Biology Archive - Page 11 of 11

Human Biology

Imagine that you’re given a puzzle to solve. But not just any puzzle—it’s a human being. The average human weighs about 137 pounds, and though it might not seem like it, it’s actually a huge puzzle of seven octillion pieces!

Each human being has about 10 major organ systems, e.g. the circulatory system or the endocrine system. Scattered among these organ systems are about 37,200,000,000 cells. The molecules in each of these cells (and outside them) could be undergoing hundreds of chemical reactions every minute. Finally, among all of these organs and cells, it’s estimated that there are 7,000,000,000,000,000,000,000,000,000 atoms.

Oh, and there are an estimated 7,449,654,529 people on the planet—and that number grows every second. Good luck puzzling it out!

How to Find More Fun Untamed Science Human Biology Information

We’ve organized the Human Biology portal into the major organ systems:

To find out more information about each of these systems, simply click the link here or in the sidebar at right. Within each organ system, you can find more in-depth articles about different components of the system. An article on blood could be under the circulatory system, for example, or an article about stomachs could be found under the digestive system page.

At the bottom of each organ systems page, we even have links to more relevant, fun articles. For example, an article about gluten-free diets can be found under the digestive system page. And throughout, our signature videos to help explain the concepts.

Why study human biology?

Luckily for us, we don’t have to solve the puzzle of ourselves from scratch. We know a lot about the human body today thanks to millions of curious people before us who had the ability to write down what they learned. Each day that passes brings even more knowledge from scientists and doctors all over the world studying the human body.

Human health is potentially much better today than it ever has been in history due to this collective knowledge. Humans used to die young from infectious diseases, like tuberculosis, whooping cough, and dysentery (which you may recall from the Oregon Trail video game). Even if you didn’t die young, you’d probably face a whole suite of parasites, low-level infections of all kinds, and no way to cure them.

Today, we hardly ever die from these problematic diseases (with a few exceptions). Even better, we’ve completely eradicated the deadly disease smallpox, and are on track to eradicate many more devastating threats, like polio and guinea worm disease (warning: don’t watch if you’re very squeamish!):

Where is the study of human biology going now?

Due to dramatic improvements in health care, we gradually started living even longer. This was a great thing (grandparents could finally meet their grandkids), but it brought a whole host of other challenges. Now that people are living longer, they may merely shift their problems from infectious diseases to more preventable diseases, like heart disease and obesity.

Understanding and curing preventable diseases are some of the most pressing issues that contemporary human scientists study. There are plenty of other opportunities as well; as the study of other areas of biology like genetics and ecology advance, new possibilities to cure diseases, give everyone a better life, and allow people to push their biology to the edge become open to us.

For example, scientists are trying to figure out how the human body can cope with being in space, starting with astronaut bone metabolism. Other scientists are trying to figure out how to prolong human lifespans, so we can enjoy a longer life. No matter which way you look at it, there will always be things that scientists can study to make our own lives better.

Why is it important for everyone to understand human biology?

Having a good understanding of how the human body works is essential for more reasons than just showing off for your friends at trivia competitions. Without a good understanding of basic human biology, you’re more likely to make bad health decisions, like not getting vaccinated for infectious diseases, buying into the latest fad (scam) product or trendy diet, or even believing that you could be a zombie:

There is an endless amount of fascinating information for people to learn about themselves, but luckily, you don’t have to learn it all. There are a few basic things that everyone needs to know about their own bodies, and you can explore that information in the panel at right or in the following articles on various topics of human biology!

Evolution

What is Evolution?

Have you ever heard of the “gene pool”? It’s not actually a pool filled with denim trousers but something much more interesting!

Gene pools are simply the collection of all the genes that make a species. Genes themselves are simply the codes, or blueprints, that make the building blocks of a living organism. There’s a separate gene pool for every species of organism, from Canada geese to portobello mushrooms to iguanas.

Gene pools don’t always stay the same; they are constantly shifting and changing as brand new genes come into the gene pool and others move out and are lost forever.

In fact, this is the definition of evolution: changes in the gene pool that happen over time. By studying evolution, scientists can get a handle on how organisms changed in the past, what’s happening to them now, and how they might differ in the future.

