A Review of The Most Memorable Concepts and Lessons I Learned From High School Biology
By Amirali Banani
Noteworthy Topics
Evolution
1) Natural Selection is a simple mechanism that causes populations of living things to change over time. It is defined as the differential survival and reproduction of organisms based on differences in their phenotype, which is ultimately determined by their genotype. As a result of this variation in phenotype, some individuals have traits that will allow them to adapt to their environment better than others when a change occurs.
2) The Five Tenets of Evolution by Natural Selection explain that:
1. Individuals have a lot more offspring than they should
Species tend to produce an excess of offspring, and since resources are limited, this means that there is a lot of competition
2. Not all the offspring can survive
Offspring will compete for survival based on their biological fitness
3. Each offspring is different
If all the offspring were the same, then it would be completely random who survives and who doesn’t
Each offspring has different genes, meaning that some are more physically fit to survive than others
4. Parents can pass on their traits to their offspring
Offspring that are fit to survive grow to become parents and have their own offspring
Therefore, they pass on the advantageous traits that allowed them to survive long enough to become parents to the next generation
5. Different traits give offspring different abilities to survive
Some traits will help offspring survive, and some will hurt them (i.e., reduce their chances of survival)
Nature is essentially a strict judge that selects which traits survive and makes sure the traits that aid survival stay in the gene pool while less ideal traits disappear through adaptations
3) The Phylogenetic Tree of Life, originally proposed by Sir Charles Darwin, shows the evolutionary descent of species through lines depicting the lineage of different organisms from a single common ancestor. Darwin claimed that a unique hierarchical pattern of relationships between all organisms based on their genetic and phenotypic similarities and differences (which is where the idea of a tree of life originated) was a fact of nature for which evolution, and in particular a branching process of descent with generational modification, was the explanation.
Microbiology
1) Bacteria, like other prokaryotes, essentially contain two sets of genetic information. They contain a nucleoid, which is an irregularly shaped region within the cytoplasm of bacteria (and all other prokaryotes) that contains almost all of its genetic information and is not surrounded by a nuclear membrane. Bacteria also contain plasmids, which are circular pieces of DNA that consist of genes that provide them with certain genetic advantages, such as antibiotic resistance.
2) The streak plate method was originally developed to determine by two bacteriologists in Robert Koch’s laboratory as a way to obtain microbiological cultures of bacteria to study them. A streak plate lab is used to obtain isolated colonies of bacteria from an inoculum (often yeast) by creating areas of increasingly diluted bacterial colonies on a single agar plate. It requires constant resterilization of the inoculation loop to ensure that no microorganisms other than the inoculum are introduced into the agar plate. With each streak on each quadrant of the agar plate, the inoculum becomes more and more diluted until a single colony of bacteria remains.
3) The Bacterial Growth Curve represents the growth of a population of bacteria, and consists of four phases: 1. Lag; 2. Exponential; 3. Stationary; 4. Death.
During the Lag Phase of the bacterial growth cycle, bacteria adapt themselves to growth conditions. This is the period during which the individual bacteria are maturing and are not yet able to divide. In the Lag Phase, the synthesis of RNA, enzymes and other molecules occurs within the cytoplasm of the bacteria as they continue their development and prepare for reproduction.
After they have fully matured, the bacteria enter the Exponential Phase. During this phase of the bacterial growth cycle, the growth rate of the bacteria increases as the cells grow and divide at an exponential rate. This is the period during which the number of new bacteria appearing per unit of time is proportional to the present population of bacteria.
At the Stationary Phase, the population of bacteria has climaxed, meaning that it has reached a point at which there are not enough resources to sustain it. This is where the number of dividing cells is equal to the number of dying cells, resulting in a net population growth of zero. Under these less favourable conditions, competition for nutrients increases and the bacteria become less metabolically active to conserve energy.
