Writing in Biology - Section 1

There are a few hormones involved in the regulation of digestion, but we’re only going to talk about a few of them. Gastrin stimulates the stomach and the small intestine. Histamine is another hormone, stimulates HCl production in the stomach (to acidify the contents). Secretin is a hormone that inhibits the stomach while also stimulating the small intestine. Cholecystokinin stimulates the small intestine and digestion but inhibits stomach. Secretin and cholecystokinin are active during the intestinal phase of digestion (they’re stimulating the small intestine and not the stomach). Undigested food enters the duodenum and inhibits gastric emptying in the Intestinal phase. The distension from the gastric phase leads to gastrin release in the blood. Secretin and cholecystokinin inhibit stomach activity until contents are digested.

Phase 1 is the cephalic phase: neural control of the GI tract. This is when we see, smell, think of food and our mouth waters. It’s us thinking about food and getting hungry. The parasympathetic branch stimulates digestion (think rest and digest from skye’s class, easy to remember). The sympathetic nervous system would be more of energy expenditure while parasympathetic is storage.
Phase 2 is the gastric phase: mechanical, endocrine, and neural control. This is when food enters the stomach, and its activated by stomach distension (when the stomach fills up and stretches because of the food that’s in it) as well as chemicals in the food. This stimulates nerves as well as hormones that help regulate digestion (endocrine factors). The gastric phase also has something called short reflexes. They’re neural reflexes that don’t go to the brain. It connects one part of the GI tract to another part so signals can be transmitted quickly. Long reflexes also happen in the gastric phase. They go via the medulla and the vagus nerve that can go to other parts of the GI tract but they are processed through the brain. Gastrin is a hormone that comes from G cells (involved in endocrine control). Note: ALL THREE OF THESE PHASES CAN BE INHIBITED
Phase 3 is the Intestinal phase: mechanical, endocrine, and neural control. This phase is stimulated by partially digested food that enters the small intestine. We see inhibition (negative feedback) the more acidic the intestine, the less contents are going to be ejected into the intestine. Hormonal control: gastrin released in the stomach and stimulatory effects of others.

From the esophagus, we get to the stomach, where more mechanical digestion happens (the stomach churns and moves around to further break down food) and more chemical digestion occurs simultaneously. The stomach secretes gastric juices to help break apart the food further and into the nutrients we need that get absorbed later on in the digestive system. The movement of food within the stomach is called segmentation; it’s the mixing motion that basically sloshes food around haha. Within the stomach, we have gastric pits that hold important cells which provide different things to the stomach. Parietal cells are found in the gastric pits, and they secrete hydrogen ions (Hydrochloric acid) that enters the lumen of the stomach to acidify the content. We also have chief cells that secrete an enzyme called pepsinogen that becomes pepsin and helps breakdown proteins. Pepsinogen starts off as a pro enzyme, which is an enzyme that is not yet active, into the stomach. Pepsinogen is then activated by the low pH in the gut and becomes pepsin. Pepsin is what breaks down the proteins found in the stomach. There are also surface epithelial cells that produce a thick coating of mucus, which protects the gastric mucosa from acid and enzymes. Surface epithelial cells also secrete bicarbonate.

The digestive system helps us get nutrients from the outside world into our bodies. Technically, the digestive tract is the outside of the body (the mouth and the anus are the holes at either end). So to begin, we’re gonna go over the anatomy of the digestive system, we start at the mouth, which is where ingestion and mechanical breakdown (chewing) of food happens. The mouth and the esophagus are made up of stratified squamous epithelial tissue because the goal here is protection, not absorption or secretion. Saliva moistens the food and starts to break it down (chemical breakdown by an enzymes called amylase (breaks down carbs, is also known as CHO) and lipase (breaks down lipids). Saliva also helps lubricate the food and this helps it travel down the throat more easily.