The Untamed Science evolution portal is a gateway for learning about various topics on evolution. Check out the articles on the right, or see some of them below:

How does evolution work?

Evolution is simply the change in the gene pool of a population over time. Individual organisms don’t evolve; once you have your genes, they can’t really be changed except for a very few rare circumstances. But there are five different ways that genes can change a population over time:

Mutation

Mutation is very important in evolution because it’s the only way that completely new genes ever happen. In fact, every single gene in the world started as a mutation! The other four mechanisms are just different ways that genes can be reshuffled, but with mutation, it’s something new that’s never been seen before.

Most mutations don’t have any effect on the organism, or they may even have a negative effect. But, every once in a while, a mutation happens that actually improves the organism in some way. Maybe it’s just a bit faster, has sharper teeth, or a better brain. When this happens, the organism is more likely to survive, reproduce, and pass on the new gene to its offspring. When those genes spread in the population, it’s said to have evolved.

Migration

When organisms move in and out of an area, they also take their genes with them!

In conservation, one of the main concerns is how the wild landscape is becoming increasingly fragmented. More roads, farms, and shopping malls are built, and shy animals don’t move around like they did historically.

Now, a very real possibility is that some populations will become too isolated and may eventually evolve to become inbred. If this happens, they’re more likely to succumb to disease or be unable to adapt to a changing environment because they won’t have access to new genes that may help them survive better.

Natural Selection

It might seem like “natural selection” is a difficult-to-understand concept dating back to Darwin and his Galapagos finches, but it’s actually pretty simple.

Organisms are exposed to different conditions that affect how likely they are to survive and have babies. That’s it! These different conditions, called selective pressures, can be external (in the environment) or internal (within their own bodies).

Examples of selective pressures might be the pH of ocean water (crab shells will dissolve when it’s too acidic), a new disease (Tasmanian devils are evolving to become more resistant to an infectious facial tumor), or how attractive an organism is to others (“beautiful” or “handsome” animals are more likely to find mates and reproduce than their “ugly” counterparts).

Artificial Selection

Artificial selection is similar to natural selection, except the limitation to which organisms are allowed to reproduce is decided by humans. We do this because we want to develop a certain trait in an organism, like high-productivity wheat or friendlier kitties.

Check out this cool example of artificial selection in some things you may eat all the time:

Dogs are a great example of artificial selection. There are 340 different breeds of dog in the world, all created by people for a certain purpose. In some cases, such as English Bulldogs or Chihuahuas, these dogs’ genes are manipulated to make them physically attractive but can actually cause unhealthy side effects. It’s not very likely that these dogs would have evolved as such in the wild.

Genetic Drift

Most genes don’t have selective pressures on them forcing them to evolve one way or another. They just casually float along in a population, and each time a new organism is born, its genes from its parents get reshuffled randomly.

This has some interesting effects. If a population is very small, it’s more likely to show a phenomenon called genetic drift—random changes in the gene pool. Larger populations serve as big reservoirs of rare genes so it’s hard to lose them completely. On the flip side, it’s easier for rare genes to be lost from small populations because there aren’t very many to begin with.

For example, let’s think of a small population of just 20 birds. If only one of these birds has a rare gene and that bird dies, that gene is lost from the population. But, if there are 10,000 birds and 50 of those birds have the rare gene, that gene is much more likely to stay in the population by passing it on to offspring. It’s unlikely that all 50 of the special birds would be struck by lightning at the same time!

Ecology

Jay-Z might have had 99 problems, but ecologists have trillions. To find out why, let’s talk about what ecology actually is.

Ecology is simply the study of how and why organisms interact with their environments. Even though that sounds like a simple statement, there are literally worlds of complexity behind it, and there is a whole army of technicians and ecologists around the world to prove it!

People want to know how and why organisms interact with their environments for all sorts of reasons. Wildlife managers might want to know what’s causing an endangered species to go extinct, for example, so they can take measures to stop it. Or maybe health officials want to know how mosquitoes spread diseases so they can help people stay healthy.

How to Find More Fun Untamed Science Ecology Information

We’ll talk about what ecology actually is in this article, but to get specific, click through the sidebar at right. You’ll find more in-depth articles on the basics of ecology, and if you click on Ecology Articles, you’ll find even more detailed topics.

