* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Lesson 8 Ecosystems
Survey
Document related concepts
Biogeography wikipedia , lookup
Ecological resilience wikipedia , lookup
Pleistocene Park wikipedia , lookup
Ecosystem services wikipedia , lookup
Biological Dynamics of Forest Fragments Project wikipedia , lookup
Triclocarban wikipedia , lookup
River ecosystem wikipedia , lookup
Tropical rainforest wikipedia , lookup
Sustainable agriculture wikipedia , lookup
History of wildlife tracking technology wikipedia , lookup
Theoretical ecology wikipedia , lookup
Renewable resource wikipedia , lookup
Lake ecosystem wikipedia , lookup
Transcript
Ecosystems The organization of the biosphere, from the broadest level of organization to the most specific level of organization, is shown below: biosphere → biome → ecosystem → community → population → organism Biosphere The biosphere includes any part of the Earth where organisms live. It extends from the crust of the Earth to the atmosphere. All of the ecosystems on the Earth are included within the biosphere. All of the ecosystems on Earth are part of the biosphere. The biosphere is the broadest level of ecological study. It includes interactions between different ecosystems that can only be studied by viewing the entire Earth as one large system. The lithosphere, hydrosphere, and atmosphere are all part of the biosphere. Biome A biome is a geographic region that has a distinct climate. A biome is made up of separate (but similar) ecosystems, so it contains characteristic types of plants and animals adapted to the region and its climate. Deserts, grasslands, and rainforests are all examples of biomes. Ecosystem An ecosystem is made up of the biotic, or living, community and its abiotic, or nonliving, environment. Abiotic factors include rocks, air, dirt, sunlight and water. An example of an ecosystem would include all of the living and nonliving factors that are inside a pond. The water in the pond, the algae and plants that grow in the water, the animals and bacteria that live in the water, the dirt and rocks on the bottom of the pond, and the sunlight that hits the water would all be considered a part of this ecosystem. All of the living and nonliving factors of this coral reef are part of the coral reef ecosystem. Ecosystems can vary greatly in size and conditions. The abiotic factors that make up an ecosystem determine what kinds of plants and animals that can live there. For example, a desert ecosystem that is very hot and does not receive much water can only support certain kinds of organisms, such as cacti and lizards. Community A community includes all of the populations that live and interact in the same area. An example of a community is all of the plants and animals inside of a forest. All of these organisms interact and depend on one another for survival. A community makes up an ecosystem's living, or biotic, portion. All of the plants and animals in this forest belong to the same community. At the community level, interactions between organisms can be observed. For example, predator/prey and consumer/producer interactions occur at this level. Competition and cooperation between different species are also part of community ecology. Population A population is a group of individuals of the same species living in the same area at the same time. An example of a population of organisms is a grove of orange trees. All of the orange trees in this grove belong to the same population. Populations can be defined at different levels of size. For example, a local population could occupy a very small habitat, such as a puddle. A population could also include every member of a species of monkey that occupies a large island. There is generally a boundary between populations of the same species, such as an ocean or an area of land that the animals do not freely cross. Changes in Ecosystems The survival of organisms depends greatly on physical factors in their environment. Any changes to either the biotic or abiotic factors can impact an ecosystem. Some changes that might appear to be minor could have a large effect. For example, minor changes in the pH of a body of water can cause massive fish kills. But not all changes are negative, some could be positive. By simply moving through the soil, worms are able to help break up the soil and add air. This improves the quality of soil, which plants benefit from. Changes in an environment also have ongoing effects. For example, if some or all of the plants in an ecosystem were to die, the animals that feed on the plants would have less food, so fewer of the animals would survive. As the population of these primary consumers becomes smaller, secondary consumers would begin to compete with each other more for food, and this population would also begin to shrink. Biotic & Abiotic Factors Factors which can affect change in a population or species are usually divided into two types: abiotic and biotic. Abiotic refers to the nonliving environmental factors, while biotic refers to the influence or effect created by a living organism. Both abiotic and biotic factors can limit or enhance a population’s success in a particular environment. Biotic Factors The word biotic comes from the Greek word for "life". Biotic factors include not only living organisms but also factors from formerly living organisms. Biotic factors include both living things and things that were once living. This means that the cotton plant and a cotton shirt are both considered biotic. For example, both a cotton plant and a cotton t-shirt would be considered biotic factors because they are derived from the same living organism. Biotic factors typically influence the viability of a community and include interactions between members of the same species and members of different species. Abiotic Factors Abiotic factors include any nonliving geological, geographical and climatological factors. Specific abiotic factors are water, air, soil, light, temperature, and natural disasters. These things are a part of each species’ ecological niche because they influence how populations affect, and are affected by, resources and enemies. Abiotic factors shown here include air, water, light, soil, and even the forest fire. Biomes The term biome refers to a geographic region that has a distinct climate. A biome contains characteristic types of plants and animals adapted to the region and its climate. Characteristics of Biomes The climate of a location determines which types of organisms are able to live there. Climates that are very cold are home to plants and animals that have adapted to the extreme temperatures. The same is true for climates that are extremely hot and dry. The major biomes on Earth include: tropical rainforest, temperate rainforest, desert, grassland, deciduous forest, coniferous forest, tundra, estuary, savanna, and taiga. Tropical Rainforest The climate of a tropical rainforest is hot and wet. Heavy rainfall (around 150 cm per year) and year-round warm temperatures make it very humid. This climate is found near the equator. A tropical rainforest is very dense with lots of large trees that block out sunlight. Very little sunlight reaches the rainforest floor. Tropical rainforests are very hot and wet. Temperate Rainforest The climate of a temperate rainforest is mild and wet. Temperatures are moderate and change with the seasons. Rainfall amounts are very high. Like tropical rainforests, temperate rainforests have a thick canopy of trees that block most sunlight from hitting the forest floor. However, while tropical rainforest canopies are generally broadleaf trees, temperate rainforest canopies may be broadleaf or coniferous trees. Temperate rainforests commonly have coniferous canopies, with smaller broadleaf plants in the understory. Image courtesy of NPS. Temperate rainforests are farther from the equator than tropical rainforests and can be found in the U.S. Pacific Northwest, Asia, South America, Europe, and Australia. Desert The climate of tropical deserts is generally hot and dry. However, temperate deserts, such as the Gobi in Asia, are much cooler. The amount of precipitation in all deserts is less than the amount of water that could potentially evaporate. Deserts get less than 25 centimeters of rain every year. Desert plants and animals are adapted to store water and withstand year-round hot temperatures. Deserts are very dry and generally hot. Succulents, snakes, scorpions, and mice are examples of organisms that live in desert ecosystems. Temperate Grasslands Temperate grasslands are located in the dry temperate interiors of continents. In North America, they are called prairies, in Asia they are referred to as steppes, and in South America they are pampas. Temperate grasslands receive enough rainfall to support grasses, but not enough to support the growth of large trees. The temperatures are generally warm in the summer and cold in the winter. Drought and wildfires are also common in this biome. The temperate grassland is characterized by thick, mixed grasses. Prairies are often converted into farmland due to the rich soils found there. Some of the animals that can be found in this ecosystem include grasshoppers, prairie dogs, and bison. Deciduous Forest The climate of a deciduous forest is temperate with four distinct seasons (spring, summer, fall, and winter). Deciduous forests have warm summers and cold winters. They have moderate precipitation throughout the year. Deciduous forests have four distinct seasons. During winter months, however, the precipitation is usually frozen and unavailable to the organisms that live there. Trees in a deciduous forest usually lose their leaves during the winter and have thick bark to conserve water and protect them from the cold. Taiga The taiga, known also as a boreal forest, is the largest continental biome. It experiences long, cold winters; short, warm summers; and low precipitation. It is characterized by coniferous forests. Taiga covers most of Canada and Siberia and is not found in the Southern Hemisphere. The taiga is characterized by coniferous forests; long, cold winters; short, warm summers; and low precipitation. Arctic foxes, wolves, and snowy owls are