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.
The answer to the question above is letter D. <span>Chromosomes found in the cell nucleus.</span>
In the cell nucleus, DNA is tightly packed into the
thread-like structure known as chromosomes. Every chromosome is made up of
tightly coiled DNA around proteins (histones) that support its structure.
Chromosomes are not visible when there is no cell division. It cannot be seen
in the cell’s nucleus nor under the finest microscope. They are only visible
when the cell is dividing and is apparently visible under a microscope.
A reaction in which heat energy<span> is absorbed is said to be endothermic. You </span>can<span> show this on simple </span>energy <span>diagrams. For an exothermic change: Notice that in an exothermic change, the </span>products<span> have a </span>lower energy than<span> the </span>reactants<span>.</span>
Answer:
I'm pretty sure the answer is a Tundra.
Explanation:
It's the only biome that has snow out of every other answer choice. Snowy places are naturally cooler than humid ones.
Human rights and equality. One of the EU's<span> main </span>goals<span> is to promote human rights both internally and around the world. Human dignity, freedom, democracy, equality, the rule of law and respect for human rights: these are the core values of the </span>EU<span>.
- google</span>