At the final stage of the bacterial growth cycle, the Death Phase, the bacteria have exhausted all their resources and begin to decay. As toxic products build up and nutrient-rich media are depleted, this is the point at which the living cells terminate metabolic functions and begin the process of death. As the bacteria are no longer able to replicate due to both the lack of nutrients and the cellular damage incurred by the accumulating waste, the population begins to decay exponentially until the cycle eventually terminates with the death of the last bacterium.
4) Bacterial conjugation is the process by which one bacterium transfers genetic material in the form of a plasmid to another through direct contact, specifically through a pilus. It is often used as a parasexual form of reproduction in bacteria, forming recombinant DNA. Conjugation not only represents the most sophisticated form of horizontal gene transfer in bacteria, but it also serves as a platform for the spread and persistence of antibiotic resistance genes — which explains the tremendous ability of bacteria to rapidly and efficiently develop resistance to antibiotics when exposed to them in excess amounts.
Birds - Fascinating Avian Biology
1) Wing aspect ratio (ratio of length to width of a wing) and wing loading can significantly impact the flight of a bird. A higher aspect ratio wing has a lower drag and a slightly higher lift than a lower aspect ratio wing. Because the glide angle of a glider (such as an albatross) depends on the ratio of lift to drag, a glider is usually designed with a very high aspect ratio. On the other hand, birds such as passerines and woodpeckers have wings that taper down more or less to a point at their outer tip. Such wings have a low aspect ratio designed for rapid takeoff and swift twisting flight, but not they are not ideal for sustained high-speed flight. A higher aspect ratio corresponds to higher wing loading, and vice versa.
2) Light pollution is a significant human-induced contributor to bird death. An average of 30 million birds die annually in Canada due to collisions with glass, often those of tall skyscrapers. Why does this occur? Birds use cues such as sunlight as a navigation tool when migrating. When birds are flying at night and they spot the light that’s emitted from a city in the distance, they interpret that light as the sun. Therefore, they move towards that light and all of a sudden are trapped inside an intensely-lit urban environment.
As they are trapped inside a city, they are then attracted to the light from inside apartments. There is glass around each of the apartments, and since the birds do not perceive the glass, they fly straight into it at high speeds and are killed by the force of the collision. For this reason, initiatives have been developed to reduce light pollution, for instance by building new apartments with non-reflective glass so that less light is reflected and scattered into the sky.
3) There are 4 different types of flight in birds:
Gliding — stationary wings guided solely by the wind
Flapping — pushing air down and back to propel the bird forward and/or upward
Hovering — remaining stationary in mid-air by rotating wings or holding the body in a vertical position by beating the wings rapidly and closing tail feathers
Soaring — taking advantage of atmospheric air currents created by updrafts thrown up by the dynamics of wave action. This is the most energy-efficient method of flying
Enduring Understanding
The theory of evolution, as proposed originally by Charles Darwin, is a scientific theory that essentially states that species change over time. There are many different ways species change, but most of them can be described by the idea of natural selection. The theory of evolution through natural selection was the first scientific theory that put together evidence of change through time as well as a valid mechanism for how it occurs.
Humans are both the products of evolution and one of the key drivers of evolution by human activity such as urbanization. Our incredibly intelligent and capable brains — which we often take for granted — are the pinnacle of millions of years of evolution, with each part of the brain intricately designed by nature for a specific and unique function. The human brain itself, a valuable commodity of evolution and natural selection, is now a key driving force of natural selection in many species with the development of civilization — the epitome of human ingenuity — influencing the survival of organisms in many different ways, with only the “fittest” surviving the effects of the Anthropocene Epoch. By learning more about how evolution shaped us and how we are now shaping the evolution of other species, we can better understand the mechanisms of this phenomenon and the underlying force of natural selection.
Microorganisms play a significant role in our lives. Although they often go unnoticed, these organisms — the first forms of life to ever appear on Planet Earth — have influenced our development and the development of almost all other species of organisms more than we can ever imagine. Although they are often perceived as dangerous beings who pose a threat to our health, what many do not understand is that we can’t live without them. Although there are microbes that can make you ill, the vast majority of them are beneficial to us as they aid in digestion, promote the development of the immune system, detoxify harmful chemicals, and produce vitamin K, among other benefits.
