🧠 What is Parthenogenesis?
Parthenogenesis (from Greek: parthenos = virgin, genesis = birth) is a type of asexual reproduction where a female produces offspring without fertilization — meaning, no sperm is involved.
It’s like the egg starts growing into a baby on its own.
🧬 Where Does It Happen?
You find parthenogenesis mostly in:
Invertebrates like aphids, bees, ants, and some wasps
Reptiles like some lizards, snakes, and geckos
Fish like some sharks and rays
Birds rarely (like in some turkeys)
No natural parthenogenesis in mammals (including humans)
🔬 How Does It Work at the Cell Level?
Normally:
A sperm (n) + an egg (n) fuse to form a zygote (2n)
This zygote grows into a full organism
In parthenogenesis:
The egg either stays diploid (2n) by copying its DNA,or it undergoes a modified meiosis where chromosomes don’t reduce fully
There are 2 types of parthenogenesis:
✅ 1. Apomictic Parthenogenesis (mitotic)
No meiosis
The egg is cloned from the mother
Offspring is genetically identical
Common in some lizards and insects
🧬 Example:Whiptail lizards — whole populations are female!
✅ 2. Automictic Parthenogenesis (modified meiosis)
Meiosis occurs, but the egg restores diploid state
May use a fusion of egg with a polar body (extra cell from meiosis)
Offspring are not identical, but still mostly like the mother
🧬 Example:Some bees, komodo dragons, and sharks use this when males aren’t around.
🐝 Examples of Animals That Use Parthenogenesis:
🐜 Ants & Bees (Haplodiploidy system):
Fertilized egg → female (diploid)
Unfertilized egg → male (haploid)So, males are born from parthenogenesis!
🦎 Whiptail Lizards:
Entire species = all female
Use parthenogenesis to clone themselves
Some even do pseudo-mating (one plays male role) to trigger egg development, but no sperm involved
🦈 Sharks:
Seen in zebra sharks and blacktip sharks
Females alone in aquariums gave birth
Rare, but proves it's possible in vertebrates
🐦 Birds (rare):
Domestic turkeys and chickens can show parthenogenesis, but most embryos die early
⚛️ Why Does It Happen?
✅ Advantages:
No need to find a mate → great for isolated environments
Can rapidly multiply (good in stable conditions)
❌ Disadvantages:
No genetic diversity → can't adapt to changes
Mutations build up → harmful long-term
🧬 Can Parthenogenesis Happen in Humans?
No natural parthenogenesis in humans.
But scientists can artificially activate human eggs in labs, creating embryos without sperm — only used in research, and they do not develop into full humans.
🧠 Key Concepts to Remember:
Parthenogenesis = virgin birth
Egg develops without sperm
Creates clones or near-clones
Common in insects, reptiles, fish
Not sustainable long-term due to low genetic variation.