When a man and a women come together it is called sexual reproduction.
(had to keep it pg for the kids)
its necessary to keep the generations of humans alive. if this doesn't happen the human race will be no more.
There are all kinds of people who have different kinds of kids(skin color and features)
I'd say zoology.
Zoology is the study of animals, generally speaking, and since birds are animals, the study of these fall into the field zoology. The study of birds though, is called ornithology.
Hope it helped,
BioTeacher101
1.other cells
2. Growth, reproduction
4.nucleus
6. It makes 2
10.46
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5. Sex chromosomes
6. XX is female, XY is male
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3.zygote
4. No
The excretory and urinary are not the same because the excretory system is collective for all system performing the function of eliminating waste from the body like excess water,urea, carbon dioxide and lactic acid but the urinary system focuses on removal of excess water and urea from the body