Bone Marrow

When we hear the word “bone(s)”, we normally think of the classic science class skeleton hanging or standing somewhere in a corner, or the tv show about forensics and criminal investigation. Some might also be reminded of a time when they suffered terrible pain in the breaking of their bones. Whatever the case, we rarely think of an essential structure that helps us avoid fatal endings, known as “bone marrow”.

The bone marrow is a living, sponge-like tissue that resides within the inner spaces of long bones and flat bones in our bodies. Bone marrow is incharge of creating all types of blood cells, such as red cells, white cells, and platelets. There are two types of bone marrow, red bone marrow and yellow bone marrow. While yellow bone marrow is largely inactive, it aids in the functions of the red marrow.

Red bone marrow is where the action happens. This area of the bone marrow covers 100% of the bone medulla in newborns and reduces to 50% when we become adults. However, if we have lost much blood, yellow marrow will convert into red marrow to produce more red blood cells. Red marrow creates billions of all kinds of blood cells each day in a process known as hematopoiesis. In hematopoiesis, stem cells give rise to all of the different mature blood cell types and tissues. Without bone marrow, our body wouldn’t be able to be oxygenated, fight infections, and close injuries to stop bleeding.

The Kidneys and Osmosis

I believe that one of the greatest satisfactions we human beings experience is the instant we excrete a yellow substance called urine. Or in a more colloquial manner, the moment we pee. I know that this is perhaps not the best way to begin a scientific essay, but I want you to be relaxed when you receive this wonderful piece of information. This might seem like a tough question to many, and it is, but here you will know the answer: What is the relationship between the kidneys and osmosis?

First, let’s understand what osmosis is. Basically, osmosis is when water or any other sort of liquid moves across a semipermeable membrane from an area of high concentration to an area of low concentration. At one side you have lots of solutes to which water will be bound to and on the other the water is “free”. Therefore, because water has an adhesion trait, the “free” one will pass through the semipermeable membrane and bind to the solutes on the other side and dilute them to create an equal amount of concentration on both sides. The side of “free” water and little solutes is known as hypoosmotic and the other that attracts water and has many solution is hyperosmotic.

Now, the kidneys are very complex organs that are shaped like a bean. They are extremely essential for they serve as removers of excess organic molecules from the blood and of waste products in our metabolism. Without them, the environment within our body would be looking something like Chernobyl. In other words, they maintain homeostasis (their specialty) in us by regulating electrolytes (e.g. salt), maintaining the pH balance, and regulating the blood pressure by equalizing the amount of water and sodium. In practical terms, they serve as a filter of the blood and remove water soluble wastes such as urea (nitrogen-filled) and ammonium through urine. Kidneys also produce hormones and reabsorb water, glucose, and amino acids into the body.

Okay, so now that we understand the basics, let’s look at the organisms inside the kidneys that carry out the process and then relate them with osmosis. These include, the nephron, loops of Henle, the adrenal cortex, and the renal medulla.

Containing the structures of the nephrons in charge of keeping the balance of water and sodium in the blood is the renal medulla. The nephron holds the proximal tubule, the loops of Henle which, the distal tubule, and the collecting tubule.

Things function like this. A ball or network of capillaries called the glomerulus passes through a dome shape known as Bowman’s capsule. The cells belonging to Bowman’s capsule are permeable to small solutes and water, but not to large molecules, proteins, or large blood cells. This enables blood to be filtered correctly and nutrients to not be excreted in urine. This means that the renal medulla is hypertonic (adds higher osmotic pressure) to the filtrate in the nephron and this aids in the reabsorption of water. Having less concentrations of vitamins, salt, glucose and other solutes equal to the concentrations in the blood, the resulting filtrate will pass to the proximal tubule.

Inside the proximal tubule, reabsorption will occur. Epithelial cells will return sodium ions to interstitial fluid by active transport. Negative ions and water will passively follow sodium and diffuse back into the capillaries. Glucose, amino acids, and other desired compounds will do similarly in an active and passive transport pattern. To maintain the pH balance, transport epithelium cells actively pump hydrogen ions to lower acidity, while adding ammonia to buffer it. Bicarbonate reabsorption is aided by the proximal tubules to increase the pH and keep stability. As water and other useful solutes are reabsorbed, urea becomes more concentrated in proximal tubules.

