Assignment: 01.02 Biomes

• Assignment 01.02 Biomes

The six major biomes are:

• Marine
• Freshwater
• Desert
• Grassland
• Forests
• Tundra

Lesson Focus

This lesson focuses on the diversity of terrestrial and aquatic environments in our biosphere. Use these questions to make new connections between your existing knowledge and this lesson’s focus:

• Have you been to a country or region where the climate, landscape, or animals were unfamiliar to you? Or did you view some other landscapes or climates in a show or a movie?
• Have you visited lakes, rivers, or beaches recently? Did you have any curiosity about why there is diversity of fish in different waters?

There are two defining groups of biomes: terrestrial and aquatic. Let’s look at both of these types in this lesson. Examine the lesson below and the learning objective and essential knowledge that will be included:

Enduring Understanding

The result of biotic factors and abiotic factors makes ecosystems.

Learning Objective

Identify where terrestrial and aquatic biomes are found and their major environmental characteristics.

Essential Knowledge

• The characteristic communities of plants and animals are found in a biome as a consequence of, and adaptation to, the climate.
• The major terrestrial biomes are: Taiga, temperate rainforests, temperate seasonal forests, tropical rainforests, shrubland, temperate grassland, savanna, desert, and tundra.
• The distribution of nonmineral terrestrial natural resources (water and trees for lumber, for example) differs between regions of the world because of a combination of climate, geography, latitude, altitude, nutrient availability, and soil.
• The global distribution of biomes is dynamic; distribution has changed in the past and could change as a result of global climate change.
• Streams, rivers, ponds, and lakes are all examples of freshwater biomes. They are an important source of fresh water.
• Marine biomes are the ocean, coral reefs, marshland, and estuary. In marine biomes, algae can produce a significant amount of oxygen for the Earth as well as absorb carbon dioxide from the air.
• The marine natural resources include various kinds of fish, which are not evenly distributed throughout the entire globe due to salinity, depth, turbidity, nutrients, and temperature.

Terrestrial Biomes

Latitude, humidity, elevation, and vegetation are the four factors used to distinguish terrestrial biomes from each other. Within a biome, the variation and distribution of species are affected by abiotic factors, including topography, precipitation, and temperature. Biomes closer to the equator with more moisture and warmer weather tend to be more diverse, in terms of numbers of species, than are those biomes closer to the north and south poles.

Take a trip through the 9 terrestrial biomes: tundra, taiga, temperate rainforest, temperate seasonal (deciduous) forests, tropical rainforests, shrubland, temperate grassland, savanna, and desert. Click on each of the sites on the map to find out more about the biome around them.

Misconception Alert

All deserts are dry but not necessarily hot. Deserts can be very cold at night and very hot in the day. However, deserts are not necessarily hot, as is the case at the poles, where there is little snow. Also, keep in mind that deserts are found near mountains, where they may be relatively cool.

Aquatic Biomes

The type and number of organisms in a terrestrial biome depend on climate (temperatures and precipitation averages). Salinity, dissolved oxygen, and light are important factors that determine organism abundance in aquatic biomes.

Aquatic biomes can be divided into:

• Freshwater biomes (ponds, lakes, streams, rivers) and freshwater wetlands.
• Marine environment, such as estuaries and coastal wetlands (also referred to as marshlands), coral reefs, and oceans.

Embark on a virtual tour of aquatic biomes in a canoe! Water runs downhill, so begin your journey at as high a spot as possible and paddle (or float) towards the waterfall. You’ll begin in a lake in the mountains.

Ponds and Lakes

Ponds and lakes are also lumped into the category of inland fresh water. The water that you’re in, you can tell that it’s a lake-sized because it’s pretty big. The amount of sunlight received can be used to classify lakes into four zones.

It’s summertime, and you want to take a dip in the lake, and once you’re off the canoe and into the lake, you can feel the thermocline in the bottom of your feet. The top layer of a lake that you swim in is the epilimnion. If you were to dive below the thermocline during the summer, you may encounter the hypolimnion, the cold water in the summer.

In lakes, thermal layering is frequently seen and is not present year-round. A fall overturn occurs with surface winds in the fall that churn the water, and the thermal layering of the water is lost. Many species are found to be burrowing in the mud of the bottom, and ice may form on the surface of the lake in the winter. In the spring, surface winds are the mechanism for mixing, and in the summer, the thermal layers form.

Lake inputs of organic matter, sediment, and nutrients from human activities like building housing and commercial centers, clearing forests, and developing the land for fields. This may result in a temporary overall increase in the biomass in the lake, because the phytoplankton benefit from the added nutrients. Eventually, though, the increase in productivity is followed by a decrease in the overall health of the lake.

Lakes may be categorised according to their productivity. Lakes with low nutrient levels and low productivity are called oligotrophic lakes. A high-nutrient and high-productivity lake is called eutrophic. Mesotrophic lakes fall between the two extremes of the spectrum of nutrient levels and productivity of oligotrophic lakes and eutrophic lakes. Cultural eutrophication is caused by excessive nutrient and/or productivity inputs by humans, typically caused by nitrate and/or phosphate pollution.

More than 70% of the Earth is covered with water. But only 3% of the water on earth is readily available fresh water. A significant portion of fresh water on Earth is locked up in glaciers, polar ice caps, or in underground storage. Only 1/100 or less is found in rivers, streams, and lakes.

Freshwater biomes are determined by nutrient levels. Aquatic organisms can be found in these biomes.

Case Study: Lake Baikal

It is the oldest and deepest lake in the world, Lake Baikal, Russia, and it is undergoing an enormous anthropogenic change. Logging throughout the catchment and bulldozing a nearby ski resort have added to the erosion, which adds more sediment to the lake. An increase in the turbidity decreases the amount of light that can penetrate the lake, which, in turn, decreases the number of phytoplankton that can survive.

These industries are also responsible for air pollution. Also, along Lake Baikal, sludge ponds have been formed at a paper mill that produces sludge along Lake Baikal, which contains heavy metals and dioxin.

Aquatic Biomes–Streams and Rivers

It’s now time for the streams and rivers part of your tour. Prepare your paddles.

After a while, as you paddle further downstream, the amount of water and speed you are traveling increase. The deeper the water and the faster it moves, the more you have entered into a river. The use of the river speed means that not much need to paddle is required. More is going on under your canoe than speed.

Streams and rivers are connected to (and affect) the ecosystems they flow through. They take some oxygen from the air as they run downhill and carry some nutrients from ecosystems in the form of leaves and twigs, animal faeces, and insects. Water flows from the watershed into the streams and rivers.

Water moves downhill through 3 zones. The headwaters of the river are part of a source zone. Has cold water with high dissolved oxygen concentrations. The transition zone is a broad, slow water section of the river with fewer producers and less dissolved oxygen. The flood plain zone is the area of the river that is wider with meander bends and possible deltas. Many producers (plants with roots in the bottom) and consumers are present, but the amount of dissolved oxygen is less than in the other two zones.

Rivers are a type of aquatic biome. The characteristics can differ for each river. The water in a river is not confined to a particular location, but it’s always on the move and changing. The climate of the river is dependent on the other biomes that the river passes through. The source of a river is the highest body of water that flows into the river. Water runs downhill due to the force of gravity towards the ocean. Rivers not only drain, but they also form the land.

Water is one of the most important agents of change on the Earth’s surface. The erosion of the Earth by running water. In many cases, the products of erosion are carried elsewhere, making a delta. Many types of plants and animals are affected by a river, as it molds the land.

The organisms that inhabit the shore and water of a river depend on many of the river’s environments. The border between a river and the land provides a riparian habitat. A riparian habitat is a type of ecotone and a zone of plant and animal life.

An estuary is an area that is affected by both river and ocean biomes and is a mixture of saltwater and freshwater. Estuaries provide a significant habitat and breeding area for a large number of organisms. Tidal marshes extend outwards from estuaries and are areas of very high fluctuation in water level and temperature. In a tide marsh, plants must cope with variations in salinity. Phytoplankton are a key component in a number of aquatic food chains.

Many river systems have been contaminated by human activities. Due to an increased awareness of the environment, there is pressure on the government to monitor and help improve its water quality in the rivers and lakes of the United States.

Aquatic Biomes–From Freshwater to Saltwater

The waters of the earth do not exactly belong to the categories of fresh water or salt water only. There are transition areas with increasing salinities. Organisms in such aquatic ecosystems have adaptations that allow them to thrive in areas of intermediate salinities.

