1. TWINS
Many mammal mothers give birth to large litters, but in humans, multiple pregnancies are much less common. Gather together 80 pregnant women and statistically only one will be carrying twins. The odds for bigger broods are eggs-tremely small ー one in 8,000 for triplets, one in 730,000 for quadruplets, and one in 50 million for quintuplets.

2. Mirror Image
Identical twins start off in the same way as a single baby ー an egg is fertilized by a sperm to form an embryo. But this time the embryo divides into two, and each develops into a fetus. The twins share the same genes and look almost eggs-actly alike. They are always the same sex because each inherits the same sex chromosomes (XX for girls, and XY for boys).

3. Womb for Two
Sometimes a woman’s ovaries release two eggs at the same time instead of the usual one. If both of these eggs are fertilized by separate sperm, nonidentical (fraternal) twins form. They can be the same sex or different sexes and are genetically similar as any brother or sister.

4. Identical Twins

5. Nonidentical (fraternal) Twins

6. Nature VS Nurture
Medical eggs-perts regularly recruit twins as research subjects to discover which characteristics are controlled by genes and which features are controlled by upbringing and environment.

7. Scientists look at particular traits ー such as intelligence, height, and food preferences ー to see how identical twins compare to fraternal twins. If the identical twins, with their shared genes, show more similarity than the fraternal twins, that trait is likely to be genetic.

8. Identical Twins Embryo Diagram

9. Fraternal Twins Embryo Diagram

10. Multiple Births
Fertility drugs have led to an increase in the number of large multiple pregnancies. The human womb doesn’t have enough space to accommodate lots of babies, so multiple sets are often born prematurely (early), and sadly, sometimes the babies are too small to survive. Births of sextuplets, septuplets, and octuplets are so rare that they make news around the world.

11. The human womb doesn’t have enough space to accommodate lots of babies, so multiple sets are often born prematurely (early), and sadly, sometimes the babies are too small to survive. Births of sextuplets, septuplets, and octuplets are so rare that they make news around the world.

12. Strange Coincidences
There are eggs-traordinary stories of identical twins separated at births who meet much later and realize that they have led very similar lives.
Continue Next Page to see the impossible story of these twins

13. American twins James Arthur Springer and James Edward Lewis were adopted into different families as babies.
When they were reunited 39 years later, they discovered that they had each married and divorced a women named Linda and remarried a woman named Betty. They both had sons with the same name and both owned dogs named Toy. They had the same hobbies and interests and even had headaches at the same time of the day!

14. So…...
Twins are two animal (including human) offspring that are born from the same pregnancies.
Identical twins share the same genes which come from 1 embryo.
Fraternal twins are fertilized by separate sperm.

15. Did you know? Do you want to know? Amazing Twin Facts
This is Jennifer Lopez
and her twin babies.
They are definitely cute!
Actress Mary-Kate and Ashley
Olsen are well-known fraternal twins.

16. Hope you learned things from my twins project.
P.S: We are lucky to have Yasmin in our class. Now, how about having a twin baby?