Answer: Option 3 - A and D
Let's break down the statements:
(A) Definition of biological species was given by Ernst Mayr:
Correct. Ernst Mayr proposed the biological species concept, which defines species as groups of interbreeding natural populations that are reproductively isolated from other such groups.
(B) Photoperiod does not affect reproduction in plants:
Incorrect. Photoperiod is a critical environmental factor that affects the reproductive behavior of many plants. Plants are classified based on their response to the length of day and night, such as long-day plants (LDP), short-day plants (SDP), and day-neutral plants. Photoperiod has a significant role in the timing of flowering and reproduction.
(C) Binomial nomenclature system was given by R.H. Whittaker:
Incorrect. Binomial nomenclature, the system of giving species a two-part Latin name (genus and species), was established by Carl Linnaeus. R.H. Whittaker contributed to the five-kingdom classification system, not binomial nomenclature.
(D) In unicellular organisms, reproduction is synonymous with growth:
Correct. In unicellular organisms, such as bacteria, reproduction (by binary fission) is often considered synonymous with growth, as the organism divides and multiplies into two identical cells, resulting in an increase in population size.
The two correct statements are (A) and (D), which makes Option 3 the correct answer.
A bob of heavy mass \(m\) is suspended by a light string of length \(l\). The bob is given a horizontal velocity \(v_0\) as shown in figure. If the string gets slack at some point P making an angle \( \theta \) from the horizontal, the ratio of the speed \(v\) of the bob at point P to its initial speed \(v_0\) is :