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This tree represents how evolution has progressed over time through various points. To begin, the tree has grown from the root or the common ancestor. The common ancestor is most likely a eukaryote that first existed about 2.1 billion years ago. A eukaryote reproduces through sexual or asexual reproduction. Reproduction brings mutations upon the DNA of the offspring and in other words, variation. This has caused different adaptations to occur for organisms to respond to their environmental conditions and other factors. For instance, frogs have evolved to live in water and on land to have a higher chance of survival. Through variation and adaptation, new characteristics appear, creating new species. Therefore, multiple branches or kingdoms of eukaryotes exist including plants and animals. The location of specific organisms on one branch signifies similar characteristics between them. For example, horses and humans have four limbs, so that is one reason why they are on the same branch. Essentially, this tree is similar to a phylogenetic tree since it does not necessarily indicate time, but a possible evolution illustration of several eukaryotes.

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Escherichia coli or E. coli is a foodborne disease often associated with consuming raw or contaminated ground beef, drinking pasteurized milk, or swimming in contaminated sewage water. Nonetheless, contamination can also happen during a cattle's slaughter or while milking a cow. There are hundreds of types of E. coli, however most of them are harmless and live in the human intestines. Symptoms of E. coli include abdominal cramps, bloody diarrhea, and kidney failure. A stool specimen should be completed especially if the sick person has bloody stool. Most people recover between 5 to 10 days while avoiding anti-diarrheal agents. However, there is a low chance for those under five years old and elderly people to develop hemolytic uremic syndrome caused by E. coli. Most recover without antibiotics if they only experience diarrhea. Those who experience multiple symptoms are susceptible to these possible long-term effects: high blood pressure, blindness, paralysis, and dialysis. It is particularly important for people who are infected to do proper hand washing and to avoid swimming in public areas. The best ways to prevent E. coli is by cooking beef thoroughly with the help of an instant-read thermometer, only drinking pasteurized milk, and avoiding cross contamination between surfaces that came into contact with raw meat by handling cooked meat with clean appliances.

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I believe we see or use less monocot plants compared to dicot plants. For example, we see several corn fields during the summer with narrow leaves. One of the most popular monocot plants is grass. If I were to pull grass from the ground where I do not want it to grow, I would observe fibrous roots. Meanwhile, dicots are more commonly found or consumed. In many grocery stores, we see jalapeños, spearmint, rosemary, and basil. When we planted our jalapeños, they had small tap roots. Additionally, we see roses with 5 petals as decoration in front of buildings and homes like mine. My least favorite dicot has to be poison ivy because of the symptoms it can cause. Nonetheless, I have seen its oval or palmate leaves from afar.

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The phylum Porifera is most likely the first phyla of how the animal kingdom came to be about. Porifera means "pore-bearer" which have ostia or pores on their surface. Porocytes control what enters and exits the sponge's pores. Sponges are usually described as asymmetrical with no organs nor tissues. This means they have no digestive system, so water must enter their central cavity and exit through their osculum to survive. The water is the key factor that brings nutrients to the sponge. Additionally, sponges are made up of two layers of cells with mesohyl or collagen between each layer. The outer layer is called the pinacocyte which allows it to stick to a surface. An important type of cell are the choanocytes since they have flagella that controls the water flow in the central cavity. It can bring in organic material and phytoplankton. However, the ping-pong tree sponge does not use water to receive nutrients, but instead consumes crustaceans.

Moreover, spicules, made in sclerocytes, are a form of physical defense against predators. Spines and toxins are also forms of defense. Spermatocytes and occytes are the cells that allow for reproduction to occur for sponges. Another important type of cell are the amoebocytes because they can turn into any cell that is needed within the sponge. Sexual reproduction occurs due to water as well since sperm cells try to find another sponge. They can also asexually reproduce through gemmules, budding, or fragmentation.

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Homeostasis is explained through various scenarios such as body temperature, blood glucose, blood clotting, and childbirth. Specifically, there is a diagram where the body temperature is trying to be lowered. The stimulus is the first part of the cycle, where it indicates that the body temperature is higher than 37 degrees Celsius. Next, the sensor measures the values from the stimulus. Then, the sensor or the nerve cells in the brain and skin sends this information to the control centre. The control centre or the hypothalamus processes the data and decides if an effector should be signaled to proceed. The effector could be a muscle, gland, organ, or another body part. Its responsibility is to lower the body temperature back to normal. In this scenario, the effector is the sweat glands. This is an example of the body using negative feedback since the body is trying to return to homeostasis.

