In this third presentation in the Biomes Journey, we will focus on one of the two major classes of biomes on Earth – terrestrial biomes. In the next presentation, we will focus on the other major class of biomes – aquatic biomes.

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This slide simply shows the two major groups of biomes on Earth, terrestrial and aquatic biomes. These major divisions can be further divided based on physical and biological factors. For example, aquatic biomes can be divided into saltwater and freshwater biomes. Each of these, in turn, can be further subdivided – deep ocean versus coral reef biomes, for example.

Let’s begin by focusing on terrestrial biomes.

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In this section of the Biomes Journey, students will explore several terrestrial or land biomes.

Reinforce the concept that terrestrial biomes are classified by the temperature, precipitation, and vegetation in a geographical area. 

Introduce four examples of terrestrial biomes to students.

Explain that this list is one way of classifying biomes. Students should notice that some of the groups contain smaller subgroups. For example, one group of biomes is forests. However, within that large group are different types of forests, such as rainforests, temperate or deciduous forests, and alpine forests. Students may encounter other resources that list these types of forests separately. Neither method is incorrect.

Explain to students that as they continue through the presentation, they will have an opportunity to view where on Earth these biomes are found and examples of the types of vegetation found in each biome. 

Explain that the plants and animals in each biome type will have ADAPTATIONS that help them survive the climate in the biome.

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Because the classification of biomes is based upon climate, one of the easiest ways to understand biome distinctions and to remember the location of biomes is to focus on the differences in temperature that occur with differences in latitude. From their previous exploration of the solar system and their understanding of the tilt of the Earth on its axis, students should recall that, in general, areas of the Earth near the Equator are warmer, and areas near the poles are colder. In addition, as one travels from the Equator toward the poles, there would be a gradual decrease in overall seasonal temperature. 

It is important to note this Earth temperature diagram focuses on GENERAL temperature variations from the poles to the Equator. It does NOT include a discussion with respect to seasonal temperature changes. Thus, a student may point out and be correct in stating that the temperature in Pennsylvania in July might be hotter or equal to the temperature at the Equator. 

Although not presented here, students should recall that the tilt of the Earth’s axis not only sets up a temperature gradient from the equator (warm) to the poles (cold), but it is also responsible for seasonal differences. When the northern hemisphere is tilted toward the Sun, it is warmer (summer). When the northern hemisphere is tilted away from the Sun, it is colder (winter). The same is true for the southern hemisphere. Because the equator always receives direct light from the Sun, the temperature is essentially the same year round.   

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As students view this slide, they should not be surprised to see the three basic biome classifications based on temperature. From the previous slide, students should have been able to predict the different temperatures that would be found in different regions of the Earth.  Because temperature is ONE of the factors in determining climate, it is also one of the ways in which biomes can be grouped or classified.

Students should be able to see that the grouping of biomes in this slide differs from that shown previously. Again, neither method is incorrect. Both still represent the same biomes. They simply present them under different types of headings or grouping. Students may find the grouping by temperature easier to remember.

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As students view this slide, they should notice from the map that both areas are found around similar latitudes and therefore similar temperature “zones.” In addition, from reading the text, students should see that these areas also have the same precipitation. In other words, they have the SAME CLIMATE.

Students should realize that these areas are the same type of biome because these two areas have the same temperature AND amount of precipitation – the same climate. This is an important concept for students to understand.

This slide should be used to reinforce the idea that it is the CLIMATE which includes BOTH temperature and precipitation that governs the type of biome that exists in an area. Therefore, if students know that the climate is the same, then it is likely that the biomes of the two areas will be the same. If the climate is different, then it is likely that the two areas will have different biomes.   

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The tropical rainforest is one of the biomes that illustrates extremes in precipitation and near extremes in temperature. It receives over 200 cm of rain annually, one of the highest amounts of precipitation of terrestrial biomes, and has an average daily temperature of 20-25° C (70-80° F).

A large amount of precipitation results in tremendous plant growth, as students should observe from the picture in the slide. In this biome, the plants grow so rapidly that they consume nutrients from decomposed leaf litter almost immediately. Thus, most nutrients are found within the plants and not within the soil. As a result, the soil of the rainforest is relatively infertile. 

Unfortunately, many people associate rich vegetation with fertile soil. So there have been many cases in which rainforest has been cleared in an attempt to use what was assumed to be rich fertile soil for farming. These attempts have almost always failed, as the nutrient-poor soil does not produce significant agricultural yields. 

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This slide helps students re-focus on the concept that climate and that biomes depend not only on temperature but also on precipitation.

