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While they can both make you sick, as well as both help with various factors in your body (such as digestion), these two are quite different. Let’s first start by defining what viruses and bacteria even are.

What are bacteria?

Bacteria are single-celled microbes that do not contain a nucleus or membrane-bound organelles. There are 5 structural types of bacteria, each one determined by its shape: spherical (cocci), corkscrew (spirochaetes), rod (bacilli), comma (vibrios), or spiral (spirilla). They can form chains and clusters and can be in pairs or alone.

There are about 10 times more bacteria in the human body than there are human cells. This is because they are much smaller than human cells. Bacteria are vital in human digestion, helping to break down carbohydrates and short-chain fatty acids so that the body can absorb them. They most often cause disease when a single species dominates the gut ecosystem, which tends to follow the prolonged use of antibiotics.

What is a virus?

A virus is an infectious replicating agent, a parasite, that contains strands of DNA or RNA surrounded by a protein coating. Viruses place their genetic information into a cell where it may get incorporated into the genetic code of the cell or it will only use the cells machinery (i.e. ribosomes and enzymes) to make more copies of them. This method is how viruses spread.

Unlike bacteria, a virus is not a living cell and is unable to survive without a host. They are much smaller than bacteria and are far more common, outnumbering bacteria 10:1.

Despite often causing harm, it is believed that viral DNA/RNA is vital when it comes to biodiversity. In fact, 8% of the human genome is thought to have come as a result of viral DNA.

What is the difference between an antiviral and an antibiotic?

As you might have guessed, antibiotics do not work on viruses and vice versa. Some doctors might prescribe an antibiotic if you are sick, without knowing if you have an infection, or something like the common cold (caused by rhinoviruses and sometimes coronaviruses).

This is because the symptoms of both are very similar. For instance, a sore throat can be caused by a virus but so can streptococci (the bacteria that causes strep throat). Whooping cough is caused by bacteria, while bronchitis can be caused by both. So quite often, unless a doctor tests for the strain of the bacteria/virus, it is unknown whether antibiotics will even work. All that said, doctors may prescribe antibiotics in clinical settings to prevent a secondary infection from occurring due to a compromised immune system after battling a serious viral infection. This treatment is not infrequent in patients recovering from severe Covid-19 for instance.

Antivirals work by either eliminating the virus or preventing the virus from spreading. For instance, they might target specialized proteins or other parts of the virus to prevent it from being able to grab ahold of a cell. These are often only effective when administered before exposure, or shortly after exposure before symptoms occur, giving your body time to defend against the intruders. They are mostly ineffective if you are already sick.

Antibiotics work to interfere with the reproduction of bacteria. This prevents bacteria from spreading, giving your body the ability to fight them off. However, overuse of antibiotics can cause major issues, like the overgrowth of certain strains of bacteria over others, as well as the bacteria developing a resistance to the drugs.

References:

https://newsroom.uw.edu/news/genes-%E2%80%98fossil%E2%80%99-virus-human-dna-found-be-active

https://www.genome.gov/genetics-glossary/Virus

https://askabiologist.asu.edu/beneficial-bacteria

https://microbiologysociety.org/why-microbiology-matters/what-is-microbiology/bacteria.html

https://www.merriam-webster.com/words-at-play/virus-vs-bacteria-difference

https://www2.gradymem.org/getpage.php?name=Bacteria_vs_Virus

https://eswi.org/knowledge-center/difference-between-vaccines-antivirals-and-antibiotics/

Piecing out the exact course of human evolution is kind of like trying to figure out the shape of a 1000 piece puzzle while only having 300 of the pieces. Every newly discovered fossil or piece of DNA evidence helps make the shape clearer, but it will likely be a long time before we have a full and detailed picture of exactly where we came from.

What we do know, is that the evolutionary lineage that would become modern humans diverged from the lineage of chimpanzees and bonobos about seven million years ago. It is a common misconception that humans evolved from chimpanzees; in reality we just shared a common ancestor with them.

According to the fossil record, our earliest human-like ancestors were apes that developed the ability to walk upright for extended periods of time. An example of this would be the famous “Lucy” or Australopithecus afarensis.