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Created by CK-12 Foundation/Adapted by Christine Miller

This device (Figure 7.8.1) looks simple, but it controls a complex system that keeps a home at a steady temperature - it's a thermostat. The device shows the current temperature in the room, and also allows the occupant to set the thermostat to the desired temperature. A thermostat is a commonly cited model of how living systems - including the human body- maintain a steady state called homeostasis.

Homeostasis is the condition in which a system (such as the human body) is maintained in a more or less steady state. It is the job of cells, tissues, organs, and organ systems throughout the body to maintain many different variables within narrow ranges compatible with life. Keeping a stable internal environment requires continually monitoring the internal environment and constantly making adjustments to keep things in balance.

Set Point and Normal Range

For any given variable, such as body temperature or blood glucose level, there is a particular that is the physiological optimum value. The set point for human body temperature, for example, is about 37 degrees C (98.6 degrees F). As the body works to maintain homeostasis for temperature or any other internal variable, the value typically fluctuates around the set point. Such fluctuations are normal, as long as they do not become too extreme. The spread of values within which such fluctuations are considered insignificant is called the normal range. In the case of body temperature, for example, the normal range for an adult is about 36.5 to 37.5 degrees C (97.7 to 99.5 degrees F).

A good analogy for set point, normal range, and maintenance of homeostasis is driving. When you are driving a vehicle on the road, you are supposed to drive in the centre of your lane - this is analogous to the set point. Sometimes, you are not driving in the exact centre of the lane, but you are still within your lines, so you are in the equivalent of the normal range. However, if you were to get too close to the centre line or the shoulder of the road, you would take action to correct your position. You'd move left if you were too close to the shoulder, or right if too close to the centre line - which is analogous to our next concept, negative feedback to maintain homeostasis.

Maintaining Homeostasis

Homeostasis is normally maintained in the human body by an extremely complex balancing act. Regardless of the variable being kept within its normal range, maintaining homeostasis requires at least four interacting components: stimulus, sensor, control centre, and effector.

1. The stimulus is provided by the variable being regulated. Generally, the stimulus indicates that the value of the variable has moved away from the set point or has left the normal range.

2. The sensor monitors the values of the variable and sends data on it to the control centre.

3. The control centre matches the data with normal values. If the value is not at the set point or is outside the normal range, the control centre sends a signal to the effector.

4. The effector is an organ, gland, muscle, or other structure that acts on the signal from the control centre to move the variable back toward the set point.

Each of these components is illustrated in Figure 7.8.2. The diagram on the left is a general model showing how the components interact to maintain homeostasis. The diagram on the right shows the example of body temperature. From the diagrams, you can see that maintaining homeostasis involves feedback, which is data that feeds back to control a response. Feedback may be negative (as in the example below) or positive. All the feedback mechanisms that maintain homeostasis use negative feedback. Biological examples of positive feedback are much less common.

In a negative feedback loop, feedback serves to reduce an excessive response and keep a variable within the normal range. Two processes controlled by negative feedback are body temperature regulation and control of blood glucose.

Body Temperature

Body temperature regulation involves negative feedback, whether it lowers the temperature or raises it, as shown in Figure 7.8.3 and explained in the text that follows.

The human body's temperature regulatory centre is the hypothalamus in the brain. When the hypothalamus receives data from sensors in the skin and brain that body temperature is higher than the set point, it sets into motion the following responses:

Blood vessels in the skin dilate (vasodilation) to allow more blood from the warm body core to flow close to the surface of the body, so heat can be radiated into the environment.

As blood flow to the skin increases, sweat glands in the skin are activated to increase their output of sweat (diaphoresis). When the sweat evaporates from the skin surface into the surrounding air, it takes heat with it.

Breathing becomes deeper, and the person may breathe through the mouth instead of the nasal passages. This increases heat loss from the lungs.

Heating Up

When the brain's temperature regulatory centre receives data that body temperature is lower than the set point, it sets into motion the following responses:

Blood vessels in the skin contract (vasoconstriction) to prevent blood from flowing close to the surface of the body, which reduces heat loss from the surface.