Two different biomes are presented. In looking at the maps, they are both found around similar latitudes and, therefore similar temperature “zones.” However, they are classified as two different biomes because although these areas have relatively the same temperature during each season, they receive different amounts of precipitation. Thus these two areas have different climates. It is important that students understand this distinction so that they do not incorrectly infer that two areas with the same temperature (or latitude) will always be the same type of biome.

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Direct students’ attention to the difference that precipitation makes to the vegetation of the grasslands and forest. 

Ask students: Which biome do you think receives more precipitation? Answers may vary. The temperate forst receives more annual rainfall than the grasslands.

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In this slide, student should observe that the temperature of both biomes is essentially the same. Each has four seasons, with summer being warm/hot, winter being cold and spring and fall as intermediate temperatures between the two. 

However, the precipitation differs between the two biomes. The temperate forest receives what scientists would call moderate amounts of precipitation year round. In contrast, the grasslands biome receives moderate amounts of precipitation only during a small portion of the year, the late spring and early summer.

Thus the amount of precipitation received by both biomes during late spring and early summer is essentially the same.  However, because the grasslands biomes receives little precipitation during other times of the year, the total amount of precipitation in the temperate forest is greater than in the grasslands. 

The result of the difference in vegetation is easily seen in these two pictures. The greater amount of precipitation in the temperate forest supports a large variety of plants from grasses, flowers, and bushes to large trees. In contrast, the lesser amount of precipitation in the grasslands biome can support grasses but cannot support large bushes and trees.

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As students view this slide, begin by reinforcing the differences in vegetation that results from differences in precipitation.

Draw students’ attention to the prevalence of herbivores (animals that only eat plants) in grasslands. The temperate forest has a mixture of herbivores, carnivores (animals that eat other animals), and omnivores (animals that eat both plants and other animals).

One of the reasons that there are more carnivores in the temperate forest is that the underbrush combined with the larger bushes and trees provides more shelter and places to “hide” for predators than grasslands which are essentially wide open. 

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In the last series of slides, students investigated biomes with similar temperature but different levels of precipitation. They may wonder whether temperature or precipitation has a greater influence on climate and biomes. The answer is that both are powerful contributors to climate and therefore to differences in biomes. 

This slide and the two that follow are designed to help students investigate this concept by illustrating two biomes that have similar levels of precipitation but very different temperatures.

As students look at the maps, they should once again be struck with the relationship between distance from the equator and temperature. The farther from the equator, the colder the temperature. Thus, deserts (near the Equator) are much warmer than tundra (far from the Equator).

As with the other series of slides, students should consider how the similarities in precipitation but differences in temperature affect the climate, plant and animals in each biome, and the adaptations present in the organisms of each biome.

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Students should notice that both biomes are considered dry climates. They receive little precipitation year round.  As a result, students should notice the almost complete absence of large bushes and trees from either biome. 

In addition, students should notice the temperature difference between the two biomes. The desert is hot year round and the tundra cold/cool year round. In general there is less variability in seasonal temperature in the desert than the tundra. The temperature remains almost the same year round in the desert. Although the tundra is described as cold year round, it does have a period in which the temperatures rise which is referred to as its “cool/warm” growing period. This short period in which the temperatures rise above freezing allows the growth of small plants.

Plant growth is sparse in both of these biomes as compared to the forest or grasslands biomes as a result of the low levels of precipitation. However, plants do live in both biomes. In general deserts are said to have MORE vegetation and diversity of plant life than tundras because of the difference in temperature and winds. 

In the tundra, high, cold winds would dry and destroy tall plants, trees or shrubs.  In addition, the temperature is so cold that there is a layer of permanently frozen soil called permafrost that exists year round.  Permafrost is as impenetrable as concrete. Therefore, roots cannot move deep into the ground and plants tend to be low lying.  In addition, permafrost is one cause of the limited nutrient supply in the soil as it does not allow for the mixing of organic materials into the soil. This lack of plentiful nutrients also limits plant growth.

In addition, plant structure differs between the desert and tundra as a result of different adaptations plants must make in hot versus cold climates. Thus, the differences in the type and amounts of plants that inhabit both biomes is linked to the differences in temperature between the two. 

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The last terrestrial biome that students will explore in this Journey is the Taiga (or Boreal forests).

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The Taiga (or Boreal forests)  is a biome associated with northern latitudes as well as higher altitudes. 

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Use this map to review the locations of the Earth’s many different biomes. In particular, review the biomes that we specifically covered in this presentation:

• Tropical rainforests
• Grasslands
• Temperate forests
• Deserts
• Tundra
• Alpine forests