Here comes the important part, the Henle Loop. The loop of Henle is a U-shaped tube that extends from the proximal tubule and leads to the distal tubule. It consists of a descending limb and ascending limb. It begins in the cortex, receives filtrate from the proximal tubule, extends into the medulla as the descending limb, and then returns to the cortex as the ascending limb to empty into the distal tubule. The primary role of the loop of Henle is to concentrate the salt in the interstitium (tissue surrounding loop).

As the interstitial fluid descends in the loop, it becomes progressively more concentrated. Since it is permeable to water, this descending limb will cause more water to be reabsorbed. The transport epithelium is permeated by aquaporins (water channels), which easily let water through by osmosis, allowing salt to continue flowing into the ascending loop. The ascending limb epithelium is impermeable to water (very rare in biology) and is responsible of absorbing ions as it is dotted with specialized channels for it. Finally, salt diffuses out of the tubule near its thinner tip and as it moves farther up into a thick membrane, salt is removed via active transport. All of this causes the resulting filtrate to be more dilute as it enters the distal tubule.

The hypoosmotic fluid in the distal tubule will receive a secretion of potassium for the regulation of concentration of salt and potassium in bodily fluids. Aditionally, it will receive hydrogen ions secreted by the tubule to regulate pH and absorb bicarbonate. Much of the ion transport in the distal tubule is regulated by the endocrine system. Here is when the adrenal cortex comes in as it produces the hormone aldosterone to reabsorb more sodium and secrete more potassium in the distal tubule. To conclude the process, the filtrate is transported to the collecting duct. Here the filtrate will pass through the medulla towards the renal pelvis, where it will ultimately be turned into urine. Hormones will aslo control the permeability of the epithelial tissue and regulate the urine’s concentration.

In very short terms, if there is too much water, the kidney uses more water in the urine. If there is not enough water, the kidney uses less in the urine. This is why we make less pee when we are dehydrated. Osmosis and diffusion help regulate the whole process without utilizing too much energy. While the filtrate of the blood travels into the kidney, the concentration of sodium increases and water dilutes it via osmosis. Then, the ascending Henle loop becomes water resistant to not allow the water to dilute the salt. The end result is urine in the collecting duct ready to be flushed away. All of this happens so that we do not lose more water than we need to.

Respiration

Stop breathing for 10 minutes and what happens? You won’t be alive to answer that question. You see, have you ever thought about what happens when you inhale (take air in) and exhale (take air out)? As almost all of the things that occur within our body I’m pretty sure you haven’t, unless you’re some sort of scientist. Respiration is perhaps the most essential system for the preservation of our lives and we’re barely even conscious of it when it takes place.

A practical definition of respiration is “the process of ventilating the lungs through an alternation of inhaling and exhaling air”. We inhale oxygen and exchange it for carbon dioxide which we exhale. For certain, many reading this essay will know that the nose, the lungs, the ribs, and the brain are part of breathing, but other features include the trachea, bronchi, bronchioles, alveoli, and diaphragm. Let’s analyze in depth our respiration process.

The lungs are divided and subdivided into numerous compartments. They are a sponge-like organ which is interpenetrated with blood vessels and capillaries. At the instant you allow air inside your body, this one will pass through the trachea (part of the throat that leads to lungs), which is behind the esophagus (part of the throat that leads to stomach). The trachea separates into two bronchi which are too branched into bronchioles. Then, the bronchioles are divided into even smaller branches, ultimately ending in the alveoli aligned with capillaries where gas exchange occurs.

Oxygen-rich air we breathe is dissolved in the moist lining of the alveoli. The blood in the capillaries is carrying much carbon dioxide and very little oxygen. This difference in partial pressure causes highly concentrated oxygen in the lungs to diffuse into the blood in the capillaries and carbon dioxide to diffuse out of the blood into the alveoli to be exhaled. With this exchange process, more oxygen is able to be inhaled enabling us to prevail in the continuous living of our lives. When the air pressure is high inside the lungs, the air from the lungs flows out. When the air pressure is low inside, then air flows into the lungs.

