Context:
Recently, an aquarium Stingray got pregnant without mate.
Parthenogenesis:
- Also known as ‘virgin creation’.
- A rare and natural form of asexual reproduction where an embryo develops from an unfertilized egg (i.e a female produces an embryo without fertilization by a male’s sperm)
- An egg produced may be either haploid (one set of dissimilar chromosomes) or diploid (a paired set of chromosomes).
- It has been observed in more than 80 vertebrate species, including California condors and a crocodile.
- Many species of sharks and rays are also capable of this.
- Parthenogenic species may be –
- Obligate – Incapable of sexual reproduction
- Facultative – Capable of switching between parthenogenesis and sexual reproduction depending upon environmental conditions
Round stingray, has never been reported to give birth this way and thus it will be the 1st such incidence if confirmed.
Types of Parthenogenesis:
- Haploid parthenogenesis –
- A rare form of parthenogenesis that occurs in a few species of offspring to develop from haploid eggs to produce haploid adults.
- Happens in – Bees, nematodes, and plants.
- Diploid parthenogenesis –
- When an unfertilized diploid egg is developed into a new individual directly without any meiotic division
- Two types are – Automixis and Apomixis
Automixis:
- Also known as automictic parthenogenesis
- Process by which a mammal can undergo virgin birth
- A postmeiotic process in which a haploid cell may either duplicate its chromosomes or join with another haploid cell.
Apomixis:
- Also known as apomicitic parthenogenesis
- A process where the egg is fertilised with cells from the mother rather than by a male.
- A smaller cell known as a “polar body,” which forms at the same time as the egg and contains DNA similar to the mother’s, merges with the fertile egg.
- The offspring’s are similar to the mother but not exact clones.
- It is more common in low-density populations, such as those on the verge of extinction.
Source: Deccan Herald
Previous Year Question
Which of the following statements are correct regarding the general difference between plant and animal cells?
1. Plant cells have cellulose cell walls while animal cells do not.
2. Plant cells do not have a plasma membrane, unlike animal cells which do.
3. Mature plant cell has one large vacuole whilst animal cell has many small vacuoles.
Select the correct answer using the code given below:
[UPSC Civil Services Exam – 2020 Prelims]
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer: (c)
Explanation:
Statement 2 is not correct:
The plasma membrane is present in both plant cells and animal cells.