The Tree of Life page has links to information about all kinds of living organisms, with information about their ecology as well. Finally, if you have something specific you’re looking for, hit the magnifying glass above to search the site. And throughout, you’ll find our signature videos, like this one on remote sensing:

What do ecologists study?

Ecologists rely a lot on the scientific method when doing research. They have to come up with questions that they can try to answer. Here are some examples of research questions that an ecologist might ask. See if you can spot the interactions they’re studying:

What do bears in Yellowstone National Park prefer to eat?
Can plants use mycorrhizae to talk to each other?
What type of grass grows best in soils that have been damaged by mining?
How and why do koalas visit different trees in a forest?
What caused the last wooly mammoth to die?

As a comparison, here are some examples of research questions that are not considered ecology. See if you can spot why:

How many people have autism?
How should we classify newly-discovered slime mold beetles, named after the U.S. politicians Bush, Cheney, and Rumsfeld?
How symmetrical are wolf skulls?
How long do people survive after having surgery to fix the Tetralogy of Fallot heart defect?
How does caffeine work inside your body to keep you awake?

Did you notice a pattern? Non-ecologists generally focus on describing something that is happening in nature, much like how a reporter describes the facts of what happened. Non-ecologists also focus on things that happen entirely within individual organisms.

Ecologists, on the other hand, focus on what causes things to happen between different organisms. Their versions of these questions might be: Are there any environmental effects that cause autism?; What caused so many different types of slime mold beetles to evolve?; Why are wolf skulls asymmetrical?

What types of ecology are there?

As you can see, ecology is an extremely broad topic because it’s basically a way to understand how our entire world works together. There are literally trillions of different things you can study, and they change every day.

To make things a bit easier, scientists often refer to specific types of ecology. You can take almost any topic, slap “ecology” behind it, and it’s a new discipline. You can study armadillo ecology, soil ecology, banana ecology, etc. Nevertheless, there are some general, all-encompassing categories. Here are a few:

Biogeochemistry

Biogeochemists study big-picture issues of how organisms affect the geology and chemistry of the Earth. This involves studying a lot of cycles, such as the carbon cycle or the water cycle.

These scientists focus on how and why elements and molecules move around in the ecosystem. For example, how much methane does the cattle industry produce, and how does this contribute to climate change?

Population Ecology

Population ecologists are math nerds who spend most of their days crunching numbers in front of a computer, punctuated by brief periods of extreme excitement where they collect data on number of individuals in a population.

Population ecologists generally try to solve problems about how and why populations change over time. They are very important to land managers who want to know what’s happening on their land. They also sometimes make recommendations about how to increase or decrease certain populations, depending on what land managers want.

Restoration Ecology

Restoration ecologists focus on how to turn an area back into a more natural state after some big disturbance has happened, like mining, development, or desertification. Usually restoration ecologists are most concerned with plants—if they can figure out the best plants to grow in a disturbed area, the wildlife and other critters will usually follow.

Humans have caused a huge amount of disturbance to the landscape, so nowadays restoration ecology is a big business. Just cleaning up former large industrial mining sites, for example, costs up to $681 million per year—it’s one of the reasons these places are called Superfund sites!

Nutritional Ecology

Nutritional ecologists focus on how an organism’s quest for food affects how it interacts with its environment. To study this, a nutritional ecologist needs to find out how many nutrients an organism needs, where it can get those nutrients from, and how many nutrients it can get from each source.

Once a nutritional ecologist has answered these questions, they can start to ask other questions: What would happen if the main source of certain nutrients disappeared? What if an area was developed and an animal couldn’t get there to eat? Why do animals migrate? These are just a few questions that nutritional ecologists can help answer.

Putting It All Together

Different types of ecology can nest within each other, too. For example, if you’re studying bandicoot populations, it would be considered both bandicoot ecology and population ecology. A single research project can actually be considered several types of ecology. The opportunities for research questions and exploration in ecology are endless!

Genetics

Did you know that within every single cell of your body, you store the blueprints to create an entirely new you—from scratch? Those blueprints, called DNA, dictate everything about how to build our bodies, from how to make our toenails to how to wire our brains. The way we’re put together affects who we are and how we function and interact with the environment. Pretty impressive, huh?