a few examples of the animals that live in the taiga. Tundra The tundra has very low temperatures and very little precipitation. Winters in the tundra are long and extremely cold; summers are short, mild, and cool. The animals living in tundra ecosystems have adaptations that allow them to stay warm in the very low temperatures. For instance, Arctic foxes, grizzly bears, and ermines (a kind of weasel) all have thick fur that protects them from the cold. The tundra is very cold and dry. Tundra is characterized by its frozen subsoil, which makes only a small layer of soil available to plant life. This limits the plants that can grow to small low growing plants such as mosses and grasses and makes it impossible for trees to grow. Estuary An estuary is an area in which fresh water and salty ocean waters mix together. These areas may include bays, mouths of rivers, salt marshes, and lagoons. These brackish (salt mixed with fresh) water ecosystems shelter and feed marine life, birds, and other wildlife with nutrients from the ocean. Estuaries provide a place where young animals can grow up. The plants in estuaries are marsh grasses and other plants that are adapted to water levels that change with the tides. Muskrats, herons, egrets, shrimp, and crabs are animals often found in estuaries. Savanna A savanna is a dry tropical grassland where trees are present but more widely scattered than in forest ecosystems. The savanna climate has a temperature range of 68° to 86°F. Savannas receive around 125 centimeters of rain every year, with most of the rain falling during the summer. Because of the vast differences in precipitation, the summer is referred to as the "wet season," and the winter is the "dry season." The trees in a savanna are very sparse and spread out. Zebras, giraffes, lions, and acacia trees are found in the savannas of Africa. Ecosystems - Trophic Levels The organization of communities is based on the use of energy from the Sun within a given ecosystem. Organisms within a community are dependent on the survival of the other organisms because energy is passed from one organism to another. The Sun's energy cycles through ecosystems from producers through consumers and back into the nutrient pool through decomposers. A trophic level describes the feeding level of an organism. Producer, decomposer, primary consumer, secondary consumer, and tertiary consumer are all trophic levels that can be used to describe an organism's place in an ecosystem. Producers Producers are organisms that are able to synthesize food molecules from inorganic compounds. Green plants, such as sunflowers, are producers because they can make their own food using energy from the Sun during a process called photosynthesis. Other producers include algae and some kinds of bacteria and protists. All other organisms in an ecosystem depend on producers for energy. Consumers Consumers are organisms that get energy by feeding on producers (e.g., plants) or other consumers. There are three main kinds of consumers: primary consumers, secondary consumers, and tertiary consumers. The classification given to a consumer depends on where it is located in a food chain. Primary consumers are animals that eat producers. Primary consumers are also called herbivores because they eat only plants. A deer that eats only leaves and grass is a primary consumer and an herbivore. Secondary consumers are organisms that eat primary consumers. Secondary consumers can be carnivores if they eat only animals. Or, they can be omnivores if they eat both animals and plants. A wolf that kills and eats a deer is a secondary consumer and a carnivore. Consumers eat other organisms. Deer are primary consumers. Wolves are secondary consumers. Tertiary consumers eat secondary consumers, and they may be carnivores or omnivores. A bear that eats a fish that has fed on other fish is a tertiary consumer. Since the bear also eats berries and other plants, it is an omnivore. Decomposers Decomposers are organisms that consume dead organisms. As they break down dead organic matter, decomposers release nutrients back into the soil, water, and atmosphere. The role that decomposers play in an ecosystem is crucial. Decomposers are important for the carbon, nitrogen, phosphorus, and oxygen cycles. The nutrients that decomposers release into the soil are also used by producers to make complex organic molecules. Fungi, such as mushrooms, are examples of decomposers. Some kinds of bacteria are also decomposers. The Flow of Energy Through an Ecosystem The ultimate source of energy for all ecosystems is the Sun. Only producers can convert solar energy into food energy. Therefore, all other organisms depend on producers for their energy needs. Food Chains A food chain describes the feeding relationships and energy flow between species within an ecosystem. Producers receive energy from the Sun and make food. Producers are the beginning of a food chain because all of the other organisms in the food chain depend on the food energy that is made by producers. The next organisms in the food chain are primary consumers, which