SSC CGL Science – Genetics, Evolution & Plant Biology – Level 2 · Exam Level · Tier I Sprint

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SSC CGL Science – Genetics, Evolution & Plant Biology – Level 2 · Exam Level · Tier I Sprint – 17 questions, subject: General Science. Every question has the correct answer with a one-line explanation; tap "Show Answer". Free practice for TNPSC, UPSC, SSC, Bank and RRB exams – Shanmugam IAS Academy, Coimbatore.

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1.  
Diagram-basedTwo pink snapdragon plants (Rr, incomplete dominance) are crossed. Which boxes of the Punnett square will give pink flowers?

Correct Answer: C [X and Y]

Explanation:

X and Y are Rr = pink; W (RR) red; Z (rr) white.

2.  
Diagram-basedIn the same cross, the ratio red : pink : white is:

Correct Answer: B [1 : 2 : 1]

Explanation:

RR : Rr : rr = 1 : 2 : 1 – phenotype equals genotype here.

3.  
Match the followingMatch the plant hormone with its main effect:
P. Auxin Q. Ethylene R. Cytokinin S. Abscisic acid
1. Cell division 2. Bending towards light 3. Closing of stomata 4. Fruit ripening

Correct Answer: C [P-2, Q-4, R-1, S-3]

Explanation:

Auxin – phototropism; ethylene – ripening; cytokinin – division; ABA – stomata close.

4.  
Match the followingMatch the scientist with the idea:
P. Lamarck Q. Darwin R. Hugo de Vries S. Stanley Miller
1. Natural selection 2. Amino acids from simple gases 3. Use and disuse of organs 4. Mutation theory

Correct Answer: A [P-3, Q-1, R-4, S-2]

Explanation:

Lamarck – use/disuse; Darwin – selection; de Vries – mutation; Miller – amino acids.

5.  
The phenotypic ratio in the F2 generation of a dihybrid cross is:

Correct Answer: D [9 : 3 : 3 : 1]

Explanation:

Counted from the 16-box square: 9 : 3 : 3 : 1.

6.  
Assertion–ReasonAssertion (A): A colour-blind son of normal parents gets the allele from his mother.
Reason (R): A son receives his X chromosome from his mother.

Correct Answer: A [Both A and R are true and R is the correct explanation of A]

Explanation:

R explains A – the father gives only Y to a son.

7.  
Assertion–ReasonAssertion (A): The wings of a butterfly and of a bird are homologous organs.
Reason (R): They perform the same function.

Correct Answer: D [A is false but R is true]

Explanation:

They are analogous (same function, different structure); A is false, R is true.

8.  
Odd one outOdd one out (by the type of inheritance):

Correct Answer: B [Haemophilia]

Explanation:

Haemophilia is X-linked; the other three are autosomal recessive disorders.

9.  
Which of the following pairs are homologous organs?

Correct Answer: A [Forelimbs of a whale and a bat]

Explanation:

Same bone plan, different function.

10.  
Which hormone is used to increase the length of grape stalks?

Correct Answer: C [Gibberellin]

Explanation:

GA – stem and stalk elongation.

11.  
2,4-D, used as a weedicide against broad-leaved weeds, is a synthetic:

Correct Answer: B [Auxin]

Explanation:

Synthetic auxins – NAA, 2,4-D.

12.  
The Calvin cycle (dark reaction) takes place in the:

Correct Answer: D [Stroma of the chloroplast]

Explanation:

Light reaction – grana; dark reaction – stroma.

13.  
Chronological orderarrange in the order in which they happened:
P. Watson–Crick model of DNA
Q. Darwin's On the Origin of Species
R. Publication of Mendel's paper on pea plants
S. Completion of the Human Genome Project

Correct Answer: A [Q → R → P → S]

Explanation:

1859 (Q) → 1866 (R) → 1953 (P) → 2003 (S).

14.  
A tall pea plant crossed with a dwarf plant gave 50 % tall and 50 % dwarf offspring. The tall parent was:

Correct Answer: D [Tt (heterozygous)]

Explanation:

Answer: Tt (heterozygous). Test cross 1 : 1 → hybrid.

15.  
Klinefelter's syndrome has the chromosome condition:

Correct Answer: B [XXY (47)]

Explanation:

Answer: XXY (47). Turner XO; Klinefelter XXY.

16.  
Leaves of the touch-me-not plant fold when touched because of:

Correct Answer: C [changes in the water content of cells]

Explanation:

Answer: changes in the water content of cells. Not a growth movement.

17.  
The first stable product of carbon fixation in C₄ plants such as maize is:

Correct Answer: D [Oxaloacetic acid (4-carbon)]

Explanation:

C₄ plants – OAA (4 C); C₃ plants – PGA (3 C).

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