Answer: b. Water molecules
When sunlight is absorbed by one of many pigments present in photosystem II the light energy is distributed from pigment to pigment until it reaches the reaction center of photosystem II. The electrons present in the reaction center jumps to higher energy state on receiving light energy. Each high energy electron is passed to an acceptor molecule (plastoquinone) and replaced with an electron produced by splitting of water. The splitting of water produces oxygen and electrons. The high energy electrons are transferred to electron transport chain. The energy present in these electrons creates a gradient in the thylakoid membrane of chloroplast. The gradient facilitates the flow of H⁺ ions across thylakoid membrane and which lead to the production of ATP by enzyme ATP synthase.
Therefore, water is required to produce electrons in photosystem II.
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I would have to say C but not sure
<span>Answer: optio b. Healthy ecosystems. The other three options design trheatens on biodiversity because invasive species, climate change and pollution may kill many species that cannot adapt to a sudden change and will benefit a reduced number of species that can adapt and survive. Healthy ecosystems promote biodiversity, so it is a value.</span>
Answer:
Water erosion refers to the removal of the top most or surface layer of soil by the flow of water. The long term effect of water erosion can be because of drastic rain fall and may be because of flood. These two reasons can adversely effect the human life. The water erosion is responsible for the removal of fertile layer of soil, therefore, the region will not be appropriate to grow vegetation. The long term effect may result in stagnation of water, therefore, long time is required so that the region gets dried. The long term accumulation of water over an agricultural field can spoil the crop production.
Prevention that can be taken to reduce long term effect of water erosion:
1. Plantation of long root bearing trees over flood prone regions and around the agricultural field: This will allow the trees to tightly hold up soil and prevent it's erosion.
2. Add rocks over the soil: In an agricultural field or flood prone area, the rocks will act as barrier for the movement of run off water, hence, will prevent water erosion. It will increase the absorption of water by soil.
3. Building of walls: This will also act as a barrier in a flood prone region and will prevent the water being added up to the agricultural land.
4.Remove soil compaction: If the soil compaction of the effected region is removed, the water retention property of the soil can be improved. Machines, animals and humans can be used for this purpose to remove the compaction of upper layer of soil.