Writing in Biology - Section 1

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.

The principal and secondary eyes are also sensitive to different types of visual information compared to the principal eyes. The principal eyes are thought to process detail, while the secondary eyes are highly sensitive to moving stimuli (Land 1995; Zurek & Nelson, 2012; Morehouse et al., 2017). For example, Spano et al. (2012) tested which set of eyes mediates the response to looming stimuli. When presented with such stimuli, spiders with their principal eyes masked but their ALEs unmasked reacted to it by retreating, while spiders with their ALEs masked and principal eyes unmasked were less likely to do so. The researchers concluded that the secondary eyes are primarily responsible for the loom response. 

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 eyes. 

Most animals must integrate input from different sensory organs. For example, females might choose mates based on multimodal signals, such as vibratory and visual cues (Hebets and Uetz 1999). Other animals have several sense organs within the same modality. For instance, many insects have both compound eyes, which discern image detail, and ocelli, which are sensitive only to light and dark (reviewed in Cronin et al. 2014). Spiders are particularly interesting because most species have eight eyes of two different types. Most well studied are the jumping spiders (Family Salticidae) are characterized by their powerful visual acuity, which is used for many complex behaviors such as predation and courtship. They have four pairs of eyes, which consist of a single cornea and retina, of two morphological types: the principal and the secondary eyes (Figure 1). The corneas of jumping spiders are integrated in their exoskeletons and do not move. The tiny, boomerang shaped retinas of the principal eyes have the best resolution but are restricted by a narrow field of view. In order to examine a visual scene, jumping spiders use a set of six muscles to move the retinas, which are situated at the back of long tubes within the cephalothorax (Land, 1969; Figure 2). This scanning can increase the angle of view from approximately 10°to 58°(Land, 1969).

Proteins are classified by four levels of structure. The primary structure of a protein is the sequence of amino acids which make up the protein. The protein's secondary structure involves two configurations within the protein. These are referred to as alpha-helices (α helices) and beta-sheets (β-sheets). These are two ways that proteins organize themselves that contribute to their spatial arrangement and three-dimensional shape, which is their tertiary structure. A protein's quaternary structure is the arrangement and number of polypeptide chains within a protein, and therefore only exists if there is more than one polypeptide chain present in the protein. Protein structure is largely determined by intramolecular interactions, as well as the protein's function and where it will be located when it does its job. Proteins generally have a hydrophilic exterior and a hydrophobic interior, due to its environment in the cell containing a lot of water. These interactions help to hold the protein together, otherwise a hydrophobic exterior would denature the protein. By analyzing these aspects of a protein, we can begin to deduce how the protein might function.

Unfortunately, a broken wing can be deadly for a bird since it won't be able to fly anymore. Luckily, researchers were able to develop a treatment for broken bird wings using the bones of sheep and dogs. The treatment included an insertion of sharp bone pins into the bone breaks. Dog bones came from dogs that were euthanized due to illness or injury. The birds that received this kind of treatment to their broken wings flew flawlessly, as reported by the researchers. Other treatments included insertions of metal pins to heal the bones but this caused the animals' wings to be weighed down since bird wing bones are hollow. Further advances in this research can make pins and other impants made from animal bones a useful technique in treating animals with wing bone damage.

I was actually surprised about our results. I believed that seeds with a tampered seed coat would not germinate as well as a normal seed. However, the graphs reveal that for most types, seeds with a nicked coat germinated sooner and in greater numbers. From handling the seeds, I also believed that seeds with a thicker coat may actually germinate faster if they are nicked. Again, there was no distinct difference found between seeds of thick or thin coats. If we had more time to run this experiment again I would have liked to use seeds of more varying coat thickness. 

We wanted to figure out how important the seed coat is to the germination of a seed. For our experiment we focused on six types of seeds, ranging from green peas to chickpeas. We soaked 30 seeds of each type then removed the seed coat of 10 seeds, nicked another set of 10 seeds, and left the remaining 10 seeds alone. The seeds were then placed in petri dishes with a moist paper towel, all conditions being held constant. Over the course of four days we checked on the seeds every twelve hours. We noted the number of seeds germinated and any other traits that stood out to us.

Professor Seydoux went onto explain what really happened in order. At the very beginning, anterior PARs stop posterior PARs from entering the membrane . When the sperm enters, it brings along a centrosome that bursts into microtubules and there was a correlation between that and the posterior PAR proteins at the membrane. Blocking of the microtubule formation of the sperm, stopped the PAR proteins from reaching the membrane. However, when the oocyte nucleus about to undergo meiotic division – the spindle formation allowed the PAR protein to access the membrane. This is suggested that it was not a question of sperm vs oocyte, it was more of a question of which cell made a rich microtubule first. In wild type, meiotic spindles are more transient, whereas the sperm asters are much more dense and stable. 

The activity of P. occidentalis, harvester ants, has been shown to enrich soil nutrients around their mounds due to the ants’ movement of particles¹  from soil nearby. The rudimentary soil composition in certain areas has also influenced the density and variation of ant populations²  present in that environment. In our experiment, the effects of salinity on the harvester ants burrowing behaviors were tested. 

Hypothesis: The ants will burrow more in the sand where the salinity is lower.

Half of an ant farm was filled with regular, untouched sand, while the other half was filled with sand where the salinity was manipulated to be that of seawater (35 ppt). Eight ants were added to the farm and left to burrow for 6 days, while every few days their food and water were restocked. The burrowing  length results and general observations were recorded and the Mann-Whitney U test was used to analyze the results. 

 I really like this article and am very happy that this experiment was conducted on the mice to prove that healthy gut bacteria can cause a healthy life. This can be used on humans once more research is done, and provide antibiotics to humans to provide them with a healthier life and reduce their chance of developing things such as schizophrenia. There were different patterns of neural activity in the amygdala and the prefrontal cortex when the gut bacteria was disrupted, so in turn brain regions associated with fear and learning. Hopefully the research can continue in this topic, and hopefully one day this antibiotic tested on mice will be available for humans.