Environmental Science Biomes Environmental Science

What is a Biome? A biome is a major type of ecosystem with distinctive temperature, rainfall, and organisms. The biome is the largest category that scientists use to classify ecosystems. On land, the type of biome that occurs in a given area depends on the average temperature and amount of precipitation the area receives. In water, the type of biome is determined by water depth, nutrients, and nearness to land.

Terrestrial Biomes The terrestrial biomes of Earth can be broken down into eight major biomes including: Desert Covers 25% of Earth’s land surface, but only contains 1% of Earth’s biomass. Receives very little water, and can’t support much life. Typically hot and dry. Tundra Typically cold and dry. Coniferous forest & Deciduous forest Forests contain 75% of Earth’s biomass. Forests in general receive abundant precipitation over the course of a year.

Terrestrial Biomes Terrestrial biomes (continued) Rain Forest Covers only 6% of Earth’s land surface, but contains more than 50 % of all Earth’s biomass. Most diverse biome; contains the most different types of plants and animals. Steppe, Prairie, Savanna Grassland Biomes cover about 22% of Earth’s land surface, and contain about 8% of Earth’s biomass. Grasslands receive less precipitation than do the forest biomes and may have long dry seasons. Grasslands may be frequently disturbed by fires. Large herds of migrating herbivores are common grassland organisms.

Deserts

Deserts Deserts receive very little rain over the course of a year. Deserts soils tend to be rich in minerals but poor in organic material. Desert Climate Deserts rarely get more than 25 cm of precipitation in a year. Most get around 10 cm a year. The lack of moisture makes desert temperatures able to go from really hot during the day to really cold at night.

Deserts Desert Organisms Organisms that live in the desert are adapted to survive two main challenges: lack of water and extreme temperatures. Some of their adaptations can be physical and some involve behaviors by the organisms. Desert Plants Plants must be able to absorb water from the ground while also preventing the water from transpiring from their bodies. Plants like Cacti and Aloe Vera are called succulents because they have thick, water-filled tissues that help them prevent water loss. Plants roots in the desert grow widely instead of deeply to help absorb as much water as possible from the ground.

Deserts Desert Organisms (continued) Desert Animals Most desert animals get the water that they need from the food that they eat, and fight the same battle as plants against water loss. Insects and reptiles evolved a hard outer coating that helps prevent water loss. Most desert animals have adaptations to help them survive the heat including burrowing underground and being nocturnal. Nocturnal: animals that are active at night and sleep during the day.

Tundra

Tundra The tundra is a cold, windy, dry biome located in the Northern Hemisphere just south of the North Pole. The tundra makes up about 10% of Earth’s surface, but has the fewest number of organisms of any biome. Tundra Climate The Tundra is like a desert in the fact that is receives little to no precipitation. The tundra receives less than 25 cm of precipitation per year. The main difference between a deserts climate and the Tundra's climate is temperature. Temperatures rarely go above 10o C. Because it is so cold the Tundra gets most of its precipitation in the form of snow and ice. The soil rarely thaws out, even during the summer months. The frozen soil below the non-thawing ground is called permafrost.

Tundra Tundra Organisms Tundra Plants Tundra Animals The most common Tundra plants are mosses, shrubs, grasses, lichens, and colorful wildflowers. Most plants in the Tundra are short and grow close to the warm ground. They typically grow short due to a short growing season and little room for the roots to spread out. Tundra Animals Many of the animals that live in the tundra are seasonal visitors. Seasonal travel is called migration. There are few predators in the Tundra which makes it safer to raise young. Most animals in the Tundra evolve thick coats to be able to survive the cold temperatures.

Grasslands

Grasslands A grassland is an ecosystem in which there is more water than in a desert, but not enough water to support a forest. Grasslands can be found in Africa, central Asia, North America, South America, and Australia. There are three types of grasslands: steppe, prairie, and savannah. Grassland Climate Grasslands are a little wetter than the climate of deserts. The desert-grassland boundary is the area between deserts and grasslands where increased rainfall enables some grasses to grow. If rainfall increases, a desert can turn into a grassland. If a grassland becomes to dry it will turn into a desert.

Grasslands Grassland Organisms Without rain, grasslands cannot develop the soil to support plant or animal life. Lighting can cause fires in the grasslands which help maintain their balance. Fires can also burn away the dead grass that accumulates throughout the year. Grazing animals such as bison, wildebeest, and antelope are found in the grasslands.

