Biology Archive - Page 4 of 11

Desert Scrub Biome

You might think that one desert would be the same as any other, but did you know that there are multiple types of deserts? There is the dry, barren desert we normally think of and the chaparral that is not quite a forest but also not a typical desert. Then there’s the desert scrub biome (also known as a xeric shrubland): a place that’s still very dry, but also quite full of various shrubs and animals that have developed unique ways to cope with drought.

The desert scrub biome gets its name from the large amount of shrubs it contains, making the landscape look rough and “scrubby” (not from TLC’s song No Scrubs!). It’s a unique ecosystem that has tons of biodiversity and cool features!

Where are desert scrub biomes found?

Desert scrub biomes can be found all over the world, not just in areas around the equator. They can be found in three consistent types of locations because there are a predictable set of abiotic factors that cause them to consistently form:

Desert biomes tend to form in the middle of continents, far away from moist, cool oceanic air. The Gobi desert and the Great Basin are two of these types of deserts.

Other deserts, like Death Valley and the Colorado Front Range, form in rain shadows on the leeward side of mountains. As the air rises up to go over the mountains, it loses most of its moisture in the form of rain and snow, leaving little to no precipitation for these rain shadow deserts on the other side.

Finally, some deserts form on the west side of continents, far away from moist, oceanic winds that blow in from the east side of the continent. The Atacama Desert and the desert around Baja, California, are two examples of these types of deserts.

These are all places where typical deserts form, too, and it’s not by coincidence. Deserts and desert scrub biomes are closely intertwined because they form under similar conditions. In many deserts, both are present next to each other, or they may even gradually blend together.

What are the abiotic factors that make desert scrub biomes?

Desert scrub biomes have many of the same abiotic properties as typical desert biomes. They receive very little precipitation each year, usually less than 10-20 inches. In low areas, this falls as rain, but in high-altitude or high-latitude areas, this can also fall as snow.

Although there are some plants here, there still aren’t as many as a regular forest. As a result, the soil in desert scrub biomes doesn’t have a lot of organic matter (decomposing leaves and plants) in it. Organic matter is important not just for plant nutrients but also for moisture: without much organic matter, the soil doesn’t “hang on” to water as well.

Instead of soaking in like a sponge in a forest ecosystem, water in a desert scrub ecosystem tends to flow over the surface. This is especially troublesome because typically when it does rain in the desert, it comes down in torrential downpours. When this happens, you get huge floods of water over the surface, and it only takes a few good rainstorms before deep flood channels are cut into the ground.

After it rains, the water evaporates quickly from the soil. This causes another desert phenomenon: salt crusting. As soils repeatedly wet and rapidly dry, salts are brought to the surface of the soil. If you’ve ever been out to the western U.S., you might have seen big white patches on the ground—these are salt crust formations.

They can also form when lakes dry up, and then they’re called playas (pronounced “ply-ah”; not the Taylor Swift kind of playa). If climate change continues, we might see more of these odd formations in the future as more and more lakes dry up.

What do desert biomes look like?

When you look out over the desert scrub, it looks pretty even across the top: as far as the eye can see is a sea of shrubs. When you look at the ground, it’s a whole different story (an understory – get it?!). The shrubs are usually well-spaced out, with plenty of ground in between them. Some of this space is filled with small grasses and forbs (herbaceous plants), but much of it is bare.

Aside from the occasional salt-crust patch and playa, it’s a pretty homogenous place. There aren’t any very big trees to provide a canopy, and with the soaring temperatures, you can often see wavy heat lines off in the distance.

What types of plants are found in the desert scrub biome?

Have you ever forgotten to water a houseplant for a long time and returned to find it wilted and dead? This type of plant would never survive in the desert scrub biome. Instead, desert scrub plants are drought-tolerant and have evolved all kinds of fascinating tools to hang onto what little water they are able to get.

Some of these tools are mechanical. Many desert scrub plants have thorns or needles, to deter animals from eating them. For others, small, narrow leaves means minimal surface area so that less of the plant is hit by hot sun rays. Some plants are even pubescent, meaning they have a light fuzz of miniature hairs that also help to diffuse hot sun rays.

Other adaptations are chemical in nature. Sage brush, for example, has a lot of aromatic oils to deter herbivory. These give the plant a weird, turpentine-like smell and an unpleasant taste—would you want to eat that?

Other plants have gone another route—they are better at finding or hoarding water supplies. Phreatophytes, like mesquite and welwitschia, for example, are drought-adapted plants that grow one single deep tap root that can be many feet long in order to tap into deep ground water supplies. Other plants store water in their own tissues and slowly release it over time. These plants would be juicy morsels to animals, so they often grow spines to defend themselves! Cacti and succulent plants fall into this category.

Most desert scrub plants are slow-growing and have hardy adaptations, but other plants go the opposite route: they are fragile but fast-growing so they’re able to take advantage of good growing conditions in the desert whenever they do occur. These are typically small forbs and grasses, and they can complete their entire life cycle—seed to plant to flower and seed again—within two weeks of a single big rainstorm!

Although shrubs make up the bulk of the plants in desert scrub ecosystems, there are a few small trees that can also be found here as well. Pinyon pine, juniper, and bristlecone pine (including the world’s oldest tree) can be found in these ecosystems as well.

What types of animals are found in desert scrub biomes?

Life in the desert scrub biome isn’t easy, but there are still a surprising number of animals there, thanks to all the shrubs. There are small mammals like mice, voles, chipmunks, kangaroo rats, jack rabbits, prairie dogs, etc.

Larger mammals can also be found in the desert scrub biome, but they aren’t as common. Mule deer and wild horses are usually the most common herbivore, although in some areas you can find domestic cattle that ranchers are grazing on the land.

In order to survive very well in the dry landscape, many mammals have come up with a host of amazing adaptations. Large ears with lots of blood vessels act as radiators that help dissipate heat. Some animals also experience estivation—a sort of temporary hibernation, either every day or for a short period of time over several days, in which they go semi-dormant in order to avoid the hottest periods.

