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.
As you move up to the food chain, the energy will decrease. This explains that the more the consumers, the lesser the energy that the last consumer will get from the sunlight. This is because each energy will decrease as it passes by the consumers because each consumers takes a portion of the full energy from the sun.
Protein synthesis occurs in the cytoplasm, specifically in the ribosomes. Proteins that are meant to be excreted, such as in the pancreas, are produced in the rough endoplasmic reticulum which is a membrane studded with ribosomes. In organs that primarily function to produce and secrete proteins, there will be a larger rough endoplasmic reticulum with more ribosomes.
So Mendel got roughly 75% yellow and 25% green in f2. This means that f1 contains all heterozygous genes, as shown below
Y y
Y YY Yy
y Yy yy
Summary: 75% YY or Yy, 25% yy
Which means that green (y) is a recessive phenotype, while yellow (Y) is a dominant phenotype, since plants with heterozygous genotype Yy express the yellow trait.
