion of harmful bacteria and viruses.
Answer:
but you need to do this at home
Explanation:
Answer:
Endosymbiont theory was proposed by Lynn Margulis in 1967 which suggested the origin of Chloroplast and mitochondria in eukaryotic cells.
The theory suggested that chloroplast and mitochondria organelle originated by engulfing the cyanobacteria and proteobacteria by other prokaryotic bacteria.
This shows that Prokaryotes exhibit the following characters:
1. These were the first organisms on Earth
2. Lack membrane-bounded
3. Aerobic bacteria are these types of cells
Eukaryotes exhibit:
1. Have mitochondria
2. Includes organisms that carry out aerobic respiration
3. Can be a multicellular organism
4. Includes organisms that are photosynthetic
5. Might have chloroplasts
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Answer:</h2><h2>
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the Cell Theory was give by German scientists, Schleiden and T.Shwan in 1839. It stated that,
- All organism are composed of one or more cells
- The cell is the structural and functional unit of life
- It is a de novo structure, that means it COULD arise from non living thing which was incorrect.
It was corrected by the German pathologist Rudolf Virchow in 1855. He made a convincing case, corrected and added the third point of the cell theory. It is,
- Cells can arise only by a division of pre-existing cell. It is <u>NOT</u> a de novo structure.
Cell theory brought a great evolution in the field of biology which established the function of organism is the result of activities and interaction of the cell units.
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- <u>Flask 1</u>: It is observed that there are no micro-organism, this is because the meat is sealed and no micro-organism could enter through it.
- <u>Flask 2</u>: It is observed that there are micro-organism present because meat is not sealed but open.
- <u>Flask 3</u>: As the S tube is used, the micro-organism are not able to reach the meat because of the curvy path
These observations support the point that<u> cells could arise only by a division of pre-existing alive cells</u> because in Flask 1 when there were no micro-organism present so there was no organisms found so no micro-organism arised, In flask 3 the S tube was used so no micro-organism could reach the meat thus there were no organism there which could divide to reproduce. The flask 2 was open, so the micro organisms reached the meat so they divided which means Cells can only arise by a division of pre-existing cells.
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