Consider statements about scientists: 1. Robert Hooke coined the term 'cell'. 2. Antonie van Leeuwenhoek discovered the cell nucleus. 3. Matthias Schleiden proposed that all plants are made of cells. Which are correct? MCQ with Answer and Explanation
Consider statements about scientists: 1. Robert Hooke coined the term 'cell'. 2. Antonie van Leeuwenhoek discovered the cell nucleus. 3. Matthias Schleiden proposed that all plants are made of cells. Which are correct?
A. 1 and 3 only
B. 1 and 2 only
C. 1, 2 and 3
D. 2 and 3 only
Answer: Option A
Solution (By JKExamLibrary)
Robert Hooke observed cork tissue in 1665 and coined the term 'cell' to describe the box-like structures. Matthias Schleiden, a botanist, concluded in 1838 that all plants are composed of cells, forming a core tenet of the cell theory. The cell nucleus was discovered by Robert Brown in 1831, not Antonie van Leeuwenhoek, who is famous for discovering living microorganisms. Thus, statements 1 and 3 are correct.
Explanation:
Alfred Russel Wallace independently conceived the theory of natural selection and sent his manuscript to Darwin. In 1858, both presented their papers jointly at the Linnean Society. Darwin's 'On the Origin of Species' (1859) elaborated the theory. Mendel discovered genetics, Lamarck proposed inheritance of acquired traits, Malthus influenced Darwin with his ideas on population growth.
Assertion (A): Mitochondria are called semi-autonomous organelles. Reason (R): They possess their own DNA and ribosomes and can synthesize some proteins.
A.Both A and R are true, but R is not the correct explanation.
B.A false, R true.
C.A true, R false.
D.Both A and R are true, and R is the correct explanation.
Explanation:
Mitochondria have circular DNA and 70S ribosomes, enabling them to transcribe and translate some proteins independently, hence semi-autonomous. They still depend on nuclear genes for most proteins. The reason correctly explains the assertion.
Photorespiration in C3 plants occurs when RuBisCO acts as an oxygenase instead of a carboxylase. This process primarily takes place in which organelles?
Explanation:
Photorespiration is a wasteful pathway that occurs when RuBisCO fixes O2 instead of CO2, producing phosphoglycolate. This 2-carbon compound is metabolized through a complex pathway involving three organelles: it is processed in the peroxisome, then the mitochondria, and finally returns to the chloroplast. This process consumes ATP and releases CO2 without producing any sugar.
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