1. Testing only one variable
A controlled variable means its the one that stays the same. In a controlled experiment, it means there is only one manipulated, (changed) variable.
Well, when chromosomes cross over during prophase 1 of meiosis, the homologous pair of chromosomes exchange segments of DNA which happen to be the genes. So the significance of crossing-over during prophase 1 is that it adds genetic variation to sexually reproducing organisms.
Answer:
Explanation:
1. Which chamber receives blood from all the body veins?
= Right atrium
2. The blood passes from this chamber into the ...
= Right ventricle
While this is happening, the valve between the right atrium and right ventricle is (open OR closed)
= open
3. The blood in the right ventricle is high in (oxygen OR carbon dioxide)
= carbon dioxide
4. The body (can OR cannot) and low in (oxygen OR carbon dioxide) use this blood.
= cannot
= oxygen
5. Where must this blood go to get a fresh supply of oxygen?
= lungs
Hope this helps!
We would need to see the insect mouth to help you