On Earth, water has a very important role in cycling through different forms and uses to be brought to all forms of life and help sustain them. The water cycles may begin as water in the oceans and largest fresh water sources. These are stores of water reserves, pools, from which most water leaves and returns to. The water here is evaporated up into the atmosphere by the solar rays that eject molecules from the surfaces of the water. The vapor is carried up because of its low density travels up into the atmosphere. The vapors are carried by the wind and coriolis effect across countries. Certain elevations can capture the clouds and force them into valleys. Here it hits cold air and can no longer maintain the energy to stay as a gaseous molecule so it condenses into water droplettes that hang in the high atmosphere. When enough water drops condense the gravity becomes to much and it falls back down to the ground in various forms of precipitation. The water then soaks into the earth and is used by different organisms: plants suck it up and it evaporates out the leaves, aquatic organisms swim in it and breathe oxygen through it, birds and small critters drink it off of leaves, etc. Eventually, the water runs down elevation in creeks and streams and through the soil until it finds itself back into a pool where the cycle once again takes place. 

Kappaphycus and Eucheuma red seaweeds are closely related genetically are currently the most widely and largely produced by volume compared to other varieties (Hurtado.) The development of seaweed aquaculture is a viable source for carbon offsetting in the oceans. Other forms of aquaculture (fin-fish and crustaceans) produce a large proportion of the emissions in aquaculture, around 300 thousand tonnes of CO2 per year. Seaweed aquaculture produces around 1.1 thousand tonnes per year per every square kilometer. Based on this data, we can calculate it would take a comparatively small area to make the industry carbon-neutral when compared to the other forms of aquaculture. Agriculture produces around 12% of the global emissions annual and has for the past thirty years, totaling around 5.1 billion tonnes of CO2. 

Basic principles of biological evolution say the organism most suited for its environment will win out over other organisms and no two organisms can inhabit the same niche. Why is it then that planet earth houses such incredible biodiversity? Shouldn't there be a few dominant species and maybe some stragglers? Well, it turns out many species have been able to co-exist with other similarly functioning species by partitioning their resources. There are two ways this can be accomplished. First is through specialization. If in an ecosystem, there are different sizes of the same food then different organisms may slowly develop adaptions that would allow them to better capitalize on a specific part of that food. For example, some birds may develop beaks better designed for small seeds while others could go for large seeds. Both species are feeding on seeds, however, the size of the seed is divided. The second way is through broadening the food types. If there is an increase in variability of the necessary resource then more species can be included in the partitioning. It is important to keep in mind that neither of these methods is based on altruism. Life on earth always looks out for its best interest.

Our group has decided to go ahead and follow the lichen project proposal to do. For this project, we will observe and record the number of the three different types of lichens mentioned in the proposal. After all of the data is recorded, we hope to see a lower diversity of lichen in urbanized areas and be able to detect the level of air pollution. Based on the amount of air pollution in the area, further steps can be taken to lower this pollution. 

A 2017 study found that non-smoking adults were four times more likely to start smoking traditional cigarettes after only 18 months of vaping, which includes “juuling.” On October 16, 2019, an article has been posted online stating a mother has filed a lawsuit against Juul as her 18 year-old son has died in his sleep. The mother has stated in the article that her son had started using the Juul at age 15, which is an age that tobacco should not even be in question. He had used it so often that he would have mood swings if he did not have it. Already, this is a major sign of a psychological downside.  Less than a year after he began vaping, the teen was hospitalized three times for breathing and lung complications — and hospital staff gave him nicotine patches because he was “so addicted to Juul,” the suit says

One model of ecological succession is facilitation. This mechanism takes place when a large disturbance has taken place in an environment rendering it useless to the organisms who once called it home. A pioneer species able to survive in this environment gains a foothold and begins to transform its surroundings by simply existing. The type of change it may produce will likely be in favor of its own species while simultaneously making the habitat not suitable for other species. After some time this initial species has become a prominent figure in the budding ecosystem, however, the modifications to the environment have made it ideal for other species. With their upcoming, the pioneer species population may be reduced in size until there is little to none left. The dominant species could not have lived in this environment if it weren't for the pioneer species. For this reason, the model was named 'facilitation, as one pioneer species facilitated the means by which another organism can come up.