Diffusion is the proper name for this basic process of trade. The word diffusion is derived from the Latin word, “diffundere”, which means “to spread out”. If a substance is “spreading out”, it is moving from an area of high concentration to an area of low concentration. Carbon dioxide in the capillaries “spreads out” and allows a higher concentration of oxygen to enter and expel the CO2. Both oxygen and carbon dioxide are transported around the body in the blood through arteries, veins and capillaries. They bind to hemoglobin in red blood cells, although oxygen does so more effectively.

Inside our thoracic cavity are the lungs approximately contained by the rib cage. A muscular partition known as the diaphragm forms the bottom wall of the thoracic cavity. When we respire this muscle contracts, the intercostal muscles (between the ribs) pull the ribs up, pull the sternum out enlarging the cavity and reducing air pressure in the lungs. The air containing higher pressure than the alveoli rushes inside our lungs and the pressure in the air and alveoli are relatively equalized. However, the concentration of oxygen is greater in the newly arrived air than that one of the alveoli. After this happens, the oxygen and carbon dioxide will diffuse as previously described within the capillaries.

In a nutshell this is what happens when we breathe. Inhalation is initiated by the diaphragm and intercostal muscles expanding the lungs and allowing a high pressure of air to enter the lungs and oxygen to enter the alveoli to exchange carbon dioxide in the blood through the capillaries. Carbon dioxide is expelled through exhalation to begin the cycle all over again. All of this in a matter of seconds.

Digestion Process

Before you take a bite of your favorite food, your mouth is already watery and filled with saliva containing enzymes and other chemical molecules ready to help in the mashing and dissolving of your food. Of course, one is more focused in the delicious taste of the aliment, than in what is occurring within your body. Let’s analyze the process of nutrition and digestion that takes place when we eat.

Perhaps you didn’t know this, but there are different modes of ingestion (taking food in) which are used by different organisms to adapt to their body structures and environments. There are suspension feeders, substrate feeders, fluid feeders, and bulk feeders, this last one pertaining to human beings and other familiar animals. Bulk feeders eat large pieces of food and they either chew it or swallow it whole.

In our mouth, our saliva begins to break down carbohydrates with a special enzyme called amylase. The instant we swallow our food it will go through the pharynx (throat), pass through the esophagus, and land on the stomach to initialize the real process of digestion.

Inside the stomach, a gastric juice will be secreted in its main chamber (lumen) where the food and the juice will be churned into chyme. The lumen is lined with epithelial cells specialized to secrete a mucus that protects your stomach from damaging itself with the extremely acidic substance it forms. The epithelial gastric chief cell in the stomach will release pepsinogen into the lumen. Then, the gastric juice contains parietal cells that release hydrogen and chloride ions into the lumen. Hydrogen and chloride will combine to form hydrochloric acid, which is so acidic that it can dissolve metal. This acid will kill almost all bacteria and denature most proteins.

The epithelial gastric chief cell in the stomach releases pepsinogen into the lumen. After this, the pepsinogen mixes with the hydrochloric acid and becomes pepsin. Pepsin is an enzyme that will digest proteins by breaking their peptide bonds. In this way, proteins are converted into smaller polypeptides that will travel to the small intestine.

Within the small intestine, polypeptides will be disaggregated into amino acids. The first several inches of the small intestine are known as the duodenum. This part of the intestine basically receives chyme mixed with secretions from other organs to continue the digestion process. Specifically speaking, the pancreas delivers bicarbonate to neutralize acid, trypsin and chymotrypsin to break down proteins, and the enzyme amylase to break down starches and carbohydrates. On the other hand, the liver gives bile to start breaking down fats.

Lined with villi, the nutrients in the small intestine will be absorbed into the cells of the villi by passive and active transport. Capillaries in the core of the villi will lead nutrients to the blood and carry them to the liver. Detoxifying the blood, the liver will then distribute it to the heart. Special enzymes in the small intestine will convert fat into water-soluble compounds. These compounds are absorbed by the villi and passed into the lymphatic system.

