They only have one electron in their outer most shell which makes them very reactive.
Because in winter 1 habitat might get too cold so the bird might have to move to a warmer habitat in winter
I say it is all of the above.
Answer:
1. Egg fertilized to form a zygote
2. Cell division in the zygote to form a morula
3. Cell division to form a blastocyst
4. Differentiation of cells in the blastocyst
5. Development of tissues
6. Development of organs
Explanation: