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:
b. How does food yield energy?
Explanation:
The main question is how energy is produced from food such as carbohydrates, fats and proteins etc. First the carbohydrate is converted into glucose molecule and then glucose is absorbed by the cell and is broken down in the mitochondria of the cell with the addition of oxygen and generate energy in the form of adenine tri phosphate. All the scientists wants to know that how a food is converted into energy.
C.All organisms have cells with different shapes and functions
Answer: Hi.... I hope it helps!!
Skin Pigmentation in humans
Explanation: Polygenic inheritance- It is simply a single characteristic which is controlled by more than two genes. Human skin's color is determined by the amount of dark pigment it has which is melanin
. Minimum four genes are involved in the melanin production.
It is a case of continuous variation as the combination of melanin producing allele are responsible for degree of pigmentation
