I'd say stone tools. Stone can be chiseled or left alone and be used as a weapon to defend one's self, or as a way of getting food.
PCR (polymerase chain reaction) is a relatively new advance (1980's) but it has a great impact in our lives. Specifically, in forensic science, PCR is useful in many sorts of crimes . Up until the PCR method, in order to identify a person forensic scientists would use fingerprints or some other ambiguous methods like teeth marks etc. But now, with PCR, we can compare the genetic material found on a crime scene and compare it with a suspect's genetic material, definitively concluding whether they are the same person or not. The way this works is that we collect a sample from the crime scene with DNA and then PCR amplifies the quantity of DNA in that sample. One of the apparent advantages of this method is that PCR works with even a very small sample, often not even a single cell is required. This makes crime scenes full of information. Hence, succinctly, PCR has helped modern forensic science in that:
1) its results are more definitve than traditional identification methods and subject to less ambiguity
2) it is relatively fast
3) new pieces of evidence can be of value (like some hair cells) and identify the crominal in cases that in older times would be impossible to solve.
Answer:
Cohesion and adhesion of water molecules
Explanation:
Cohesion has to do with the ability of water to adhere together .
The cohesive properties of water which is occasioned by hydrogen bonding between adjacent water molecules allow the column of water to move up through the plant irrespective of the force of gravity as water molecules are evaporating at the leaf surface.
The adhesive properties of water, which means, the attraction between the water molecule and the xylem wall also ensure continuity in the movement of the water column in the xylem.
Hence the cohesive and adhesive properties of water molecules are important for transpiration to occur.
The most common organisms with exoskeletons are arthropods which include insects (bees, ants), arachnids (spiders) and crustaceans (lobsters and crabs).