From these bipedal apes evolved our more recent ancestors: the members of the Homo genus. These species left behind artifacts that proved they created and utilized crude stone tools, setting them apart from earlier ancestors. Some famous examples of species in the Homo genus include Homo habilis, Homo erectus, and Homo neanderthalensis (also known as Neanderthals).

Modern humans (also known as Homo sapiens) coexisted and even interbred with Homo neanderthalensis for a significant period of time. We know this because all modern human lineages, apart from those originating in Africa, contain evidence of Homo neanderthalensis DNA. There are even scientists that believe modern humans may have played a role in the eventual extinction of Homo neanderthalensis.

Understanding our own evolutionary lineage helps us to better conceptualize where we come from and who we are as a human species. This is why we continue to study fossil and DNA evidence to continue piecing together the puzzle of human evolution.

We’ve discussed the extinct species of primitive humans that were our ancestors, but what about living relatives. Which surviving members of the animal kingdom are our closest genetic relatives?

According to fossil evidence and genetic comparisons, our closet relatives are chimpanzees and bonobos. Our DNA is about a 98% match with these species, which tells us that we had a relatively recent common ancestor. It’s important to note that modern humans did not evolve from chimpanzees and bonobos, we simply shared a chimp-like common ancestor with them.

Within the animal kingdom, humans are considered to be primates, so we fall within the same group as monkeys, lemurs, and apes. After chimpanzees and bonobos our next closest relatives are the other members of the Hominidae subfamily, which also includes other Great Apes like gorillas and orangutans.

Modern humans share many traits with the Great Apes. Like humans, apes are highly intelligent and emotional creatures compared to the rest of the animal kingdom. Chimpanzees and bonobos are both omnivorous like us, though they are slightly more herbivorous leaning than we are. Most Great Apes can also walk on their hind legs alone for short periods of time, a hint at the full bipedalism that human ancestors would eventually evolve.

And we don’t just share traits with apes! We share our opposable thumbs (thumbs that allow us to grasp and hold things), forward facing eyes, and excellent color vision with most members of the primate kingdom.

Looking back on the history of science, it’s clear that we’ve come a very long way. It’s also clear that the desire to systematically learn about the natural world has never been limited to one culture or time period; people have been doing at least a version of science for a very long time.

In the beginning, the main motivations for biological scientific learning were either to learn how to cure illnesses and keep people healthy (medicine) or to discover new information about nature and animals (natural history).

For example, we know that basic medical science was practiced in Ancient Egypt due to the discovery of several papers detailing medicine preparation and even rudimentary surgical techniques. In Ancient Greece, Hippocrates developed the idea of the four humors; various liquids found within the human body whose imbalance he believed was the root cause of many illnesses.

In terms of natural history, ancient scholars commonly dissected animals in order to learn more about their internal anatomy. Aristotle in particular was known for dissecting many species of animal and classifying them based on their physical characteristics.

Much of this early science was based entirely on personal observations, hypothetical thought experiments, and individual anecdotes. The idea of controlled, unbiased experiments and the scientific method had yet to come into vogue.

In Western culture, the transition to a more modern scientific philosophy began during the European Renaissance with the rise of empiricism, which valued direct observation from the senses over theoretical ideas. Galileo is sometimes credited as the “father of the scientific method” due to his systematic studies in astronomy and physics. The momentum of his ideas were built upon by other philosophers, and eventually led to Francis Bacon formalizing a version of the scientific method in 1621.

The scientific method made studies more empirical, comparable, and replicable. It allowed science as a whole to progress, rather than just the ideas of one particular scholar or philosopher.

The 1600s saw the invention of more accessible and powerful microscopes, and with it the beginning of microbiology. Scientists were now able to study living things smaller than what could be seen with the naked eye. These early microscopes eventually led to the discovery of cells, and then to cell and germ theory in the 1700s and 1800s. Although it sounds crazy now, it wasn’t until we developed a more nuanced understanding of germs and other microorganisms that physicians learned to wash their hands and disinfect tools when tending their patients.