Then comes the large intestine formed by colon, appendix, and cecum. 90% of the water from chyme, digestive juices, ingestion, etc. is absorbed by the colon. Many bacteria live in the colon and are responsible for producing foul-smelling gas, most of them are the known as “Escherichia Coli”. Our feces or “poop” are about 50% of bacteria in weight. Finally, the appendix seems to play a minor role in the immune system.

In short, but this is how food becomes poop for the toilet and nutrients for the body.

Chordates and Vertebrates

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

Chordates are a phylum within the kingdom Animalia. They are animals that commonly possess a notochord, a hollow dorsal nerve cord, pharyngeal clefts, and a muscular tail. Some of their traits are only present within their embryonic phase of development.

A notochord is a long and flexible rod-shaped body found between the digestive tract and the dorsal nerve cord and is in all of chordates´ embryos. In some chordates, like certain fish, the notochord remains perpetually to be their area of support for their bodies. The notochord for these animals is made of stiff, fibrous tissues and fluid-filled cells, with which their muscles push against to enable their swimming. In other chordates, the notochord develops in their embryonic stage to further become their spinal discs.

Only chordates have a hollow nerve cord, non-chordate animals have a solid nerve cord, if any at all. Most non-chordate animals have a ventral nerve cord, which means that their stomach resides “on the back” of their bodies. Anyway, in chordates, this nerve cord is created from the outer layer of cells after gastrulation occurs. During this process, a flat plate of cells basically rolls up into a tube. In embryos, the nerve cord will unfold to become the brain and the spinal cord of animals and humans.

A pharynx is a region of the head and neck posterior to the mouth. Chordates have pouches or clefts on the sides of their pharynx, these are known as pharyngeal clefts. For aquatic animals these become into their gills or suspension-feeding organs. In the case of humans and terrestrial animals, these come to be the head and neck structures, like the ears.

Finally, chordates contain a muscular tail that extends beyond their digestive tract. Nevertheless, this structure often shrinks or disappears throughout development. For example, the embryo of humans has this tail that is later reduced to the coccyx or popularly known “tail bone”.

Out of chordates derive craniates. Given this name, we understand that craniates consist of a head. Normally, inside of the head, these organisms carry a brain at the front end of the dorsal nerve cord and they also hold sensory organs in it (eyes, ears, etc.). Craniates own highly complex and coordinated feeding and movement.

Inside the group of craniates are the vertebrates. Vertebrates have an extensive skull and a backbone composed of vertebrae. All animals and humans have homeobox (hox) genes that withhold the specific design for the skeletal, nervous, and muscular structure of each animal. For this reason, every animal species is different, but the same in their group. In other words, all frogs have a frog-like skeletal structure that differs from the dog skeletal structure, thus all frogs are not dogs. Likewise, all vertebrates have hox genes to design for them the brain, skull, and backbone.

Therefore, in conclusion, vertebrates practically differ from chordates in that only vertebrates are completely formed with a skull, a backbone, and a spinal cord, while other chordates are not. In short terms, all vertebrates are craniates and all craniates are chordates, however, not all chordates are craniates and not all craniates are vertebrates.

The Earth and Plants

Perhaps you have never asked yourself of the importance of soil. Maybe you have not even attributed to it any special function or importance in your life or society. These sort of thoughts may be forming in you because, today, most urban western societies live in almost a soil-free environment. Now, I am not against having concrete or whatever, and the purpose of this essay is not to speak of the negative impacts of urban civilization on earth. But I am writing this because we need to become more conscious of the importance of earth than the one we give to our world. Why?

Life was not created with our world, but with earth (soil, dirt, etc.) and water. Out of the earth and the water came all of the living organisms we have knowledge of, and even those of which we do not know. The truth is that even in the most arid area there is life, for the mere reason that there is earth.

Therefore, if everything came from the earth and water, what then, were the first major organisms that came to be from these elements? If we can know those that were formed primarily, then we can come to understand an intrinsic relationship between those initial organisms and the earth.

These organisms are seeds and plants. Did you know that plants have a consciousness? They can detect the frequency of your thoughts and know, for example, if you will hurt or not hurt them. Plants are here on earth to serve us and they have an intimate relationship with earth because without it they would not be capable of birthing, growing, and reproducing, including underwater plants.

