There are all sorts of ways to reconstruct the history of life on Earth. Pinning down when specific events occurred is often tricky, though. For this, biologists depend mainly on dating the rocks in which fossils are found, and by looking at the “molecular clocks” in the DNA of living organisms.
There are problems with each of these methods. The fossil record is like a movie with most of the frames cut out. Because it is so incomplete, it can be difficult to establish exactly when particular evolutionary changes happened.
Modern genetics allows scientists to measure how different species are from each other at a molecular level, and thus to estimate how much time has passed since a single lineage split into different species. Confounding factors rack up for species that are very distantly related, making the earlier dates more uncertain.
These difficulties mean that the dates in the timeline should be taken as approximate. As a general rule, they become more uncertain the further back along the geological timescale we look. Dates that are very uncertain are marked with a question mark.
Answer:
Either due to mistakes when the DNA is copied or as the result of environmental factors such as UV light and cigarette smoke.
ANSWER:
Electromagnetic energy is monitored by scientists forecasting future space weather
EXPLANATION:
Electromagnetic energy has such type of waves which propagate or radiate through space, carrying photons. Electromagnetic energy has radio waves, microwaves, infrared, light, ultraviolet, X-rays, and gamma rays.Space weather includes any activity happening in space that might affect Eath's environment.Space weather can interrupt mobile signals,air communications and can damage our satellites.So Electromagnetic waves are monitored to control all the above situations.
The theory of common descent states that all living organisms are descendants of a single ancestor. Phylogenetic trees and cladograms are often used to hypothesize the evolution of various organisms and shared common descent.
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