Through centuries of experimentation and the development of techniques — such as the streak plate method — humans have been able to develop an understanding of the internal anatomy, physiology, morphology, and genetics of different types of bacteria, archaea, fungi, protists, and viruses. This knowledge has allowed us to develop certain medicines against harmful microbes — such as penicillin as the first antibiotic — to eradicate certain diseases. This, however, is just the beginning of the story, as we continue to learn more about things such as the genetics of bacteria through their antibiotic-resistant properties. With a greater understanding of the properties of these tiny organisms, there is no limit to how much we can apply our knowledge to foster innovation in the field of microbiology.
Birds have evolved to become avian species capable of achieving magnificent feats of flight, from high-powered descents to capture prey at over 250 km/hr to soaring over the Atlantic Ocean for days on end. Each aspect of their anatomy is specially designed for flight, taking on an aerodynamic body shape that optimizes flight efficiency, wings with defined aspect ratios that enhance their flight performance, and strong but light feathers and bones that contribute to their optimal performance during flight.
Humans and birds have lived side by side for millennia, but decaying populations of certain birds in the past century — primarily due to climate change and habitat loss — have not only sent a dire warning to humans about the state of our climate and biodiversity but have also been a major contributing factor to the population decline or even extinction of many other species. Birds are crucial to life on Earth. They help keep the climate stable, oxygenate the air and transform pollutants into nutrients. Furthermore, they play a crucial role in the effective functioning of ecosystems, and as they are high up in the food chain, they are also good indicators of the overall state of our environment and biodiversity. Therefore, it is essential to increase our conservation efforts to preserve the population of birds and therefore the biodiversity that exists on our planet. Without birds, much of the ecosystems on Earth would be unstable and unsustainable, which can directly affect our survival and well-being.
The Most Significant ‘Life’ Themes
1) Life is Opportunistic. This theme truly resonates with me because it has not only been a significant and recurring one in high school biology, but it also relates to other aspects of my life. We have constantly witnessed in class that many different organisms tend to take advantage of resources at their disposal to favour their growth and development and maximize their chances of survival. As we learned in the Forest Dynamics Unit, life truly exists everywhere, from the scorching climate of the hottest deserts to the freezing reserves of ice in the earth’s poles. The genetic code and protein structure of living organisms permit marvellous flexibility, which is why life forms are opportunists, meaning that they adapt to their environment and utilize whatever they find around them to their advantage → which explains why life can flourish even in the world’s harshest places. I can relate strongly to this, because I, like other human beings, am an opportunist. I seek opportunities to learn more, to improve my abilities, to become a better person, and ultimately to take advantage of what I have to become the best and most successful version of myself. This is a theme that is common among all life forms on Earth.
2) Life Tends to Optimize rather than Maximize. To optimize means to achieve a value in the middle range between too much and too little — just the right amount. The rule of optimization generally applies to minerals, vitamins, and other nutrients that the body requires, as well as behaviours such as exercise and sleep. For instance, too much or not enough glucose in the blood, or too many essential minerals such as iron and calcium in the body, could kill you as it can be toxic. At the molecular level, cellular signalling and management systems maintain optimum levels in organisms (homeostasis). For example, certain proteins can regulate the concentrations of essential chemicals, shutting down their production when optimum levels are reached and re-initiating their production when concentrations fall below critical levels. At an organismal level, optimization is an intricate dance involving many interacting components and values.
Organisms, however, may occasionally drift from optimizing to maximizing — from adaptation to addiction. For instance, humans try to maximize values such as prosperity, pleasure, security, and power. However, in restoring balance, we must take note of nature’s dictum: too much of a good thing is not a good thing. There is one value that life aims to maximize, and that is the survival of DNA. Every organism has as its most elemental goal the transfer of its genetic information to the next generation, and in this sense, all optimization of function aims at this ultimate maximization. This is not only the aim of plants, animals, bacteria and the rest, but is also the ultimate goal of human beings.
