Osmoregulators (L160)

Think of marine mammals, which breathe air 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 the different concentrations of salt in the water?

Marine animals use osmoregulation to regulate the use of salt and water inside of their cells. Considering that marine mammals only drink salt water, and salt water is high in solutes (it is hyperosmotic to the cells), water tends to be drawn out from the cells. (To be hyperosmotic, there must be less ‘free’ [salt-free] water and more solutes than the liquid in the cells.)
Fresh water on the other hand is low in solutes, and offers lots of ‘free’ water. This means that the solute-rich cytoplasm (of the freshwater fish) is hyperosmotic. (In other words, cells tend to absorb more fresh water). Aquatic animals face the danger of absorbing too much water and bursting their cells if their is no regulation.
Osmoconformers are organisms that maintain equilibrium (by being able to keep the concentration of solutes in their cells equal to that of the solutes in their environment). This ability is dependent on a stable water composition, and is carried out through the process of active transport (most of the time).
Osmoregulators are organisms that can regulate the concentration of solutes and water inside their body; due to this ability, they are able to tolerate a much wider range of environments (from fresh water, to salt water, to land) and are known to switch from one to another throughout their life cycle. Using active transport, excess chloride ions are removed and excreted, sodium follows the chloride closely after. Pumping out the salts allows the marine animal to maintain a hypo-osmotic state on the inside of their cells.

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Hard at Work Breathing; The Tale of the Almighty Lungs (L150)

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

alveoli

(The Respiratory System)

trachea

(Trachea)

When you find yourself breathing hard, or deeply (and gasping), it is actually due to an excess of carbon dioxide, rather than a lack of oxygen. But before we get into this, let’s go back to the beginning. This whole process starts with the lack of recognition for the millions of cells and signals at work for the lungs! There is an entire world of hustling and bustling under your skin that puts the pieces in motion for you to thrive! The thoracic cavity (basically enclosed by rib-cage) enlarges, reducing the air pressure, when we breathe in. High pressure air is rushed in through the mouth and nose, and down the trachea into the bronchi and alveoli. (For a pretty cool interactive chart of the lungs, click here.) This then causes the diaphragm (located directly under the lungs) and intercostal muscles to relax. As you breathe out, the volume of the thoracic cavity shrinks, and air is pushed out as the pressure increases. Now to understand the body, you must keep in mind that every organ reports to the brain. Cerebrospinal fluid can be found on and in the brain and in the spinal cord; its job is to absorb the liquid and chemicals from inside the blood. This also includes absorbing carbon dioxide, which then turns into carbonic acid and dissolves into ions that lower pH. (This next set of stages is called feedback.) The decrease in pH in blood leads to a decrease in cerebrospinal pH. (Lower pH in this case simply indicates a high concentration of carbon dioxide) and finally the medulla oblongata signals faster, deeper breathing. Jacob Bear offered his own chart on feedback during lesson 149. I have created my own to help break this down simply!Learn Paper - 3 Bibliography
The Respiratory System. Digital image. Natural Health School. N.p., n.d. Web. 16 June 2015. <http://www.naturalhealthschool.com/bronchi_trachea.html&gt;.
Trachea. Digital image. The Free Dictionary By Farlex. Farlex, n.d. Web. 16 June 2015. <http://medical-dictionary.thefreedictionary.com/trachea&gt;.

Be a Biological Detective (L140)

Suppose you found the bones of an unidentified animal. How could you learn about what the animal ate? What specific structures would give you clues about the creature’s diet?

There are multiple ways to identify the diet of an animal after death. One way to find key identifying clues would be to study the animals dentition; this is the development and arrangement of teeth. There are two types of animals (as far as teeth categorization goes); homodonts and heterodonts. In the mouth of a homodont, all the teeth are the same shape and makeup (with the exception of fangs in some reptiles). In the mouth of a heterodont however, one will find many different types of teeth; like in humans. The shape and makeup of each tooth can then be used to narrow down and determine its specific function, and the animal to which it belongs. Sharp long teeth are used for tearing, shredding and getting a good grip on flesh; whereas flat, blocky teeth are used to grind and mash plant matter. It take more effort to break down the cell wall in plants, so smashing up the food allows for the most surface area to be exposed at a time.

Extra: If one had found a carcass with fresh-ish remainders still inside, (obviously unlikely, but…) they would be able to come to the conclusion about the animals diet based upon the length of the intestines as well. Herbivores have a longer small intestine than carnivores; this is because they are maximizing the amount of surface area being exposed and processed at once. Plant matter is more difficult to digest than animal flesh.
Humans have intestines (for the most part) that are, lenghtwise, in-between that of carnivores and herbivores; surprisingly, length can vary by as much as five feet between two people, but nonetheless, humans have the build of an omnivore. 

Mammals / Amniotes (L130)

Amniotes are creatures that can reproduce on land, thanks to the amniotic egg. Why are mammals considered to be amniotes, given that most mammals do not lay eggs? What structures do mammals have that are the same, or comparable to an amniotic egg?