In the 1700s, the naturalist Carl Linnaeus revolutionized how living things were classified in the Western sciences. His idea of “binomial nomenclature” is still used today, in the form of the scientific names (or Latin names) that we use to refer to species. This earned Linnaeus the title “father of taxonomy”.

One essential feature of science is that it each new scientific idea builds on the ideas that came before it. Linnaeus’s idea of organizing living things based on physical characteristics and relatedness to one another also would eventually help set the stage for Darwin’s revolutionary theory of evolution.

It was in the 1800s that Charles Darwin spent time on a fateful voyage, which included the Galapagos Islands, and from his observations formed the Theory of Natural Selection. In the words of biologist Theodosius Dobzhansky, “nothing in biology makes sense except in the light of evolution”.

Darwin’s theory opened the doors for a more complete understanding of the living world and how the current species living on Earth came to be. Evolutionary theory impacts all parts of biology, from animal behavior to genetics to taxonomy to ecology. All modern biology relies on evolution as a central tenet, which was built out of hundreds of years of previous biological knowledge.

Life on Earth originated in the ocean, but what was the first group of organisms to move onto the land? When thinking about life moving to land, many people imagine the classic image of a primitive fish species evolving legs and crawling onto a beach. Although that is more or less how vertebrates first made the transition to terrestrial life, there were already many other organisms thriving on land by the time they got there.

Although it’s difficult to determine for certain from fossils alone, most scientists believe that the first organisms to take to the land were freshwater plants. These plants originally inundated swamps and wetlands, before eventually evolving into fully terrestrial plants that could live and reproduce away from the water.

Early terrestrial plants had to overcome several obstacles to adapt to their new lifestyle. These included being able to hold themselves upright without support from the water, and withstanding more intense levels of sunlight. These new adaptations allowed them to take advantage of otherwise unclaimed habitat.

Once the first land plants had established habitat and food, the first animals to move to land were early arthropods. These included the forbearers of myriapods (millipedes and centipedes), arachnids (spiders and scorpions), and insects. Arthropods had been living on land of thousands of years before vertebrates came on the scene.

The first vertebrates to move to land were primitive fish, probably resembling lungfish or mudskippers, which eventually evolved into the fist amphibians. Adaptations like breathing air and legs to move on land allowed them to take advantage of the terrestrial prey and habitat created by plants and arthropods.

The transition of vertebrate life from the ocean to the land has always been a fascinating example of evolution. Imagining an early fish evolving simple legs and dragging itself onto dry sand for the first time is certainly a dramatic image.

Of course, to live on land these early fish had to be able to breathe air. When living in water, most fish use organs called “gills” to get oxygen. Gills have a high surface area and are able to perform gas exchange to pull oxygen from the surrounding water. It seems intuitive that lungs would have evolved from gills to allow fish to breathe air; however, this is not the case.

It turns out that another fish organ, the swim bladder, much more closely resembles a primitive lung. Swim bladders help many fish regulate their buoyancy, but some fish can also use them to breathe. For example, fish that are found in very stagnant water with low levels of dissolved oxygen may need to gulp air from the surface and “breathe” through their swim bladder rather than through their gills.

Darwin believed that lungs must have evolved from swim bladders, but more recent scientific evidence suggests that swim bladders and modern lungs both evolved from an earlier, more primitive organ that served the purpose of both a lung and a swim bladder. This early organ may have originally come from gill tissue or a sac of tissue in the digestive system used for regulating gas.

One of the incredible feats of evolution is its ability to adapt the same organ or piece of tissue to serve completely different purposes in different species. Who would have thought that our air-breathing lungs could have the same origin as the buoyancy-regulating swim bladder of a fish!

What exactly is a filter feeder? Filter feeders are animals that obtain their food by filtering water through a sieve-like structure that catches food particulates. Filter feeding only works in water, and most filter feeders are found in marine environments (meaning they live in the ocean).

A wide range of marine species use filter feeding as a strategy. Filter feeders can be motile (meaning they can move by themselves) or non-motile (meaning they remain in one place unless moved). They can be small enough to fit in the palm of your hand, or larger than a car.

