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:
plant propagation
Explanation:
Plant propagation is the process which grows new plants from a variety of sources: seeds, cuttings, and other plant parts. Plant propagation can also refer to the man-made or natural dispersal of seeds.
Answer:
1,000 kcal
Explanation:
As a general rule, every trophic level only gains 10% of the energy from the trophic level.
So, the grass has 100,000 kcal of energy. Assuming the bird eats grass, it only gets 10,000 kcal of energy. Assuming the fox eats the bird, it only gains 1,000 kcal of energy.
Answer:
Mitosis is when a diploid cell becomes 2 haploid cells with single chromosomes
Explanation:
Answer: Non-falsifiable hypotheses: Hypotheses that are inherently impossible to falsify, either because of technical limitations or because of subjectivity. E.g. "Chocolate is always better than vanilla." [subjective].
A statement, hypothesis, or theory has falsifiability if it can be proven false by contradicting it with a basic statement or observation.
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Explanation:
