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The correct sequence is: Seminiferous tubules → Rete testis → Vasa efferentia (efferent ductules) → Epididymis → Vas deferens → Ejaculatory duct → Urethra → Urethral meatus. This aligns with NCERT, where sperm pass from seminiferous tubules to rete testis, then through the efferent ductules into the epididymis, onward via the vas deferens, then the ejaculatory duct and finally the urethra and its external opening.
Rete testis acts as a network connecting seminiferous tubules to the efferent ducts, facilitating sperm collection before their transport.
Semen path: seminiferous tubules → rete testis → efferent ductules → epididymis → vas deferens → ejaculatory duct → urethra.
In flowering plants, two male gametes are released from the pollen tube. One sperm nucleus fertilizes the egg cell to form the zygote, while the other sperm nucleus fertilizes the central cell (which contains the two polar nuclei) to form the endosperm nucleus. The central cell fertilization typically involves the fusion of one sperm with the polar nuclei, resulting in the triploid endosperm. After fertilization, the synergid degenerates. Thus, one male gamete fuses with the egg and the other fuses with the central cell nuclei, matching option 1.
Double fertilization is unique to angiosperms and leads to diploid zygote and triploid endosperm formation.
Two male gametes: one fuses with egg to form zygote; other fuses with central cell to form endosperm.
The second polar body is formed when the egg completes its second meiotic division. In human/animal oocytes, this division is completed after the sperm enters the ovum, but before the actual union of genetic material (fertilization) is complete. Thus, extrusion of the second polar body occurs after entry of the sperm but before fertilization, making option 4 correct as per the given answer.
The first polar body is formed after the first meiotic division and is often smaller; the second polar body forms at the end of meiosis II in the egg.
Meiosis II in the egg completes after sperm entry; the second polar body is extruded during this process before fertilization completes.
According to NCERT, lactational amenorrhea method (LAM) is a natural postpartum method that works when the mother exclusively breastfeeds and remains amenorrhoeic for the first six months after childbirth. Along with pills (hormonal oral contraceptives) and emergency contraceptives, it forms part of the contraceptive options discussed. Therefore, option 4 (Lactational amenorrhea, Pills, Emergency contraceptives) correctly lists three recognized methods. The other options mix methods that are also valid, but they do not align with the specific grouping given in NCERT as the correct trio here.
Lactational amenorrhea method is effective only under strict conditions: exclusive breastfeeding, no return of menses, and within six months of birth.
LAM is a natural method; combined pills and emergency contraception are hormonal/post-coital methods discussed in family planning chapters.
The cross red x white in Antirrhinum shows incomplete dominance, yielding pink in F1. In F2, segregation of alleles gives 1 red : 2 pink : 1 white, confirming incomplete dominance and that the Law of Segregation does apply (gametes carry alleles, and they segregate during formation). Therefore statement 1 is incorrect. Statements 2, 3, and 4 are consistent with NCERT: ratio 1/4 red, 1/2 pink, 1/4 white; pink in F1 results from incomplete dominance; and the experiment does not follow complete dominance.
In incomplete dominance, heterozygotes show a third phenotype (pink) distinct from either homozygote (red or white).
Antirrhinum shows incomplete dominance; F2 phenotype ratio is 1:2:1 (red:pink:white) due to segregation of alleles.
In population genetics under Hardy–Weinberg, if the dominant allele A has frequency p and recessive allele a has frequency q, then p + q = 1. Given p = 0.4, q = 0.6. Genotype frequencies are: AA = p^2 = 0.16, Aa = 2pq = 2 × 0.4 × 0.6 = 0.48, aa = q^2 = 0.36. So the distribution is 0.16 (AA); 0.48 (Aa); 0.36 (aa).
The Hardy–Weinberg principle predicts genotype frequencies from allele frequencies in large, randomly mating populations with no evolution.
In a trait governed by a single gene with two alleles, genotype frequencies are p^2, 2pq, q^2 for AA, Aa, aa respectively, where p is frequency of A and q of a.