3) Life Recycles Everything it Uses. In the living world, the intake of nutrients and the output of wastes are balanced; the end product of one process becomes the starting point of another — one creature’s waste becomes another’s food, one creature’s exhale becomes another’s inhale -and all these events repeat in a cycle. This circular flow of materials between living organisms occurs so fluidly from the standpoint of the entire ecosystem that it is often very difficult to distinguish between nutrient and waste production and consumption. We are part of this cycle of life — in fact, a huge contributor to it. Plants and other photosynthetic organisms rely on our carbon dioxide to photosynthesize and produce glucose, our activities such as burning fossil fuels and applying nitrogen-based fertilizers to soil affect the nitrogen cycle by increasing the amount of biologically available nitrogen in ecosystems around the globe, and, of course, especially following the industrial revolution, we have significantly impacted the carbon cycle through activities such as deforestation and carbon sequestration, completely shifting the balance between geological and atmospheric carbon.
4) Life Uses a Few Themes to Generate Many Variations. The various combinations of just a few different biological growth patterns and rules can lead to a vast array of unique living organisms. While the outward appearances of all organisms may vary, the pattern of relationships between organisms, even those from different species, may be indistinguishable. Nature often takes advantage of mathematical patterns — such as the Fibonacci Sequence — to create unique and distinct designs in the formation of petals on flowers, the shapes of shells on snails and turtles, and the arrays of hexagonal cells in a honeycomb, among others. This theme resonated with me a lot because it essentially simplifies the immense variation that can be seen in the natural world into a few rules and patterns that nature uses to create all the variety that can be seen in the biological world.
5) Life Creates with Mistakes. Nothing in the world is perfect, and the same applies to life. During reproduction, life creates new combinations of genes by exchanging information. You can think of genes as 2 decks of cards (with each deck representing a set of 23 chromosomes). Events like recombination in meiosis reshuffle the information in chromosomes and cut that mixed information in half, which ultimately forms the gametes (this is represented by the reshuffling of cards and then splitting them in half). The combination of genetic information in gametes (as represented by the combination of the mixed deck of cards) is essentially reproduction.
Mutations as a result of errors in replication can result in genetic defects in offspring, but could occasionally result in improvements that make a species better adapted to its environment. Errors in replication and the process of reproduction can result in genetic variation, which often benefits a population as it reduces the probability of population wipeout by factors such as disease. With the birth of each new organism comes the introduction of more variation into the general population, and this variation — which can be seen on the macro level — is the direct consequence of events that occur on the molecular level.
My Favourite Podcasts
1) Bacteria Survive Freezing Arctic. The bacteria living in the Arctic, known as Planococcus halocryophyllus, have particular genes that allow them to thrive in subzero environments where most other organisms can not even survive. These bacteria are different both genotypically and phenotypically and could be a possible candidate for life on other planets and moons. After 200 bacterial isolates were taken and screened, it was determined that this particular bacterium has halophilic (salt-loving) and cryophilic (cold-loving) properties that allow them to tolerate temperatures down to -50 degrees Celsius and salinity concentrations of up to 18%. Since these beneficial traits have persisted over time as a result of Natural Selection and particularly due to constant genome duplication, these extremophiles now dominate much of arctic permafrost and can thrive in them.
What fascinated me about this podcast was the incredibly powerful role that evolution plays on the micro level. We often perceive evolution as a “macro force” that only acts on large organisms, but this magnificent podcast unveiled a completely different perspective for me on both evolution and microbiology at the same time. Based on my viewpoint, the fact that Planococcus halocryophyllus has evolved to become a bacterium that can withstand extremely cold temperatures and highly saline environments is a testament to the influence of genes on the physical capabilities of organisms — whether it is the smallest microbe or the largest animal.
