Main content
Course: Class 12 Biology (India) > Unit 1
Lesson 3: Sexual ReproductionTypes of reproduction review
Key Terms
| Term | Meaning |
|---|---|
| Sexual reproduction | Process of creating new individual using two parent organisms |
| Asexual reproduction | Process of creating new individual using one parent organism |
| Offspring | New organism that results from reproduction |
| Gamete | Sex cell (in males: sperm; in females: eggs) |
| Fertilization | The joining of gametes to form a new organism |
| Zygote | Cell formed during the fusion of two gametes |
Types of reproduction
There are two major forms of reproduction: sexual and asexual.
Sexual reproduction
Sexual reproduction requires two parents. Each parent contributes a gamete - a sex cell that has half of the normal DNA of a regular body cell. In males, the gametes are sperm and in females, the gametes are eggs.
When these two gamete combine during fertilization, the result is a zygote, which then continues to develop into an embryo.
Asexual reproduction
Asexual reproduction requires only one parent.
There are many types of asexual reproduction. Four major types are:
1) Binary fission: Single parent cell doubles its DNA, then divides into two cells. Usually occurs in bacteria.
2) Budding: Small growth on surface of parent breaks off, resulting in the formation of two individuals. Occurs in yeast and some animals (like the hydra below).
3) Fragmentation: Organisms break into two or more fragments that develop into a new individual. Occurs in many plants, as well as some animals (like coral, sponges, and starfish).
4) Parthenogenesis: An embryo develops from an unfertilized cell. Occurs in invertebrates, as well as in some fish, amphibians, and reptiles.
Comparing sexual vs asexual reproduction
| Sexual | Asexual |
|---|---|
| Requires 2 parents | Requires 1 parent |
| Sperm fertilizes egg | Single organism makes an exact copy of itself |
| Used by animals, flowering plants, some fungi | Bacteria, some plants and fungi, few animals (sponges) |
| Offspring are different from parents | Offspring are identical to parent |
| Provides genetic variation, but time-consuming | Fast and easy, but no genetic variation |
Common mistakes and misconceptions
- Sexual reproduction is not necessarily "better" than asexual reproduction, or vice versa. If one type of reproduction was clearly advantageous over the other, we would see all organisms reproducing in that manner. However, both types of reproduction still exist in various organisms, telling us that each type of reproduction carries some kind of evolutionary advantage.For example, sexual reproduction allows for variation, but gestation usually takes a long time and it requires heavy parental input. Asexual reproduction occurs quickly, but because all of the offspring have the same genetic information, individuals are more susceptible to disease.
- Budding and fragmentation are not the same thing. Although they do appear similar, in fragmentation, the parent body breaks into distinct fragments and each fragment develops into a new individual or offspring. In budding, there must be an outgrowth (bud) that develops on the parent.
- Some organisms are able to do both sexual and asexual reproduction. This is particularly true for fungi and plants (and rarely, animals - as in parthenogenesis). Often, the type of reproduction that they undergo depends on their environmental conditions or the point in their growth cycles.
- Although sexual reproduction requires two parents, they do not always have to be two separate individuals. This may sound confusing, but some organisms are hermaphroditic, meaning they contain both male and female gametes. In this instance, those organisms are able to self-fertilize. Despite the fact that these gametes come from the same individual, we still consider this sexual reproduction, as two gametes are involved.
Want to join the conversation?
In a hermaphroditic situation, is it similar to asexual reproduction in terms of variation in genetic information?(19 votes)
from what i understand of this. . It is a sexual mode of reproduction,since both of genitals are present and technically it is a variation and can mostly happen in sexual reprod. while in parthenogenesis it is inherently present and all the offsprings are considered female as we call it.(2 votes)
what is a sperm(7 votes)
Sperm is a male gamete(sex cells of an organism). It has three parts- a head, a middle piece and a tail. Head contains all the cytoplasm, cell membrane and nucleus. The middle piece contains mitochondria which contains ATP. The tail is for locomotion.(21 votes)
Can humans reproduce through Parthenogenesis.(3 votes)
Yes and no. It usually results in tumors called teratomas and abnormal fertilized eggs called hydatidiform moles. It happens in females from what I know, I haven't seen any males. In the sense of true parthenogenesis- no.(17 votes)
what are parthenogenesis(3 votes)- reproduction from an ovum without fertilization, especially as a normal process in some invertebrates and lower plants.(15 votes)
parthenogenesis occurs in some invertebrates, as well as in some fish, amphibians, reptiles. is it related to them being cold blooded?(8 votes)- What causes parthenogenesis to occur in a species?
In certain insects, salamanders, and flatworms, the presence of sperm serves to trigger parthenogenesis. Sperm cells launch the process by penetrating the egg, but the sperm later degenerates, leaving only the maternal chromosomes. In this case, sperm only sparks an egg's development––it makes no genetic contribution.(5 votes)
- How do yeast cells reproduce? Is that budding?(7 votes)
When cells divide, they make new cells. A single cell divides to make two cells and these two cells then divide to make four cells, and so on.(4 votes)
How is yeast different from bacteria?(5 votes)- yeast is a uni-cellular(kingdom) Fungus while bacteria are bacteria mean they belong to Kingdom Monera.(7 votes)
Does asexual reproduction require DNA similar to how sexual reproduction requires it?(5 votes)
Yes, both require DNA. While there are some viruses which only have RNA, they're still not living. A big part of the reason they don't count as alive is because in order to replicate themselves, they need a host (so this doesn't count as reproduction).(5 votes)
- so would a beluga whale reproduce sexually?(4 votes)
Yes it does because beluga whale is mammal and their reproduction process includes the fusion of the male gamate (sperm) and female gamate (egg), which is according to the definition of sexual reproduction.(6 votes)
So for the Fragmentation reproduction (For instance a starfish that gets a part cut off resulting in a new starfish) that would have the same exact DNA as the original starfish right?(4 votes)
Yes. Right idea but I think a better example would be propagating a plant cutting. That is a clone of the parent plant with the same D.N.A.(3 votes)