Which of the following is an example of a human-caused disturbance to an ecosystem?

a. a tsunami destroys a coastal forest and causes flooding.
b. a river is diverted to irrigate farmlands during a drought.
c. after a volcanic eruption, global average temperature lower.
d. the snow cover of a region grows and shrinks throughout the year.

FURTHER EXPLANATION

FALSE A tsunami is a natural occurrence. It is a result of underwater earthquakes, landslides, or meteorite impacts that shakes and disturbs the ocean water violently. While human activity can contribute to landslides, the movement of tectonic plates is still largely beyond human control or influence.

TRUE Irrigation provides water in controlled amounts for the growth of agricultural crops. Having an irrigation system during a drought is beneficial since the water is delivered to crops in a manner and pattern that is deemed most efficient for plant growth. Diverting the water from rivers to farmlands is definitely a human-caused disturbance to the ecosystem. Areas where the river used to flow will have organisms that are dependent on plentiful water supply. When the water no longer flows to that area, plants and animals that  are reliant on the river will have to search for a new water supply or will simply dry up due to absence or lack of sufficient water.

FALSE. As with tsunamis, volcanic eruptions are beyond human influence. Volcanic eruptions result from the build up of gas pressure inside the volcano. Increased gas pressure may propel magma to the surface or cause it to flow quietly as lava on the sides of the volcano.

FALSE. Snow cover melting and growing results from the variations in temperature throughout the year and is a natural occurrence. Humans may have an indirect effect on the melting of snow cover, but growing and shrinking of snow cover still largely remains as something directly related to the global temperatures.

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Keywords: irrigation, ecosystem, disturbance

"menstrual cycle is a complex cycle that consists of several processes. order of occurrence of steps in menstrual cycle are as follows:

1. high progesterone levels maintain the endometrium lining of the uterus.

2. endometrium lining breaks down and low levels of estrogen stimulate the pituitary to release fsh and lh.

3. fsh and lh stimulates the follicles to develop and the oocyte to produce estrogen.

4. rising estrogen levels suppress fsh production and development of other follicles.

5. a spike in lh causes follicle to rupture.

6. a breakdown of corpus luteum causes progesterone level to drop."