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Science scientific reasons[2 marks ]

Cell Structure and Functions · Gujarat Board (GSEB) STD 8 (GSEB - English Medium). 5 questions.

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scientific reasons[2 marks ]

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5 questions · self-marked practice — reveal the answer and mark yourself.

Question 12 Marks
Offsprings are resemble their parents by characters.
Answer
$-$Gene is a unit of inheritance in living organisms.
$-$Genes are located on chromosomes present in nucleus.
$-$The genes control the transfer of a hereditary characteristic from parents to offsprings.
$-$Offsprings receive parental genes by a process called inheritance.
$-$So, offsprings are resemble parents by characters.
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Question 22 Marks
Plant cell is rigid while animal cell comparatively soft.
Answer
$-$Cell wall is outermost layer / envelope in a plant cell.
$-$It provides rigidity to plant cell.
$-$Animal cell has cell membrane as outermost layer.
$-$Animal cell does not have cell wall.
$-$So, due to the presence of cell wall plant cell is rigid and because of absence of cell wall animal cell is soft.
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Question 32 Marks
Even though living cell is independent from external environment, it can exchange materials with it.
Answer
$-$In each living cell the cytoplasm and the nucleus are enclosed within the cell membrane.
$-$The cell membrane seperates cells from one another and also the cell from the surrounding medium.
$-$The cell membrane is porous.
$-$The cell membrane allows the exchange of materials with external environment through pores.
$-$So, even though living cell is independent from external environment, it can exchange materials with it.
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Question 42 Marks
The cells of an elephant are not larger in size than the cells in a rat.
Answer
$-$The size of an elephant is much larger than the size of a rat.
$-$The size of the cell is related to its function.
$-$The sizeof the cells has no relation with the size of an organism.
$-$All the functions occurring in an elephant body are also performed in a rat.
$-$Nerve cells, both in the elephant and rat, are long and branched.
$-$They perform same function, that of transferring messages.
$-$So, the cells of an elephant are not larger in size than the cells of a rat.
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Question 52 Marks
Life of multicellular organism begins with single cell.
Answer
$-$Generally sexual reproduction occurs in multicellular organisms.
$-$Zygote is formed by fertilization of egg cell in sexual reproduction.
$-$Zygote in unicellular.
$-$The fertilised egg cell $($zygote$)$ multiplies and the number of cells increase as development proceeds.
$-$Thus, multicellular organism is formed.
$-$So, an organism with millions of cells begins life as a single cell. i.e. zygote.
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scientific reasons[2 marks ] - Science STD 8 Questions - Vidyadip