The study of DNA and genes is known as genetics. It’s one of the most recent fields of science to pop up on the map, starting around 200 years ago. Every day, there are legions of scientists around the world scurrying to learn more about genetics. It’s one of the fastest-moving areas of modern science.

What are genes and how do they make you?

Genes are the basic element that geneticists look at when studying organisms. A gene is simply a piece of DNA that codes for a trait (also called a phenotype, or a phenotypic trait), which is some observable characteristic. Traits range from simple things, like hair and eye color, to the more complex, like intelligence or susceptibility to disease.

There can be many different types of genes that code for the same trait, or even one gene that affects many traits. That’s what makes us so variable! For example, the MC1R gene helps dictate coloration in your skin, hair, and the iris within your eyes. There are many different variations of this one gene, called alleles. Depending on what types of alleles you have in your DNA, you could end up with one of any number of skin color, hair color, eye color, or even freckles!

Yes, you read that right: you have more than one allele for each gene. You have two alleles for each gene, in fact—one from each biological parent. Depending on what types of alleles they pass on to you, you could end up with two copies of the same allele or two copies of different alleles.

Having two alleles creates some interesting effects. Generally, your body will read both copies of the alleles and try to create you based on both blueprints. If your two sets of blueprints code for the same thing (known as being homozygous, or possessing two copies of the same allele), then there’s no problem: your body is on the same page with itself.

But, if your two sets of blueprints code for different variations of a trait (known as being heterozygous, or possessing two copies of different alleles), then some interesting mash-ups can happen. Sometimes one allele will take charge and become the dominant allele, and suppress the other, recessive allele, so that you wouldn’t even know you had it unless you tracked it down. Other times, they’ll both be expressed equally to different degrees.

These examples where one gene controls one trait are indicative of Mendelian, or simple, inheritance. It’s often not that easy: sometimes one gene is involved in creating many different traits, or one trait may be controlled by several different genes. It can get really complex!

How do scientists study genetics?

There are more specific elements that a scientist can study involving genes. Here are just a few sub-fields branching from the main field of genetics:

Heredity

Heredity is simply the study of how traits are inherited between generations. We’ve already discussed how heredity works, but it gets even more complicated, and that’s where scientists really dig in. In particular, scientists want to know how traits are passed along so we can understand our own biology better, or predict what might happen if two people have children.

The field of heredity started with Gregor Mendel back in the 1800s. He started a series of experiments involving peas that launched the whole field of genetics. It’s come a long way since then; here’s what it was like for him back in the day:

Population Genetics

A population geneticist looks at all the genes and alleles in a population as a whole. They’re interested in how the gene pool affects the population. They might look at how well different alleles contribute to the success (or failure) of a population, or track genetic influences in a population from a long-distant ancestor, for example.

A famous case of population genetics at work is with the blood disease known as sickle-cell anemia, where different alleles can cause red blood cells to become shaped like a crescent (or sickle). Scientists have figured out that having two copies of the sickle-cell allele (a.k.a., being homozygous) means that someone will have the disease.

However, if a person only has one of the sickle-cell alleles and a normal allele, they won’t get the diseases, but instead, they’ll be more resistant to malaria! As a result, population geneticists have noted that the sickle-cell allele tends to be very common in malaria-prone areas because having just one copy of the allele in this location makes a person more fit, or likely to survive and have children.

Evolutionary Genetics

Evolutionary geneticists also focus on genes and alleles within populations, much like population geneticists. However, evolutionary geneticists focus more on how the different genes and alleles within a population change over time. This process is actually what happens when a population evolves, hence the name evolutionary genetics.

Darwin’s finches are the most famous example of how genes cause a population to change over time. As one type of ancestral finch made its way to the Galapagos islands and began breeding and spreading out, different alleles started showing up in the population that changed the shape and behavior of the birds. Suddenly, some birds had long beaks that were good for one type of food, and some birds had short beaks better for other types.

