Lesson 8 ·Class 10 · The Reproductive System · Sort Lab
Parturition and Twins
One egg or two? The whole difference is right there
One egg or two? Sort each fact into the right kind of twin.
Sorted 0/8
All items sorted — check each bin.
VS
Free play — sort every item into the bin it belongs in; each correct drop tells you why. Switch to when you're ready to test yourself.
Parturition is the act of expelling the full term foetus from the uterus at the end of gestation, which lasts about 280 days. The baby is pushed out head first by powerful contractions of the uterine muscles, and about 15 minutes later the placenta breaks away and is expelled as the after-birth.
What this lesson covers
What you do
- Triplets may come from one zygote splitting into two with one of those parts splitting again, or from two eggs where one zygote gives identical twins and the other develops into a single baby.
- The newborn announces its arrival with a sharp cry. That cry is nature's way of clearing the baby's respiratory passage.
Challenges to clear
- Sort all eight facts.
- Fill the identical twins column.
- Fill the Fraternal twins column — two eggs, two sperms, two separate stories.
The task
One egg or two? Sort each fact into the right kind of twin.
What this lesson covers
- Identical twins — One egg, split in two: A single fertilised egg splits into two parts during early cell division (Each split part then behaves like an independent egg and produces one complete individual, so both come from one zygote.); Always either both boys or both girls (Both individuals came from the same fertilised egg, so the sex was already decided once, for both of them.); Very similar to each other in appearance (Being produced from a single egg, they carry the same genetic material, which is exactly why they are called identical.); Fingerprints, birth marks and even handwriting are still not the same (Selina is careful here: they are identical in most respects, but not in all. This is a favourite one-mark question.)
- Fraternal twins — Two eggs, two zygotes: Two eggs are released at a time and both get fertilised (Two ova and two zygotes give two separate individuals, which is why they are also called diovular or dizygotic.); May be both boys, both girls, or one boy and one girl (Two separate fertilisations mean the sex of each is decided independently, so any combination is possible.); About 75 per cent of all cases of twins (This is the figure Selina gives. Fraternal twins are by far the commoner of the two kinds.); In all respects like ordinary sisters and brothers, only of the same age (They came from two different eggs, so they are no more alike than any other siblings; they simply happened to be born a few minutes apart.)
Hint
Parturition is the act of expelling the full term foetus from the uterus at the end of gestation, which lasts about 280 days. The baby is pushed out head first by powerful contractions of the uterine muscles, and about 15 minutes later the placenta breaks away and is expelled as the after-birth.