In plant reproduction, the phenomenon where the pollen tube enters the ovule through the micropyle is called:
A. Porogamy
B. Apogamy
C. Mesogamy
D. Chalazogamy
Answer: Option A
Solution (By JKSSB Mock Tests)
In angiosperms, the pollen tube must enter the ovule to deliver the male gametes to the embryo sac. The most common and typical pathway is through the micropyle (the small opening at the tip of the integuments), which is called porogamy. In some plants (like Casuarina, Juglans), the pollen tube enters through the chalaza (the base of the nucellus), which is called chalazogamy. Entry through the integuments is called mesogamy. Apogamy is the formation of a sporophyte without fertilization.
Explanation:
Secretin, released from the duodenum in response to acidic chyme, stimulates the pancreas to secrete bicarbonate-rich fluid to neutralize the acid. Gastrin stimulates HCl, CCK enzyme secretion, motilin GI motility.
Explanation:
'Survival of the fittest' was a phrase used by Herbert Spencer but adopted by Darwin to describe natural selection—organisms best adapted to the environment survive and reproduce. Lamarck proposed inheritance of acquired characters, Mendel discovered laws of heredity, De Vries proposed mutation theory. Darwin's theory emphasizes differential reproductive success of variants.
Explanation:
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 (
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