The eons that make up 90% of Earth's history are the Precambrian eons, which consists of Hadean, Archean, and Proterozoic eons.
Answer:
The initial amount, 1.3 million = 1,300,000 is the 100%.
now, 640,000 is a given percentage (lower than 100%) of that.
How we can find it?
suppose that 640,000 represents an x%.
Then we have that the quotient between the actual quantities and the percentages must be the same
(640,000/1,300,000) = x%/100%
x% = (640,000/1,300,000)*100% = 49.23%
Then the percentage declined is:
100% - 49.23% = 50.77%
The other question can not be answered with the given information.
The shuffling of chromosomes that occurs during both fertilization and meiosis can lead to genetic variation. This is because of the independent assortment and crossing over. Hope this answers the question. Have a nice day. Feel free to ask more questions.
<span>The process must occur before the gametophyte generation is Sporophyte. A sporophyte is the diploid generation of a plant or alga that has a double set of chromosomes. [ All land plants, and some algae, have life cycles in which a multicellular haploid gametophyte generation alternates with a multicellular diploid generation. In the Gymnosperms and flowering plants (Angiosperms), the sporophyte generation is the most prominent phase, comprising the familiar green plant with its roots, stem, leaves and cones or flowers. In the flowering plants, the gametophytes are very reduced in size, and are represented by the pollen and the embryo sac.</span>