Biology: Lesson 160 Essay- “What is bone marrow? What two types of bone marrow exist and why are they important to the overall health of the body?”

The two types of bone marrow are yellow and red. Yellow marrow is mostly fat cells. Yellow marrow is inactive most of the time, but it helps red marrow activity. Red marrow is important because it goes through a process known as hematopoiesis. Hematopoiesis is the creation of blood cells. This process can create any of three types of blood cells. Red marrow contains stem cells that can differentiate into neurons, osteoblasts, and others. Red marrow is important because it can create new blood cells in case you bleed a lot. Yellow marrow is important for the overall health of the body because it can change into red marrow when you lose extreme amounts of blood. This is important because it could save your life if your body has all the marrow producing blood cells. Red marrow is also important in the case of you being low in one specific type of blood cell (red, white, platelets), because the red marrow can make new cells and get that specific blood count back to normal.

Biology: Lesson 170 Essay- “Think of marine mammals, which breathe like we do but drink only salt water, and think of fish such as salmon which live part of their life in saltwater and part in freshwater. How do aquatic organisms deal with different concentrations of salt in the the water?”

The animals listed in the prompt above are all osmoregulators. This means that those animals can regulate the concentration of solutes and water in their bodies. This allows fish like salmon to live in a broader range of environments.

Animals that live in saltwater or drink only salt water have to deal with an excess of salt. Saltwater animals drink a lot of saltwater. Extra chloride ions are removed by active transport and leave the body through the gills or kidneys of the animal. The extra sodium then passively follows the chloride. These animals have to drink large amounts of saltwater to get a sufficient amount of water. Their bodies then remove the large amounts of salt in their bodies through the process described above.

Freshwater animals have the opposite problem, which is taking in too much water and not enough salts. Freshwater animals will normally drink little or no water. These freshwater animals urinate large amounts and the urine is very watery. Once they have ridden themselves of the extra water, they eat salty foods to balance out the water.

Salmon and other aquatic animals that live in both salt and fresh water have a cycle like this. Their bodies function how freshwater fish bodies function when they are in freshwater. Then when they enter salt water they produce cortisol. The cortisol causes chloride cells to grow. The larger chloride cells will secrete more salt than previously and the salt will leave from the gills of the fish.

Biology: Lesson 150 Essay – “When you find yourself breathing hard or gasping for breath, is this due to a lack of oxygen or an excess of carbon dioxide? Explain your answer, including a discussion of feedback systems and the mechanisms that are at work when you breathe.”

When you are breathing heavy and having a tough time it is because there is an excess of carbon dioxide in the blood. You breathe heavy to expel more carbon dioxide from your lungs.

Your body has a feedback system that regulates your blood pH. The stimulus in this feedback system is that there is too much carbon dioxide in the blood, which lowers your blood’s pH. Your body wants to maintain homeostasis and keep your blood pH at 7.4 so it is not good if it drops. Holding your breath or engaging in heavy exercise can cause the stimulus. Sensors in your blood vessels detect the low pH and send signals to the medulla oblongata. Your cerebrospinal fluid’s pH level will drop as well and this tells the medulla oblongata that there is too much carbon dioxide in your body. The medulla oblongata carries out the response in this feedback system. The medulla oblongata signals your rib muscles to contract deeper and faster. This makes you breathe heavier. The result is that more carbon dioxide is expelled from the lungs and the homeostasis of your blood pH is restored. Your breathing will return to normal after your homeostasis is restored.

Biology: Lesson 140 Essay – “How does your body “know” when you are hungry/not hungry? Describe the organs, chemicals, and mechanisms that affect feelings of hunger and satiety.”

Your body knows when you are full when hormones signal the satiety center in the brain that make you feel satisfied. When the satiety center is not satisfied you feel hungry. There are four primary hormones that affect the satiety center.

One of the four hormones is Ghrelin. This is the “hunger hormone” because it is released when the stomach is empty. The release is stopped when the stomach is stretched from food. Another important hormone is Insulin because it can suppress your appetite when released. It triggers the “full” feeling in the satiety center. Leptin is important because it can help suppress your appetite. It is released from fat cells. When losing weight, Leptin levels will drop which will make you feel hungrier. Fat people have high levels of Leptin, but it seems to have less of an impact because fat people still get very hungry. Peptide YY (PYY) helps suppress appetite. It is released by the small intestine at the end of a meal. Then it suppresses your appetite by counteracting the effects of the previously released Ghrelin. The cycle of hormones and signaling to the satiety center repeat.

Biology: Lesson 130 Essay – “What does it mean to say a creature is ‘intelligent?’ Describe some of the intelligent behavior of various animals, and compare it to human intelligence.”

Animals are considered intelligent if their neo-cortex is highly developed. Most intelligent animals also have large brains. This is not always the case because a lion might have a larger brain than a raven, but the raven is more intelligent than the lion. This is because ravens have a high brain mass to body mass ratio. Ravens’ brains have a brain mass to body mass ratio close to as high as primates’ brain to body ratio. Animals that are considered to be intelligent can normally do some of these things: count, use tools, teach/learn, and recognize individuals of their own species and sometimes other species.

One example of an animal that displays intelligence is the raven. Ravens can open zippers to backpacks and steal your sandwich. They can also recognize traffic signals that way they don’t get hit by cars when they are larfing it up in the middle of the road. Humans can do these things for the same reasons. Elephants can recognize themselves in mirrors, which was proved when some elephants touched a white mark painted on their heads. The elephants did this only once they had seen it in the mirror and not before. As humans we can also recognize ourselves in mirrors so that we can look on point for the ladies. Primates use their intelligence to use sticks to help them eat and for weapons. We as humans make our own tools for eating and weapons for beating people up.

