Geologic Time Scale.Scientists decide when an era begins<span> and </span>ends<span>, due </span>to<span> mass extinction. ...</span>Scientists determine<span> when drastic changes </span>are<span> made by the fossil record, which shows earths past organisms that have become extinct.</span>
Because the cell is considered an organelle which is a biological mechanism which consists of different parts, whereas a molecules is a single part and not a mechanism.
The first one, ii. Natural selection and the formation of inseticide resistant insects or antibiotic resistant bacteria.
This can be explained in very simple way. As we all know, natural selection works in a way that only that adapted living beings are going to survive through a specific environment, whether it's because they can grab their food without too much work, or even that they can adapt to the weather. When we use inseticide, we are killing lots of non-resistant insects, and what's left are those that are resistant to this inseticide, and they'll reproduce again, and again we'll go through the same process, but remember, this insect is now stronger and more resistant that before.
The second case, iii. speciation and isolation give three examples how it may occur.
Well. the allopatric speciation and isolation will happen when theres a geographic barrier between one species. This one then is divided into two diffent habitats, but what can divide than could be a mountain, a tree, a river, a rock, anything. And this could be too called as a geographic isolation, because in this new environment, species are going to develop in a different way.
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