Writing in Biology

The Hill Reaction, used in the 1930s, used Spinacia oleracea to discover that chloroplasts separated from plants containing their thylakoid membranes will still continue to create oxygen, so long as they are given light and an appropriate electron acceptor in place of NADP+. Normally chloroplasts need to use NADP+ as an electron acceptor, but using a centrifuge to separate the chloroplast from the thylakoid membrane, NADP+ is lost.  In our Hill Reaction experiment we chose to compare the effects of using purple light vs. normal light on the effect of photosynthesis. Plants absorb both red and purple light waves, however because purple wavelengths are shorter, they emit a higher frequency and contain more energy (Different Wavelengths of Light Affect on Photosynthesis Rates in Tomato Plants). Light is normally at 600 nm, while purple is at 400 nm and has higher absorbance. Using purple light rather than normal light should mean the absorbance process will take longer. The presence of purple light will cause there to be a higher absorbance level in the chloroplasts in experimental group in comparison to the control group which will have lower absorbance levels exposed to natural light. If correct, then the spectrometer will detect that the solution in the cuvette will reach 0 absorbance at a slower pace than it did with natural light, but not by a large margin. If incorrect, the spectrometer will show the solution reach 0 absorbance at either a quicker pace than our control group or a much more elongated rate.

Cheetahs are the world's  fastest land animal. They can reach speeds up to 68 miles per hour (110 km/h). Gazelles can also run fast about 50 mph (80 km/h). With that in mind they are able to escape from a cheetah's grasp. A cheetah is a smallish cat, they take longer strides at a faster pace. They can generate energy quickly but they also can lose it just as quickly. A cheetah can only run at its top speed for 400 yards. Gazelles are large African deer, they take shorter strides at a slower pace and have elastic recoil to store and use energy. They have great endurance, able to go 5468 yards (5 km) at top speed. That is a lot further than the cheetah. The gazelles can also change direction fast and easily due to their elastic recoil. So while they are not as fast as the cheetah, gazelles have ways to escape predation.

Spinacia oleracea is a hardy leafy annual of the amaranth family (Amaranthaceae), a commonly used vegetable in the world, commonly referred to as spinach. Deep within the cells of these spinach leaves lies chloroplasts, a type of organelle characterized by its two membranes and a high concentration of chlorophyll. They are structures by which photosynthesis, the process by which carbohydrates are made from carbon dioxide and water in the presence of chlorophyll, use energy captured from sunlight by chlorophyll. This results in the production of oxygen and energy-rich organic compounds. Chloroplasts contain thylakoids, flattened sacs. Light energy (sunlight) reaching the thylakoids excites the chlorophyll pigments, causing them to drive electrons and hydrogen from water to NADP+, an electron acceptor. The electrons enter the electron transport chain, resulting in the products of ATP and NADPH (converted from NADP+). These are then used in the light-independent reactions of photosynthesis, where carbon dioxide and water are used to make organic compounds.

Based on the article and Mayr’s definition of a species, it is correct to say that coyotes (Canis latrans), wolves (Canis lupus), and dogs (Canis lupus familiaris) are separate species. The article mentions that in the past, and today, that all three species had the ability to breed with one another, but in Mayr’s definition there is an emphasis on “interbreeding natural populations.” In his article Kays says the last recent account of wolf and coyote mating took place a hundred years ago and was due to low numbers of wolves in the Great Lakes area. This forced both species to interact. The same occurred between dogs and coyotes as coyotes began moving east but could not find others and instead bred with feral dogs. Kays states that while interbreeding can happen, they are usually exclusive within their own group.

Most mammals use all four limbs to move and so are called quadrupedal. Animals that spend most of their time walking are called ambulatory, and are generally plantigrade, which means that they walk on the soles of their hands and feet. Animals that do a lot of running are called cursorial, and are either digitigrade or unguligrade. Digitigrade mammals are mostly carnivores, and are called digitigrade because they run on their toes. Hoofed animals have unguligrade foot posture, which means that they have extended limbs with reduced digits, and elongated and fused tarsal bones. Another form of locomotion is saltatory locomotion, which includes jumping and ricocheting. Jumping is saltatory locomotion that uses all four feet, whereas ricocheting primarily only uses the two hind limbs, and most animals that use it are bipedal. Other types of locomotion include swimming, flying and gliding, and digging and burrowing.

