Which one of the following statements regarding
post-fertilization development in flowering plants is incorrect?
AI-generated explanation. Check against your textbook.
Explanation:
The incorrect statement is 1. In NCERT, the embryo sac (female gametophyte) develops inside the ovule after megasporogenesis; the ovule itself does not become the embryo sac. The ovary, after fertilization, develops into fruit; the zygote develops into embryo; and the central cell with polar nuclei fertilizes to form endosperm. Thus, 2, 3, and 4 are true statements.
🧠 Did You Know?
The embryo sac forms within the ovule and later participates in double fertilization with the sperm, leading to embryo and endosperm formation.
💡 NCERT Memory Line:
The ovary develops into fruit; the ovule contains the embryo sac; the zygote forms the embryo; the central cell forms endosperm.
Is some plants, the female gamete develops into
embryo without fertilization. This phenomenon is
known as:
AI-generated explanation. Check against your textbook.
Explanation:
Parthenogenesis is the development of an embryo from the female gamete without fertilization. In some plants, the female gamete can develop into an embryo without a sperm cell, which is why option 1 is correct.
🧠 Did You Know?
Syngamy is the fusion of male and female gametes. Parthenocarpy refers to fruit development without fertilization. Autogamy is self-fertilization within a flower.
💡 NCERT Memory Line:
Parthenogenesis is the development of the female gamete into an embryo without fertilization.
Select the correct sequence of transport of sperm
cells in male reproductive system:
AI-generated explanation. Check against your textbook.
Explanation:
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.
🧠 Did You Know?
Rete testis acts as a network connecting seminiferous tubules to the efferent ducts, facilitating sperm collection before their transport.
What is the fate of the male gametes discharged in the synergid?
AI-generated explanation. Check against your textbook.
Explanation:
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.
🧠 Did You Know?
Double fertilization is unique to angiosperms and leads to diploid zygote and triploid endosperm formation.
💡 NCERT Memory Line:
Two male gametes: one fuses with egg to form zygote; other fuses with central cell to form endosperm.
Extrusion of second polar body from egg nucleus
occurs:
AI-generated explanation. Check against your textbook.
Explanation:
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.
🧠 Did You Know?
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.
💡 NCERT Memory Line:
Meiosis II in the egg completes after sperm entry; the second polar body is extruded during this process before fertilization completes.
Colostrum, the yellowish fluid, secreted by mother
during the initial days of lactation is very essential to impart immunity to the newborn infants because it contains:
AI-generated explanation. Check against your textbook.
Explanation:
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.
🧠 Did You Know?
Lactational amenorrhea method is effective only under strict conditions: exclusive breastfeeding, no return of menses, and within six months of birth.
💡 NCERT Memory Line:
LAM is a natural method; combined pills and emergency contraception are hormonal/post-coital methods discussed in family planning chapters.
In Antirrhinum (Snapdragon), a red flower was
crossed with a white flower and in F1 generation, pink flowers were obtained. When pink flowers were selfed, the F2 generation showed white, red and pink flowers.
Choose the incorrect statement from the following :
AI-generated explanation. Check against your textbook.
Explanation:
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.
🧠 Did You Know?
In incomplete dominance, heterozygotes show a third phenotype (pink) distinct from either homozygote (red or white).
💡 NCERT Memory Line:
Antirrhinum shows incomplete dominance; F2 phenotype ratio is 1:2:1 (red:pink:white) due to segregation of alleles.
A gene locus has two alleles A, a. If the frequency
of dominant allele A is 0.4 then what will be the
frequency of homozygous dominant, heterozygous
and homozygous recessive individuals in the
population?
AI-generated explanation. Check against your textbook.
Explanation:
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).
🧠 Did You Know?
The Hardy–Weinberg principle predicts genotype frequencies from allele frequencies in large, randomly mating populations with no evolution.
💡 NCERT Memory Line:
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.