Perhaps even more amazing, some animals have altered kidneys so that they reabsorb as much water as possible from urine. Some animals, like kangaroo rats, don’t even really need to drink water at all, partially because they are so good at minimizing its loss!

Many birds also love living in the shrubs and small trees, such as the greater sage-grouse, Pinyon jay, and western scrub-jay. So much animal diversity and an open landscape are also prime opportunities for birds of prey, like turkey vultures and peregrine falcons. Still other birds prefer to use old prairie dog burrows, like the burrowing owl.

Many reptiles also call the desert scrub home. Lizards and snakes are especially well-adapted to dry conditions, due to their thick, scaly skin and eggs which minimize moisture loss.

What types of natural disturbances shape desert scrub biomes?

Unlike the Coniferous Forest biome, the desert scrub biome is not adapted to have massive, devastating disturbances on a regular basis. Nevertheless, there are many natural disturbances that occur in desert scrub biomes.

Floods are a major source of disturbance, due to infrequent but torrential rains. Because of these floods, deep ravines and channels can suddenly appear where they didn’t occur before, causing all sorts of problems for plants and animals.

Domestic livestock grazing can also be a major source of disturbance, especially around water holes. These animals will often camp out and wallow in any available water source, quickly turning it foul for wildlife and humans. It’s not uncommon to find fences around springs in the western U.S., where people have tried to keep water sources clean and pure by excluding domestic livestock.

Wildfires aren’t a big factor in desert scrub biomes, but they do occur. In recent years, they’ve also been increasing, resulting in much loss of habitat for animals around the world.

Another factor causing loss of the desert scrub biome is agriculture and land conversion for human use. Many former desert scrublands have been cleared and irrigated to allow for crops to be planted. These soils are frequently marginal at best, and oftentimes salt accumulation makes the land unusable after a period of time.

Although you’d think that desert scrublands would be well-adapted to droughts, they have their limits. Desert scrub plants (and the animals that rely on them) can go without water for a long time, but they do require some water. Droughts have been increasing worldwide, and as a result, many desert scrublands are slowly being converted to typical deserts, and all the plants and animals that went with them are disappearing.

Many of these changes are expected to worsen with climate change. We’ll only be able to tell with time how much of these fascinating landscapes survive.

Gluten and You

If you’ve been in a grocery store or a restaurant at all in the past few years, chances are you’ve noticed more and more products being labeled “gluten-free.” Lately, gluten has been getting a bad rap, and for a potentially good cause: some people do have legitimate health problems when they eat gluten and need to avoid it.

But thanks to a series of celebrity endorsements, gluten-free diets are the new big trend. If you believe celebrities (the same people who brought you the likes of alkaline dieting and vitamin IV drips for hangovers), a gluten-free diet apparently cures everything from acne to Sasquatch infestations.

But what is gluten really? How does it actually interact in our digestive systems? Does it really benefit people to be on gluten-free diets?

Why is gluten important?

Gluten isn’t some big bad wolf coming to get you. It’s a natural plant storage substance composed of two proteins—glutenin and gliadin. Some grain-producing plants, like wheat, produce gluten in the seeds as an energy-storage mechanism for future seedlings, allowing them to grow until they can take off and photosynthesize on their own.

For humans, though, gluten serves very little function. In fact, gluten is mostly indigestible, meaning we don’t even get any nutrients from it at all! But it’s not the gluten itself that is important to our diets, it’s the stuff that comes along with the gluten.

Gluten is just a component of whole grains, which are generally very healthy things to consume. Whole grains contain all kinds of things you need in your diet to stay healthy, like fiber, vitamins, and minerals. In fact, people who are on very strict gluten-free diets really struggle to replace all of the nutrients that we take for granted everyday with our gluten-inclusive diets.

And, if nothing else, gluten is responsible for a lot of the texture and even flavor of many of our foods. You can even see (and taste) the effect of gluten when you bake bread.

Why can’t some people tolerate gluten?

There are three diseases associated with gluten that require people to adopt gluten-free diets. Each disease has its own unique method of action, symptoms, and ways to cause a person’s health to go haywire.

The most serious disease associated with eating gluten is celiac disease. This illness causes a lot of problems—it has over 200 different symptoms. Celiac disease is an autoimmune disease, and when someone eats gluten-containing foods, the body mounts an immune reaction to its own enterocytes—cells lining the digestive tract.

These enterocytes are gradually killed off, and the villi lining the small intestine shrink back and disappear. Without villi and enterocytes, it’s difficult or impossible to absorb nutrients, and if left uncorrected, a person suffering from celiac disease may become malnourished.

Wheat allergies are another potential problem. Unlike celiac disease, wheat allergies are just that—an allergy. They don’t cause the body to attack itself; they have more traditional symptoms like swelling of the mouth, hives, watery eyes, etc.

Finally, many people also suffer from gluten sensitivity. This is the least understood of all gluten-related diseases. Typically, people report celiac-like symptoms, but they don’t have the devastating loss of intestinal villi that accompanies celiac disease. The only way to diagnose gluten sensitivity is by process of elimination. If celiac disease and wheat allergies are tested for and ruled out, and symptoms go away with a gluten-free diet, then gluten sensitivity is diagnosed.

Do gluten-free diets really work?

The short answer is yes and no. For people who have legitimate health conditions—celiac disease, wheat allergies, or gluten sensitivities—these diets are not just a fad but a restrictive and necessary way of life.

This means a good chunk of the population has legitimate grounds for adopting a gluten-free diet. It’s estimated that 1% of the population suffers from celiac disease, less than 1% from wheat allergies, and anywhere from 0.5%-13% from gluten sensitivity.

