B. Chitin- its a hard and tough substance that occurs widely in nature, particularly in the shells (exoskeletons) of arthropods such as crabs.
Answer:
The correct answer is <u><em>B. Cell Wall</em></u>
Explanation:
A <u><em>cell wall</em></u> is a rigid layer that is found outside the cell membrane and surrounds the cell. The cell wall contains not only cellulose and protein, but other polysaccharides as well. The cell wall provides structural support and protection. Pores in the cell wall allow water and nutrients to move into and out of the cell.
Answer:
b. false
Explanation:
The cell cycle consists of three states: Interphase, Cell division (mitosis) and Resting.
Interphase is composed of phases G1, S and G2. during this state the cell replicates the genetic material of its chromosomes to prepare itself for cell division
In G1 the cell synthesizes mRNA and proteins that the cell will need during mitosis.
In S the cell replicates the genetic material of its chromosomes to prepare itself for cell division. At the end of this phase each chromosome is composed of two sister chromatides.
In G2 the cell grows and and more proteins synthesized for mitosis.
Mitosis is the production of two daughter cells from a sinlge one. During the entire mitosis the chromosomes are duplicated in the cell until finally, the genetic material is distributed in two cells after cytokinesis.
According to the above, it can be seen that the chromosomes in a cell that is in the cell cycle do not necessarily have sister chromatids. For example, chromosomes during G1 do not have sister chromatids.
The correct answer is: [B]: "False" .
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<u>Note</u>: To the contrary, "ethyl alcohol" (or "ethanol" {EtOH}, the kind people drink) is a "central nervous system (CNS) depressant .
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The quickest way for an ant to go from the ground to the tree trunk is by walking straight towards the tree and climbing the tree trunk. Ant will walk straight if it is guided by the pheromone trail left behind by the other ants.
The ant first decides to explore the area for food and threats before taking a decision to walk away from its current location, i.e, the ground. The ant then starts to climb the bark of the tree to reach a higher ground. It does so by leaving a pheromone trail behind. This pheromone trail helps in guiding the other ants towards a possible food source.
