Zonation on a Local and Global Scale, Essay Example
Describe zonation on a local and global scale. Include in your answer: a. the reasons for tides and the global circulation of air and water masses, b. (local) the adaptations of animals that restrict them to certain tidal zones from the splash zone to nearshore coastal waters, c. (global) the influences of latitude, altitude and geographic position on plant communities across the North American continent.
The Earth works on a system of energy that maintains the ocean and atmosphere circulation and helps erosion occur. The atmosphere and ocean circulation is referred to as the Hydrologic System because water and its properties are the driving force. The Hydrologic system includes the movement of water on the Earth, whether on the surface or in the air. The main energy force that drives the hydrologic system is the sun. The hydrologic system has various pathways, such as water entering the oceans through rivers, glaciers and precipitation, water entering the atmosphere from rain, rivers and lakes, soil, oceans and transpiration by plants, and water movement onto the land through rain and snow. The majority of the water is found in the oceans and covers about 70% of the Earth’s surface.
Water moves across the surface of the continents to the oceans and shapes the surface of the continents. Along the shoreline of the oceans water is moved by waves and erodes and moves sediment to form beaches, sandbars, lagoons, and tidal pools. The most important physical factor along the shorelines is the rise and fall of the tides. The tides are periodic, and have short alterations in their height. This is cause by various factors through the gravitational force from the moon and sun, as well as the movement of the Earth. Tides are the longest of all waves and equal half of the Earth’s circumference. The actions of gravity and inertia on particles at five different locations on the Earth cause an attraction of the moon. The imbalance of forces causes water to move along the Earth’s surface to converge at a point toward the moon and opposite of the moon. Basically, the earth and the moon orbit a large mass. The orbital movement of the Earth and the moon cause the earth to undergo a centrifugal force exerted on the side facing away from the moon, which in turn makes the ocean move opposite from the moon. The centrifugal forces pushes water to a high tide facing the earth and the gravitational pull caused by the moon pushes the high tide on the opposite side of the earth. As the earth rotates, the high tide occurs. This is when the moon is the closest to the Earth. Another high tide occurs a half a day later when it reaches the other side. The change between high and low tide is caused by the rotation the earth has each day. These are known as tidal humps and tidal depressions. There are tidal differences in every cycle because the sun also exerts a gravitational force on the earth. The suns force is not as strong as the moon, due to its distance; however, when the moon and the sun are located at right angles to each other, their forces work against each other. Therefore, the tides are the strongest and highest when the moon and sun are working together and weakest when they work against each other. The tides that are the strongest are referred to as the spring tides and the tides that are the weakest are referred to as the neap tides.
These tides are also responsible for creating an intertidal zone at the highest high tide and low tide mark along rocky shorelines. Because the tide rise and fall, the tidal zones are drenched and dried, as well as the animals and plants that live in these zones. Therefore, the organisms that live between the high and low tidal marks experience different conditions from the organisms inhabiting the areas below the low tide line. Within the intertidal zone itself, organisms are placed in different amounts of water levels. Some organisms are able to tolerate varying amounts of time at high and low water levels; however, others organisms are more senisitive. Therefore, the different animals and plants are sorted into different horizontal bands in the tidal zones or more commonly referred to as the subzones. Each zone has plants and animals that are best adapted for the conditions within that particular habitat. The zones are also different in appearance. There is a large diversity of animals that live within these zones. For one, there is a lot of food available. Minerals from land dissolve in the water running off the land and serve as the nutrients for the inhabitants of the intertidal zone. The surf zone and strong tidal currents also keep the nutrients stirred and keep a high concentration of gases to support the autotrophs, such as plankton, in that area. This is important because many of the intertidal community depend on plankton as their primary food source. The habitats for the plants and animals in these zones vary from hot, high, salty, splash zones to cool, dark crevices. These crevices provide hiding places, attachment sites, cracks, and predation spots. For the intertidal zone exposed to the open sea, wave shock is a physical factor. Intertidal plants must be strong, elastic and slippery to avoid being shredded away from the wave energy. In addition, motile animals must be able to move to protective areas during the intense wave activity. Furthermore, attached or sessile animals must be able to hang on tightly. Also for animals that are exposed to air in the nearshore zones are being exposed to air and sunlight, leading to the factor of desiccation or drying. Motile organisms in this area are able to move to water left in the tidal pools. The attached animals; however, must wait for the water to return. Some animals are able to keep the water trapped within its shell in order to keep the gills moist for the exchange of gases. Most animals that adapted to the intertidal zones motile animals such as are crabs and sea snails and sessile or motile animals that have attachments such as sea anemones and starfish. Kelp is a type of algae that is found in the low tidal zones and can withstand the waves due to its holdfast that attaches to the sea floor.
Some intertidal areas are sandy and muddy, or made of gravel or cobbles. Organisms must be adapted to withstand sand grains and rushing water, as well as being trapped underneath the sand surface. The types of animals that have adapted here are mostly sand crabs, sturdy polychaetes and worms.
The physical factors involved in the circulation of air and water also determine the distribution of plant communities on land as well. For instance, because of the latitudinal patterns of climate, there will also be latitudinal patterns of biomes. Temperature and rainfall are correlated with the different terrestrial biomes. Terrestrial biomes are usually indicated by the type of physical or climate feature. In North America, for instance there are many different biomes for plants based on the latitude. For instance, deserts occur around the 30 degree North latitudes. In North America this is located in California, Arizona, and New Mexico. Deserts have low rainfall and the vegetation is usually slow. In deserts there are succulent plants, known as the cacti. The Savanna, another type of biome, is found near the equator and just below the equator. The Savanna experiences seasonal rainfall and is usually warm throughout the entire year. Savanna vegetation is usually large grasslands with some trees. Chaparrals are areas that are also dependent on the seasons. They can be mild, wet or dry with very hot summers. Chaparrals are found primarily in California in North America. The vegetation in the Chaparral is mostly small shrubs and trees. In addition, there are different species of grasses. Temperate grasslands are biomes that have some droughts throughout the year with some fires as well. There is also a large difference in temperatures throughout the year. Most of the grasslands in North America have been converted to farmland and are the referred to as the Central Lowlands and High Plains. There are also California grasslands and desert grasslands located in the Southwest United States.
Coniferous forests, or taigas, are the biggest terrestrial biomes on the planet Earth. They experience long and very frigid winters with short rainy summers. The vegetation in these areas are conifer trees. In North America it covers most of Canada and Alaska, as well of the northern sections of the United States. The Tundra covers the areas in the Arctic. Alpine tundra can be found on mountains at all types of biomes. Tundra vegetation consists of lichens, grasses, mosses, and different types of shrubs and trees.
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