Behavioral experiments have shown that the principal and secondary eyes work together to precisely target moving stimuli. For example, Dr. Beth Jakob and colleagues investigated how the secondary anterior lateral eyes direct the principal eyes of Phidippus audaxwhen tracking moving objects. Phidippus audaxwere tethered in front of an eye-tracker that recorded the movement of the principal eye retinas. When spiders with their anterior lateral eyes unmasked were shown a moving disk, the principal eye retinas moved close together and were able to track it. Meanwhile, masked spiders were unable to track moving disks with their principal eye retinas. This indicated that principal eyes can precisely target moving stimuli only with the guidance of the secondary eyes (Jakob et al., 2018). Furthermore, Cupiennius salei, a wandering spider from the family Ctenidae, has also been shown to have closely cooperating principal and secondary eyes. Cupiennius saleihave moveable principal eyes that are controlled by four muscles (Kaps, 1996) (Land, 1969). Masking the Cupiennius saleisecondary eyes reduced their principal eye movement (Neuhofer et al., 2009).
You are here
In the developing tooth, enamel deposition varies among organisms. In omnivorous homo sapiens, enamel strength and quantity is much less than that of a sea otter, who prodominantly feeds on hard shellfish. It is important, then, to understand this pathway that results in this differential deposition of enamel in developing teeth. Stem cells in the developing teeth that express Sox2 travel to the inner enamel epithelium within the developing tooth1. There, they give rise to transit amplifying (TA) cells that rapidly divide, move to the distal tip of the developing tooth, and differentiate into ameloblasts1. Ameloblasts deposit enamel matrix proteins. As a result, Sox2 overexpression could lead to increased enamel deposition and a hardening of teeth.
(1) Li, J., Parada, C., & Chai, Y. (2017). Cellular and molecular mechanisms of tooth root development. Development, 144(3), 374–384. doi: 10.1242/dev.137216
My name is Ziwei, and this is my poster on how the removal of the seed coat affects the seed germination rate. So, what is the seed coat? The seed coat is a protective covering that surrounds the seed and protects the seed from the environment that the adult plant may not be able to survive in. In addition to the protective role that the seed coat plays, the seed coat also plays a role in controlling germination and produces some compounds that are beneficial to the seed. This indicates that while it may seem like the seed coat is not doing anything, the seed coat is actually biologically active. One of the things that have been suggested recently is that the seed coat actually impedes seed growth. The reason why the timing of germination is important is if the seed starts germinating, there is no going back. There is no way for a germinated seed to become ungerminated. However, there are situations where a faster germination rate would be an advantage. To see if the removal of the seed coat increased the germination rate, we removed the seed coat of the seed, and allowed it to germinate, and measured the rate. Our result indicates that the seed germination is somewhat faster in certain types of seeds, however, we were not able to get a definite answer of whether removing the seed coat caused the seed to germinate faster. Due to the small sample size. My personal theory is that because there are so many compounds that seed coat produces, there may be some compounds that are produced by the seed coat that is needed for germination. Because of this, my next experiment would be to remove half of the seed coat and see if that would make the seed germinate faster because if only half of the coat was removed, there would be a beneficial compound without the physical barrier of a seed coat. That's basically what this project is about. Do you have any questions?
To understand just how devastating an increase in greenhouse gases could be for our planet we must first understand how greenhouse gases work. Energy reaches our planet in the form of solar radiation and is either reflected or absorbed and released as infrared radiation. Normally this radiation would leave the planet, however, gases in the atmosphere act as a one way mirror allowing solar radiation in but trapping IR radiation. Without any gas we could not survive, however, too much will cause problems. Our atmosphere is made of 78% N2, 21% O2, 1% Ar, 0.4% H2O and <0.1% of other gases with carbon dioxide at 0.041%. Carbon dioxide levels are 'low' compared to the rest of the gases in the air, so why do speakers use it as a key point of climate change conversation? Airborne concentrations of this gas have been steadily increasing since data was first recorded in 1960. A longitudinal study by the NOAA Earth System Research Laboratory has shown that from 1960 to today carbon dioxide levels have risen by 90 ppm (parts per million). This seemingly small increase could have devastating affects on our enviornment. Global temperatures have been rising from the increase in efficient green house gases such as carbon dioxide, and also notably, methane, and nitrous oxide. A 2018 study of temperature increases and it's affect on organsim ranges predict that at a 3.2 C change in average temperature could result in the geographic range loss greater than 50% for 49% of insects, 44% of plants, and 26% of vertabrates. These results are worrying. The future of our species and others lies in question. We must make a change now in order to avoid catastrophe.