Grasslands Grassland Activities Grasslands have both a rainy season and a drought season. These two types of seasons determine the organisms and abundance of organisms that can grow. Grasshoppers, insects, mice, gophers, birds are all supported within this biome.

Grasslands Steppes and Prairies

Steppes and Prairies Steppes Prairies Steppes are grasslands of short bunchgrasses that get less than 50 cm of rain a year. Some scientists consider these semi-arid deserts. Prairies Prairies are grasslands characterized by rolling hills, plains, and sod forming grasses. Breads and cereals come from grains grown on the prairies, this gives them the nickname “breadbaskets”.

Steppes and Prairies Steppe and Prairie Climates The major factor that distinguishes a steppe from a desert is rainfall. Steppes receive greater than 25cm of rain annually, while deserts receive less than 25cm of rain annually. Prairies receive 50 – 75 cm of rain annually. Occasionally they can receive up to twice this amount during unusually wet years. Temperatures in the steppe and prairie range from - 5oC to 30oC throughout the year.

Steppes and Prairies Steppe and Prairie Organisms Steppes contain mostly bunchgrasses. Bunchgrasses are short, fine-bladed grasses that grow in a clump. Clumping helps to conserve water. Prairie soil holds water better than the steppe, and as a result can support “grass mats” , otherwise known as sod.

Steppes and Prairies Steppe and Prairie Organisms cont. Animals of the steppe and prairie adapt to the changing conditions by migrating, hibernating, and burrowing underground. Grasses are only slightly affected by the grazing animals because the animals tend to move from place to place. However, if grazing animals stay in one place too long, as is the case sometimes with ranching, the animals can eat too much of the grasses.

Steppes and Prairies Steppe and Prairie Organisms cont. If too much of the grasses are eaten, the grasslands can become deserts. The grasses help to hold the soil together, and without the grasses the nutrient-rich soil is blown away. Overgrazing created the “Dust Bowl” of the 1930s in the Midwestern United States. Farmers are trying to avoid this effect by reintroducing native grasses to prevent these areas from becoming deserts.

Grasslands Savannas

Savannas Savanna Climate A savanna is a tropical or subtropical grasslands ranging from dry scrubland to wet, open woodland. Savannas are found in India, Southeast Asia, Africa, Venezuela and Brazil. Savanna Climate Savannas have rainy seasons along with long periods of drought. Savannas can receive as much as 150cm of rain. However, most of the rain falls heavily during the short rainy season. During the rest of the year, the savanna may be very dry.

Savannas Savanna Organisms Grasses, shrubs, and trees must be resistant to drought, fire, and grazing animals. Plants use runners that are below the ground to reproduce. The runners are protected from fire and grazing animals. Savanna grasses grow in tufts. Tufts are large clumps of tall, coarse grasses.

Savannas Savanna Organisms cont. Animals in the savanna concentrate in areas around streams and watering holes. Because of the large number of animals in a small region, animals have adapted to a vertical feeding pattern. This means that organisms eat at different heights. Vertical feeding decreases the competition for food, and allows more organisms to live off limited resources.

Forests Coniferous Forests

Coniferous Forests Located in the subarctic regions of North America, Europe, and Asia. The summers in these regions are warm lasting between 2-5 months; the winters are long, cold, dry, and there is very little sunlight. Precipitation falls as rain during the summer and snow in the winter; these forests can receive 40-200 cm of precipitation a year. Conifers are trees that produce seed cones; the leaves of these trees are long, thin, and covered with a waxy coating to help the trees conserve water. Conifers are also typically evergreen, which means that they don’t lose their leaves at a given time each year.

Coniferous Forests Coniferous Forest Plants Most of the species of trees that are found in these forests are pine, hemlock, fir, spruce, cedar, aspen, and birch. Some other plants that are found in these areas are ferns, lichens, and mosses. Due to harsh winters and nutrient poor soils there are only a few species of plants that can survive in these conditions. The snow that falls in these regions acts as an insulating blanket that helps to keep the roots of the trees warm, which protects them during the winter months.

Coniferous Forests Coniferous Forest Animals Animals that can be found in these regions include seed eaters such as mice, squirrels, jays, and other rodents and birds. Insects can be present during the summer months. Other animals that can be found in these regions are moose, elk, beavers, snowshoe hares, grizzly bears, wolves, and lynxes. All these animals have adapted to allow them to survive the long winters. Many species migrate to and from these regions.

