Answer:
The hardness rating is 4.
Explanation:
Calcite sits at a hardness rating of 3 and is very easily scratched with a knife and/copper coin. This is where most Marbles, limestones, travertines, rate.
Meanwhile, Fluorite sits at hardness 4 and can be scratched by a knife.
Answer:
The correct answer is B. Worms move through changes in body structure caused by contraction of muscles compressing their watery fluid.
Explanation:
The hydroskeleton consists of a fluid-filled cavity, surrounded by muscles. The fluid pressure and the action of the muscles that border it, serve to change the body's shape and produce a movement such as digging or swimming. The successive contraction of various metamers, which are provided with bundles of circular and longitudinal muscle fibers, stretching and thickening parts of the body, allow it to move horizontally. Hydrostatic skeletons have a role in the locomotion of annelids, nematodes and other invertebrates. The hydroskeleton has similarities with the hydrostatic muscles.
Answer:
Pushing the diaphragm causes air to flow out of the lungs, which pushes the blockage out.
Explanation:
Answer:
If you did not follow the procedure as you should have.
Explanation:
You may have to repeat an experiment for several reasons. It can be because you need to be certain of the results so that you have to perform it several times. Or you need more precise results so that you can fine-tune the variables and repeat the experiment again.
The most common scenario where an experiment would be replicated would be in a situation where you did not follow the procedure that you have outlined exactly like you should have so that the results you got are not 100% reliable. In such a case, the experiment would need to be replicated for the correct results.
I hope this answer helps.
Answer:
Until recently, most neuroscientists thought we were born with all the neurons we were ever going to have. As children we might produce some new neurons to help build the pathways - called neural circuits - that act as information highways between different areas of the brain. But scientists believed that once a neural circuit was in place, adding any new neurons would disrupt the flow of information and disable the brain’s communication system.
In 1962, scientist Joseph Altman challenged this belief when he saw evidence of neurogenesis (the birth of neurons) in a region of the adult rat brain called the hippocampus. He later reported that newborn neurons migrated from their birthplace in the hippocampus to other parts of the brain. In 1979, another scientist, Michael Kaplan, confirmed Altman’s findings in the rat brain, and in 1983 he found neural precursor cells in the forebrain of an adult monkey.
These discoveries about neurogenesis in the adult brain were surprising to other researchers who didn’t think they could be true in humans. But in the early 1980s, a scientist trying to understand how birds learn to sing suggested that neuroscientists look again at neurogenesis in the adult brain and begin to see how it might make sense. In a series of experiments, Fernando Nottebohm and his research team showed that the numbers of neurons in the forebrains of male canaries dramatically increased during the mating season. This was the same time in which the birds had to learn new songs to attract females.
Why did these bird brains add neurons at such a critical time in learning? Nottebohm believed it was because fresh neurons helped store new song patterns within the neural circuits of the forebrain, the area of the brain that controls complex behaviors. These new neurons made learning possible. If birds made new neurons to help them remember and learn, Nottebohm thought the brains of mammals might too.
Other scientists believed these findings could not apply to mammals, but Elizabeth Gould later found evidence of newborn neurons in a distinct area of the brain in monkeys, and Fred Gage and Peter Eriksson showed that the adult human brain produced new neurons in a similar area.
For some neuroscientists, neurogenesis in the adult brain is still an unproven theory. But others think the evidence offers intriguing possibilities about the role of adult-generated neurons in learning and memory.
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