You have traveled along the river through the watershed from the high elevations close to the lake to the low elevations close to the ocean. Now you are in an open space, with a rather funky and salty odor. An estuary or tidal marsh is a transition zone between the freshwater and saltwater found where a river flows into the ocean.

Here, the waters are brackish, and the areas are rich in nutrients due to inflowing tides and outflow at the river mouth.

Dams of rivers may deprive downstream areas of sediment and nutrients, which can lead to declines in estuary health. Estuaries need land surrounding them, which is at risk from the development of homes and roads, which are likely to destroy habitat and lead to air, water, and noise pollution.

Estuaries and tidal marshes are in a class of wetlands – wetlands are water-saturated areas such as marshes, swamps, bogs, and fens. Wetlands provide a number of ecological benefits, such as:

• They are a source of habitat for many different organisms
• They consume a lot of oxygen (O2)
• They filter waters providing water quality control
• They recharge aquifers
• They are flood and erosion control features

What has led to the loss of wetlands? They are frequently located in commons, and they can have negative externalities. Further, there has been a lack of uniformity between government policies covering economics, environment, and planning. In Louisiana, for instance, 15 square miles of coastline have been lost annually, and the majority of this loss has been in wetlands. Oil and gas companies have dug 10,000 miles of canals in the wetlands in Louisiana, which has encouraged erosion of the wetlands. Unfortunately, wetlands also function as buffer zones for hurricanes, and the destruction of wetlands magnifies the effects of hurricanes on inland areas.

You have paddled about the estuary in your canoe, so now check out a swamp.

Global Distribution of Biomes

NASA is keeping an eye on the Terra satellite, which carries an instrument called MODIS, the Moderate Resolution Imaging Spectroradiometer. Data is retrieved from the surface of the Earth by MODIS. Based on this information, Boston University scientists were able to construct maps illustrating the location of different biomes around the world. View the animation of land mapping from the National Oceanic and Atmospheric Administration (NOAA) below:

Each has a different effect on the biosphere. Tundra ice reflects the sun’s heat back to space and helps to keep the planet cool. In temperate and tropical rainforests, forests and vegetation consume a significant amount of carbon dioxide from the atmosphere, and photosynthetic species of the marine biome absorb CO₂ in all aquatic biomes.

Unfortunately, the increase in urban areas and croplands, combined with the melting of Arctic tundra, is increasing the amount of surface area on Earth that absorbs heat instead of reflecting it. This, in turn, amplifies the impact of global warming and hastens the global climate and biomes changes.

When a biome is lost, it also takes with it the natural resources the biome offers, like fresh water, lumber, food, and a source of energy. This applies to many tropical rainforest biomes of Central America, Mexico, and the Caribbean. Because of the lumber industry, they are losing acres of their tree biodiversity. The World Wildlife Federation has added trees such as big leaf mahogany, which are in great demand for lumber, to their endangered species list of fauna and flora.

The same changes occur in marine biomes. Warming and acidification of oceans, coupled with overfishing, are leading to the extinction of oceanic life. The changes in many of the grassland biomes are also a projected decrease in food resources; they are becoming drier and drier and less able to sustain vegetation.

• Tundra – is associated with – Permafrost is frozen all year round and only partly thaws in the summer.
• Taiga – A biome of evergreens; has well-defined seasons, long cold winters with snow.
• Temperate Rainforests – aligned to – This bioregion is valued for its natural resources, soil fertility, and high production of biomass.
• Savannas – go with – Biome is a lowland biome, with a low tree density.
• Lakes – go with – Biome known for thermal layering and four distinct zones based on the amount of sunlight received by the respective zones.
• Marshlands are associated with A transitional area between fresh water and salt water, found where a river flows into the sea.

Assessment

During this lesson, you’ve learned about biotic and abiotic characteristics of Earth’s six major biomes and subbiomes. You studied the differences between the characteristics of coastal, estuary, and freshwater ecosystems. You also learned about some of the differences in climate and season in Earth’s biomes and what they offer.

Biomes Virtual Tour

You have toured (virtually) various terrestrial and aquatic biomes. For this assessment, you will make a virtual tour of a biome of your choice, either using a slide presentation, a word processing document, a video, a brochure, or a webpage. Other options are allowed, provided prior approval from the instructor.