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:
An energy pyramid is a model that shows the flow of energy from one trophic level to the next along a food chain. The pyramid base contains producers—organisms that make their own food from inorganic substances. All other organisms in the pyramid are consumers
Explanation:
I'm not sure if you needed a translation or an answer but i'll give both:)
"Why is it that in some countries it is day while in others it is night"
because at different times of the day the sun hits different areas of the earth. I hope this helps!
porque en diferentes momentos del día el sol golpea diferentes áreas de la tierra. ¡Espero que esto ayude
A. Metaphase I b. Metaphase II<span>c. Anaphase I
</span>
