Consider statements about evolution: 1. Variation is necessary for evolution. 2. Natural selection acts on phenotype. 3. Evolution occurs in individuals. Which are correct? MCQ with Answer and Explanation
Consider statements about evolution: 1. Variation is necessary for evolution. 2. Natural selection acts on phenotype. 3. Evolution occurs in individuals. Which are correct?
A. 1 and 2 only
B. 2 and 3 only
C. 1 and 3 only
D. 1, 2 and 3
Answer: Option A
Solution (By JKSSB Mock Tests)
Genetic variation within a population provides the raw material upon which evolutionary forces act; without variation, evolution cannot occur. Natural selection acts directly on the phenotype (observable traits) of an organism, determining its survival and reproductive success. However, evolution is a population-level phenomenon; it involves changes in allele frequencies over generations, not changes occurring within a single individual's lifetime. Thus, statements 1 and 2 are correct.
Explanation:
The micropyle is a small opening in the integuments of the ovule through which the pollen tube usually enters to deliver sperm cells for fertilization (porogamy). The chalaza is the opposite end, funicle is the stalk, hilum is the point of attachment. The micropyle also allows water entry during germination.
Explanation:
Parasitism (+/-) is a symbiotic interaction where the parasite benefits at the expense of the host. Examples: tapeworms, Plasmodium. Mutualism is +/+, commensalism +/0, amensalism -/0. Parasites may live on (ectoparasites) or inside (endoparasites) the host.
Explanation:
Anabaena azollae is a heterocystous cyanobacterium that lives symbiotically in the dorsal leaf cavities of the water fern Azolla. It fixes atmospheric nitrogen, providing a natural nitrogen source for rice paddies when Azolla is used as green manure. Nostoc is free-living or lichen symbiont, Rhizobium and Azotobacter are bacteria.
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