The diagram shows an alveolus. blood from alvoolus
blood to alveolus
(4)
AIR
blood capillary
(a)
© Label structure M on the diagram above
(1) Name gas Y shown on the diagram above,
(h) Explain how gas X passes from the alvoolus into the blood capillary
121
(2)
(1)

the level of progesterone is low at the pre-ovulatory phase of the cycle but it gradually increases and the levels are high at the luteal phase. if pregnancy occurs, the level of progesterone will be high throughout the pregnancy.

if egg is fertilized and the mother gets pregnant, progesterone starts preparing the uterus for the implantation. it starts building up the lining of uterus and make it hostile of the period of pregnancy.

the fossil record provides evidence of a common ancestor to many species.

the most common type of reef is the fringing reef. this type of reef grows seaward directly from the shore. they form borders along the shoreline and surrounding islands.