Nevertheless, 30% of Americans are actively trying to adopt a gluten-free lifestyle. For most of these people, it’s completely unnecessary as far as scientists can tell. Furthermore, many people believe they have gluten sensitivity when in fact they do not. In one study, doctors tested hundreds of people who thought they had gluten sensitivity, but when they actually tested them, the majority were able to tolerate gluten in their diets just fine.

Adopting a gluten-free diet isn’t without its risks, either. Gluten-free foods are often much more expensive than regular foods. By cutting out whole grains from your diet, you’re also missing out on great sources of fiber and other nutrients necessary to sustain good health. You can get those nutrients elsewhere, of course, but it requires a careful and deliberate plan.

This is why people who have to go on gluten-free diets are strongly urged to work with a dietitian, so they can plan to replace all of the nutrients they’re missing out on when avoiding whole grains and gluten.

Why do so many people report feeling better after cutting out gluten?

It’s common to hear celebrities and people who have voluntarily given up gluten tout the benefits of a gluten-free diet. These people aren’t necessarily lying: they probably do perceive a difference. Why?

Scientists have come up with two plausible explanations. The placebo effect is almost always present in cases like this—if you switch to a new diet and everyone around you is cheering you on and telling you how great it is, you’d probably feel better, too. Secondly, when people cut gluten out of their diets, they often switch from highly processed foods, like cupcakes and white bread, to healthier alternatives, like fruits and vegetables. Of course that would make anyone feel better!

Going gluten-free is a hot trend nowadays, but in general it’s probably best to avoid gluten-free diets unless you have a legitimate, confirmed health condition. If you do think you have problems eating gluten-containing foods, it’s very important to go see your doctor to be tested. Otherwise, you can enjoy healthy, whole-grain foods worry-free!

This article’s content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

Arctic Tundra Biome

Arctic tundra is a very cold, windy, and treeless biome that’s snow-covered for much of the year. It’s found in the northern hemisphere, encircling the north pole and extending south across parts of Alaska, Canada, Russia, Greenland, Iceland, and Scandinavia, to the coniferous forests of the taiga. It covers one fifth of the Earth! To get a feel for the arctic tundra, we made this short little video of some interesting research going on here.

Underneath Arctic Tundra

The most important feature of arctic tundra is one you can’t even see. It’s a layer of permanently frozen soil called permafrost, which lies about 25 to 95 cm underground. Permafrost acts as a barrier to tree roots, so no trees can grow above it. It can’t even be penetrated by water, which is why the soil above permafrost gets very soggy in summertime, when bogs, lakes, and marshes lie on the land.

Dry, Windy Deserts

Although arctic tundra ecosystems are wet underfoot in the summer, they actually receive very little rain, with less than 25 cm falling every year. This makes them as dry as many of the world’s deserts. Unlike rainfall, wind is plentiful in the Arctic, often blowing across these stark landscapes at 50-100 km/h and making the cold temperatures here feel even colder.

Cold, Colder, Coldest

During summertime in the Arctic, temperatures often sit somewhere between -3°C and 12°C, and the sun is out—although low on the horizon—for 24 hours a day. Plants of the arctic tundra do all their yearly growing during the summer because it’s the only time when growing isn’t biologically impossible due to cold. And when it’s cold here, it’s very cold. Winter brings temperatures averaging -34°C, dropping as low as -50°C, and lasting most of the year. Then there’s the darkness to deal with. Close to the North Pole the days in winter time aren’t just short, they’re non-existent; the sun doesn’t even peep over the horizon for a period of about two months every year!

What on Earth can survive here?

Even though conditions in the world’s coldest biome are harsh, many plants and animals call it home. Tundra plants tend to be small and live in clumps, and they include mosses, lichens and liverworts, plus grasses, sedges, and dwarf shrubs. These plants are food for animals like arctic hares and squirrels, caribou, lemmings and voles; eating these animals in turn are arctic foxes, wolves, and polar bears. Migratory birds also visit the arctic tundra in its summertime to feast on the bazillions of insects that breed here during this warm-ish, wet-ish time of year.

Visiting the Arctic Tundra

A trip to the far north isn’t for everyone, but many people love the extremes of adventuring in arctic tundra environments. If you’re one of them there are plenty of destinations to set your compass for.

Sweden

At the Abisko station in Northern Sweden you can check out the amazing tundra habitat. This is one of our favorite places to go see it. Check out this image we shot from the station while filming this video on the northern lights:

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Alaska

There are loads of accommodation options in the city of Fairbanks, and from here you can hop on a tour (by car, plane, or boat) organized by a company like Northern Alaska Tour Company. Alternatively, you could head off on your own arctic tundra explorations—providing you’re exceptionally well-prepared!

Iceland

A small, chilly country it may be, but Iceland really packs a punch as a tourist destination. Volcanoes, glaciers, lava wastes, boiling lakes, and frozen fjords all feature in tours that leave from Iceland’s capital city, Reykjavik. Arctic Experience offers trips all year round and can help make your arctic tundra trip happen.

North Pole

If cost is not a problem for you, the North Pole itself is within your reach! Trips to the North Pole leave from a number of countries, including Russia and Canada. Transportation ranges from icebreakers and helicopters to sled-dogs, hot air balloons, and skis, and all tours require extreme fitness on your part. Polar Travel Company and Quark Expeditions are there to help you reach the top of the world.

Integumentary system

The integumentary system is the organ system that protects the body from various kinds of damage, such as loss of water or abrasion from outside. The system comprises the skin and its appendages (including hair, scales, feathers, hooves, and nails). The integumentary system has a variety of functions; it may serve to waterproof, cushion, and protect the deeper tissues, excrete wastes, and regulate temperature, and is the attachment site for sensory receptors to detect pain, sensation, pressure, and temperature. In most terrestrial vertebrates with significant exposure to sunlight, the integumentary system also provides for vitamin D synthesis.

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What Happens When you Get a Sunburn?

