The 'Emerson enhancement effect' demonstrated that photosynthesis is more efficient when:
A. Plants are exposed to only red light
B. Plants are exposed to both red and far-red light simultaneously
C. Plants are exposed to only far-red light
D. Plants are kept in complete darkness
Answer: Option B
Solution (By JKExamLibrary)
The Emerson enhancement effect, discovered by Robert Emerson in 1957, provided crucial evidence for the existence of two distinct photosystems (PSI and PSII) in photosynthesis. He observed that the rate of photosynthesis (measured by oxygen evolution) under far-red light (>680 nm) alone was very low. However, when far-red light was combined with shorter wavelength red light (
Explanation:
Oxytocin, released from the posterior pituitary, stimulates uterine smooth muscle contractions during parturition (childbirth) and milk ejection during lactation. Prolactin stimulates milk production. Estrogen and progesterone regulate reproductive cycle and maintain pregnancy. Oxytocin is also known as the 'love hormone' and functions through positive feedback during labor.
Explanation:
Convergent evolution occurs when distantly related organisms independently evolve similar traits or structures to adapt to similar ecological niches or environmental pressures. The resulting structures are called analogous organs (e.g., wings of birds and insects, eyes of octopuses and mammals). Divergent evolution is when related species evolve different traits (homologous organs). Coevolution is when two species evolve in response to each other.
Explanation:
Penicillin, the first true antibiotic, was discovered by Alexander Fleming in 1928. He observed that a mold contaminating a Staphylococcus culture plate was inhibiting bacterial growth. The mold was identified as Penicillium notatum (now P. chrysogenum). Penicillin is extracted from this fungus and is effective against many Gram-positive bacteria.
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