Earth and its soil provides plants with the necessary minerals, nutrients, and habitat to keep them alive and well. Hence, soil is not just simple “dirt” to hold the plant up and still, there exists a mutual influence between abiotic (nonliving) factors and biotic factors with soil. Weather/climate, temperature, moisture, acidity, minerals, insects, worms, fungi, microbes, animals, manure/wastes, and of course, vegetation, just to name a few, are all dependent of and affect soil.

Earth helped in the unfolding of life within the planet, and thus, it is important we begin to think differently of it. Let´s appreciate it.

Angiosperms and Gymnosperms

The great majority of plants are classified into two different groups, gymnosperms and angiosperms. The name gymnosperm comes from the greek words gymno (naked) and sperma (seed). Their name literally means “naked seeds” because gymnosperms are nonflowering plants that produce their seeds in the open spaces of cones. On the other hand, angiosperm is formed by the greek words angeion (vessels) and sperma (seed). With this said, angiosperms are flowering plants that are formed inside containers basically known as fruits. However, in order to comprehend in greater detail the differences between angiosperms and gymnosperms we must also take note of their forms of reproduction and ultimately, their life cycles.

Angiosperm and gymnosperm life cycles are similar to each other, in that they have a sporophyte to produce spores, a gametophyte to produce gametes, and use meisosis and mitosis to pass from one stage to the other. Nevertheless, their are major distinctions found in the details of each one of these processes.

Gymnosperms are more primitive than angiosperms and therefore, you could probably say that their reproduction and life cycles are much simpler than those of angiosperms. At their sporophyte stage (dominant stage of plant with which we are all familiar with), gymnosperms have two sets of chromosomes, which undergo meisosis and produce two kinds of diffrent spores in a process denominated as heterospory.

The two spores produced are megaspores and micropsores. Megaspores have one set of chromosomes. These are those of the female formed in the ovulate cone where they go through mitosis to later develop into a female gametophyte which will create unfertilized eggs. Micropsores have one set of chromosomes and belong to the male, where they grow in the pollen cone, go through mitosis, and later unfold into pollen grain.

The male gametophyte (pollen grain) will contain two nonflagellated sperm. This means that the sperm will not have flagella (tales) because they will not travel through water to reproduce. As a matter of fact, the nonflagellated sperm will be carried in the pollen grain propelled by the wind to pollinate an ovulate cone and fertilize a different plant’s egg to create genetic diversity. For this purpose, gymnosperms will normally produce exagerated amounts of pollen for them to reach at least one ovulate cone.

When the sperm and the egg join in fertilization, they will end up generating the next generation’s sporophyte. This will first occur through the creation of seeds. The seeds will possess three parts, the embryo (baby sporophyte), food for the embryo, and a seed coat to protect it from being damaged.

Angiosperms, just as gymnosperms, have a sporophyte phase which has two sets of chromosomes, undergoes meiosis, and creates two types of spores with one set of chromosomes: a megaspore and a microspore. The megaspore (of female) grows in an ovary, suffers mitosis and forms an embryo sac (female gametophyte). The microspore (of male) evolves in the Anther, submits to mitosis, and gives shape to pollen grain. The ovary will pass through mitosis and create eggs or female gametes and the pollen grain will also have mitosis and form two nonflagellated sperm or male gametes.

Some angiosperms like to use wind pollination, but many others stick to a more efficient route and utilize animals such as insects, birds, bats, and other sorts to disperse their pollen. Unlike gymnosperms, these guys encounter a double fertilization event, where one sperm fertilizes the egg and the other fertilizes a central cell. This central cell has two sets of chromosomes and the sperm has one. When they unite, they form a substance called an “endosperm” which is triploid or has three sets of chromosomes. The endosperm will be the food surce of the developing embryo. Let’s understand this process a bit better.

Flowers hold a female part recognized as carpel or pistil. This area within the flower consists of a stigma, a style, and an ovary that has many ovules. The stigma is a sticky place at the entrance of the pistil that catches pollen grains. Then, the pollen begins to institute a pollen tube into a long tube-like structure known as the style, to finally access the ovary of the carpel.