Wolf Reintroduction at Yellowstone National Park

Everyone’s heard the story that bringing back wolves to the Yellowstone ecosystem suddenly returned it to normal, but did you know that claim may be only partially true? To see both sides of the story, let’s look at one of the most successful wolf reintroduction programs in history, at Yellowstone National Park.

What happened to Yellowstone when wolves were gone?

Wolves were officially declared extinct in the park by 1926. This set off a chain of ecological events known as a trophic cascade – when one tiny change in an ecosystem ripples out and causes many other effects.

After the wolves were gone, the bears and coyotes that were left weren’t able to kill as many elk as the wolves had done. Soon, the elk population skyrocketed, and they devastated the ecosystem by eating too much young, tender willow and aspen trees. Once those trees were gone, a whole host of other animals left: birds, beaver, and fish that lived in the beaver ponds.

The beaver dams broke and allowed water to flow through too fast to soak up in the surrounding landscape. The land converted to grasslands and dry shrub-lands. Compared to its former glory, it was now a barren wasteland.

What happened when the wolves returned?

After the successful reintroduction of the wolves, beginning in 1995, it seemed like the landscape changed and did a complete 180 from where it had been heading. More wolves meant less elk, and the elk that survived spent less time eating because they were keeping an eye out for wolves. The surviving trees weren’t being eaten as much, so they started to grow taller and to spread.

As the trees grew taller, birds returned to nest in them. Finally, the beaver came back as well, and started building dams that drew fish and even more water and trees back to the area.

It seemed like just the simple act of adding in one key species—wolves—allowed the system to return to normal.

This is the story that became popular in the years right after the wolf release. Unfortunately, things aren’t often what they appear to be, and the Yellowstone wolf reintroduction story is no exception.

Wolves restored the Yellowstone ecosystem…partially.

Ecology is a field of science that studies relationships among all the different things in an environment. In the case of the wolf reintroduction, it’s impossible to say with total certainty that the wolves were the only reason that the Yellowstone ecosystem recovered. And even more surprising, it seems like parts of Yellowstone may have even not recovered at all!

There are countless other factors that could have acted together to cause the response seen in Yellowstone. Yellowstone has been in and out of big drought cycles for years, wreaking havoc with both the plants and the animals that eat them. Bear predation on elk has also increased in recent years, meaning that the wolves alone aren’t causing the elk decline. These are only a couple of many explanations that could have affected elk numbers and the subsequent recovery.

Additionally, some areas of the park seem to have not recovered at all and still look like a pre-wolf ecosystem, with dry former wetlands, fast-flowing creeks, and low biodiversity. Scientists were trying to wrap their head around why these areas weren’t responding, and they decided to create an experiment to test some different explanations.

The experiment had three scenarios: first, they had a control stream to measure willow growth as it was already occurring. Second, they had an elk exclosure to keep elk from eating willows along a stream. Finally, they had an elk exclosure and made some simulated beaver dams. The results were startling: keeping elk out of an area alone had no effect on willow growth. You needed a combination of less elk and more water from beaver dams to bring the ecosystem back to normal. Without both, it wouldn’t work.

Did wolf reintroduction really save the ecosystem?

Many people believe that the wolf reintroduction didn’t do anything to restore the Yellowstone ecosystem; others believe that the wolf was the sole factor causing the recovery. The truth, as with most things, probably lies somewhere in the middle: wolves were responsible for some, but not all, of the ecosystem response seen in Yellowstone.

It might seem like scientists are just nit-picking details at this point, but as Arthur Middleton, a former Yellowstone ecologist pointed out in a New York Times article, “We now know that elk are tougher, and Yellowstone more complex, than we gave them credit for. By retelling the same old story about Yellowstone wolves, we distract attention from bigger problems, mislead ourselves about the true challenges of managing ecosystems, and add to the mythology surrounding wolves at the expense of scientific understanding.”

You may also be interested in learning about reintroduction efforts of the red wolf. Read more here.

Sunburns

Everyone knows the familiar feeling of a hot flush starting to spread over their skin a few hours after spending some time outside under the sun. Oh no—you didn’t cover the spot with sunscreen! Sunburns may seem harmless enough (albeit annoying), but did you know that they’re actually a type of radiation burn?

Sunburns actually cause a huge amount of damage on a cellular level, but how do they do it? Why do they take so long to form? Why does the sun damage your skin? Isn’t sunlight supposed to be beneficial? Why do they hurt so bad? To find out more, read on!

How does sunlight interact with skin?

Sunlight is more than just nature’s way to wake you up in the morning. Sunlight is actually a form of electromagnetic radiation, along with radio waves, microwaves, and radioactive waves found in places like Chernobyl. By the time sunlight reaches you on Earth after traveling through space, its radiation comes in two flavors depending on the wavelength: Ultraviolet A (UVA) and Ultraviolet B (UVB).

In small doses, sunlight is beneficial. It allows your body to create the necessary nutrient vitamin D and sets your body on track for normal circadian rhythms (24-hour sleep/wake cycles), for example. But like anything else, too much of a good thing can actually harm you. Most sunlight is composed of UVA radiation, which has slightly less energy than more damaging UVB rays.

UVA rays are less likely to give you a sunburn, but they can penetrate deeper into your skin and cause more cumulative damage over time in the form of saggy, aging skin (maybe the Cryptkeeper should have worn more sunscreen as a young‘un). UVB rays, on the other hand, contain more energy that can harm your skin immediately. It’s like the difference between a hot pad for sore muscles and a burning flame.

How does sunlight damage skin?

UV radiation basically damages skin by transferring energy to molecules in your skin, such as DNA, fat, proteins, etc. These molecules, which are already in their proper arrangement, absorb this energy. If the molecules absorb enough energy, the bonds holding them together can break, forming a new shape completely. For a cell that already has been chugging along smoothly thanks to specific molecules with specific shapes doing specific jobs, this is a big deal and causes serious problems.

UV radiation damage to DNA is a particular problem. DNA is a huge molecule and actually quite fragile. When a molecule of DNA is present in a cell, it resembles a zipper: it has two strands, with each strand tightly bound to corresponding molecules on the opposite side, called bases.

