Category Ecology

WHAT TREE HAS 2 TYPES OF LEAVES?

Redwood trees have been studied extensively but only recently did the scientist discover that they have two types of leaves – peripheral leaves and axial leaves – that look different and perform different tasks. They help redwood trees adapt to both wet and dry conditions – an ability that could be key to their survival in a changing climate. Redwoods are among those super-trees that can survive pest attacks, fire and even perhaps climate change. They are also among the planet’s biggest, tallest and oldest trees.

Unlike each other

While the peripheral leaf takes care of the food preparation via photosynthesis, the axial is devoted to absorbing water. A large redwood can absorb up to 14 gallons of water in just the first hour its leaves are wet!

The two types of leaves look different from each other, inside out. When scientists looked at the leaves under a microscope, they understood that they were completely different from each other. The axial leaves were packed with water storage cells, but their phloem- tubes in the leaves that export photosynthetic sugars to the tree – appeared to be blocked and useless.

Adaptation technique

Analysis showed that the redwoods’ axial leaves account for only about 5% of the trees’ total leaf area, and barely produce enough energy through photosynthesis to maintain themselves. But they contribute up to 30% of the trees’ total water absorption capacity.

Together these two types of leaves balance the dual requirements of photosynthesis and water absorption, allowing redwoods to thrive in both wet and dry habitats.

Redwoods are found in both wet and dry environments with intense seasonal variation. In the wet, rainy areas, the axial is found on the tree’s lower branches, leaving the upper, sunnier levels to the peripheral leaf type. This completely flips for redwoods in drier areas: The axial leaves live among the tree’s higher levels to take more advantage of fog and rain, which occur less often in the drier environment.

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WHAT IS A WADI?

A wadi is a freshwater ecosystem and a type of fluvial landform, which is considered any type of geological feature that is related to rivers or streams. The term wadi comes from both the Arabic and Hebrew languages. Specifically, it refers to a dry riverbed that contains water during rainy seasons and is located in a valley-like area of the desert.

Characteristics Of a Wadi

Wadis are generally located in the flat or slightly rolling areas of deserts and often leads to dry lakes as well. A wadi can be recognized by its braided appearance, which is caused by a lack of constant water flow and an excess of sediment build-up. Sometimes, this sediment may collect in significant amounts, blocking water flow and effectively changing the direction of seasonal rivers. In addition to the low water levels, wind also affects sediment buildup by bringing in dry sands that collect on top of moist sand.

The bottoms of wadis are often covered in sand and loose gravel. The lower levels of this sediment are often packed very densely. This means that during rainy season, water is not quickly absorbed by the ground and has nowhere to drain, resulting in rapid flooding. Flash flooding in wadis is made even more dangerous because of the previously mentioned directional changes, which can send waters into communities unexpectedly.

Credit: World Atlas

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WHAT IS AN OASIS?

An oasis is where water from a source deep underground comes to the surface in a desert, supporting life and vegetation.

An oasis is a lush green area in the middle of a desert, centered around a natural spring or a well. It is almost a reverse island, in a sense, because it is a tiny area of water surrounded by a sea of sand or rock.

Oases can be fairly easy to spot—at least in deserts that do not have towering sand dunes. In many cases, the oasis will be the only place where trees such as date palms grow for miles around. For centuries, the sight of an oasis on the horizon has been a very welcome one for desert travelers.

Scientific Explanation

It seems amazing that trees could sprout in an oasis. Where do the seeds come from? As it happens, scientists believe that migrating birds spot the glint of water from the air and swoop down for a drink. Any seeds that they happen to have swallowed earlier will be deposited in the damp sand around the waterhole, and those seeds that are hard enough will sprout, providing the oasis with its tell-tale splash of color in the sand.

Caravans in desert areas such as Africa’s Sahara or the dry regions of Central Asia have long depended on such oases for food and water, both for their camels and their drivers, during difficult desert crossings. Today, some pastoral peoples in western Africa still depend on oases to keep themselves and their livestock alive as they travel through deserts between different grazing areas. In addition, many kinds of desert-adapted wildlife will seek water and also take shelter from the blazing sun in local oases.

Credit: ThoughtCo

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WHAT ARE FJORDS?

Fjords are very deep, long and narrow inlets with steep sides or sheer cliffs, seen along the coasts of Norway, New Zealand and Canada. A fjord is formed when the sea comes in to fill the U-shaped valley left by a glacier after it has retreated.

A fjord is a long, deep, narrow body of water that reaches far inland. Fjords are often set in a U-shaped valley with steep walls of rock on either side.

Fjords are found mainly in Norway, Chile, New Zealand, Canada, Greenland, and the U.S. state of Alaska. Sognefjorden, a fjord in Norway, is more than 160 kilometers (nearly 100 miles) long.