The ovary sustains many parts. First, it has the micropyle, which is in its essence a small opening that enables the pollen tube to enter an ovule. Once inside the ovule, the pollen will deliver its two nonflagellated sperm. Inside the ovule is the embryo sac made of 7 different cells: three antipodal cells at the hind of the ovule, one central cell, and three cells next to the micropyle. Those last ones are of great attention. They practically consist of the egg cell and two cynergids beside it that generate chemicals to make a concentration gradient that leads the pollen tube into the egg cell.

Once in the egg cell, one sperm will fertilize it and the other will head to the central cell with two polar nuclei, fertilize it, and create the endosperm. Hormones will then be produced and a seed will develop. To form the seed coat will be the ovule and the ovary will become the future fruit, whether edible or small enough to stick on an animals fur and deposite the seed somewhere else.

Finally, about 98% of angiosperms can be divided into dicots and monocots. Monocots usually have petals in multiples of three, vertical veins, adventitious roots that look like spread fibers, scattered vascular bundles in their stem, and one cotyledon (a seed leaf) inside the seed. Dicots have petals in multiples of four or five, are net veined, have a taproot (main or central root), have their vascular bundles at the edge of their stem, and have two cotyledons.

In conclusion, the basic difference between gymnosperms and angispoerms is that ones have naked seeds and the others are flowering plants. Notwithstanding, in their life cycles they are very similar, except when you go into detail about each’s reproductive organs and ways.

Photosynthesis and Energy

Photosynthesis is one of the most fundamental processes to help in the sustainability of life on earth. This process converts luminous energy originating from the sun into stable chemical energy. Being light their primary soure of energy, green plants, some algae and other microorganisms utilize chlorophyll in a type of cytoplasmic organelle known as chloroplast to convert inorganic matter, like atmospheric carbon dioxide and water, into organic matter, such as glucose, lipids, and proteins. Oxygen , which is basic for respiration, is a “waste” product of this whole process.

The great majority of orgnisms to carry out photosynthesis are denominated photoautotrophs, many of them which are green plants. In their ecosystems, green plants are primary produces, for they are the main or “primary” source of energy for other organisms. This is not only because they are consumed by heterotophs, but also becasue they provide the necessary oxygen for aerobic cellular respiration to take place.

Therefore, photoautotrophs utilize the sun’s energy to supply indispensible organic matter and vital oxygen. These components are consumed and absorbed by other organisms to use for energy and survival. In short words, food webs lead back to the energy produced by plants and microbes through photosynthesis.

 

Prokaryotes

Today it is widely known that one of the smallest and most abundant living organisms on earth go by the name, “prokaryotes.” These microorganisms have been the center of much scientific investigation. The more biologists understand these creatures, the more they grow in fascination of them and the things they can do to help us advance in medicine, technology, and further scientific investigation.

Prokaryotes are normally unicellular organisms and are well known in how they differ from eukaryotes. However, here you will not learn about the differences between eukaryotes and prokaryotes, but about the importance prokaryotes have in biology and for future human development and understanding.

Prokaryotes are the oldest, most abundant, and most adaptive organisms on earth. They can handle extreme conditions, such as lethal radiation and metal-dissolving acidity.  A handful of soil could contain more prokaryotes than the total number of human beings that have ever lived. Yes, they are astonishing. These tiny little organisms come in a variation of shapes like spherical (cocci or coccus), rod-shaped (bacillus or bacilli), and spiral-shaped. In order to better study these creatures, the prokaryotic domain has been divided into two well differentiated ones, bacteria and archaea.

Archaea are considered to be the oldest living things on earth that adapted to the planet’s early and “extreme” conditions. For that reason archaea are also referred to as extremophiles. Because they have been found in the most impossible places to sustain life on earth, some research has taken scientists to hypothesize in the fact that these organisms might also be found in other planets. If this is correct, then micro-extraterrestrial life might pretty well exist in other planets. Archaea also consume 300 billion kilograms of methane per year, reducing the greenhouse effect! To add to your knowledge, know that archaea have structures similar to those of bacteria and contain a DNA structure that also resembles the one of eukaryotes.