There are four different bases—adenine, guanine, cytosine, and thymine. Thymine and cytosine, when occurring right next to each other, are particularly susceptible to forming dimers. When sunlight hits these sections, thymine and cytosine will “let go” of the other side of the chain and form bonds with each other. Suddenly, the DNA code is broken, and if this DNA section codes for a specific protein, it won’t make the right protein anymore.

The good news is that each cell has its own small army of auto-correct molecules which can go in and fix the broken DNA section. The bad news is that when your skin is out in full sun, this process is happening on an epic scale—and sometimes the auto-correct function can’t keep up with the damage.

If a cell becomes too damaged, it also has its own auto-delete function: it will go through a process called apoptosis and essentially commit suicide. This seems harsh, but without it, too many damaged cells can accumulate and soon your skin wouldn’t work at all like it’s supposed to. You really might turn into the Cryptkeeper at that point!

There’s a bit of a catch-22 though: your own DNA codes for the auto-delete function, and if that section of your DNA is damaged, or if a damaged DNA section just happens to evade repair, the auto-delete won’t function like it’s supposed to. The cell won’t kill itself, and it might even start growing out of control. This is how skin cancer forms.

How does your body react to damaged skin?

Have you ever noticed how sunburns take a few hours to form after you’ve been out in the sun? That’s because the apoptosis process takes a bit of time to occur. If you’ve accumulated too much UV damage, your skin becomes full of dead skin cells. This sets off an immune reaction which also takes some time to get going.

White blood cells are attracted to your skin where the dead cells are scattered. They circulate and gobble up the dead cell bits, cleaning the area like a Roomba. To help even more white blood cells get to the area, your capillaries swell up and fluid leaks out, causing the red, swollen, and painful skin. After the dead cells are all cleaned up, the process shuts itself off and your skin goes back to normal—although it’ll start producing more melanin, a sort of natural sunscreen that makes your skin tan, to protect it from sunburns in the future.

What’s the best way to prevent sunburns?

Sunburns won’t kill you—not immediately, anyway. Sunburns only happen when your cells are seriously damaged by UV radiation, and with each damaging event, there’s a small chance that it’ll be the one that can lead to cancer. The good news is that there are many ways to prevent sunburns and the DNA damage that comes with them.

The best way to prevent sunburns is to keep your skin covered. Wide-brimmed hats, sunglasses, and long-sleeved shirts and pants are the best way to avoid sun damage. You can’t stay completely out of the sun 100% of the time, and that’s where sunscreen comes in.

The Skin Cancer Foundation offers several guidelines for how to maximize sunscreen use. Use a broad-based sunscreen with an SPF of at least 15, which will protect against both UVA and UVB rays. The higher the SPF, the better. Make sure you apply the sunscreen at least 30 minutes before you head outside—that way, it’ll fully absorb into your skin and protect you even better. Finally, make sure you reapply sunscreen every two hours.

Twenty percent of people in the U.S. will get skin cancer at some point in their life, but it doesn’t have to be that way. As long as we take proper precautions we can stay healthy—and even avoid those pesky sunburns.

Coniferous Forest Biome

Coniferous forests can be found throughout the world, but don’t let their commonness fool you. They contain some of world’s most extreme trees. The world’s tallest tree, a coastal redwood named Hyperion, reaches up to 379 feet—as tall as a 35-story building. A giant sequoia named General Sherman isn’t quite as tall as Hyperion but it is the world’s largest tree, clocking in at around 2.5 million pounds—as much as eight blue whales combined! The world’s single oldest tree is a Great Basin bristlecone pine, dating back more than 5,000 years—almost as old as my grandma.

Coniferous forests grow in a wide range of climates, from the coldest polar regions to the warmest tropical regions and everything in between. The reason they’re so prevalent worldwide is because they take advantage of certain environmental conditions that other trees aren’t able to live in as well. As a result, they can look a lot different from other types of biomes.

What do coniferous forests look like?

Conifers can grow quite happily alongside deciduous trees in many biomes, like the temperate deciduous biome or the taiga biome. But conifers really reign supreme and dominate the landscape in areas where it’s too difficult for finicky deciduous trees to live.

Each type of coniferous forest will look different depending on the environmental conditions and the types of conifer species involved. In general, coniferous forests have a pretty sparse understory. This means that there aren’t a lot of shrubs, grasses, or flowers growing underneath the conifers. You can often see for a long way through the understory of a coniferous forest!

Abiotic Factors: Where to Find Coniferous Forests

Coniferous trees succeed in this type of biome because they’re adapted to take advantage of conditions that other trees cannot. Conifers specialize at growing in poor soils that are often sandier and drier than the richer soils found in deciduous forests.

Deciduous trees have a live-fast-die-young approach to their life cycle; each year, they put out a whole tree-full of new leaves, only to have them all die in the fall. Deciduous leaves are great at soaking up lots of sunlight and energy for the tree, but they’re also expensive to make. Trees get their nutrients from the soil, but not all soil has enough nutrients to support a deciduous tree in its yearly leaf-making endeavors. That’s where conifers surpass them.

When there aren’t enough nutrients in the soil, coniferous trees flourish because they take the opposite approach: they grow slow and die old. Rather than putting out new “leaves” each spring, they take care of their existing needles and keep them for many years. That way, they don’t need massive amounts of fresh soil nutrients each spring, so they aren’t limited by poor nutrient conditions in the soil. Each winter, the needles enter a state of suspended animation, much like Rip Van Winkle, only to wake up in the spring again and start cranking away.

What’s so special about conifers?

Conifers have developed a lot of really neat adaptations to survive and thrive in nutrient-limited conditions. One of the biggest adaptations are their needles.

