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Science [3 Mark Questions]

MODEL PAPER - 1 [2026] · CBSE STD 10 (CBSE - English Medium). 2 questions.

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[3 Mark Questions]

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Question 13 Marks
"If there were no algae there would be no fish in the sea." Comment.
Answer
Algae are the main source of productivity in sea. they prepare there own food with the help of photosynthesis. they are food for many small aquatic animals living in the sea. hence the algae is food for small fishes and small fishes are food for big fishes. it is like a food chain.
Algae produce $\mathrm{O}_{2}$ as a result of photosynthesis. This oxygen is utilized by fishes in the sea for carrying out respiration. If there were no algae, no oxygen would have been produced. Thus fishes might have died. Hence we can say if there were no algae there would be no fish in the sea.
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Question 23 Marks
A red-eyed individual is crossed with a white-eyed individual to produce $F_{1}$ progeny with red eyes. When $F_{1}$ individuals are intercrossed, $\mathrm{F}_{2}$ progeny is formed with both red as well as white-eyed individuals.
a. How is the dominant trait identified?
b. What are recessive traits?
c. If 12 individuals are produced in $\mathrm{F}_{2}$ generation, then how many white-eyed individuals would be obtained? Calculate the ratio of red-eyed individuals to white-eyed individuals.
Answer
a. The dominant trait is identified by observing its expression in the F1 generation.
b. The recessive trait is the one that is masked in the presence of the dominant trait and only expressed in the homozygous recessive state.
c. The ratio of red-eyed to white-eyed individuals is $3: 1$
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[3 Mark Questions] - Science STD 10 Questions - Vidyadip