If the inner lining of the air sacs neither thin nor highly vascularized, then it can be inferred that AIR SACS ARE CANNOT BE THE SITES OF GASEOUS EXCHANGE BETWEEN AIR AND BLOOD. Air sacs are generally lined with mucus and surrounded with blood capillaries.
In case of birds, air sacs play an important role in respiratory system.
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Low levels of estrogen is a sign that the ovaries of a woman are beginning to fail. This is a common occurrence when one is at menopausal stage. Estrogen and progesterone naturally decrease and eventually stops the menstrual cycle. Hope this helped.
Answer:ovary develops into fruits
Explanation: fertilization occur after the fusion of a haploid male and female gametes to give a diploid zygote. The male sperm fuses with the female egg in the ovule to give an embryo. For angiosperms the male sex cell is located in the pollen in the anther which is carried to the stigma where the female sex cell is located either of the same plant or different plant. For gymnosperms the male pollen is found in the cone from where it is then transfer to the female cone. The ovule developed into the seeds after fertilization and the ovary develops into fruits.