4
votes
3answers
185 views

Are humans the only animal that requires “clean water”?

I've seen a number of animals - dogs, cats, squirrels, ducks and geese, etc drink from puddles, some of them were muddy, others had green flora growing under water. Same goes for lakes and rivers. A ...
6
votes
4answers
1k views

Why we have no enzyme to digest cellulose?

As we know, cellulose is the most abundant polysaccharide in nature. Why don't we have any enzyme to digest cellulose?
6
votes
2answers
512 views

Do animals get sick from eating dirty food or eating off the floor?

Humans have very strict tradition of hygiene, such as washing hands before eating, using utensils, and in general keeping as much distance between food and dirt as possible. At the same time, most ...
1
vote
2answers
632 views

What organs are absolutely needed by the human body?

The title is my question: what organs are absolutely needed (fatal if injured/removed) by the human body and perhaps animals in general? I'm not asking which organs are mechanically replaceable, but ...
2
votes
2answers
235 views

How to know if a woman is fertile without actually making her pregnant?

How to know if a human female is fertile (can give birth to child in future) without making her pregnant? Any signs, tests?
5
votes
1answer
541 views

Is there a relationship between efficiency of cellular metabolism and warm-blooded-ness?

My BIO 101 book states that when human cells convert glucose to ATP, the process is only approx 35% efficient, and much of the potential energy is lost as heat. However, that heat is useful to us in ...
2
votes
1answer
211 views

Why apes started to contemplate and become altruistic? [closed]

I was asking this first on philosophy forums, but it is suggested, that answer could be found from evolutionary view of point, so here we go: Again my question raised when thinking of myths, their ...
5
votes
3answers
1k views

Fetal development, gastrulation and embryonic disc

I am completely confused by the images circulating on the internet of human gastrulation. First, lets see how it happens in deuterostomes. This image depicts the process: (image is from Wikipedia) ...