All non-motile filter feeders are also invertebrates, or animals that lack a backbone. These include sponges, tunicates, and bivalves like oysters and mussels. Non-motile filters feeders feed by pumping water through gills or other structures in their body, which brings in a constant flow of food particles.

In some habitats, filter feeders like oysters play a big role in removing toxins and other particulates from the water column. Their filters catch not only food, but also pollution, sediment, and other tiny debris. This helps keep the water clean and healthy for other organisms.

Motile filter feeders include massive animals like whale sharks and baleen whales. Whale sharks feed by swimming with their mouth open and pushing water through their gills. Baleen whales, on the other hand, feed by gulping huge amounts of water that contains krill or other food items. They then force the water out through their baleen (a stiff, comb-like structure), which allows the water to escape but keeps the food inside.

The largest animal to have ever lived, the blue whale, is a filter feeder. Blue whales are so large that an adult human could crawl through their aorta, yet they feed on tiny creatures like krill that are almost too small to see without a microscope.

When vertebrate animals first moved from the water to the land they had one major problem: How to reproduce without access to water. The earliest vertebrates to live on land somewhat resembled modern day amphibians. They had eggs that needed to stay wet to survive and began life as aquatic larva, much like modern tadpoles. These primitive animals also participated in external fertilization, where eggs and sperm are released into the water beside one another in order for fertilization to occur.

In order for vertebrate life to move away from the water and further inland, internal fertilization needed to evolve. Internal fertilization is what modern day reptiles, mammals, and birds employ; sperm enters the female animal and the eggs are fertilized inside her body.

Early terrestrial vertebrates also needed eggs that wouldn’t desiccate outside of the water. This obstacle was solved by the “amniotic egg”. Amniotic eggs have a hard external shell that prevents water from escaping, as well as a series of moist membranes called the “amnion”. Together these protect the developing embryo and prevent it from drying out.

In modern times, fish and amphibians both lack amniotic eggs and their reproduction is tied to the presence of water. Reptiles, birds, and mammals, on the other hand, are amniotes with internal fertilization and eggs that can survive outside away from the water.

Yes, mammals are amniotes even though most of them don’t lay eggs! Although mammals usually gestate their offspring internally instead of in an egg, they still have an amnion and evolved from ancestors that laid amniotic eggs. Some mammals, like echidnas and platypuses, still lay eggs just like their ancient ancestors.

Let’s start with the word “tetra”, which means “four”. Combine it with the word “pod”--meaning “foot”--and you’ve got a very basic definition of a tetrapod, which is an animal with four feet.

Most animals you encounter in your daily life probably have four feet, but there was a point in evolutionary history where four-footed body plans were unheard of. Obviously feet of any kind were not needed when all animal life was confined to the oceans. As plants and invertebrates colonized the land, some ancient fishes began to develop foot-like fins that would allow them to take advantage of this new habitat.

The eventual evolutionary result was the first four-footed animal, the first tetrapod. This first tetrapod probably looked like something between a lungfish and a salamander and was still very dependent on proximity to water to reproduce. It was the last common ancestor shared by amphibians and amniotes like reptiles, birds, and mammals.

As a result of their evolutionary history, all amphibians, reptiles, birds, and mammals are considered “tetrapods”. You may be wondering, how are animals like snakes, birds, or whales considered tetrapods when they don’t have four feet? When it comes to deciding which animals are tetrapods, it’s the evolutionary lineage that matters not the actual number of feet.

Snakes, birds, and whales are still evolved from four-footed species, and many of them still have remnants of the four-footed body plan even without having four feet. For example, whales have vestigial hipbones where their hind limbs used to be before they fully adapted to life in the water. Another example is the wings of birds: Under those long, specialized feathers the wings are just modified front legs made from the same basic evolutionary building blocks as a human arm or elephant foot.

To put it very simply, a placental mammal is any mammal that produces a placenta during pregnancy. However, that definition isn’t exactly helpful if you don’t know what a placenta is to begin with.

