The earth has always had oxygen in the atmosphere.

a) true
b) false

the right answer is a. skin cells forming from sunlight.

the liver is an organ endowed with a fantastic ability to regenerate

. thus, if a hepatectomy (ablation) of 70% of the hepatic mass is performed in the rat, there is complete recovery in 7 to 10 days.

prokaryotes are beings that have existed since the existence of life on earth, and do not come from another realm.

ribosomes are organelles that exist naturally in eukaryotes, either in free form or attached to the endoplasmic reticulum.

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after receiving a stimus, the sensory receptors send(s) signals to the appropriate area of the body.  

the must be sensory neurons.  

hope its .

wha is what i will use to get my free points