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.
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.
(The Respiratory System)
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! Bibliography
The Respiratory System. Digital image. Natural Health School. N.p., n.d. Web. 16 June 2015. <http://www.naturalhealthschool.com/bronchi_trachea.html>.
Trachea. Digital image. The Free Dictionary By Farlex. Farlex, n.d. Web. 16 June 2015. <http://medical-dictionary.thefreedictionary.com/trachea>.
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.
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.
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.
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/>.
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>.
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.
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.
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?
Gymnosperms and angiosperms are both types of plants; but the main difference between them is that gymnosperms are plants with “naked seeds,” and angiosperms have seeds that are protected inside ovaries (as pictured on the left). Angiosperms are also classified as either monocots or dicots, which means that if one were to cut a cross section of a seed, they would either see one or two cotyledons (pictured below on the right). One way to tell the difference between a monocot and a dicot without opening the seed would be to wait until it sprouted; a dicot first sprout will typically have two small leaves at the top, and a monocot sprout will just be a strand with a nub at the end, no leaves.
Gymnosperms have seeds that are on special sporophylls, which are leaves that bear sporangia. (A sporangium is a spore-bearing plant.) Gymnosperm seeds often form cone shapes. Angiosperms are seed-bearing plants that produce flowers and fruits, and they make up about 90% of all plant species. One huge difference in their life cycles is that angiosperms use a technique of double pollination. This is done when the generative cell divides into two haploid sperm cells, and the pollen tube forms from the tube cell. One sperm cell will fertilize the egg, and the other sperm cell with form an endosperm with the polar nuclei to serve as a food source for the seed.
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.
Plants that inhabit desert environments are called crassulacean acid metabolism plants, or CAM plants for short. The CAM plant group is generally comprised of different succulents, such as pineapples and cacti. What makes their photosynthesis process unique from that of normal plants is the fact that they do things in a somewhat delayed, more complicated and elongated process. Normal plants are able to “work” throughout the day, and the sunlight it crucial to their schedule; during the daylight they will open their stomata (leaf pores) to absorb carbon from the air. Then, during the night, they will will close their stomata to conserve water. Desert plants function in quite the opposite fashion, and due to the ravenous dry heat, they are forced to close their stomata during the day, and open them at night. This makes it possible for the plant to both conserve water throughout the day, and absorb carbon through the night. The only trouble with this is that ATP and NADPH aren’t available at night, and so the CAM plants have the ability to absorb their intake of carbon using organic acids. This carbon is stored until the daylight returns and it can be released to begin producing energy.
What are some of the challenges of systematics and taxonomy?
Should a biologist’s classification be taken as absolute, inviolable truth? In your opinion, is taxonomy necessary and/or important? Why or why not?
Taxonomy is the science of naming and classifying organisms. One of the earliest challenges faced by scientists in taxonomy was that each organism, everywhere you traveled, had more than one name. Not only was this making factual communication more difficult, but it was also an issue that there was not much information on each organism. This lack of organization slowed many processes, and made it more difficult to seek out connections between organisms (systematics) that would later benefit scientific research of all types. Systematics is the discovery and research of the relationships between species based on the use of data; this includes data from (but not limited to) fossils, genes, and even molecules like proteins.
Although these studies are all based off of researched facts, I do not think that any classifications should be thought of as an inviolable truth. It is impractical to assume that just because one has a piece of the puzzle, that they can guess the rest of the picture correctly. There is always more to be discovered, things aren’t usually what they seem at first. I am a firm believer that everything can and should be challenged, and eventually, having disputed everything one thought they knew, they’ll be left with only the burden of pure truth. In my personal opinion, I do believe that taxonomy plays an important role in science, and in everyday life; how functional could we be if everyone had their own word for lion, or duck, and nobody could truly communicate? Aside from this, (assume we all had one word for each organism and communication was not an issue), how could we develop medicines and discover natural cure-alls if we had no understanding of the relationships between organisms. Ignorance is bliss until you accidentally kill yourself because you had no idea you were consuming substances toxic to humans. Understanding both how we affect others, and how others affect us is crucial to a healthy life, and vital to a functioning society, as well as the planet as a whole.