Life Cycle of Sexual Reproducers - Online Tutor, Practice Problems & Exam Prep

The life cycle of sexual reproducers involves both mitosis and meiosis. Meiosis produces haploid gametes—sperm in males and eggs in females—each containing half the number of chromosomes. Fertilization occurs when these gametes merge to form a diploid zygote, the first cell of a new organism. This zygote undergoes mitosis, developing into a multicellular baby, which matures into a diploid adult. Understanding meiosis is crucial for grasping how genetic diversity arises in sexual reproduction.

Life Cycle of Sexual Reproducers

In this video, we're going to talk about the life cycle of sexual reproducers. The life cycle of sexual reproducers includes both mitosis, which we covered in our previous lesson videos, and meiosis as well. Once again, mitosis and meiosis sound very similar. They have some similarities, but at the same time, they're still very different from each other. Moving forward in our course, we're going to talk more and more about meiosis. Meiosis is the form of eukaryotic cell division that produces haploid gametes. Gametes is the scientific term for sex cells, either sperm cells in males or egg cells in females.

If we take a look down below at our image at the human life cycle, notice up above here we have these adults. These adults can undergo the process of meiosis to create these gametes. The gametes again are going to be the sex cells, either sperm cells in males or egg cells in females. Notice that the sperm cells and egg cells are haploid, which is being represented by the letter n here in this image. Recall that haploid means that they have half the number of chromosomes or just one copy of every gene or chromosome.

The next step in the sexual life cycle here of the human sexual reproducing life cycle is that these gametes, the sperm and the egg, are going to merge together in this process that's called fertilization. Fertilization is the process of merging the gametes together, basically the sperm and egg fusing together to create a single cell called a zygote. This single-celled zygote is really the very first cell, the very first diploid cell or 2n cell of the new developing organism where mitosis is going to start.

If we take a look at our image down below, we can see that the process of fertilization here includes the sperm fusing with the egg. Of course, both the sperm and egg are haploid so they have half the number of chromosomes, just one copy of every chromosome. But when they fuse together, they create a single cell called a zygote which is now diploid. It has two copies of every chromosome, where one of the copies of the chromosome was inherited from the father's sperm and the other copy of the chromosome was inherited from the mother's egg.

This diploid zygote can begin to divide by the process of mitosis, which we already covered in our previous lesson videos, allowing the single-celled zygote to develop into a baby with trillions of cells. Notice that the baby is a diploid organism here. The baby can continue to develop into a fully mature adult, either male or female, which the human adults are also going to represent diploid organisms.

Really, it's just this process of meiosis that we're going to talk more and more about moving forward that allows these adults to create gametes, the sex cells either sperm in males or eggs in females. This here concludes our introduction to the life cycle of sexual reproducers, and once again, we'll be able to talk more and more about the process of meiosis as we move forward in our course. So I'll see you all in our next video.

All eukaryotic sexual life cycles include:

a) Mitosis, gamete formation, and fertilization.

b) Mitosis, meiosis, gamete formation, and fertilization.

c) Mitosis, meiosis, and gamete formation.

d) Mitosis, fertilization, and meiosis.

e) Mitosis, meiosis, apoptosis.

f) Gamete formation, meiosis, mitosis.

• A. Mitosis, gamete formation, and fertilization.
• B. Mitosis, meiosis, gamete formation, and fertilization.
• C. Mitosis, meiosis, and gamete formation.
• D. Mitosis, fertilization, and meiosis.
• E. Mitosis, meiosis, apoptosis.
• F. Gamete formation, meiosis, mitosis.

Here’s what students ask on this topic:

What is the difference between mitosis and meiosis in the life cycle of sexual reproducers?

Mitosis and meiosis are both forms of cell division, but they serve different purposes in the life cycle of sexual reproducers. Mitosis results in two genetically identical diploid cells, maintaining the chromosome number of the original cell. It is crucial for growth, development, and tissue repair. Meiosis, on the other hand, produces four genetically diverse haploid gametes (sperm in males and eggs in females), each containing half the number of chromosomes. This reduction is essential for sexual reproduction, ensuring that when gametes fuse during fertilization, the resulting zygote has the correct diploid chromosome number.

How does fertilization contribute to genetic variation in sexual reproducers?

Fertilization contributes to genetic variation by combining the genetic material from two different gametes—sperm and egg. Each gamete is haploid, containing one set of chromosomes, which are a mix of the parent's genetic material due to the process of meiosis. When these gametes merge, they form a diploid zygote with a unique combination of genes from both parents. This genetic recombination during fertilization increases the genetic diversity of the offspring, which is crucial for the adaptability and evolution of species.

What role does meiosis play in the life cycle of sexual reproducers?

Meiosis plays a critical role in the life cycle of sexual reproducers by producing haploid gametes—sperm in males and eggs in females. This process involves two rounds of cell division, reducing the chromosome number by half. Meiosis ensures genetic diversity through mechanisms like crossing over and independent assortment. The resulting gametes are genetically unique, which, upon fertilization, combine to form a diploid zygote. This zygote undergoes mitosis to develop into a multicellular organism, maintaining the species' chromosome number across generations.

What is a zygote and how is it formed in sexual reproduction?

A zygote is the initial cell formed when two gametes (sperm and egg) merge during fertilization in sexual reproduction. Both gametes are haploid, containing half the number of chromosomes. When they fuse, they create a diploid zygote with two sets of chromosomes—one from each parent. This zygote is the first cell of a new organism and undergoes mitosis to develop into a multicellular organism. The formation of the zygote is crucial as it marks the beginning of a new individual's life cycle, combining genetic material from both parents.

Why is genetic variation important in the life cycle of sexual reproducers?

Genetic variation is vital in the life cycle of sexual reproducers because it enhances the adaptability and survival of a species. Variation arises from meiosis, where processes like crossing over and independent assortment shuffle genes, and from fertilization, which combines genetic material from two parents. This diversity allows populations to adapt to changing environments, resist diseases, and avoid the negative effects of inbreeding. It is a key driver of evolution, enabling species to evolve over time and maintain healthy, resilient populations.