Over one week, the germination rate in a variety of seed species was tested between seeds with and without testa. Particular species of seeds provided evidence of fast germination while others did not. Visual analysis sees no significant difference between the germination rates of seeds with or without testa. The germination rate of seeds with testa is equal to the germination rate of seeds without a testa. Uncertainties in our experiment include meeting optimal germination environments, as well as the uneven distribution of water to the seeds.
Furthermore, a small sample size experiment increases the likelihood of falsely accepting the null hypothesis. Future questions that can be asked to follow up on our experiment include whether pH or external factors such as soil conditions, temperature, and fertilizers affect the germination rate. These questions would lead the experiment towards figuring out how optimal germination rates vary by seed species.
A study done by researchers at the University of Michigan show that some oxidative stress at a young age can actually lead to a longer life. Oxidative stress occurs when cells produce more oxidants than they can deal with. Studying C. elegans, researchers were able to determine that worms that produced more oxidants during development lived longer than worms that did not produce as much oxidants during development. Of course, there are other factors that can aslo determine ones life expectancy. Genetics and enviornment are two factors that can affect lifespan. If your parents live a long life, the offspring will have a good chance of living a long life as well. Experiencing stress at a young age may make you better in fighting stress later on in life when you encounter it again. Since stress and age-related diseases are closely connected, scientists are looking into whether early exposure to stress in life have an affect on the predisposition for age-related diseases. Some of these diseases include Alzheimer's and dementia. In a next study, researchers want to look at what changes during development in worms that experience stress at a young age make them have a longer life expectancy.
Within mammals, humans are one of the few species which cater to their taste preferences using spices. One of the spices used in cooking contains the active ingredient capsaicin which causes a burning or spicy sensation when eating. Of the mammals, humans and tree shrews are two of the few species who have been documented to consume plants containing capsicumoids as part of their diet (“Tree shrews can tolerate hot peppers,” 2018). Chili peppers are one of the most common cooking plants containing capsaicin, a type of capsaicinoid (Tsuchiya, 2001). Other mammals avoid the Capsicum plant species due to the spicy burning sensation caused by their consumption. Within tree shrews, they have a mutation on the reception TRPV1 which decreased the effects of capsaicin on the receptor (Han, Li, Yin, Xu, Ombati, Luo, & Lai, 2018). From this mutation, tree shrews were able to expand their diet due to their tolerance of capsicumoids in a similar pattern of convergent evolution. With humans, the burning sensation is variable depending on food preference of the individual but humans are the only species known to actively seek out the consumption of very spicy foods (Han et. al., 2018). TRPV1 receptors are apparent throughout mammals in their avoidance of spicy foods but only humans and tree shrews have evolved to utilize capsaicinoids in their diet. Of other vertebrates species, birds are one of the only other species to have no response to eating Capsicum plants (Han et. al., 2018). Birds are often used by plants to spread their seeds and it is likely that mammals do not do this job as well leading to the plant’s possible evolution to prevent their consumption by mammals.
The principal and AL eyes may also work together to gather visual information. A recent study (Jakob et al., 2018) investigated how lateral eyes direct the principal eyes of jumping spiders when tracking objects. In order to test this,Phidippus audax spiders were tethered in front of an eyetracker that recorded the gaze direction of the principal eyes. Visual stimuli of different shapes and movement speeds were presented before and after masking the ALEs with removable paint. When unmasked spiders were shown a moving disk, the principal eye retinas moved close together and were able to track it. Meanwhile, spiders with their AL eyes masked were unable to track moving objects, with their principal eye retinas remaining further apart and reacting only briefly when the objects crossed their field of view. However, when the spiders were presented with a motionless object that appeared in the center of the principal eye’s field of view, they actively scanned it regardless of whether the secondary eyes were masked or unmasked. This indicates that masking the secondary eyes does not prevent the principal eyes from investigating stationary objects, but they are needed for targeting stimuli outside of the principal eye’s field of view (Jakob et al., 2018). The integration between principal and secondary eyes has also been studied in Cupiennius salei (Family Ctenidae). The principal eyes of ctenids are moveable, but they are controlled by four muscles instead of six as in jumping spiders (Kaps, 1996) (Land, 1969). Thus, they are not able to engage in complex movements such as torsion. When spiders had their principal eyes masked, they maintained the same eye muscle activity, but masking the secondary eyes reduced principal eye movement (Neuhofer et al., 2009). The researchers concluded that the secondary eyes of C. salei are involved in movement detection, while the principal eyes require input from the secondary eyes to move normally.