Today in comparitve physiology we learned about how different animals respire in various ways. Most animals in the water breathe via gills. Gills are not well designed for respiration in air, but there are a few terrestrial organisms which breath through gills. One of these organsims is the coconut crab. Gills are essentially lungs that are not invaginated into the body. Instead they project into the environmental medium. There are both external and internal gills. Internal gills have a protective coating over them. There are also different typed of lungs. One type of lungs are diffusion lungs which respire air via diffusion and ventilation liungs which respire via tidal flow of air.

Despite the study having many positive findings it is lacking many important aspects. These gaps are important to the study and can make it unreliable. First, there are no control subjects to compare the DPN subjects to (no non-diabetic subjects or diabetic subjects without DPN). Therefore it is not a randomized study with a placebo present. The participants are all older individuals with a wide range of diabetes duration (12.2 years). The authors also do not define what stage of neuropathy the patients are experiencing at any point in the study. Also, there is no specific regimen on what equipment is used for exercise training. Although it is a supervised exercise intervention, the subjects are allowed to choose from a variety of options and are only encouraged to utilize different equipment. A nerve conduction study is used to test conduction velocity, motor action potential, and amplitude, but no significant changes were found. Lastly, skin biopsies are used to test intraepidermal nerve fiber density and epidermal axon branching. 

One system within the endocrine system, known as the male HPG axis, is responsible for a variety of different physiological functions such as spermatogenesis and the development of sex organs. HPG axis stands for hypothalamus-pituitary-gonad axis and is characterized by neurons in the hypothalamus region of the brain releasing hormones that signal receptors in the anterior pituitary gland. The pituitary gland then releases its own hormones that signal receptors in the gonads and leydig cells, initiating its physiological functions. The hypothalamus releases a hormone called GnRH, or gonadotropin releasing hormone. Hormones released from the hypothalamus set for the pituitary travel through a specialized pathways called the portal system. Once the GnRH has bound itself to receptors in the pituitary, two more hormones are released from the gland: LH and FSH. LH, or luteinizing hormone, will leave the pituitary and enter the bloodstream, traveling to leydig cells. This will stimulate the leydig cells to release testosterone, initiating spermatogenesis and reducing the secretion of LH from the pituitary. FSH, or follicle stimulating hormone, however, takes on a different role. FSH goes straight to the testis to upregulate the production of sperm.

The first step in genotyping adult zebrafish generally is fin clipping. Like the name probably already indicates, it involves clipping the fin of the zebrafish specimen. However, some important protocols must be observed to do so optimally, with as little distress and mortality as possible. First, a water bath is set up to contain 200ml of system water i.e. water used to fill up the fish tanks. To this bath, about 15ml of tricaine should be added. This will anaesthetize the fish, temporarily rendering the fish immobile and unconscious, making the clipping process easier and causing the fish less distress. If the fish does not stop moving when placed in the bath, more tricaine can be added, no more than 10ml. Too much tricaine can kill the fish. When the fish is finally floating sideways in the bath, unconscious, a razor blade should be used to carefully amputate roughly half the caudal fin. Again, living tissue must not be cut, as this will cause the fish to bleed. Bleeding may lead to infection or, worse, death. The clipped fin should be placed in a tube, labelled properly, according to the tank the fish was obtained from and the crosses done to obtain the fish. The fish can, then, be returned to fresh system water. The fish should regain consciousness and become mobile again in about 5 minutes. If this is not the case, then, the fish is probably dead, due to some error in fin clipping. The fin tissue obtained can then be taken to the lab and DNA extracted from it. Subsequent genotyping steps will follow once DNA is extracted.

The first step in genotyping adult zebrafish generally is fin clipping. Like the name probably already indicates, it involves clipping the fin of the zebrafish specimen. However, some important protocols have to be observed to do so optimally, with as little distress and mortality as possible. First, a water bath is set up to contain 200ml of system water i.e. water used to fill up the fish tanks. To this bath, about 15ml of tricaine, an anaesthetic, should be added. This will temporarily render the fish immobile and unconscious, making the clipping process easier and causing the fish less distress. If the fish does not stop moving when placed in the bath, more tricaine can be added, no more than 10ml. Too much tricaine can kill the fish. When the fish is finally floating sideways in the bath, a razor blade should be used to carefully amputate roughly half the caudal fin. Again, endeavor not to cut living tissue, as this will cause the fish to bleed. Bleeding may lead to infection or, worse, death. The clipped fin should be placed in a tube, labelled properly, according to the tank the fish was obtained from. The fish can, then, be returned to fresh system water. The fish should regain consciousness and become mobile again in about 5 minutes. If this is not the case, then, the fish is probably dead, due to some error in fin clipping. The fin tissue obtained can then be taken to the lab and DNA extracted from it. Subsequent genotyping steps will follow once DNA is extracted.