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.