Forests Deciduous Forests

Deciduous Forests Located at the mid-latitudes in the temperate zones of the planet which have four well-defined seasons. Deciduous trees are trees that shed their leaves during a particular season of the year. Temperature varies greatly in these areas going from 30oC in the summer to -30oC in the winter. Precipitation falls as either rain or snow depending on the temperature and season. The growing season in these forests lasts about 6 months. During this time the tree grows quickly and produces and stores food. As the growing season ends the tree sheds its leaves and becomes dormant.

Deciduous Forests The losing of leaves is an adaptation by the tree to conserve water during the cold winter months. Deciduous Forest Plants Maple, oak, beech, ash, hickory, and birch are all deciduous trees that exist in these forests. Shrubs also grow in the lower layers of these forests and can include mosses and ferns. Deciduous Forest Animals Fungi (decomposer), insects, birds, mice, other small mammals, deer, reptiles, amphibians, wolves, mountain lions, birds of prey, and foxes all can inhabit these forests. Migratory birds are also known to come to these forests.

Forests Rain Forests and Jungles

Rain Forests Climate Rain forests are located in the tropical zone. The tropical zone gets direct sunlight almost all year and maintains a temperature of about 25oC. Precipitation falls as rain except for the tops of the high mountains. Precipitation ranges from 200 to 450 cm each year. Climate is NOT a limiting factor for growth, as in other land biomes.

Rain Forests Rain Forests are the most diverse land biome. It is a biome that has a dense canopy of evergreen, broadleaf trees supported by at least 200cm of rain each year. Rain Forests contain 70% of all land species on Earth. They only cover 6% of the Earth’s surface.

Rain Forests Structure Trees are the basis of the rain forest. The tree tops form the canopy, which captures 99% of the light that falls on the forest. The remaining 1% supports the lower levels of vegetation. There is not much vegetation on the forest floor due to the lack of sunlight that reaches the lower levels.

Rain Forests Structure cont. Any organic matter on the forest floor is quickly decomposed and recycled. Warm and wet conditions are ideal for decomposers Nutrients are quickly absorbed by the trees. The topsoil is thin and poor. As a result, tree roots are shallow and trees are supported by buttresses, ridges of wood at the tree base.

Rain Forests Animals Many animals in the rain forest are arboreal, or tree- dwelling, who live their whole lives without touching the ground. The enormous diversity of plants leads to enormous diversity of animals. Each animal is adapted to specialized niche provided by the various plants.

Rain Forests Niches vary not only in type of plants available, but also in the levels within the forest. The levels of the rain forest are the understory, lower canopy, upper canopy, and emergent trees. Food webs in the rain forest are complex, with many species that are specially adapted to their environment. Diversity of organisms is enormous in the rain forest. Scientists estimate over 50 MILLION species of insects alone exist in the rain forests.

Aquatic Biomes Water

Aquatic Biomes Water covers more than 70% of Earth’s surface. Aquatic biomes are not grouped geographically like terrestrial biomes are, and it is difficult to show them on a map. For aquatic biomes there are four important characteristics between the different types of biome. Dissolved salts Depth of water Rate of flow of water Dissolved oxygen

Aquatic Biomes Fresh Water

Freshwater Biomes There are two major categories of freshwater biomes: standing water and flowing water. Standing Water Ecosystems Lake- deepest type of standing water; light may not reach the bottom Pond – light reaches the bottom; created by rainfall and may be seasonal

Freshwater Biomes Standing Water Ecosystems cont. Marsh – very shallow water with land occasionally exposed; water often lacks oxygen Florida Everglades is the largest freshwater marsh in the US Swamp – land is soaked with water as a result of poor drainage; usually found along streambeds and flat land Mangrove swamps are salt water and found along the coast Bog – inland wetland with little inflow or outflow of water; soil is acidic and plants decompose slowly

Freshwater Biomes Flowing Water Ecosystems Rivers, streams, creeks, brooks, etc. are all names used to describe flowing water. Scientists call ALL flowing water ecosystems streams.

Aquatic Biomes Salt Water

Saltwater Biomes The world ocean can be divided into many different ecosystems. Neritic zone, benthic zone, intertidal zone, oceanic zone, etc. are all subdivisions of the ocean with different forms of life. Reefs are special subdivisions of the neritic zone. A reef is a natural structure built on a continental shelf. Reefs are found in warm, tropical waters. Reefs are the “rain forest of the ocean”.

Saltwater Biomes Estuaries – a region where a freshwater source meets the salt water of the ocean Water is brackish (between fresh and salt) and the salinity varies over time. Estuaries are used by many species as a place to spawn or reproduce. Estuaries function as buffer zones, filtering sediments and pollutants from the water