Bacteria are more abundant than archaea. Even though much popular belief toward bacteria is that they are harmful, much of bacteria are beneficial to the environment and ultimately to human beings. To fight and destroy harmful bacteria, we have developed drugs denominated, “antibiotics”. Bacteria have a cell wall that is made out of a substance called peptidoglycan. What some antibiotics basically do is destroy the peptidoglycan to penetrate the microbe and eliminate it. We are told that humans have no peptidoglycan, and this is why antibiotics supposedly have little to no effect in us.

There are bacteria that contain a thick layer of peptidoglycan within them and others that have a thin layer “sandwiched” between two plasma membranes. Bacteria with a thick layer of peptidoglycan are called, Gram Positive Bacteria, and those that have a thin layer are known as Gram Negative Bacteria. How do we know which are positive or negative?  Through a process known as Gram staining. Here people in a laboratory use a substance to analyze the cell wall of the bacteria. If the bacteria turn violet, it is positive. If the bacteria turn pink, it is negative.  Gram- negative bacteria tend to be harmful.

We know that about 50% of prokaryotes are capable of taxis or movement towards and away from stimulus using a complex structure called a flagellum. The flagellum is made of 42 different proteins and looks like a tale that can function like a propeller and in many other ways to move the prokaryotes around. The velocity of a prokaryote can exceed 50 times its body length per second, this is equivalent to a human running as fast as 190 miles per hour.

Now let’s deepen our understanding; the word prokaryote literally means “before a nucleus”. Therefore, the question arises of “where or how do they contain their DNA?” Well, the answer is that prokaryotic DNA is in a ring-shaped chromosome that is supercoiled together by specialized proteins inside the cell (this is not applicable to the Archean domain).

For a longtime, the manner in which prokaryotes reproduce was fairly unknown. However, it has currently been understood that prokaryotes reproduce through a process similar to that one of mitosis known as “Binary Fission”. In this process, prokaryotes can reproduce very rapidly and double their population size in an hour. This rapid reproduction enables frequent genetic mutations within the cells, creating diversity in their genes or DNA. Their genetic diversity can be maintained by the transformation, transduction, and conjugation of genes.

In transformation the cells pick up or “download” genetic material from the environment, ultimately altering their own DNA. Different from transformation, is transduction, where special viruses called “phages” insert genetic material in prokaryotes. These survive the “invasion”, assimilate the new genes and change their original structures. Finally, in conjugation, two bacteria “conjugate” or join together to transfer genes from one to the other. This process is also known as “horizontal gene transfer”.

Certain types of prokaryotes provide ecosystems and eukaryotic cells with usable nitrogen. These prokaryotes are like the ones of cyanobacteria and methanogens. They carry out nitrogen fixation and convert atmospheric N₂ (nitrogen) into ammonia (NH₃). Cyanobacteria only need light, carbon dioxide, nitrogen and some other minerals to survive in a variety of habitats. Cyanobacteria are perhaps the most successful microorganisms on earth.

Some prokaryotic cells live in colonies or filaments. In colonies, prokaryotes cooperate with each other, divide labor and share resources between them to satisfy each other’s needs. Then, these colonies might form biofilms, which are micro structures of cells that stick together on living or nonliving surfaces.

Finally, prokaryotes are extremely important for the ecology within our planet, business, and even for the correct functioning of our bodies. Prokaryotes are decomposers and unlock many valuable nutrients in the tissues of dead organisms to make them for other species to consume them. One of these nutrients is nitrogen, which is unlocked through the process of nitrogen fixation that some prokaryotes undergo.

There are about 150 sorts of bacteria living on our skin. You can find about 10 million of them in every square centimeter of our dermis (skin), but don’t worry, they usually don’t harm us. However, that is not all, but nearly 1,000 beneficial species of bacteria live in our intestines. One of the most studied ones is Escherichia Coli. Bacteria living in our intestines help us in our digestion, like in the processing of proteins and carbohydrates to produce vitamins that enable us to be healthy. Some intestinal bacteria emit signals to human intestine cells, inducing the production of blood vessels, useful proteins, and etcetera. Research has also suggested that having an abundance of bacteria with us improves our emotional well-being. Yes, we are never lonely.