2) Germ Code. Going to war with microbes has cost us more harm than good; it has resulted in one of the biggest crises humanity has ever faced: the Antimicrobial Drug Resistance Crisis. Microbes have evolved and developed resistance to the therapeutics (often in the form of medications) typically used to treat the infections that they cause. A significant moral lesson that this crisis has taught humanity is that going to war with the microbes is not the right path to take and that we must re-establish our relationship with them — especially the beneficial ones — because they can do us more good than harm.
The thing that struck me most about this podcast was how the scope of our knowledge has shifted over the past century since the discovery of the first antibiotic, penicillin, by Alexander Fleming, which won him a Nobel Prize. At the time, this was widely regarded as one of the most profound discoveries in the history of medicine — one that had the potential to cure millions of lives. This was the case for about two decades until the first antibiotic-resistant bacteria began to appear. As more and more bacteria become resistant to the antibiotics that were used against them (primarily due to overprescription by physicians and misuse by patients themselves), scientists investigated the genes that were responsible for their “resistance traits” and learned more about the behaviour of certain bacteria, eventually concluding that we humans have essentially “underestimated their capabilities”. We are now in an era in which most antibiotics have been rendered useless and are scrambling to seek solutions to this catastrophic problem. Listening to this podcast made me ponder about how much more the war we have initiated against microbes will cost us, and potential solutions that can offer a promising way out of this crisis.
3) Birds Butt Out. Cigarette butts are used by birds such as the house finch and the house sparrow for insulation and protection by repelling parasites. While for the most part, it is beneficial for the birds, these cigarette butts could be toxic at the same time as insecticides may be left in them.
This podcast stood out to me because it shows how birds such as the house finch can take advantage of seemingly useless materials (life is opportunistic!) to create more protection for themselves and their young. However, due to the presence of insecticides in these cigarette butts, which are of course toxic to these finches, I wonder if they are now looking for similar chemicals that can provide the same benefits and functionality but are less harmful at the same time.
4) Costa’s Hummingbird. These fascinating hummingbirds, found in California and Southern Mexico, try to impress females using their high-speed aerial movements to create songs in thin air. They do this by spreading out and vibrating their outermost tail feathers, which, combined with high-speed flight, produces a loud, high-pitched sound. They travel above the females in a particular trajectory that minimizes an acoustic phenomenon known as the Doppler Effect, which enhances the elegance of the sound that they produce.
What I find captivating about Costa’s Hummingbird is the way it takes advantage of two of its most gifted traits — high-speed flight and their ability to vibrate their outermost tail feathers in unique patterns — to attract females. The mating strategy that it uses is truly distinctive and requires quite a stellar display of both flight and sound pitch to achieve.
5) Albatross Same-Sex Parenting. The Lecan Albatross uses female-female pairings as a mating strategy in colonies that are short on males. Newer colonies will have more females, as characteristically, females are the birds that venture away from their original colonies to expand the species. First, the females will both mate with a male and both lay a fertilized egg. One female will stay behind and incubate the egg while the other will go off and hunt, and this continues in shifts. This phenomenon exists due to the biparental care requirement of albatross chicks which limits the number of chicks that can be cared for per season.
What I like about the socially monogamous Lécan Albatross is that it has adapted itself to social monogamy to meet the biparental care requirement to raise its chicks. In most other birds that I’ve seen with highly imbalanced populations in terms of sex, which at the same time require biparental care, they often do not adapt well to monogamy and thus do not take care of their chicks well enough, contributing to their population decline. However, the reason that the Lécon Albatross has been able to keep their population stable is because of their socially monogamous relationships, which allows them to raise their chicks with other members of their species — regardless of their sex.
Notable Learning Experiences
Streak Plate Lab. This lab is one of my favourite experiences of the year. It is arguably the most common experiment in Microbiology and I feel very privileged to have done it twice (although the first time it did not work). Learning about how to create proper streaks on agar, ensuring the resterilization of the inoculation loop after each round of streaking and ultimately being able to isolate a single colony of bacteria/yeast/other microorganisms was a significant practical highlight for me in high school biology. These are skills that I will carry with me throughout the rest of my academic career and will certainly come in handy in future experiments.
