Answer:
is B
Explanation:
volcanic activity was more common in the past than it is today.
Answer:
DNA replication follows semi conservative mode of replication
Explanation:
The results of Meselson and Stahl's experiments can be explained by semi conservative mode of DNA replication. According to it, the two DNA strands separate and both are used for synthesis of new DNA strands such that the new DNA molecule has one parental and one new strand.
In the experiment, originally the medium was 15N so all the DNA molecules had 15N. Later the medium was changed to 14N. In first round of replication in new medium, the two 15N strands in a DNA molecule separated and formed new strands using 14N. So all the DNA molecules had one 15N and one 14N strand.
In the second round of replication, the 15N-14N hybrid DNA molecule separated again. Now, 15N gave rise to 14N strand and 14N strand also gave rise to 14N strand such that half of the DNA molecules were 15N-14N hybrids and half were 14N-14N. Hence, researchers concluded that DNA replicated according to semi conservative mode of replication.
A<span>nother nutrient, fat, stores energy. Before your body can use these nutrients, they must be broken into smaller substances. is the </span>process<span> of </span>breaking down food<span> into usable materials. Your digestive system transforms the energy and materials in </span>food<span>into forms your body can use.</span>
Question-
Which seismic waves are felt first at a seismic station
Answer-
Seismic waves are the waves of energy caused by the sudden breaking of rock within the earth or an explosion. They are the energy that travels through the earth and is recorded on seismographs.
There are several different kinds of seismic waves, and they all move in different ways. The two main types of waves are body waves and surface waves. Body waves can travel through the earth's inner layers, but surface waves can only move along the surface of the planet like ripples on water. Earthquakes radiate seismic energy as both body and surface waves.
BODY WAVES
Traveling through the interior of the earth, body waves arrive before the surface waves emitted by an earthquake. These waves are of a higher frequency than surface waves.
P WAVES
The first kind of body wave is the P wave or primary wave. This is the fastest kind of seismic wave, and, consequently, the first to 'arrive' at a seismic station. The P wave can move through solid rock and fluids, like water or the liquid layers of the earth. It pushes and pulls the rock it moves through just like sound waves push and pull the air. Have you ever heard a big clap of thunder and heard the windows rattle at the same time? The windows rattle because the sound waves were pushing and pulling on the window glass much like P waves push and pull on rock. Sometimes animals can hear the P waves of an earthquake. Dogs, for instance, commonly begin barking hysterically just before an earthquake 'hits' (or more specifically, before the surface waves arrive). Usually people can only feel the bump and rattle of these waves.
P waves are also known as compressional waves, because of the pushing and pulling they do. Subjected to a P wave, particles move in the same direction that the the wave is moving in, which is the direction that the energy is traveling in, and is sometimes called the 'direction of wave propagation'. Click here to see a P wave in action.