Conifer needles may look pretty mundane, but the tree has put a lot of work into making them, and it expects to get a lot out of them. Each needle has a waxy coating called a cuticle (not to be confused with the cuticle on your fingernail!) that helps keep precious moisture from leaking out. Needles are also pumped full of a mixture of chemicals like tannins and terpenes to make them distasteful to herbivores. It’d be sad for a tree to spend so much time and energy making a needle only to have a moose come along and eat it!

Conifers usually grow slower than their deciduous counterparts because they’re often already growing in nutrient-limited soils, and they’re spending a lot of the nutrients they do have in creating super-needles. They use these needles for a long time, though—from two to five years or longer.

Conifers are often known as evergreens because they keep their needles throughout the winter and stay green year-round. But, there are actually a few species of deciduous conifers! They’re known as tamaracks, or larches, and they have soft needles that turn yellow and fall off each autumn. Tamaracks employ a strategy halfway between that of a conifer and a deciduous tree, and it’s very successful in some environments. They’re an oddity and fun to find in the woods!

If left to their own devices, without interference from humans or other disturbances, many mixed deciduous/conifer forests will eventually go through a process called forest succession, where the types of trees in the forest slowly change over time. Conifers themselves often end up dominating many landscapes over time because they will slowly make it harder for other types of trees to grow. Remember how conifers are best at growing in poor soil conditions? That’s exactly what they do to the soil over time: they make it too poor for other species to grow.

The way conifers affect soil is pretty interesting. Although they don’t shed their needles every fall, they still do drop needles occasionally. Over time, these needles pile up around the base of the tree. The needles don’t decay like deciduous leaves—they have far too many chemicals and waxes for that. Instead, they break down slowly and make the soil even more nutrient-limited. Tannins in the needles are also acidic and leach out into the soil, making it even harder for other deciduous plants and trees to get nutrients.

In some coniferous forests, there are so many acidic tannins in the soil that they leach into rivers and stain the water yellow. The Taquamenon Falls in the upper peninsula of Michigan are famous for their colored water.

What types of plants can be found in coniferous forests?

There are many types of conifers that can dominate coniferous forest biomes, such as pine, spruce, cypress, kauri, and redwood.

Other plants still grow in coniferous forests, but they’re not as prevalent as the conifers themselves. Many grasses and herbaceous plants can still survive or even flourish in the coniferous understory. Some plants and fungi are even adapted to live specifically with conifers, like slipper jack boletes and some mosses.

What types of animals can be found in coniferous forests?

Animals like pine marten, spotted owls, pine beetles, and crossbill birds have adapted to live almost entirely within coniferous forests. Crossbills, for example, have unique beaks where the upper and the lower parts of their beak completely overlap each other. While this looks odd, it serves in important purpose: it allows the crossbill to pry open cones to get to the delicious seeds inside:

Some animals rely only partially on coniferous forests and travel elsewhere for other sources of food and cover. Moose, porcupines, mice, deer, and fox, among many other animals, can often be found in coniferous forests, although oftentimes they still require trips to other types of habitats. Moose, for example, prefer to eat deciduous leaves but will frequently travel through coniferous forests.

Think forest fires are always bad? Think again.

One of the most surprising things about many coniferous forests is that they actually need regular forest fires in order to be healthy. We typically think of forest fires as catastrophic occurrences that wipe out all living things for miles. Forest fires certainly can do that, but they also have a less-well-known beneficial side.

A healthy coniferous forest fire looks a lot different from the raging fires we see blazed across the evening news. Healthy forest fires burn low to the ground and don’t even really make it up into the crown (top) of the forest at all. Instead, they burn with smaller flames across the forest floor, cleaning up any understory, so that all that’s left behind are the big coniferous trees that are the hallmark of this biome.

After a fire, the ground is changed. The burned plants release nutrients into the soil and make it even more fertile than it was before—almost like fertilizer for the next group of plants! The understory is also cleared of any domineering plants, allowing other types of plants a chance to grow. Because the fire frequently gives new plants a chance to get a foothold (get it?), fire-adapted coniferous forests can be some of the most diverse ecosystems in the world.

What types of coniferous forests need fire?

A prime example of how fire creates more diverse ecosystems is southern long-leaf pine forests. These forests once ranged across most of the southeastern U.S., yet due to conversion to agricultural land, over-logging, and fire suppression, these forests only occupy a tiny fraction of the lands they used to dominate. Check out this video to see how important fire is to longleaf pine ecosystems:

Scientists have only recently realized how important fire is to these types of ecosystems, and now they’re changing gears: they’re actually using fire as a management tool to preserve some of the coniferous forests that we do have left. Rob caught up with a group of southern fire scientists to check out how this process works:

Other types of coniferous forests need fire for other reasons. Jack pine forests in the northern part of the Midwest and Canada, for example, actually can’t reproduce at all unless a forest fire comes through. They produce serotinous cones, which means that they’re always glued tightly shut by resins and waxes, and the seeds physically cannot get out of the cone—unless a forest fire comes through and melts the wax, releasing the seed.

Jack pine forests are unique on their own, but they also have another rare inhabitant: Kirtland warblers. These tiny gray and yellow birds have some of the most specific habitat requirements you can think of: they only nest in large, pure stands of jack pine forests, and the trees themselves must be between 5-20 feet tall and 6-22 years old.

As with many other fire-adapted coniferous forests, jack pines ecosystems have been on the decline, and the population of this tiny bird fell along with them. By 1974, there were just 167 known birds in existence, and they all bred in a single county in northern Michigan. Thanks to intensive management programs for jack pine forests, the population is finally increasing: in 2011, biologists counted 1,828 birds. They were even recently sighted for the first time in completely new states:

How economically important are coniferous forests?

Aside from being one of the most widespread biomes and chock full of biodiversity, coniferous forests also are some of the most economically valuable types of ecosystems. Most of the lumber that we use to build structures comes from conifers themselves, as well as a whole host of other products like paper, pencils, turpentine, and even cancer drugs like Taxol.