The placenta is an organ that develops during pregnancy in mammals that gestate their offspring internally and give live birth. This organ allows the mother to pass nutrients and oxygen to the developing fetus while also removing wastes from the fetus’s bloodstream. The placenta also works to prevent infection in the uterus and releases important pregnancy hormones.

Despite its very important role in pregnancy, if you were to see a placenta in real life you would probably think it looked like a clear plastic bag full of blood. The placenta is made of dense, squishy tissue and full of blood vessels that allow for exchange of materials between the mother and the fetus. It also includes the umbilical cord, which is where the fetus is connected to the placenta. Your bellybutton is where you were connected to the placenta as a baby!

When a female mammal gives birth, the placenta is also ejected from the body. It’s part of what some people call the “afterbirth”. This occurs because the temporary organ is no longer needed; many mammals consume their placenta in order to recycle its nutrients.

The vast majority of mammals are placental mammals. Exceptions include all marsupials (such as kangaroos, wallabies, and opossums) and monotremes (such as platypuses and echidnas). This means that humans are placental mammals too!

Most early mammals probably laid eggs similar to the monotremes, so the placenta is a relatively new adaptation in terms of mammalian reproductive strategies. It is found in so many mammalian lineages because carrying offspring internally confers a big evolutionary advantage; more offspring survive when they can be carried safe and sound inside their mother’s body.

Hominin, hominid, and hominoid are all words that we use to talk about humans, their ancestors, and their closest relatives, but they mean different things.

A hominin refers to a species within the Homini tribe of Hominidae, which encompasses modern-day humans as well as extinct human species and their ancestors. Non-human apes such as gorillas or chimpanzees are not considered to be hominins. Hominins are distinguished specifically by their degree of bipedalism (the ability to walk primarily on two legs).

A hominid, on the other hand, is any member of the Hominidae subfamily. This includes all the Great Ape species; orangutans, gorillas, chimpanzees, bonobos, and all hominins (modern and extinct humans). Hominins are essentially a smaller subset of hominids.

Hominoid, on the other hand, encompass an even larger biological group. A hominoid belongs to the superfamily Hominoidea; this includes all hominins, all hominids, and includes lesser apes like gibbons as well as the Great Apes. Hominoids are distinguished from other primates by their lack of tails and flexible shoulder joints for brachiating (swinging from arm to arm).

The word “ape” is a less scientific term used for hominoids, although this can get confusing since some people do not think of humans and ancestral human species as “apes”.

Essentially, all hominids are hominoids, and all hominins are hominids. The words sound very similar and can be confusing, but it’s important to use them correctly so people know which group you’re referring to.

A long, long time ago, roughly 2 billion years ago according to most scientists, there was no oxygen in Earth’s atmosphere. Nearly all life on Earth was anaerobic bacteria, or bacteria that break down their food and obtain energy without oxygen. The oxygen-lacking atmosphere of early Earth was perfect for these organisms, and the oceans were full of them.

Then cyanobacteria, also known as blue-green algae, entered the scene and everything changed. Up until now, energy entered the food chain via chemosynthesis (obtaining energy from the breakdown of non-living chemicals) or a primitive form of photosynthesis fueled by non-visible light that produced sulfur as a waste product. Cyanobacteria were different; they could harvest energy from visible sunlight and produce free oxygen.

As humans who need to breathe, we think of oxygen as something good and life giving. For the anaerobic bacteria living billions of years ago, oxygen was essentially poison.

The emergence and success of cyanobacteria triggered a mass extinction event, which scientists call The Great Oxygenation Event. Many species of anaerobic bacteria went entirely extinct, while others were relegated to sparse, oxygen-free environments like the depths of the ocean.

Cyanobacteria, as you may know, live on to this day. They can be found in nearly every aquatic habitat on Earth, from freshwater to saltwater. Some cyanobacteria were engulfed by the cells of early plants and formed a symbiotic relationship. These cyanobacteria are now known as chloroplasts, and they are what allow plants to photosynthesize.

Without cyanobacteria, and the extinction of hundreds of anaerobic bacteria species, the current, oxygen-rich atmosphere that allows us to live would never have existed.