Answer:
The correct statements would be
- Cyanobacteria allowed organisms that rely on oxygen to evolve.
- Cyanobacteria preceded the first photosynthetic organisms.
- Cyanobacteria produced excess oxygen.
Cyanobacteria, also termed as blue-green algae are the prokaryotes which are able to perform photosynthesis.
They were the major contributors of oxygen in the atmosphere and thus helped the organisms that rely on oxygen to evolve.
By the process of endosymbiosis, they lead to the origin of plants. The chloroplasts present in green plants is considered as the cyanobacteria living in the plant cell. It helps in photosynthesis and in return plants cell provides shelter to it.
It is believed that the oxygen released from early cyanobacteria reacted with dissolved iron ions to form iron oxide.
Answer:
(C) 4 beats per second.
Explanation:
As we know that the no of beats can be calculated as.
No. of beats is equal to difference in the tuning forks frequencies.
So,
.
Substitute the values of frequencies of 2 tuning forks in the above equation.
Therefore the number of beats per second will be hear by the observer is 4 beats per second.
<u>Answer:</u>
This is due to the apparent movement of the celestial bodies, seen from an observer centered on the Earth. If we did not have knowledge of the advances of science and the latest discoveries, we would think that the Earth is the center of the universe.
For example, for an observer on Earth as a reference system, the Sun moves every day from east to west, as do the planets and all the stars that we observe at night, which leads the observer to believe that those in motion are these bodies outside in the sky while the earth is still and fixed in the universe.
Keep in mind that this theory of geocentrism was widely accepted for a long time in antiquity, until the astronomer Nicolaus Copernicus proposed a completely different and opposite idea, heliocentrism (universe centered on the Sun).
However, at present it is known and accepted that the universe has no center, that the Earth revolves around the Sun and that in reality all the bodies of the universe are in movement.