Coniferous forests have been around for a long time, and with our help and protection they’ll be around for a lot longer. There are many different types of career opportunities available to help manage coniferous forests. Check out what it’s like to be a professional forester:

Allergic Reactions

It’s a bright, sunny spring day. The trees are greening up, and the flowers are starting to bloom. All of a sudden, you start sneezing like crazy, and your eyes look like you’ve been crying for days. Or, maybe your cat likes to hang out on your bed at night and your nose always seems stuffy while you’re trying to fall asleep (thanks a lot, Beeker!). While allergies aren’t too much fun to deal with, the science behind allergic reactions is amazing!

What are allergic reactions?

The heart of the problem is actually a case of mistaken identity. Your immune system normally recognizes and destroys pathogens (viruses, bacteria, fungi, etc.) that make their way into your body, which is a good thing: your body is constantly under attack by foreign invaders. But in an allergic reaction, the immune system acts like a bully and goes around picking fights with innocent bystanders. Instead of fighting harmful pathogens, the immune system starts recognizing harmless things like pollen and animal dander as dangerous and mounts full-blown immune reactions whenever it comes across these harmless things.

This can even be taken to an unfortunate extreme where your body recognizes some of its own cells as a foreign invader and kills them. This is what happens in autoimmune diseases like lupus or rheumatoid arthritis.

How do people become allergic to things?

Allergies tend to run in families, but no one is ever automatically allergic to something. There are billions of potential allergens (proteins and other molecules that cause allergic reactions) in the world—how would your body know it was allergic to something if it had never encountered it before? Instead, your body first needs to interact with something new, recognize it as an invader, and take steps to defend against it if it should ever come back. This process is called sensitization.

Some of the cells floating around your bloodstream are B cells, a type of white blood cell. They’re sort of like mall cops: they patrol the body, check things out, and make sure everything is going swimmingly. If they find something new and “dangerous” in the form of an allergen, they will actually swallow it in a process called endocytosis, and take their newly-won prize back to a lymph node.

Inside the lymph node, the B cell becomes activated by a T cell (another type of white blood cell), and it morphs into a new type of cell: a plasma cell. The plasma cell’s main job is to now produce IgE antibodies specific to that one type of protein, and it does this very well: they can crank out thousands of antibodies every second (pew pew!).

The IgE antibodies float around in the bloodstream like microscopic “Wanted” posters, and are picked up by two other types of white blood cells: basophils, which circulate around your body in your bloodstream, and mast cells, which live fixed in place in areas that are in close contact with the outside world, like your skin, mucus membranes, and intestines. The basophils and the mast cells attach the IgE antibodies to their cell membranes in a process called priming, and if the same allergen happens to come along again, they can now recognize the threat (sort of like seeing Billy the Kid come along after seeing his “Wanted” poster).

The process of sensitization is now complete: the person is now primed and ready to have an allergic reaction if they encounter the same protein again.

What happens in an allergic reaction?

Now that the mast cells and the basophils are fully primed and ready to go, all they need is to encounter the allergen again before unleashing a storm of chemicals that actually cause the symptoms of an allergic reaction.

Basophils and mast cells are both granulated, meaning that if you look at stained cells under a microscope you will see tiny, dark granules inside of them. These are actually tiny packets of chemicals like histamine, leukotrienes, and cytokines, among others. When the IgE antibodies on the surface of the basophils and the mast cells actually come into contact and bind with the specific type of allergen, it triggers the cell to degranulate—to rapidly dump the contents of the tiny chemical packets out of the cell, where they can act in the body.

This chemical cocktail creates a whole new chain of reactions that ultimately ends up causing the familiar symptoms of allergies—everything from itchy, watery eyes; stuffy noses; hives; etc. In extreme cases, it can cause the throat to dilate and cause an asthma attack, or even cause so much swelling over the body that a person could go into anaphylactic shock and die.

This is why some people need to carry EpiPens—the reaction happens so fast that there’s no time to call 911 and get to a doctor. The person could literally die before that happens. EpiPens deliver an instant dose of epinephrine, the only chemical that acts fast enough to reverse the effects of the allergy chemical cocktail fast enough to save a person’s life.

It’s a bit scary to think that right now, at this moment, your body contains huge numbers of cells with tiny chemical packets inside of them that could literally kill you if enough of them were to activate—or, they might just make you sneezy, sleepy, dopey, or grumpy (but not happy or bashful!). Scientists still have a lot to learn about how allergies work, but in the meantime, they still are a fascinating thing to think about!

Mycorrhizae

Have you ever had to work in a garden, or even just grow a single plant? If so, you know it’s hard work—you have to carefully cultivate growth by keeping the weeds at bay and providing the plant with plenty of water and sunshine. At the end, you’re rewarded with an abundance of healthy nutrients in the form of delicious, fresh vegetables or a view of beautiful flowers. But did you know that many plants have their own gardens too? Unlike our gardens, though, the plant’s gardens are entirely underground, and normally you’d never see them except for a brief period each year. They’re called mycorrhizae (my-coh-rise-eh), and they live in a symbiotic relationship with the plant itself.

What are mycorrhizae?

Mycorrhizae are actually a fungus. They exist as very tiny, almost or even entirely microscopic, threads called hyphae. The hyphae are all interconnected into a net-like web called a mycelium, which measures hundreds or thousands of miles—all packed into a tiny area around the plant.

The mycelium of a single mycorrhiza (note: mycorrhizae is plural), in turn, can extend outward, connect multiple plants (even plants of different species!), and even connect with other mycorrhizae to form a Frankenstein-like underground mash-up called a common mycorrhizal network.

In a common mycorrhizal network, it’s hard to tell where one mycorrhiza ends and another begins. Because of this vast network, a single plant can be connected to a completely different species of plant halfway across a forest!

Mycorrhizae actually connect to plants in two ways. One form, called ectomycorrhizae, simply surrounds the outside of the roots. Another form, called endomycorrhizae, actually grows inside of the plant—their hyphae squeeze in between the cell wall and the cell membranes of the roots (sort of like wedging themselves in between a bicycle tire and the inner tube).

