Parthenogenesis: Definition, Types, Facts, Introduction, Significance, Topics

What Is Parthenogenesis?

Parthenogenesis refers to the kind of reproduction in which the development of offspring occurs from an unfertilized egg. With this process, one is in a position to come up with offspring without the involvement of male gametes. All the offspring resulting from parthenogenesis are genetically identical to the parent. This occurs in different species of the animal and plant kingdom, and it has its associated advantages as well as disadvantages.

Features Of Parthenogenesis

• Asexual Reproduction: Parthenogenesis is a kind of asexual reproduction since it doesn't include the fusion of male and female gametes.

• Genetic Uniformity: All the progeny achieved through parthenogenesis are similar to the mother and are genetically identical. Parthenogenesis occurs in many organisms, including some insects like aphids, reptiles like certain lizards, and plants.

• Environmental Triggers: Parthenogenesis can also be induced by environmental cues, such as the absence of males or adverse conditions for fertilisation.

Also Read:

• Sexual Reproduction In Plants

• Asexual Reproduction in Animals

• Sexual Reproduction in Animals

Types Of Parthenogenesis

There are several types of parthenogenesis: obligate parthenogenesis, wherein it is the only way of reproduction; and facultative parthenogenesis, wherein it may happen in the absence of males, but sexual reproduction is also possible. Types of Parthenogenesis Parthenogenesis can be broadly classified into many types based on the involved mechanisms.

1. Obligate Parthenogenesis

In obligate parthenogenesis, the species only reproduces through parthenogenesis; there is no sexual reproduction. This happens in specific aphid species and some reptiles.

2. Facultative Parthenogenesis

In facultative parthenogenesis, a population can reproduce both sexually and asexually. For example, some female lizards can reproduce through parthenogenesis when males are absent.

3. Cyclic Parthenogenesis

Cyclic parthenogenesis refers to the alternating production of sexual and asexual offspring depending on environmental conditions. This can be explained by some species of aphids that reproduce sexually when conditions are favourable and then switch to parthenogenesis when the going gets hostile.

Mechanisms Of Parthenogenesis

Parthenogenesis can occur through different biological mechanisms that determine whether the offspring are clones or have some genetic variation. Parthenogenesis may result from several mechanisms, which include the following:

• Automixis

In automixis, the egg undergoes a meiosis process, but some of the cells fuse to restore the diploid state. It could donate some degree of genetic diversity to its offspring.

• Apomixis

Apomixis is when an embryo develops directly from the egg cell without stages of meiosis. Offspring produced are identical to their mother's characteristics.

Examples Of Parthenogenesis

Parthenogenesis is seen in many living organisms, like insects, reptiles, and plants. In these organisms, females can produce offspring without fertilisation. This helps them reproduce quickly and survive in harsh conditions. Below are some common examples of parthenogenesis in nature.

Insects- Parthenogenesis is common in many insects, as in aphids and some species of bees. For instance, the females of aphids give rise to offspring without mating, and the populations exhibit high growth rates.

Reptiles- Some reptiles, such as the Komodo dragon and the whip-tailed lizards, have parthenogenesis, where females produce healthy offspring without the participation of males.

Plants- Some angiosperms, such as dandelions and some species of ferns, can naturally develop seeds without fertilisation through parthenogenesis.

Advantages Of Parthenogenesis

Parthenogenesis has many advantages for survival and growth. It helps organisms reproduce quickly and without needing a mate. Some of the advantages are given below:

1. Rapid Population Growth: It can bring about an increase in population quickly when males are lacking in a particular environment.

2. Genetic Uniformity: The daughter organisms that emerge are more or less genetically identical to the mother, thus ensuring that positive traits that have developed get passed on.

3. Independence from Mates: Parthenogenesis is a means of reproduction without males and, in very adverse or isolated conditions, may be useful.

Disadvantages Of Parthenogenesis

Parthenogenesis has some drawbacks. It reduces genetic variety, which can make it hard for organisms to survive changes in the environment. Below are some disadvantages given:

1. Lack of Genetic Diversity: Offspring formed will have almost similar genetic material, making them be affected almost similarly by various diseases or changes in the environment.

2. Adaptability: Since the offspring produced are genetically similar; therefore, the population may face difficulty adapting to changes in the environment.

3. Inbreeding Potential: Since parthenogenesis occurs in some populations in the total absence of sexuality, inbreeding is possible, reducing general fitness.

MCQS on Parthenogenesis

Question 1: In some plants, the female gamete develops into embryo without fertilization. This phenomenon is known as:

1. Autogamy

2. Parthenocarpy

3. Syngamy

4. Parthenogenesis

Answer: When female gamete does not undergo fertilisation and gets developed into embryo the process is called parhenogenesis.It occurs in some plants and many animals.

E.g., rotifers, honeybees, and even some lizards and birds (turkey).

• Parthenocarpy is the formation of fruits without fertilization.

• Autogamy refers to self-pollination.

• Syngamy refers to the physical union of a male and female gamete.

Hence, the correct answer is option 4) Parthenogenesis.

Question 2: In some species, parthenogenesis may alternate with sexual reproduction This process is called

1. Complete parthenogenesis

2. Incomplete or cyclic parthenogenesis

3. Both the above

4. None of the above

Answer: In incomplete or cyclic parthenogenesis, organisms alternate between sexual reproduction and parthenogenesis depending on environmental conditions or season. This is commonly observed in aphids, rotifers, and some insects. Complete parthenogenesis occurs when the entire life cycle proceeds without fertilization (e.g., some wasps).

Hence, the correct answer is option 2) Incomplete or cyclic parthenogenesis

Question 3: The parthenogenic organisms are following

1. Rotifers

2. Honey bee

3. Lizard and turkey bird

4. All of these

Answer: Parthenogenesis—In a few organisms, the female gamete undergoes development to form new organisms without fertilisation.

E.g., rotifers, honeybees, and even some lizards and birds (turkey).

Hence, the correct answer is option 4) All of these

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