1. 6th Grade Science Unit 3: Interdependence

2. Bellringer In your own words, what is a Biome? July 22, 2012
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3. What is a biome?
A biome is a region with a distinct climate and set of organisms. Biomes are the world’s major communities. They are classified by climate, resources, and the types of organisms that live there. The two main groups of biomes are terrestrial biomes (land) and aquatic biomes (water).
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4. Terrestrial Biomes (Land Biomes): Grassland
There are 6 terrestrial biomes.
1. Grassland: There is far more grass on the land than trees or shrubs. These are also called prairies in the United States. African grasslands are called savannas. Grasslands have hot summers and cold winters. In spring and summer, the land is covered with grasses and small plants. Grasslands get a moderate amount of rain and have rich soil. They are good places to grow crops. Animals include bison, prairie dogs, and mice. African grasslands are home to lions, giraffes, elephants, and zebras.
Examples of Interdependencies: Bison eat large amounts of grasses. Their waste is broke down by decomposers, which fertilize the soil. Lions hunt zebras which also eat the grasses.
African Savanna
United States Prairie
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5. Terrestrial Biomes (Land Biomes) Tundra
2. Tundra: This biome is cold and dry with few plants. Almost no trees grow in the tundra. Tundra biomes are found in northern parts of North America, Europe, and Asia. Part of the soil is frozen throughout the year. This layer of frozen soil is called permafrost. The land is mostly covered with mosses and, in the summer, grasses. Animals include wolves, caribou, and polar bears. Some birds breed in the tundra during the summer and migrate south for the winter.
Examples of interdependencies: Birds depend on grasses for food and nesting. Caribou and artic hares feed on grasses and low growing shrubs. Wolves, which are predators, hunt in groups for young, weak, or straying caribou.
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6. Terrestrial Biomes (Land Biomes): Desert
3. Desert: Deserts receive less than 50 cm (19.7 inches) of rain per year. As a result, few plants grow in the desert. Some plants do grow there, such as cactuses, but they need little water to survive. Deserts cover about 1/5 of the Earth’s land surface. Most deserts are hot during the day and cold at night. There are some cold deserts near the Arctic. Desert animals include lizards, scorpions, insects, hawks, and jackrabbits.
Examples of Interdependencies: A bird called a cactus wren nests in a certain kind of cactus. The spines of the cactus protect their young, which could be eaten by predatory birds such as ravens. Rattlesnakes compete with hawks for preying on desert rats.
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7. Terrestrial Biomes (Land Biomes): Rain Forest
4. Rain Forest: Rain forests get cm ( inches) of rain each year. Most rainforests are on or near the earth’s equator. In tropical rain forests, tall trees form a thick canopy of broad leaves. Tropic rain forests hold more of a variety of living things than all the rest of the Earth’s terrestrial biomes combined! Up to 75% of all the Earth’s land species live in rain forests. Animals include a wide variety of snakes, insects, lizards, colorful birds, monkeys, and apes.
Examples of interdependences: To reach sunlight, flowering plants grow high on the trunks of trees. Insects and birds feed on the flowers. Funguses feed on the remains of plant and animal life upon the forest floor. Mice, frogs, and insects eat leaves and plants that fall to the forest floor.
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8. Terrestrial Biomes(Land Biomes): Deciduous Forest
5. Deciduous Forest: This biome gets a moderate amount of precipitation. Deciduous forests are generally not too cold in winter or too hot in summer. Their main characteristic is trees that lose their leaves in the fall. This is what the word deciduous means. These trees include birch, beech, maple, oak, hickory, elm, and willow. This biome is found on almost every continent. Temperate deciduous forests cover much of Tennessee. (Temperate means the trees go through 4 distinct seasons.)
Examples of Interdependencies: The trees of the forest provide nesting places for a wide variety of birds. Elm trees can absorb water through their leaves as well as their roots. Then they lose their leaves in the fall, which helps them store water through the winter. Fish in streams and berry bushes provide food for bears.
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9. Terrestrial Biomes (Land Biomes): Coniferous Forest
6. Coniferous Forest: This biome is known for its cold winters and mild summers. It also gets a moderate amount of rainfall. In coniferous forests, snow usually covers the ground during the long winters. Coniferous forests are found in lowlands as well as high up the slopes of mountains. The name of this biome refers to the cone-bearing trees that live there. These trees, which have needle- shaped leaves, include pine, fir, hemlock, and spruce. Animals in this biome include moose, elk, lynx, mice, bears, and wolves.
Examples of Interdependencies: As in all forests, trees provide fairly safe nesting places for birds. Predators such as the lynx and the wolf hunt small mammals and sometimes will hunt the sick young of larger animals.
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10. Aquatic Biomes (Water Biomes)
Aquatic biomes are divided into two main parts: freshwater biomes and marine biomes.
Freshwater Biomes include lakes, freshwater parts of rivers, streams brooks, swamps, and ponds.
Marine Biomes make up all the Earth’s large bodies of salt water. These areas are oceans, coral reefs, and estuaries.
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11. Aquatic Biomes (Water Biomes): Marine and Freshwater
7. The marine biome is divided among oceans, coral reefs, and estuaries. Marine biomes cover nearly 75% of the earth’s service.
*Estuaries are places where freshwater and saltwater mix; for example: bays, harbors, lagoons.
*Examples of marine interdependencies: The largest animals on Earth, blue whales, feed on millions of tiny shrimplike krill. The krill eat algae. Seaweed in shallow water make good hiding places for small fish. The seaweed is also food for turtles. In coral reefs, algae perform photosynthesis and help attract and provide food for coral.
8. The freshwater biome is divided into rivers and streams, lakes and ponds, and wetlands.
*Examples of freshwater interdependencies: Fish feed on water plants. Wading birds such as herons feed on the fish. Fish such as catfish and carp live in the muddier areas of rivers and streams. This provides food for bears that live near the river’s edge.
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12. Parts of the Biosphere
Biosphere: The living world and all biotic and abiotic
factors within it.
Biome: contains many ecosystems. Biomes are large
areas with similar biotic and abiotic factors.
Ecosystem: the interactions among living things
within a biome.
Community: populations that interact with one
another. Example: rabbits, hawks, certain plants.
There are many communities within one biome.
Population: a group of organisms that mate with
one another and live in the same place at the same
time. There are many populations within a biome.
Individual: One animal from a population.
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13. Now that you know about biomes and food chains…
Sometimes organisms living in the wild do not have enough food or living space. For example, the Gila woodpecker makes its nest by drilling a hole in a saguaro cactus. Sometimes Gila woodpeckers have to compete with each other for these living spaces.
Competition occurs when two or more organisms are looking for the same resource at the same time.
Competition can limit the size of a population. For example, if enough living spaces are not available, some organisms will not be able to raise their young. If there is not enough food, organisms might not live long enough to reproduce. Competition for living space, food, and other resources can limit population growth.
In nature, the most intense competition occurs among individuals of the same species. Why do you think this is?
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14. Limiting Factors
Limiting Factors are anything that restricts the number of individuals in a population. These can be food, water, space, and other resources. Limiting factors are what causes competition among populations.
A limiting factor can affect more than one population.
For example, when the plants in a meadow do not get enough rain, fewer plants survive. Because there are fewer plants, fewer seeds are produced. These seeds are a source of food for seed-eating mice in the meadow. The smaller food supply could become a limiting factor for mice. In turn, a smaller mouse population could be a limiting factor for hawks and owls that eat the mice.
How does this relate to your knowledge of food chains and food webs?
What is the limiting factor in this image?
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