The correct answer is that mammals use a closed, double loop , four chambered heart as a circulatory system of the body.
The circulatory system of mammals is closed system that consists of four chambers, two articles and two ventricles. The deoxygenated blood comes into the heart from one loop and the oxygenated blood from other loop from the heart is circulated to the whole body. This is called as double circulation.
Answer:
In the mentioned scenario, norepinephrine and acetylcholine are the neurotransmitters, which would have been present at the higher concentrations in Sean's brain. Norepinephrine signifies to a neurotransmitter that plays an important part in dreaming, emotions, sleeping, attentiveness, and learning.
It also gets released in the bloodstream as a hormone, where it augments the rate of heart and causes the blood vessels to contract. Another neurotransmitter called acetylcholine signifies the chemical that is released by the motor neurons to instigate the muscles.
CAM plants keep stomata closed in the daytime, thus reducing loss of water. They can do this because they - fix 
into organic acids during the night.
The correct option is a.
As an adaptation to dry environments, certain plants developed a carbon fixation mechanism known as crassulacean acid metabolism, or CAM photosynthesis, which enables a plant to photosynthesize during the day but only exchange gases at night.
During the day, the malate is transferred to chloroplasts where it is transformed back to 
, which is then utilised during photosynthesis. At night, the is stored as the four-carbon acid malic acid in vacuoles. The enzyme RuBisCO is surrounded by a concentration of pre-collected , which improves photosynthetic efficiency. Plants in the Crassulaceae family were the ones that initially revealed this process of acid metabolism.
To learn more about CAM plant, refer from
brainly.com/question/9292816
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An ecosystem is a community where populations of different species interact with one another and with their non-living environment.
