The reason why nost scientists thought that the first true cells formed on Earth were anaerobic is being shown in the second option :B. because there was no oxygen on early Earth. Paying attention to this fact scientists discovered that first cells were prokaryotes and greatest part of them created oxygen as a toxic by-product of their own metabolism which make them understand how the planet was provided with oxygen and made a conclusion that first cells were anaerobic.
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Answer:
The options are not given but they are gotten from another websites.
A. Capillaries surrounding the brain have no pores and are surrounded by membranes of astrocyte cells.
B. Capillaries surrounding the brain have pores and are surrounded by membranes of astrocyte cells.
C. Capillaries surrounding the brain have no pores and are not surrounded by membranes of astrocyte cells.
D. Capillaries surrounding the brain have pores and are not surrounded by membranes of astrocyte cells.
The correct answer is option A.
Capillaries surrounding the brain have no pores and are surrounded by membranes of astrocyte cells.
Explanation:
Capillaries surrounding the brain have no pores and are surrounded by membranes of astrocyte cells because
Capillaries are tiny blood vessels in the circulatory system that connect aterioles to venules. They are the most abundant or they are much blood vessels. They can penetrate the tissues of the body which allow passage of food nutrients, oxygen in the body thereby allowing exchange of nutrients and oxygen between the body tissues and the blood.
Capillaries surrounding the brain have no pores and are surrounded by membranes of astrocyte cells while capillaries in the periphery Capillaries surrounding the brain have pores and are not surrounded by membranes of astrocyte cells.
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