Answer:
C. Most plants use single nitrogen atoms, not N2 molecules.
Explanation:
The controversy surrounding the nucleic acids and proteins, regarding which one of them was formed first is the most popular controversy in the biology world today. The nucleic acids stores and the genetic information. The proteins essential for all the life processes are encoded by the genes formed of the nucleic acids (DNA and RNA). But proteins (enzymes) are required for the formation of proteins from the genes. The inter-dependency of the nucleic acids and proteins on each other possesses a dilemma to the question 'which of them arrived first'.
The answer to this dilemma was answered when it was discovered that RNA was capable of not only carrying the genetic information, but also acting as catalyst to the chemical reaction. This finding supported the notion that the RNA evolved first serving the purpose of both the nucleic acids and emzymes.
- Xylem contains tracheids, vessels, xylem parenchyma and xylem fibre.
- Tracheids: They are elongated, tubular dead cells with tapering end walls.
- Vessels: These are also known as trachea. They are elongated, tubular dead cells. They are joined to each other by end to end forming a continuous pipe. The cells are thick and lignified.
- Xylem parenchyma: They are also called wood parenchyma. This is the only living tissue of xylem.
- Xylem fibre: They are dead cells with thick walled fibre.
- Phloem consists of sieve tubes, companion cells, phloem parenchyma and phloem fibres.
- Sieve tubes: These are elongated, tubular living cells arranged in a row, with their perforated end walls forming a sieve. They are non-nucleated. Their protoplasm are inter-connected through sieve plates. They possess vacuoles.
- Companion cell: They are elongated, lens-shaped cells containing dense cytoplasm and prominent nuclei. These cells maintain connection with sieve cells through pits.
- Phloem parenchyma: They are living thin walled parenchyma cells.
- Phloem fibre: They are also known as bast fibre. They are elongated fibre like sclerenchymatous dead cells with thick walls containing pits and interlocked ends. Phloem fibre are the only dead cells in phloem.
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I think it's A....hope that helps at least
Answer: Cell differentiation is how generic embryonic cells become specialized cells. This occurs through a process called gene expression. Gene expression occurs because of certain signals in your body, both inside and outside of your cells. Cell differentiation occurs during multiple stages of development.
