The gradualist population theory states that genetic change in a population occurs extremely slowly, over a long period of time. however, the catastrophist theory claims that populations may change drastically over a short period of time, due to catastrophic events like large-scale natural disasters. the theory is a sort of hybrid of the two above, and it contends that long stretches of incremental evolution are interspersed with short periods wherein drastic evolutionary changes occur. a) uniformist b) intermittent burst c) catastrophe-bottleneck d) punctuated equilibrium

The answer is D. Punctuated equilibrium theory stipulates that species remain unchanged (or change minimally) over long period of time until a short period of rapid changes probably due to sudden changes in the environment or adverse events. It is the main principle behind cladogenesis

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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.