2) Walk w/ Christine (May 2022). Firstly, as a person who has lived at the core of the city for the past decade of my life, I have not been exposed to much of the wildlife or seen more than just a handful of species of birds. The hustle and bustle of where I live do not permit birds and many other organisms (except for the few who have adapted better than the rest due to natural selection) from residing, and their songs are rarely heard — often because they are blocked out by the sounds produced from human activity. Therefore, I did not think that there was a lot of biological diversity in the species of birds that exist in the highly urbanized Lower Mainland and only expected these very species of birds that are found in downtown Vancouver to be found in the forest.
This all changed on that one morning when I came to Camosun Bog and encountered that magical moment of a massive shift in perspective and self-knowledge. Listening to all the incredibly diverse bird songs as soon as I entered the forest along with the rest of the class and the hundreds or even thousands of birds perching on the branches of trees in and around the bog was a stunning experience that I will never forget. This experience made me all of a sudden appreciate the immense biodiversity that exists where we live. Obviously, and based on my personal experience, this incredible diversity in species often goes unnoticed in other parts of Vancouver other than a few select locations in the city — one of which is of course, Camosun Bog.
Listening to the never-ending and unique melodies produced through their songs, I pondered about everything that we had learned in our Birds Unit within the classroom. As I was walking along with the rest of my classmates, I contemplated on what exactly each of the birds that I could see on the treetops was trying to communicate; which ones were warning other birds of their nesting habitat and which were producing the beautiful songs to attract females. The ability to sing such amazing melodies is, of course, a testament to the fascinating evolutionary history of these avian species.
3) Collaborative Book Discussion on Evolution (December 2021). Working alongside four other brilliant classmates, I was humbled to be part of this group presentation to showcase the magnificent books that we read on evolution to the rest of the class. Reading my book, The Greatest Show on Earth by Richard Dawkins, was a marvellous experience in and of itself. However, being able to compile all the phenomenal concepts that each of the five of us had learned to create a 1-hour presentation for the class — connecting each big concept to a particular “patterns of life” theme while taking a deeper dive into evolutionary biology — was the special part of this unique experience.
Both from reading my book, undoubtedly one of the greatest modern pieces written on evolution, and learning from my peers as we were designing the presentation, I acquired a deeper understanding of evolution (specifically by natural selection) and began to appreciate more and more its massive influence on the natural world, which often gets overlooked by many. I used to think of evolution as a force of the past that has now climaxed with the development of our incredibly intelligent and capable brains. However, through a combination of the concepts that I learned during our Evolution Unit and the Collaborative Book Discussion, I began to realize more and more that evolution and natural selection still exist and are causing species of organisms to change physically and behaviourally faster than ever before. There is evidence supporting this everywhere in the natural world, and I only began to comprehend the sheer influence that this phenomenon still has on species of organisms through the Collaborative Book Discussion. I not only thought of the evolution of other species but of our evolution as well and where it is heading in the future.
Based on the shift in perspective that I developed through this experience, I concluded that, at our current rate of evolution, humans in several thousands of years may be orders of magnitude more intelligent and capable than we are today. As Richard Dawkins mentioned in his book, The Greatest Show on Earth, “The greatest story is, of course, the story of evolution”. Without evolution, life on Earth could never be sustained and the vast diversity of species — in terms of size, weight, colour, shape, capabilities, etc — that can be seen on planet Earth today would never exist. While it was fantastic to have a discussion with the class to broaden our overall impression and knowledge of evolution, I am personally incredibly glad to have developed an entirely different viewpoint on evolution and natural selection through this experience, because ultimately, to understand biology, you must first develop a thorough understanding of evolution. This was, without a doubt, one of the most pivotal experiences I have had in all of high school biology.