Technology, has found the hand of prokaryotes as well. Yogurt and cheese, for example, need prokaryotes for their making. Gene cloning, transgenic crops, the synthesis of PHA for biodegradable plastics, the decomposing in sewages, the breaking down of petroleum and other pollutants, the precipitation of uranium out of groundwater, the production of certain vitamins and drugs, the synthesis of ethanol and fuel, and many more, are some of the examples of the benefits that tiny microorganisms, as prokaryotes, can do for humanity and planet earth. As scientific research advances, biologists grow in greater awe of them.

 

Trophic Levels

In order to survive, organisms need energy. Without energy our bodies would not be able to function and death would be the ultimate result. Up to what we have known, most of the earth’s energy originates from the sun. This energy is divided and distributed among organisms and possesses a perfect function in each ecosystem to maintain the correct balance they require to prevail.

Different organisms carry a unique characteristic that enables them to acquire energy. There are organisms that directly use the sun’s energy to survive and also create other forms of energy, like carbohydrates for other organisms to utilize.  These organisms are denominated autotrophs or primary producers. The most commonly known primary producers are plants. Through photosynthesis, plants get energy and also create new for other organisms to consume. Organisms that consume autotrophs are heterotrophs or primary, secondary, and tertiary consumers. Heterotrophs include all sorts of herbivores, detrivores, and carnivores.

Autotrophs, herbivores, detrivores, and carnivores all consume quantities of energy within an ecosystem leaving less and less energy to consume within each level of the food chain. About 10% of energy is consumed within the levels that belong to primary producers, primary consumers, secondary, and tertiary consumers. These levels of energy consumption are known as trophic levels. The population of a species within each trophic level will determine the population of the next.

Imagine a perfectly balanced community with the trophic levels of plants, crickets, mice, snakes, and hawks. As mentioned, plants absorb the energy form the sun and likewise provide food for the crickets. When the crickets consume the plants, a percentage of the energy the plants provided will be lost within the crickets. To make things simple, let’s suppose the plants contained 100% of energy and now that the crickets have consumed a certain amount of the population of the plants, the crickets have 90% of the energy. This means that the crickets made the community lose 10% of the energy by eating some plants. Then, mice come and eat a number of the crickets consuming another 10% of the energy to leave the mice with 80% of the energy. The trophic levels left are snakes and hawks. These two can compete against each other to consume mice. However, the hawks have an advantage in their ability to also eat snakes.

If the population of snakes and hawks is considerably large, the one of snakes would have to be a bit greater than the one of hawks, because the snakes are potential food for the hawks. Notwithstanding, if the population of snakes is big, the one of mice has to be even vaster to feed both snakes and hawks. In this way, the population of crickets must be larger than the one of snakes, hawks, and mice combined in order to deliver the correct amount of energy for hawks, snakes, mice, and the crickets themselves need to not face extinction. Lastly, the population of plants would be the largest of them all, for they are the base of energy production to sustain a community like this one.

Pretending that a group of hawks immigrated to this community and made the population of hawks larger than the one of snakes, what do you think would happen to the community? I believe there are two possible outcomes, an optimist one and a pessimist one.

The pessimist one says that the hawks would eventually end up wiping out the snakes and the mice. This would lead to an ever growing population of crickets that would wipe out all the plants. In the end, the hawks and the crickets would both die of starvation. I think, though, that this is not a good manner of reasoning.

On the other hand, the optimist one says that hawks distribute the eating of snakes and mice about equally. There are hawks that prefer snakes than mice on the menu and vice versa. The mice population is still larger than the one of hawks, so they have no chance of running out and the density of the snake population is not condensed but dispersed. Therefore, being dispersed, snakes would be harder to find, making the hawks that prefer snakes to migrate to another place, leaving the community to continue to be balanced in the distribution of energy. Perhaps the population of hawks would be larger than before, but it would be good enough to conserve the energy consumption in a way that both the autotroph and heterotroph populations in this community do not die out.