As temperature falls lower, random signals to skeletal muscles are triggered, causing them to contract. This causes shivering, which generates a small amount of heat.

The thyroid gland may be stimulated by the brain (via the pituitary gland) to secrete more thyroid hormone. This hormone increases metabolic activity and heat production in cells throughout the body.

The adrenal glands may also be stimulated to secrete the hormone adrenaline. This hormone causes the breakdown of glycogen (the carbohydrate used for energy storage in animals) to glucose, which can be used as an energy source. This catabolic chemical process is exothermic, or heat producing.

Blood Glucose

In controlling the blood glucose level, certain endocrine cells in the pancreas (called alpha and beta cells) detect the level of glucose in the blood. They then respond appropriately to keep the level of blood glucose within the normal range.

If the blood glucose level rises above the normal range, pancreatic beta cells release the hormone insulin into the bloodstream. Insulin signals cells to take up the excess glucose from the blood until the level of blood glucose decreases to the normal range.

If the blood glucose level falls below the normal range, pancreatic alpha cells release the hormone glucagon into the bloodstream. Glucagon signals cells to break down stored glycogen to glucose and release the glucose into the blood until the level of blood glucose increases to the normal range.

Homeostasis and Negative/Positive Feedback, Amoeba Sisters, 2017.

In a positive feedback loop, feedback serves to intensify a response until an end point is reached. Examples of processes controlled by positive feedback in the human body include blood clotting and childbirth.

Blood Clotting

When a wound causes bleeding, the body responds with a positive feedback loop to clot the blood and stop blood loss. Substances released by the injured blood vessel wall begin the process of blood clotting. Platelets in the blood start to cling to the injured site and release chemicals that attract additional platelets. As the platelets continue to amass, more of the chemicals are released and more platelets are attracted to the site of the clot. The positive feedback accelerates the process of clotting until the clot is large enough to stop the bleeding.

Childbirth

Figure 7.8.6 shows the positive feedback loop that controls childbirth. The process normally begins when the head of the infant pushes against the cervix. This stimulates nerve impulses, which travel from the cervix to the hypothalamus in the brain. In response, the hypothalamus sends the hormone oxytocin to the pituitary gland, which secretes it into the bloodstream so it can be carried to the uterus. Oxytocin stimulates uterine contractions, which push the baby harder against the cervix. In response, the cervix starts to dilate in preparation for the passage of the baby. This cycle of positive feedback continues, with increasing levels of oxytocin, stronger uterine contractions, and wider dilation of the cervix until the baby is pushed through the birth canal and out of the body. At that point, the cervix is no longer stimulated to send nerve impulses to the brain, and the entire process stops.

Normal childbirth is driven by a positive feedback loop. Positive feedback causes an increasing deviation from the normal state to a fixed end point, rather than a return to a normal set point as in homeostasis.

Homeostatic mechanisms work continuously to maintain stable conditions in the human body. Sometimes, however, the mechanisms fail. When they do, homeostatic imbalance may result, in which cells may not get everything they need or toxic wastes may accumulate in the body. If homeostasis is not restored, the imbalance may lead to disease - or even death. Diabetes is an example of a disease caused by homeostatic imbalance. In the case of diabetes, blood glucose levels are no longer regulated and may be dangerously high. Medical intervention can help restore homeostasis and possibly prevent permanent damage to the organism.

Normal aging may bring about a reduction in the efficiency of the body's control systems, which makes the body more susceptible to disease. Older people, for example, may have a harder time regulating their body temperature. This is one reason they are more likely than younger people to develop serious heat-induced illnesses, such as heat stroke.

Diabetes is diagnosed in people who have abnormally high levels of blood glucose after fasting for at least 12 hours. A fasting level of blood glucose below 100 is normal. A level between 100 and 125 places you in the pre-diabetes category, and a level higher than 125 results in a diagnosis of diabetes.

Of the two types of diabetes, type 2 diabetes is the most common, accounting for about 90 per cent of all cases of diabetes in the United States. Type 2 diabetes typically starts after the age of 40. However, because of the dramatic increase in recent decades in obesity in younger people, the age at which type 2 diabetes is diagnosed has fallen. Even children are now being diagnosed with type 2 diabetes. Today, about 3 million Canadians (8.1% of total population) are living with diabetes.

