Sexual Reproduction: Definition, Process, Plants, Stages, Overview

What Is Sexual Reproduction?

Sexual reproduction is when two different types of gametes fuse to form a zygote. The zygote then undergoes mitosis and differentiation to form a new individual. It is among the major processes of reproduction by which the majority of species propagate their existence through the flow of genetic variation and adaptability. There are some great perks to sexual reproduction from an evolutionary perspective. It permits genetic blending that opens the way for novel traits.

Basic Concepts of Sexual Reproduction

Some of the basic concepts of sexual reproduction:

Gametes

• Sperm: Small, motile, and provided with a flagellum to enable it to move from the site of origin within the female's body.

• Egg: Relatively large, immotile, and furnished with nutrients necessary for the development of a zygote.

Gametogenesis

• Spermatogenesis: The production of sperm in the testes.

• Oogenesis: The production of eggs in the ovaries

Fertilisation

• It is the process of identification and subsequent fusion of membranes of the sperm and egg cells.

• It guarantees that both parents mix genetic material.

Formation of Zygote

• The zygote which has been formed divides and differentiates into an offspring.

Modes of Sexual Reproduction

Sexual reproduction is diversified and standard in so many ways that it is categorised into a variety of modes, all of which are classified based on different types of criteria.

Isogamy vs Anisogamy

• Isogamy has morphologically similar gametes.

• Anisogamy, morphologically different gametes in which formation for instance sperm and egg.

Internal vs External Fertilisation

• Internal Fertilization is a process of fertilisation, which occurs inside the female's body.

• External Fertilization occurs outside of the female's body and is common in water sources.

Examples Across Organisms

• Angiosperms utilise pollen and ovules.

• Birds, mammals, reptiles, amphibians, and fish all have special reproductive strategies.

Sexual Reproduction In Plants

Sexual reproduction in plants utilises structural modifications and complicated processes that lead to seed and fruit formation.

Floral Components

• Sepals, petals, stamens (male), and carpels (female).

Functions

• To attract their pollinators

• Produce gametes

• Facilitation of fertilisation

Self-Pollination versus Cross-Pollination

• Self-pollination: The pollen fertilises ovule of same plant

• Cross-pollination: The pollen from one plant fertilises another

Sexual Reproduction In Animals

Sexual reproduction in animals covers a broad spectrum of reproductive systems and strategies.

Reproductive Systems

• Males: Testes, vas deferens, prostate, and penis.

• Females: Ovaries, fallopian tubes, uterus, and vagina.

Hormonal Regulation

• Hormones like testosterone, estrogen, and progesterone regulate reproductive functions.

Gestation And Birth (Mammals)

• Gestation occurs when the embryo develops in the uterus.

• Birth marks the arrival of a complete human being.

Development Stages

• Zygote, blastocyst, embryo, and fetus, with sources of variation in development across fetal age.

Genetic Variation and Evolution

Sexual reproduction leads to genetic variation, which makes evolution possible.

How Variation Is Generated

• Crossing over generates new combinations of genes in offspring.

• Crossing over during meiosis, independent assortment of chromosomes, and fertilisation.

Evolutionary Significance

• Novel traits arise

• Natural selection acts on variation

Advantages of Sexual Reproduction Over Asexual

Advantages of sexual reproduction over asexual are:

• Higher genetic diversity

• Advanced adaptability

• Higher evolutionary potential

• Better resistance to environmental constraints.

Sexual Reproduction NEET MCQs (With Answers & Explanations)

Important questions asked in NEET from this topic are:

• Sexual reproduction in plants

• Sexual reproduction in animals

Practice Questions for NEET

Q1. In the embryos of a typical dicot and a grass, true homologous structures are:

1. Coleorhiza and coleoptile

2. Coleoptile and scutellum

3. Cotyledons and scutellum

4. Hypocotyl and radicle

Correct answer: 3) Cotyledons and scutellum

Explanation:

In monocot, the cotyledon is called scutellum. In monocots, the cotyledon called the scutellum, serves as a specialized structure for storing and absorbing nutrients during seed germination. It is typically smaller and more shield-like compared to the cotyledons of dicots. The scutellum is located next to the embryo and is crucial for the early growth of the seedling. During germination, the scutellum absorbs nutrients from the endosperm, aiding in the development of the embryo into a young plant. This adaptation allows monocots, such as grasses and cereals, to efficiently utilize stored food reserves for initial growth.

Hence, the correct answer is the option (3) Cotyledons and scutellum.

Q2. The male gametes of rice plant have 12 chromosomes in their nucleus.The chromosome number in the female gamete, zygote and the cells of the seedling will be, respectively,

1. 12, 24, 12

2. 24, 12, 12

3. 12, 24, 24

4. 24, 12, 24

Correct answer: 3) 12, 24, 24

Explanation:

For plants, gametes are haploid, meaning that they have half the number of chromosomes compared to their diploid condition. For example, if a gamete had a haploid number of 12 chromosomes, at the time when the gametes fuse during fertilization to form a zygote, the latter will have the diploid number of 24 chromosomes. The plant's somatic cells retain this diploid number, which keeps the chromosome count at 24 both in the zygote and the mature plant.

Hence, the correct answer is Option 3) 12, 24, 24.

Q3. Birth canal is formed during parturition by female accessory ducts namely

1. Uterus and cervix

2. Cervix and labia majora

3. Cervical canal and vagina

4. Oviduct and uterus

Correct answer: 3) Cervical canal and vagina

Explanation:

Just before parturition, the cervix undergoes significant changes to prepare for childbirth. Under the influence of the hormone relaxin, secreted primarily by the placenta and ovaries, the cervix becomes soft, and elastic, and dilates to allow the baby to pass through. This softening is accompanied by the widening of the cervical canal, which, along with the vagina, forms the birth canal—the pathway through which the baby is delivered. These physiological changes are critical for ensuring a smooth delivery process, as they reduce resistance and create a passage wide enough for the baby to pass through safely.

Hence, the correct answer is option 3) Cervical canal and vagina.

Also Read:

• MCQs on Sexual Reproduction

• Difference Between Sexual and Asexual Reproduction

• Morphallaxis

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