Answer: The oxygen content at the source of the streams or rivers is higher as compared to the mouth of the river. Consequently, the organisms which require more oxygen tend to find at the source of the rivers whereas the organisms which require less oxygen tend to find at the mouth of the river.
Explanation:
Chemical factors: This is due to internal stimuli. Changes in the blood such as decrease in O2, increase in CO2 and decrease in PH cause impulse in the carotid artery which stimulates the respiratory centers in the medulla and cause breathing.
Mechanical factors: also called external stimuli. Compression of the fetal chest during delivery forces small amount of lung fluid out of the lungs. This increase in pressure in the chest draws air into the lungs.
Th polluting oh the ocean is a big concern for people because the animals the some people depend on for food are being killed.
Answer:
1. dna needs to be replicated before mitosis so that the parent cell has the same amount of genetic material as the parent cell once it has split.
2. helicase is an enzyme that is so dna can unwind.
Explanation:
the explanation is in the answer.
I hope this helps!