You may at some point have your blood glucose level tested during a routine medical exam. If your blood glucose level indicates that you have diabetes, it may come as a shock to you because you may not have any symptoms of the disease. You are not alone, because as many as one in four diabetics do not know they have the disease. Once the diagnosis of diabetes sinks in, you may be devastated by the news. Diabetes can lead to heart attacks, strokes, blindness, kidney failure, nerve damage, and loss of toes or feet. The risk of death in adults with diabetes is 50 per cent greater than it is in adults without diabetes, and diabetes is the seventh leading cause of death of adults. In addition, controlling diabetes usually requires frequent blood glucose testing, watching what and when you eat, and taking medications or even insulin injections. All of this may seem overwhelming.

The good news is that changing your lifestyle may stop the progression of type 2 diabetes or even reverse it. By adopting healthier habits, you may be able to keep your blood glucose level within the normal range without medications or insulin. Here's how:

Lose weight. Any weight loss is beneficial. Losing as little as seven per cent of your weight may be all that is needed to stop diabetes in its tracks. It is especially important to eliminate excess weight around your waist.

Exercise regularly. You should try to exercise for at least 30 minutes, five days a week. This will not only lower your blood sugar and help your insulin work better, but it will also lower your blood pressure and improve your heart health. Another bonus of exercise is that it will help you lose weight by increasing your basal metabolic rate.

Adopt a healthy diet. Decrease your consumption of refined carbohydrates, such as sweets and sugary drinks. Increase your intake of fibre-rich foods, such as fruits, vegetables, and whole grains. About one-quarter of each meal should consist of high-protein foods, such as fish, chicken, dairy products, legumes, or nuts.

Control stress. Stress can increase your blood glucose and also raise your blood pressure and risk of heart disease. When you feel stressed out, do breathing exercises or take a brisk walk or jog. Try to replace stressful thoughts with more calming ones.

Establish a support system. Enlist the help and support of loved ones, as well as medical professionals, such as a nutritionist and diabetes educator. Having a support system will help ensure that you are on the path to wellness, and that you can stick to your plan.

https://www.youtube.com/watch?v=LSgEJSlk6W4

Homeostasis - What Is Homeostasis - What Is Set Point For Homeostasis - Homeostasis In The Human Body, Whats Up Dude, 2017.

Attributions
Figure 7.8.1 Figure 7.8.2 Figure 7.8.3
References
Figure 7.8.4
Amoeba Sisters. (2017, September 7). Homeostasis and negative/positive feedback. YouTube. https://www.youtube.com/watch?v=Iz0Q9nTZCw4&feature=youtu.be
Figure 7.8.5
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, April 25). Figure 1.10 Negative feedback loop [digital image/ diagram]. In Anatomy and Physiology (Section 1.5). OpenStax. https://openstax.org/books/anatomy-and-physiology/pages/1-5-homeostasis
Figure 7.8.6
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, April 25). Figure 1.11 Positive feedback loop

Cognito. (2018, December 18). GCSE Biology - Homeostasis #38. YouTube. https://www.youtube.com/watch?v=XMsJ-3qRVJM&feature=youtu.be

Mayo Clinic Staff. (n.d.). Type 2 diabetes [online article]. MayoClinic.org. https://www.mayoclinic.org/diseases-conditions/type-2-diabetes/symptoms-causes/syc-20351193

OpenStax CNX. (2016, March 23). Figure 4 The body is able to regulate temperature in response to signals from the nervous system [digital image]. In OpenStax, Biology (Section 33.3). https://cnx.org/contents/GFy_h8cu@10.8:BP24ZReh@7/Homeostasis

Whats Up Dude. (2017, September 20). Homeostasis - What is homeostasis - What is set point for homeostasis - Homeostasis in the human body. YouTube. https://www.youtube.com/watch?v=LSgEJSlk6W4&feature=youtu.be

The ability of an organism to maintain constant internal conditions despite external changes.

The smallest unit of life, consisting of at least a membrane, cytoplasm, and genetic material.

A cellular organizational level between cells and a complete organ. A tissue is an ensemble of similar cells and their extracellular matrix from the same origin that together carry out a specific function. Organs are then formed by the functional grouping together of multiple tissues.

A group of tissues in a living organism that have been adapted to perform a specific function. In higher animals, organs are grouped into organ systems; e.g., the esophagus, stomach, and liver are organs of the digestive system.