Biology: Lesson 120 Essay – “Can a poisonous arthropod provide benefits to human beings? Are there virtues in the venom? Give a few examples to support your point of view.”

Poisonous arthropods can provide benefits to human beings. One thing that could be useful is the deathstalker scorpion’s venom. The deathstalker’s venom can bind with tumors, especially brain tumors. This could be useful if scientists could alter the venom to kill the tumors they bind with. This would be a potential cancer cure.

There are also enzyme inhibitors in the deathstalker’s venom. These can help destroy bacteria and viruses if used properly. They do not harm human cells because the target enzymes are not in human cells. The chemicals in the venom could be used to disinfect things and stop pathogens without harming humans.

The venom of spiders and scorpions can also be used to create anti-venom. Anti-venom can be given to people who were bit by a certain arachnid, if the anti-venom was made using the same arachnid it can help the body fight off the effects of the venom. Anti-venom is created by taking the venom from an arachnid, then diluting it, and injecting it into a horse, goat, lamb, or rabbit. The animal produces antibodies which are harvested and then can be given to someone who was bit or stung by the same arachnid that the anti-venom was made from.

Biology: Lesson 110 Essay – “What is a chordate? How are vertebrates different from chordates?”

A chordate is an animal that is in between a vertebrate and invertebrate. The only thing that is different between a chordate and vertebrate is that the chordate lacks a backbone that a vertebrate has. A chordate is like an invertebrate except it has structures that resemble a back bone.

Chordates have a notochord in between the digestive tract and nerve cord. It is a long flexible rod that muscles can push against while the chordate swims. Chordates have a hollow dorsal nerve chord on their back. In embryos the nerve cord will develop into the brain and spinal cord. It starts as a rolled up tube. Chordates also have slits on their heads behind their mouths. In aquatic animals these slits can develop into gills and for land animals they can develop into ears. Chordates also have a muscular tail at some point during their life cycle (even as embryos). These tails can help propel the animal.

Biology: Lesson 100 Essay – “How do the laws of chemistry and physics affect a plant’s ability to obtain and transport nutrients? Use facts and examples from the lessons readings or other sources.”

From a physics standpoint we see that water is adhesive and cohesive. This helps water and nutrients stick to the xylem and phloem as they move up these membranes. Since water is cohesive it helps the water stick to itself so that it wont split and fall as it moves up through the xylem and phloem. The pressure of the plasma membrane against the cell wall also helps push the nutrients up. The concentration of solutes and water molecules affect the speed and direction the water or nutrients in when traveling through the xylem and phloem. Physics is very important when explaining how water moves through plants.

Chemistry is also important when explaining how water moves through the xylem and phloem of a plant. Chemistry helps explain adhesion and cohesion with polarity. Water is polar because the valence electrons on H2O will hover around the oxygen more than the hydrogen. This gives the hydrogen a small positive charge and the oxygen a small negative charge. This polarity shows how water will stick to itself and other substances. Imagine the positive side of one water molecule sticking to the negative side of another water molecule. That is cohesion and polarity. In this case of water inside the xylem will stick to the xylem because the xylem will have a slight charge.

Biology: Lesson 90 Essay – “On the path from pollination to germination, there are many things that will slow down or delay the reproduction of a plant. Describe two or more of these delaying factors and explain how each could actually be helpful to the plant species.”

Competition can delay the reproduction of a plant. If a seed falls into a forest that already has lots of brush and plants on the ground as well as tall trees, the seed is not likely going to germinate. Even if the temperature and moisture were ideal, once the seed used up all of its initial nutrients it started with it would likely die due to lack of sunlight, minerals in the soil, and water. Sunlight and rain would have a tough time reaching the seed if there were trees blocking the sun and water than reach the ground. The seed would also likely be starved of nutrients in the soil because of all the brush and other ground plants sucking up nutrients and water. Some of the seeds that would be in this situation have adapted to germinate after going through extreme heat. This extreme heat would likely have been a forest fire that would have cleared away the other plants that were hogging all the food supplies. With these plants gone the seed would likely be able to grow.

Seasons can also delay plants from germinating. If it is fall or early winter most seeds will stay dormant because the temperature is going to continue to decline. If the seed were to germinate in the fall/early winter it would likely freeze during the next cold snap. These plants have adapted so that they will germinate after a cold snap once the temperature starts to rise and cause things to thaw. This thaw will usually mean spring is coming soon and the plant will germinate right after the thaw so that it would be just in time for spring.

Biology: Lesson 80 Essay – “Give one or more reasons that photosynthesis is challenging for plants in a desert environment. Describe in detail the adaptations that plants have made in order to deal with this challenge. You should be thinking of biochemical issues, not merely ways that a plant conserves water.”

Photosynthesis is challenging in deserts because there is trouble accessing and retaining water. Obviously, most deserts are dry which makes it difficult for plants to obtain water. Plants have trouble retaining water because the intense sun can cause evapotranspiration. Evapotranspiration is similar to evaporation except that water moves from inside the plant to outside the plant through tiny holes in the plant’s leaves.

One adaptation that desert plants have is that they will close their stomata during the day. Stomata are the tiny pores in the leaves of desert plants that I mentioned above. If these plants were to leave the stomata open then water would escape easily during the day. The plants need to open these pores to get CO2. They will open their stomata at night to get CO2 while losing only a small amount of water. They need to complete the Calvin cycle, which requires sunlight, in order to survive. It seems that these plants would die since the factors don’t come together at the same time, but they have special carbon containing acids that will absorb the CO2 and hold it. These acids will release the CO2 during the day so that it can go through the Calvin cycle when the sunlight was present.