Under normal conditions, you’re not likely to see mycorrhizae because they’re so small. But every once in a while, something amazing happens: the mycorrhizae will reproduce and send up fruiting bodies that produce spores—we call them mushrooms! Some of these mushrooms are even edible, like truffles or chanterelles.

How do plants help mycorrhizae?

Plants make great gardeners. Just like we fertilize our gardens, plants feed their own mycorrhizae. Plants will take excess sugar produced in the leaves through photosynthesis and send it to the roots. From here, the mycorrhizae are able to absorb it to sustain themselves. There is very little sunlight underground, and even if there was, the mycorrhizae wouldn’t be able to harvest it like plants because they don’t have the equipment needed for photosynthesis. The sugar from the plants literally keeps the mycorrhizae fed and alive.

How do mycorrhizae help plants?

Plants don’t give up their valuable sugar resources just for the fun of growing fungus gardens. They get a lot of things in return from the mycorrhizae, mostly in the form of nutrients.

Plants are able to get nutrients themselves through their roots, but they have a limited ability to do so. Their roots need to be in direct contact with the soil to absorb the nutrients, and plant roots only grow so small. Fungi, on the other hand, can get much smaller. Fungal hyphae can wedge in between individual bits of soil to cover almost every available cubic millimeter of soil. This increases surface area and allows the plants much greater access to nutrients than they could get by themselves. For many plants living under difficult conditions, they wouldn’t be able to survive at all without mycorrhizae.

The mycorrhizae absorb nutrients such as phosphorus and magnesium and bring it directly to the plant roots. Here, they exchange the nutrients they’ve collected for some sugar. It’s a fair trade, and both sides benefit.

Additionally, the mycorrhizae help plants out in a whole bunch of other ways. Mycorrhizae can help protect their plants against diseases and toxins. Mycorrhizae can also serve as a sugar delivery service when plants shuttle sugar back and forth to different plants connected to the same common mycorrhizal network. Perhaps most bizarrely of all, the common mycorrhizal network can also serve as a means for plants to “talk” to each other—an Internet made out of fungus!

Putting It All Together

Mycorrhizae form an invaluable part of ecosystems around the world, and can be found in some form or another in just about any ecosystem. In many places, whole forests and ecosystems wouldn’t exist at all without their mycorrhizal friends.

The next time you’re walking in a forest and you see a mushroom growing out of the ground, be thankful and remember that there’s a whole world buzzing along beneath your feet.

Tropical Savannas

Tropical grasslands (or tropical savannas) are grass-dominated ecosystems with scattered shrubs or trees, which lie in a wide band on either side of the equator. Huge tropical grasslands exist in Africa, Australia, South America, and India, and some well known ones include the Serengeti Plains in Tanzania, Los Llanos in Venezuela and Columbia, and the Everglades in North America.View Biology Item

Warm, Wet, and Dry

Tropical grasslands are often sandwiched between tropical rainforests, which need a lot of rainfall year round, and desert biomes, which need almost no rain at all. They occur where it’s warm all the time (where temperatures rarely drop below 18 degrees Celsius) and where there’s a very rainy and humid wet season, and a drought-like and fire-prone dry season.

Coping with these extremes isn’t easy for the plants of tropical grasslands, but every species has adaptations to help it get by. Many of the grasses are dormant throughout the dry season; the trees often have leaves that fall off during the dry season to conserve water, very thick bark to protect against fire, water storage tissues in their trunks, or the ability to re-sprout really quickly after fire.

Animal Inhabitants

Tropical grasslands support diverse groups of animals, which differ from region to region around the world. The grasses and trees of these ecosystems provide food for many large herbivorous mammals, which in Africa alone include: impalas, eland, gazelles, kudu, buffalo, wildebeest, zebra, rhinos, giraffes, elephants, warthogs, and more. These browsers and grazers manage to co-exist by having different preferences when it comes to food and where and when they eat.

Of course, where there are lots of herbivores, there are bound to be carnivores, too. Lions, leopards, cheetahs, jackals, wild dogs, and hyenas eat the grass- and tree-eaters on the savannas of Africa. Birds of prey, like hawks, eagles, and buzzards thrive in these environments as well, where they have wide, clear views to search for prey, hot air updrafts to help them soar, and essential resting and nesting sites in trees.

One of the most abundant but least seen animals in tropical grasslands is the termite. These ant-sized insects eat dead grass and wood and recycle the nutrients they contain back into the grassland ecosystem. Some species of termite in Africa, Australia, and South America build colossal mud mounds their colonies to live in that can reach more than five meters high!

Looking After Tropical Grasslands

Since tropical grasslands are great at supporting big, grass-eating mammals, they are often used by farmers as grazing grounds for livestock, which can cause them to degrade. Some tropical grasslands have had their makeup of grass and trees change dramatically because animals that wouldn’t usually live there have been forced in. And large areas of tropical grasslands all around the world have been cleared to make way for development. Because of these threats tropical grasslands need protection and careful management so they can remain one of our planet’s vast, complex, and critically important biomes.

Visiting Tropical Grasslands

Want to check out a tropical grassland in real life? Well, here are a few options you could investigate:

Africa

Explore the Serengeti Plains of Tanzania in Africa while you stay in the remote, southern part of these world famous grasslands at Sanctuary Kusini. Incredible wildlife can be seen here all year round.

South America

Head to Venezuela in South America to experience Los Llanos (“the Plains”). The capital of Apure state is a town called San Fernando, and it’s located right in the heart of Los Llanos. Try not to have a close encounter with an anaconda on your Los Llanos adventures!

North America

For something more hands-on, why not travel to the Everglades in Florida and help scientists find out more about this amazing grassland by doing some volunteer research? Everglades Hostel and Tours can help with both interesting work and a place to stay.