Reproduction

Fusion of the male and female gametes forms a zygote. The zygote then divides repeatedly, and the developing group of cells becomes an embryo.

Implantation attaches the developing embryo to the uterine lining. This supports the development of the placenta, through which nutrients and oxygen can pass from the mother to the embryo and wastes can be removed.

The placenta is the exchange organ between the mother and the developing embryo: nutrients and oxygen pass to the embryo, while wastes pass away from it. The umbilical cord connects the embryo to the placenta.

The uterine lining thickens during the cycle in preparation for a possible pregnancy. If pregnancy does not occur, hormonal changes cause this lining to break down and leave the body as menstrual flow.

During adolescence, sex hormones increase and act on the body. Their effects include changes such as voice deepening and the growth of body hair.

A condom acts as a barrier that helps prevent sperm from reaching an egg and can reduce the risk of transmitting some sexually transmitted infections. It reduces risk but does not guarantee complete protection against every infection.

The correct answer is A. A Copper T is placed in the uterus, where copper reduces sperm motility and fertilising capacity. Hormonal contraceptive pills can prevent ovulation, so an egg is not released for fertilisation.

The correct answer is A. Sterilisation involves surgically blocking the vas deferens in males or the fallopian tubes in females. This prevents sperm and egg from meeting; it is intended as a permanent method, although reversal is not guaranteed.

The correct answer is A. Gametes are haploid, meaning they carry half the usual chromosome number. When two gametes fuse at fertilisation, their chromosomes combine and restore the usual number in the offspring.

The correct answer is A. If each gamete carried the full usual number, fusion would combine two full sets, doubling the number in the offspring. The number could then keep increasing in later generations; having half the number in each gamete prevents this.

The correct answer is A. In sexual reproduction, genetic material from two gametes combines to produce new combinations. Some resulting variations may help individuals survive and reproduce when conditions change, though not every variation is beneficial.

The correct answer is A. Asexual reproduction usually involves one parent and no fusion of gametes, so offspring are often genetically similar to that parent. Mutations can still introduce variation, but there are generally fewer new genetic combinations than in sexual reproduction.

The correct answer is A. Stamens are the male reproductive organs of a flower, and the pistil is its female reproductive organ. A male flower has stamens but no pistil; a bisexual flower has both.

The correct answer is A. The pistil is the female reproductive organ of a flower, while stamens are the male reproductive organs. A flower with a pistil but no stamens is classified as a female flower.

The correct answer is A. Cross-pollination requires pollen to move from a flower on one plant to a flower on another. For plants that rely on wind or insects, the absence of those agents means fewer pollen grains may reach another plant’s stigma.

The correct answer is A. Ovulation is the release of an egg from an ovary. The egg enters an oviduct, where it can fuse with a sperm; that fusion is fertilisation.

A is correct. Implantation allows the embryo to connect with the uterine lining, which supports its nourishment and development. Without implantation, a pregnancy usually cannot become established and continue developing.

A is correct. Contraceptive methods share the aim of preventing pregnancy, but they work in different ways: for example, barriers can prevent sperm from reaching an egg, while some other methods affect ovulation or fertilisation.

A is correct. Treatment can help manage an infection, but it does not by itself prevent future exposure or transmission. Measures such as using condoms correctly and getting appropriate testing can reduce risk.

A is correct. Reliable information can help people question myths, understand health risks and make informed, responsible choices. This can benefit both individual health and society.

A is correct. Growth changes the size or cell number of an existing organism; reproduction produces a new individual. They are different biological processes, even though growth also occurs during an organism’s development.

A is correct. If conditions change, a variation that is useful in the new environment may help some individuals survive and reproduce. Over generations, this can support the persistence of the species; not every variation is beneficial.

A is correct. Asexual reproduction can produce offspring rapidly from one parent, and the offspring are usually genetically similar to that parent. This can be advantageous in a stable environment where those traits remain suitable.

A is correct. In flowering plants, a male gamete delivered through the pollen tube fuses with the egg cell in the ovule. In humans, a sperm fuses with an egg. In both, fusion of male and female gametes begins the development of a new organism.

A is correct. Reproduction produces new individuals and passes genetic information to offspring. Asexual reproduction usually gives offspring genetic information from one parent, so they are often similar; sexual reproduction combines genetic information from two gametes and can create variation.