Let's Get Into the Science of It!

Organization

    To understand this video, we must unpack the definition of entropy, which is often seen as the amount of disorder in a system. Disorder in your life can often be associated with chaos or stress. You can think of it in terms of your room that you have been neglecting to clean up which gradually keeps getting messier. The state of disorder, or the entropy, in your room occurs somewhat spontaneously in the sense that it is not something that you are actively doing, it just happens without you putting in any effort, or energy. This is something that happens in our lives and in the universe every day. There are billions of reactions that lead to disorder, without any energy being applied. 

    Scientists can calculate the Second Law of Thermodynamics (the idea that the state of entropy of the entire universe, as an isolated system, will always increase over time). They use entropy to see how the reaction occurs spontaneously without any added energy. You can do this by using a formula called Gibbs Free Energy. This allows you to measure the amount of energy in the specific system you are calculating for and can also tell you if the reaction has occurred spontaneously or not. It’s written as:

 

ΔG=ΔH−TΔS

It can be read as the change of free energy (ΔG) equals the change of energy stored in the bonds of the reaction (ΔH), subtracted by the product of the temperature (T) and the change of entropy (ΔS). It’s important to note that when the change of entropy is a negative value it means that the reaction is in a state of disorder while positive means it’s in an ordered state. The answer we are left with is the amount of usable energy that is released. What’s also great about this formula is that the positive or negative sign of the value in the change of free energy (ΔG) tells us if it occurred spontaneously. A negative sign means no added energy was used for the reaction, making it spontaneous and the positive sign means the opposite. 

Going back to the room example, think about how easy it seems to get messy and how it requires energy and time to clean it up. This is what’s happening in the universe all the time; we move towards disorder or entropy. If you never stopped to clean your room it would just keep getting messier. Entropy works the exact same way. With no interruption, the universe moves towards disorder, but if you decide to put in the energy, order can be created. 

Created by Hermila Demelie & Mayet Awoke

Response

    Do plants respond? It might seem like a strange question, but you have likely not recognized just how many every day responses plants make to the stimuli in their environment. Plants are more similar to us than we think...  Just as we gravitate to the things that are good for us, so do plants. 

    Hydrotropism describes the phenomenon of how plants will orient themselves so that they can take up the most water through their roots. This means that a plant will respond differently depending on where you put their water.     

 

    They can recognize where their water source is coming from and direct their growth in that direction. 

Another way plants respond to the environment is through touch. Just like us, plants have senses and can react to changes in the environment. Thigmotropism occurs when the response is stimulated by touch. It describes plant growth being affected by the environment and how they work together. A common example of this is vines wrapping around a fence. This is the work of thigmotropism dictating the way the plant will grow in response to its environment.  Vines latching onto a wall is an example of positive thigmotropism, where it moves towards the stimuli. With the negative response, the plant will grow away from the stimuli. For instance, a root growing away from a rock in the soil after it has come into contact with it. 

    Lastly, you have geotropism, also known as gravitropism. This describes the plant’s response to gravity. It can react in both positive or negative geotropism. Positive refers to the plant growing with gravity and negative geotropism is when the plant grows against gravity. Plants will respond in these ways because of the benefits that come with growing in these directions. The roots will grow with gravity and go deeper into the soil to reach water and nutrients. Whereas, the stem will grow upwards against gravity towards the sky for more sunlight.

   In a lot of ways, plants are more like us than we think. They move towards things that benefit them and to reach nutrients. Their growth is dependent on their environment and the stimulus present. This is similar to how we become the people we are depending on our surrounding environment. While there are multiple other ways plants react to their environment, hydrotropism, thigmotropism, and geotropism are just three examples of the way they respond. 

Evolution

    “How did we get to where we are now?” is probably a question you’ve asked at some point or another. There are many explanations available and the theory of evolution is one of them! Darwin’s theory of evolution presents the idea that all species come from a common ancestor and with time, these species experience changes that are meant to boost their chances of survival. This can also lead to the rise of new species and is referred to as “descent with modification” or “evolution”.

 

    For this phenomenon to occur, Darwin suggested that certain mechanisms had to be in place. One of those was natural selection. Natural selection, also known as survival of the fittest, describes the idea that the organisms with the most favourable phenotypic traits will survive long enough to reproduce and pass on those traits. Overtime, this will allow generations to adapt and thrive in that environment which may result in a new species. The difference in favourable traits arises from the variation of genes present in populations; these variations are caused by mutations that may occur during replication of DNA... aka. reproduction. Other mechanisms include sexual selection, in which females choose mates based on how well they display their fitness.

    Natural selection can be further broken down into various modes of selection, one of them being directional selection. Directional selection, or positive selection, describes the process of an extreme phenotype being selected over other phenotypes; this causes a shift in the frequency at which the gene, or allele (a version of a gene) presents itself. This shift occurs due to a survival and reproductive advantage the trait provides. This advantage is usually felt when the population travels to a new environment and those with the trait are able to better adapt. For example, giraffes with long necks were able to reach and eat more more leaves while giraffes with short necks had trouble accessing the same amount of resources. Therefore, there was a shift in frequency of long neck giraffes and short neck giraffes became unfavourable. 

    While natural selection is a more structured mechanism of evolution, genetic drift is another that occurs randomly. Genetic drift is the change in allele frequency within a population that results due to random events, such as a natural disaster. This effect is more strongly felt in small populations as they are more susceptible to experiencing the effects of random changes. In addition, genetic drift makes variation more difficult to achieve in smaller populations as there are more chances of losing an allele to randomness; this can lead to an increase in mutation and disease.

Reproduction

    Have you ever noticed why you might look exactly like your grandmother but look hardly related to your sibling? It all depends on the random combinations of genes that mix and match during fertilization! Through sexual reproduction, 50% of the genetic material from your mother and your father randomly mix together to form new genetic material that makes up a new person. Each person has a total of 46 chromosomes and of these 46, 23 are maternal and the other 23 are paternal. This is why there are multiple versions of the same gene. Even identical twins, although they share the exact same DNA, can display various traits differently. Some genes may also present themselves more dominantly, so even if only one parent has the gene the chances of passing it on increases significantly. The presence of genes can also skip generations, explaining why you may have a trait from your grandfather that your mother doesn’t have!

    We love to believe that as individuals we are wholly unique, with no one else like us on Earth, and in a way this is true. We are each made up of a special combination of genetic material, a set of genes that doesn’t exist outside of us. Genes are the basic building blocks of life, the information that determines whether your eyes are blue or brown, if you’re tall or short, or if your hair is curly or straight. These genes are made up of an even smaller component called DNA, or deoxyribonucleic acid. DNA is the boss that gives our cells instructions on how to function. It controls how cells form and what kind of cell it becomes. These instructions come in the form of codons, three-block codes that eventually become proteins, hormones, and every other chemical necessary for our survival! These codons can be further broken down to four letters: A-T-G-C. These are the nitrogenous bases that, together with a five carbon sugar (deoxyribose) and a phosphate group, form a nucleotide; this is a structural component of DNA. The four letters stand for Adenine, Thymine, Guanine, and Cytosine; when these four pair up (A with T and G with C) they are held together with special bonds and form the twisted ladder shape we know DNA to be; groups of packaged DNA are called chromosomes.

© 2020 by Brittany Beheshti

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Digital Artist & Science Art & Biology Artist