The Untamed Science crew caught up with another fascinating example of island finch evolution in this awesome video:

Cells

Cell biology (also called cellular biology, formerly cytology from the Greek word kytos meaning “container”) is an academic discipline that studies the physiological properties of cells as well as their structure, organelles, interactions with their environment, their life cycle, division and death. This is done both on a microscopic and molecular level. Cell biology research encompasses both the great diversity of single-celled organisms like bacteria and protozoa, as well as the many specialized cells in multicellular organisms like humans.

Knowing the components of cells and how cells work is fundamental to all biological sciences. Appreciating the similarities and differences between cell types is particularly important to the fields of cell and molecular biology as well as biomedical fields, such as oncology (study of cancer) and developmental biology. These fundamental similarities and differences provide a unifying theme, sometimes allowing the principles learned from studying one cell type to be extrapolated and generalized to other cell types. Hence, cell biology is closely related to genetics, biochemistry, molecular biology and developmental biology.

The animal cell

All living things–humans, plants, animals, fungus–are actually big blobs of cells. Humans are built up of 100 trillion cells! These cells are assembled together into tissues that work as a unit to carry out a specific function. These tissues group together to form organs, such as the skin, heart and kidney.

It is amazing to think that all of the 100 trillion cells in our body are derived from only two original cells, one from our mother and one from our father. This means that even though these incredibly high number of cells have different functions, they all carry the same DNA in their nucleus. The DNA is the heritage from their parents and tells the cell how it should work and function. Essentially the cell is actually a mini-factory and the DNA is its instruction book.

Let us take a second to look at each individual cell organelle in turn.

Mitochondrion

The mitochondrion is the power plant of the cell. The energy that the cell uses for most of its functions is a small molecule called adenosine triphosphate (ATP). The mitochondrian converts glucose and oxygen to carbon dioxide, water, and ATP. This complicated process, called cellular respiration, involves many enzymes. Thanks to the mitochondrion, the cell can achieve 15 times more energy from each sugar unit than it would otherwise!

Apart from all other organelles, the mitochondrion has its own DNA and ribosomes. The genetic code in the mitochondrion DNA is somewhat different from the standard code found in the nucleus-DNA, and it is therefore believed that the mitochondrion evolved from an ancient bacteria that an animal cell engulfed. After millions of years the bacteria evolved into the mitochondrion of today with its primary purpose to contribute to cellular respiration.

Did you know…

All the DNA in your mitochondrion is derived from your mother. Since mitochondrial DNA is inherited as a single unit from your mother, scientists can use it to study the evolutionary history of populations. Mitochondrial DNA gives strong support that modern humans came from Africa. It is also being used to argue that Homo sapiens and Neanderthals were not related enough to interbreed. Mitochondrial DNA, however, reflects the evolutionary history of only females in a population, so it might be possible that men and Neanderthals are more closely related than we might think.

I want to learn more!

The mitochondrion is built up of two membranes: the inner and outer membrane. The outer membrane contains pores, in which small molecules, proteins and ions can pass freely, but bigger molecules can’t get through. The important energy-producing reactions take place in the matrix and the inner membrane that surrounds it. The inner membrane is folded to increase the surface area and therefore also increase the mitochondrion’s ability to produce ATP.

The mitochondrion can import both fatty acids (from fats) and pyruvate (from sugars) out of the cytosol and break it down to acetyl CoA, which is oxidized in the matrix via the citric acid cycle. The citric acid cycle converts the carbon atoms in acetyl CoA into CO2, which is released from the cell as a waste product. More importantly, the cycle generates electrons with high energy that are carried by two molecules, NADH and FADH2. These high-energy electrons are then passed along the electron-transport chain in the inner membrane to their final destination, oxygen. During this transport the electrons generate a proton gradient over the inner membrane. This proton gradient drives the production of ATP from ADP and phosphate by the membrane enzyme ATP synthase. (Cool fact: The 1997 Nobel Prize in Chemistry was given to the team that discovered ATP synthase.)

Lysosomes

Lysosomes are small digesting machines. They are vesicles filled with enzymes that break down the food we eat into smaller pieces. The food has to be broken down for the cell to use it as an energy source or for the cell to be able to build larger molecules and organelles. The lysosomes can also recycle old, out-of-order organelles and build new fresh organelles out of the old parts. Lysosomes are also really good bodyguards for the cell since they can break down dangerous invading bacteria and viruses.

