Peristalsis is a series of wave-like muscle contractions that move food through the digestive tract. It starts in the esophagus where strong wave-like motions of the smooth muscle move balls of swallowed food to the stomach.
Answer:
A is the image that represents the Mid Ocean ridge
Answer:
True
Explanation:
The deep parts of an ocean receive minimal or no sunlight. Hence, the survival of phototropic organisms like plants and algae is impossible or minimal here. Hence, there is a very little diversity in deep oceans. The organisms living here have to feed on dead decaying matter or on each other for survival. Mostly, the organisms living here use dead organisms as food. No other food source is available here.
<u>Answer:</u>
Cyanobacteria start producing pure oxygen around 200 million years ago.
<u>Explanation:</u>
Many scientists believed that Earth did not have any oxygen. Cyanobacteria or the blue green algae are the microbes which produced oxygen for the first time with the help of photosynthesis. This was around 4.5 billion years ago: after Hadean eon.
They were very simple, but they produced oxygen in the early earth’s atmosphere. So, they brought evolution on earth. This “blue-green algae” exists in salt water, rocks and soils and play a major role in maintaining the ecosystem.