A group of organs that work together to perform one or more functions. Each does a particular job in the body, and is made up of certain tissues.

A physiologically optimum value for a given biological variable such as body temperature.

The spread of values around the set point of a biological variable such as body temperature that is considered normal, with no negative effects on health.

A control mechanism that serves to reduce an excessive response and keep a variable within its normal range.

Something that triggers a behavior or other response.

Component of a homeostatic mechanism that senses the value of a variable and sends data on it to the control center.

Component of a homeostatic control mechanism that monitors a variable and sends signals to the effector as needed to keep the variable in homeostasis.

A component of a homeostatic control mechanism, such as a gland or an organ, that acts on a signal from the control center to move the variable back toward the set point.

A control mechanism that serves to reduce an excessive response and keep a variable within its normal range.

A part of the brain that secretes hormones and connects the brain with the endocrine system.

A large endocrine gland in the neck whose hormones control the rate of cellular metabolism and help maintain calcium homeostasis.

one of a pair of glands located on top of the kidneys that secretes hormones such as cortisol and adrenaline

A non-steroid catecholamine hormone produced by the medulla of the adrenal glands that stimulates the fight-or-flight response.

A multi-branched polysaccharide of glucose that serves as a form of energy storage in animals, fungi, and bacteria.

Glucose (also called dextrose) is a simple sugar with the molecular formula C6H12O6. Glucose is the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using energy from sunlight.

A chemical reaction that releases energy through light or heat.

A control mechanism that serves to intensify a response until an endpoint is reached.

An endocrine hormone secreted by the pituitary gland that controls a variety of functions, including during childbirth to stimulate uterine contractions and during lactation to trigger milk letdown.

A condition in which cells may not get everything they need or toxic wastes may accumulate because of the failure of a homeostatic mechanism.

A disease caused by problems with the pancreatic hormone insulin, which leads to high blood glucose levels and symptoms such as excessive thirst and urination; includes type 1 and type 2 diabetes.

A multifactorial disorder in which a combination of insulin resistance and impaired insulin production lead to loss of glucose control and high levels of blood glucose.

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Created by CK-12 Foundation/Adapted by Christine Miller This device (Figure 7.8.1) looks simple, but it controls a complex system that keeps a home at a steady temperature - it's a thermostat. The device shows the current temperature in the room, and also allows the occupant to set the thermostat to the desired temperature.

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A bicuspid aortic valve is a congenital heart defect that occurs in one to two percent of the population. This disease is also heterogenous or that is causes different symptoms within different patients. It occurs when elastin in the largest vessels becomes damaged or a changed flow pattern occurs in different parts of the heart. Some people never really find out they have this condition until it turns into aortic regurgitation or aortic stenosis. Root replacement is one of the highly advised treatments to bicuspid aortic valve disease. Additionally, people can go under surgery for root repair which is more beneficial for younger patients. They can undergo a cardiac MRI scan, an echocardiography, and other tests to correctly diagnose bicuspid aortic valve disease. Moreover, symmetry is vastly important during root repair since it deals with the folds of the fused sinuses that allow blood to flow adequately.

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The desert biome has a vastly dry and hot climate. There is also never much rainfall in the desert biome. The temperature changes from a hot day to a freezing night. As a result, there are only a few types of plants including cacti and succulents. They have to heavily depend on their water storage since there is low precipitation in the desert. Additionally, camels are one of the animals that can survive in this biome as seen in the image above. Other animals that people can see there are snakes and lizards. This biome has a low biodiversity due to its limited variety of species.

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Biodiversity is all of the species one sees out in nature. It is anything from a few bushes to a colony of ants. However, it does not only include the amount of species, but also their genetic variability and the diversity of ecosystems. Moreover, biodiversity is a recent concept from the 1980's, where people began to become concerned over the human impact on the environment. Biodiversity is important because of its economic value, ecological life support, cultural value, recreational value, and its scientific value. We all benefit from biodiversity from fishing, monitoring our clean water, creating artwork of nature to ultimately taking a hike. There is also a negative value of biodiversity like crocodiles or the smallpox virus. We consider them to be negative due to our fear over being hurt or becoming sick. Overall, people are continuing to become concerned over our impact on biodiversity and carrying out strategies to assist the prosperity of biodiversity.

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What is biodiversity and why is it important?