An amniote is a tetrapod capable of producing an amniotic egg; the egg does not need to remain outside of the body, although this is typical. Mammals for example, contain the egg inside their body for the entire duration of fetal development.  When the fetus has matured into an infant, the mother gives birth (as opposed to having laid an egg, and allowing it to mature outside of the body). The physical structure of the female human body during pregnancy clearly resembles an amniotic egg (a chicken egg for example). The amniotic egg has multiple functions; a fluid-filled sac for embryonic cushioning/protection, as well as moisture.

(Amniotic)

(Amniotic)

(Gestation)

There are four basic extraembryonic membranes that develop outward from the embryo; the yolk sac, the chorion, the allantois, and the shell and albumen. These are crucial pieces of the amniotic structure. Pictured to the left is a diagram of a human fetus; to the right is a basic amniotic egg.


Bibliography

Amniotic Eggs. Digital image. Boundless.com. N.p., n.d. Web. 27 Apr. 2015. <https://www.boundless.com/biology/textbooks/boundless-biology-textbook/vertebrates-29/reptiles-174/characteristics-of-amniotes-670-11892/images/fig-ch29_04_01/&gt;.

Gestation: Human Fetus in Uterus. Digital image. Encyclopedia Britannica Online. Encyclopedia Britannica, n.d. Web. 27 Apr. 2015. <http://www.britannica.com/EBchecked/topic/232124/gestation//images-videos/124247/gestation-human-fetus-in-uterus&gt;.

Discovering Arthropods! (L120)

Could a deeper understanding of arthropods lead to tangible economic benefits?

A deeper understanding of arthropods could absolutely lead to tangible economic benefits for humans. One huge step that scientists are currently moving towards taking is creating a way to mass produce spider silk. It is comprised of groups of beta sheets bonded together. The beta sheets themselves are separated by highly flexible proteins. Not only is it as strong as steel, but it is extremely flexible! This material could be an intense introduction into the industrial world. Currently, spider silk already has multiple different uses, including medical and luxury applications. If only this one tiny part of the largest animal phylum in the world has so much to offer, how could we not explore deeper into these animals! Discovery is a beautiful thing; nature has so much to offer us, to help and heal us, we just need to be looking for it.

Chordates (L110)

What is a chordate? How are vertebrates different from chordates?

Chordates are animals that possess a notochord, a dorsal nerve cord, pharyngeal clefts and a muscular tale (for at least some portion of their life cycle). A unique aspect of chordates is that they’re the only animals whom possess a hollow dorsal nerve cord; other animals will have a solid dorsal cord, if any. Most non chordate animals have a ventral nerve cord. Chordates belong to the kingdom animalia, and the phylum chordata.
Vertebrates belong to a subphylum of chordate animals, and represent the majority of the phylum chordata. Vertebrates are characterized by having an extensive skull as well as a backbone composed of vertebrae. They also have homeotic genes (hox genes) that serve as a blueprint for each pody part’s position and shape. All vertebrates are craniats, and all craniates are chordates (in the phylum chordata). Therefore, all chordates are animals, as are vertebrates.

Soiling the Myths of Dirt (L100)

Someone says, “Soil is just dirt to hold the plant up.” Would you agree or disagree with this statement? (Note: It is possible to do either one.) Back up your opinion with facts taken from the video lessons, readings, or other sources. Present at least one counter-argument and your own response to the counter-argument.

If someone were to say to me “soil is just dirt to hold the plant up,” I would more than likely respond by asking them “how so?”. Yes, the soil provides foundation and structure for the plants roots to anchor to; it does help hold the plant up, but it also does so much more! The roots in the soil are used to pull nutrients up through the plant.
There are many different classifications of soil, and different layers in the ground as well; these layers are called soil horizons. The first, or top layer of soil is quite appropriately named, topsoil. Topsoil is composed of many thousands of particles, both organic and inorganic ranging from minerals, to organisms’ waste, to whole live organisms like earthworms. These nutrients and minerals are crucial to a healthy plant, that will grow strong and tall. The organisms affect the soil pH, release nutrients, fix nitrogen, and some insects and worms even carry organic matter deeper into the soil, expanding the range of the topsoil. Soil nutrients are divided into two categories; macronutrients, which plants can’t get enough of, like water, and micronutrients that plants only need a small amount of, but are just as important. Soil is necessary for nutrients, support, sustenance, and much more.
One counter argument to this could be that “you can provide plants with all the nutrients they need without providing it through soil, the only thing they would then be lacking is a place to anchor themselves for growth support”. While this statement is true, it is not practical for mass agriculture. It would be unreasonable to alter the plants natural cycle in order to create a new way to grow plants. It would cost lots of space, money, time and resources, not to mention years of trial and error. Plants currently have a naturally efficient way to process sunlight and nutrients, and create energy; why change that?