Fjords were created by glaciers. In the Earth’s last ice age, glaciers covered just about everything. Glaciers move very slowly over time, and can greatly alter the landscape once they have moved through an area. This process is called glaciation.

Glaciation carves deep valleys. This is why fjords can be thousands of meters deep. Fjords are usually deepest farther inland, where the glacial force was strongest.

Some features of fjords include coral reefs and rocky islands called skerries.

Some of the largest coral reefs are found at the bottom of fjords in Norway. They are home to several types of fish, plankton and sea anemones. Some coral reefs are also found in New Zealand. Scientists know much less about these deep, cold-water reefs than they do about tropical coral reefs. But they have learned that the living things in cold-water reefs prefer total darkness. Organisms in cold-water reefs have also adapted to life under high pressure. At the bottom of a fjord, the water pressure can be hundreds or even thousands of kilograms per square meter. Few organisms can survive in this cold, dark habitat.

Skerries are also found around fjords. A skerry is a small, rocky island created through glaciation. Most of the Scandinavian coastline is cut into thousands of little blocks of land. These jagged bits of coastline are skerries. The U.S. states of Washington and Alaska also have skerries.

Even though skerries can be hard to get around in a boat, fjords are generally calm and protected. This makes them popular harbors for ships.

Credit:  National Geographic Society

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How are mountains created?

Most of the world’s greatest mountain ranges the Himalayas, the Andes, the Rockies, the Caucasus and the Alps were created as Earth’s tectonic plates collided. As the huge tectonic masses crashed into each other, they forced the layers of rock to fold. This is why these mountains form long, narrow ranges along the edges of continents. Mountains are also created as powerful earthquakes move Earth’s crust and lift up huge blocks of rock. Volcanic eruptions can also create mountains.

Mountains are formed by movement within the Earth’s crust. The crust itself is made up of several large plates, called tectonic plates, which are free floating. These huge chunks of the Earth’s crust move within molten rock called magma, which allows them to shift and collide over time. Even though humans live on the crust, they do not often feel these movements as they are very slow, and the sheer size of each plate is so large. Nevertheless, these shifts still have great impacts on human life as the movement of plates is what creates changes in the geographical structure of the surface of the earth. In this way, mountains are created over time. When these plates collide, there is a great deal of mass and pressure which suddenly comes to a stop, and it is this movement that forces the Earth into buckles or protrusions which are known as mountains. Depending on how these plates move or collide, one of three types of mountains can be formed. The three types of mountains or mountain ranges are: volcanic, fold, and Block Mountains, each of which is formed in a different way.

Volcanic Mountains:

Volcanic mountains are formed when a tectonic plate is pushed beneath another (or above a mid-ocean ridge or hotspot) where magma is forced to the surface. When the magma reaches the surface, it often builds a volcanic mountain, such as s shield volcano or a strato-volcano.

Fold Mountains:

As the name suggests, Fold Mountains occur when two tectonic plates collide at a convergent plate boundary, causing the crust to over thicken. This process forces the less dense crust to float on top of the denser mantle rocks – with material being forced upwards to form hills, plateaus or mountains – while a greater volume of material is forced downward into the mantle.

Block Mountains:

Block Mountains are caused by faults in the crust, a seam where rocks can move past each other. Also known as rifting, this process occurs when rocks on one side of a fault rise relative to the other. The uplifted blocks become Block Mountains (also known as horsts) while the intervening dropped blocks are known as graben (i.e. depressed regions).

Credit: WorldAtlas

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NAME EUROPE’S HIGHEST MOUNTAIN?

Mont Blanc, Italian Monte Bianco, mountain massif and highest peak (15,771 feet [4,807 metres]) in Europe. Located in the Alps, the massif lies along the French-Italian border and reaches into Switzerland. It extends southwestward from Martigny, Switzerland, for about 25 miles (40 km) and has a maximum width of 10 miles (16 km). The summit is in French territory. Surrounding the massif are the Graian Alps (south), the Chamonix Valley and Savoy Alps (west), the Pennine Alps (northeast), and the Valley of Courmayeur (east). Other principal peaks within the massif include Mont Blanc du Tacul, Mont Maudit, Aiguille (“Peak”) du Géant, Les Grandes Jorasses, Mont Dolent, and Aiguille du Midi.

Glaciers cover approximately 40 square miles (100 square km) of Mont Blanc (whence its name, meaning “white mountain”). Ice streams stretch from the central ice dome down to below 4,900 feet (1,490 metres). The Mer de Glace, the second longest glacier in the Alps, reached the elevation of 4,100 feet (1,250 metres) in 1930. At the beginning of the 17th century, glaciers advanced to the bottom of the Chamonix Valley, destroying or burying cultivated land and dwellings. Since that time, the glaciers have periodically advanced and retreated.

 

Credit: Britannica

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