There are many different enzymes in the lysosome that together are able to break down almost everything! Basically, the lysosomes import the things it want to digest from the cytosol, and when it is inside of the vesicle it will be broken down into small pieces. In chemistry language: large polymers are broken down to monomer subunits.

Mono..poly…what!??

Think of it as a pearl necklace! Each pearl on the necklace is a monomer, and when they are linked together they form a long chain, a polymer. What the lysosome does is separates all the pearls (the monomers) from the necklace so they are free.

Did you know…

…the lysosomes have a back-up system! First, lysosomes have a special membrane that keeps all the digestive enzymes inside of it so the enzymes won’t start eating up the cell from the inside. But even if a lysosome breaks and starts to leak out its content into the cytosol, nothing would happen! This is because the enzymes work best at the low pH that can be found inside of the lysosome. If the enzymes get outside of the lysosome, the pH is too high for the enzymes to function properly.

I want to learn more!

There about 40 different enzymes in the lysosome, including lipases that can digest fats into fatty acids, amylases that digest carbohydrates to sugars, and proteases that digest proteins into amino acids. When the lysosome has finished its digestion, it releases its final products into the cytosol where the molecules can either be utilized by the cell or excreted out of the cell.

For the lysosome to be able to keep the pH at 5 (the ideal pH for the enzymes) it has pumps in the membrane that actively import protons from the cytosol, which makes the solution acidic.

Nucleus

The nucleus is surrounded by a double membrane called the nuclear envelope. Inside the nucleus are long strands of DNA. The role of the nucleus is to maintain the integrity of the genes in the DNA and to control the activities of the cell. So the nucleus is the control center for the entire cell!

Cell Membrane

The cell membrane separates the inside of the cell from the outer environment. The membrane is selectively permeable, meaning that it can control what enters and leaves the cell. The membrane is basically made up of a double layer of lipids called the phospholipid bilayer. These lipids are hydrophilic on one side and hydrophobic on the other.

Endoplasmic Reticulum

The endoplasmic reticulum forms an interconnected network of tubules, vesicles and cisternae within cells. There are two main types. Rough endoplasmic reticula synthesize proteins. Smooth endoplasmic reticula synthesize lipids and steroids, metabolize them and regulate calcium concentration. A third type is know as the sarcoplasmic reticula which only regulates calcium levels.

Golgi Apparatus

The Golgi Apparatus, sometimes called the Golgi body, processes and packages macromolecules, like proteins and lipids. It is particularly important in the processing of proteins for secretion.

Biomes

What is a Biome?

A biome is a large geographical area of distinctive plant and animal groups which are adapted to that particular environment. Most terrestrial biomes are defined by the dominant plant life. The plant life is determined in part by the climate in a region, and climate is controlled by many factors, including latitude and geography.

A Video Introduction to Climates

This short video was made for Pearson‘s middle school curriculum. Overall we made 65 videos for grades 6-8. We’re happy to get the chance to share this one with you here. If you like it, please follow us on YouTube, Instagram, and Twitter and like us on Facebook.

Most textbooks define only terrestrial biomes. Technically this it the most precise definition. But we have included what we call aquatic biomes because many students search for them as biomes. In reality, most aquatic biomes are more correctly called aquatic zones.

Biomes of the World

To understand a world biome, you need to know:

What the climate of the region is like
Where each biome is found on Earth and what its geography is like
The special adaptations of the vegetation
The types of animals found in the biome and their physical and behavioral adaptations to their environment

Terrestrial Biomes

trees biome

Terrestrial biomes are defined by the dominant vegetation. For example, a deciduous forest is made up primarily of non-evergreen trees. A temperate grassland is dominated by grasses. A boreal forest is made up primarily of evergreen trees such as spruce and fir. Read up on each biome to learn more. We’ve created a video for most temperate biomes. (Some of these links direct you to our biome pages at thewildclassroom.com)

Aquatic Biomes

Aquatic Biomes, sometimes called “zones,” are often overlooked. Because many of the staff here at Untamed Science are marine biologists, we made sure to not forget them. In fact, we teamed up with Save our Seas to produce a video for every biome. Check them out: