The tomatoes we eat today were almost 10 times smaller years ago. So how did the size and thickness just increase over time? It was just by random chance. It is as simple as that – one day a farmer had found a tomato slight bigger than what he had been cultivating – technically an anomaly – and he grew that tomato over and over again. Domestication of tomatoes has led to us getting the fruit we take for granted so easily. The process may have been simple, but the mechanism was much more complex. The paper “A cascade of arabinosyltransferases controls shoot meristem size in tomato” (Xu, Cao, et al 2015) breaks down the mechanism through which we ended up with the mutation that gave us our tomatoes. Growing plants have shoots containing meristems which contain stem cells. Stem cells have the ability to become absolutely any cell they want. As they multiply, the meristem grows bigger and bigger, allowing more flowers and fruits etc. However, that is not what happened with these tomato plants originally. An original pathway looked something like this: a gene expressed a protein name WUSCHEL (WUS). This protein is in charge of causing the meristem to grow in size, but it also activates its repressor CLAVATA3 (CLV3). CLV3, being a ligand, attaches to the receptor protein, CLAVATA1 (CLV1). This is allows the activity of WUS to be deactivated and so the meristem cannot grow in size.
You are here
An elaborate representation of static electricity can be demonstrated through the use of a Van de Graaf. Structurally, a Van de Graaf has a base with a dial to turn it on and increase/decrease the voltage. It is plugged to a power outlet through the base. Emerging from the base, the plastic cylinder has a belt (made of felt) constantly rubbing against one another when the equipment is switched on. This causes a sea of negatively charged electrons to be produced. The electrons travel up the belt to the metal ball of the Van de Graaf (on top). Upon skin contact with the metal ball, the person will experience their hair being "static". This is due to the fact that electrons cannot stay in one place and are always looking to leave through any form conducting medium. The person has to stand on an insulating material (e.g. wooden or plastic stool) to avoid the electrons travelling down to the ground since that pathway is natural for them. This is the same mechanism as the simple "socks shuffling against the rug" or "balloon rubbing against hair".
Phytophagy can be seen almost anywhere around us. I found mine in the Durfee Conservatory on the UMass Amherst campus. The subject was a plant with long green leaves. Every single leaf was pristine clean with no other patches, holes etc. except one leaf. This specific leaf had three patches in a trianglular orientation. The patches did not have specific shape - they were irregular. They did not occupy space on the entire leaf, but were big enough to be visible They were located about two-thirds from the bottom and on the underside of the plant. This was an evidence of phytophagy because it usually means that it had been attacked by a fungus or bacteria causing the discoloration. The brown patches were slightly lighter around the borders and got darker as they got closer to the center of the each patch.
A commonality among the most living things is their circadian rhythm. The circadian rhythm is one of the most important mechanisms and it works by regulating hormones and different cellular activities based off external cues such as light. Our body has a drop in melatonin and our blood pressure is higher when we wake up and it is light out. As the day goes by, our level of alertness increases along with our coordination. Between afternoon and evening, we have the greatest muscle strength and cardiovascular efficiency. As it gets darker, our melatonin levels start to rise preparing us for sleep. These changes occur due to the biological clock set by our zeitgeibers, i.e., time keeper. These zeitgeibers are located in the suprachiasmatic nucleus of the brain. Studies have shown that lesions in the SCN can cause disorders relevant to circadian rhythm.
An elaborate representation of static electricity can be demonstrated through the use of a Van de Graaf. Structurally, a Van de Graaf has base with a dial to turn it on and increase/decrease the voltage. It is plugged to a power outlet through the base. Emerging from the base, the plastic cylinder has a belt (made of felt) constantly rubbing against one another when the equipment is switched on. This causes a sea of negatively charged electrons to be produced. The electrons travel up the belt to the metal ball of the Van de Graaf (on top). Upon skin contact with the metal ball, the person will experience their hair being "static". This is due to the fact that electrons cannot stay in one place and are always looking to leave through any form conducting medium. The person has to stand on an insulating material (e.g. wooden or plastic stool) to avoid the electrons travelling down to the ground since that pathway is natural for them. This is the same mechanism as the simple "socks shuffling against the rug" or "balloon rubbing against hair".
It is funny how the first thing that comes to my mind is Parkinson's diseases whenever someone says deep brain stimulation (DBS). DBS has proven to be helpful in treating several other movement disorders, one of them being Tourette's. Tourette's causes somebody to make involuntary movement and noises called tics. This usually happens due to abnormal connections in the basal ganglia of the brain. DBS allows two small electrodes implanted into the brain and delivering electrical impulses to potentially change the connections and prevent the impulses causing the tics. The patients are usually awake during the procedure because the activity can be measured while they are awake rather than under sedation. It is quite mind boggling whenever I think about the patients just aware of their surroundings while there are holes being drilled through their skulls.
I compared the figures on page 27. The image quality for the first one is better than the second - it is quite blurry. The first one has a close up shot of B and was most possibly taken at night rather than the day – unlike B in the second figure. Part C is also a close up shot for the first figure unlike the second one – the first one shows a single tree while the second one shows multiple and is slightly more vague since it has a greater amount of background. There is relatively less moss in the second figure for D compared to the first figure. Part E in the second figure seems to be the same image as D, but perhaps another angle or area. On the other hand, E in the first figure looks different from D.
Categories and cause:
Image quality - The blurriness could be due to the software used - Inkscape vs. Word. It could also be caused due to the camera quality.
Time of the day - Part B of the first figure has darkness in the background indicating that the image could have been taken at night while the Part B for the second image may have been taken during the day.
Distance between the person and the object - The person making the second figure may not have been entirely sure of which tree was to be photographed and so they were further away when taking the picture for C, making it quite vague.
Different areas - The second figure had less moss in comparison to the first figure. The area could have been different.
Stem cells are incredibly fascinating to look at. They possess the ability to turn into absolutely any cell in the body, performing any function. In a recent study done in Kyoto Univeristy, they were able to obtain a ball of pluripotent stem cells and place in a petri dish with liquid that was similar to the environment that a brain cells can grow in. They were able to grow the cerebral part of the brain and use it to assess the brain structures and measure activity in the neurons that were present. However, Yi Zhou from Florida State University said that the research had a long way to go since it only represented a part of the brain and not the whole organoid, and you could only measure the activity in certain neurons indirectly with calcium ion activity.
Homeostasis is one of those important phenomena that everyone takes for granted. It ensures that several of the conditions in our body are strictly regulated without us realizing. One of the prime examples is the regulation of our body temperature. When our internal temperature rises above the normal, our blood vessels undergo vasodilation, where they dilate so that the blood flows closer to the skin surface. This allows heat from the blood to escape through the skin. Another way to reduce the heat is through sweating. The sweat glands produce sweat, which reaches the surface of the skin and evaporates, taking the latent heat with it. Conversely, a drop in our body temperature causes our blood vessels to undergo vasoconstriction, which is the narrowing of the blood vessels to keep the blood from losing its heat. We also shiver, which generates heat in our body.
Figure 1: "Acetabularia" flickr photo by CameliaTWU https://flickr.com/photos/cameliatwu/4420468633 shared under a Creative Commons (BY-NC-ND) license. This is a green algae called Acetabularia with a green, cup-shaped body with a shiny surface.