eat producers. Next come secondary consumers, then tertiary consumers, and so forth until the top carnivore is reached. All organisms in the food chain are decomposed by decomposers. This food chain shows the flow of energy from a producer, algae, to the consumers in the ecosystem. Minnows are primary consumers, salmon are secondary consumers, and bears are tertiary consumers. The arrows in a food chain or a food web represent the direction of energy flow. The arrow points from the organism that is being consumed to the organism that is receiving energy. For example, in the food chain above, the arrow points from the algae to the minnow. This means that the minnow is consuming the algae and receiving energy. Food Webs A food web is a group of interconnected food chains. Organisms within a food web can belong to more than one trophic level, or feeding level. For example, in the food web below, krill are both primary and secondary consumers. Krill are primary consumers because they eat phytoplankton, which are producers. Krill are also secondary consumers because they eat carnivorous zooplankton, which are primary consumers. An Antarctic food web is shown in the picture above. Organisms in food webs can belong to more than one feeding level. Energy Pyramid An energy pyramid is a diagram that shows the relative amounts of energy located within each trophic level. The trophic levels are stacked one on top of another, with the producers on the bottom. Each level in an energy pyramid has less energy available to it than the level below. Most of the stored energy in an ecosystem is in plants and other producers. This is because most of the energy in an energy pyramid is used or lost as heat energy as it moves up the pyramid. In fact, only about 10% of the energy produced at each level is available to the one above it. This is the reason that consumers in an ecosystem cannot outnumber producers and predators cannot outnumber prey. The size of each level of the energy pyramid is determined by the amount of energy stored in the organisms at that trophic level. An average of only 10% of the energy from the previous level moves to the next level. The rest is used up or lost as heat energy. Organism Interactions Organisms within an ecosystem interact with one another in many different ways. These interactions play an important role in the survival of the organisms and the function of the ecosystem. Organisms can affect one another directly, through a shared resource, or through common enemies. Some interactions are harmful to the organisms involved, whereas others provide benefits for one or both of the organisms. Energy Relationships Food chains and food webs describe the feeding relationships between species and represent the flow of energy through an ecosystem. The Sun provides energy to producers, such as plants. Producers convert this energy into a form that can be eaten by consumers. Animals that eat producers are then consumed by animals at higher trophic levels. Eventually all organisms are broken back down into nutrients by decomposers. The food chain above shows the flow of energy from a producer, a plant, to the consumers in the ecosystem. Decomposers may feed on organisms at any stage of the food chain. Decomposers recycle nutrients back into the ecosystem. Symbiosis Symbiosis is an interaction between individuals of different biological species. At least one of the organisms receives a benefit from the interaction. The other organism can either receive a benefit, be harmed, or not be affected in any way. A symbiotic interaction involves a close relationship between the two organisms involved. There are three main kinds of symbiotic relationships: commensalism, mutualism, and parasitism. Mutualism Bees receive nourishment from flowering plants, and plants are pollinated by the bees. Therefore, the relationship is mutualism. Both organisms benefit in a mutualistic relationship. Flowers and their pollinators are one of the most common examples of mutualism because many kinds of plants depend on insects, such as moths, bees, wasps, and beetles, to perform pollination in order to reproduce. Plants that rely on pollinators attract the pollinator by the shape, color, or smell of their flowers. As the pollinator feeds on the nectar or pollen from the flower, some of the pollen sticks to its legs and body. When the pollinator visits a second plant of the same species, the pollen from the first plant is transferred to the reproductive organs of the second plant, and pollination occurs. Both organisms receive a benefit from this interaction. The pollinator receives access to a food source and the plant is able to reproduce because of their relationship. Commensalism Cattle egrets follow behind large grazing herbivores and eat the insects that are stirred up. This is a form of commensalism. One organism benefits and the other is neither helped nor harmed in a commensalistic relationship. Often, the benefit that the organism receives is the ability to find food more easily or protection from other organisms. For example, large grazing herbivores, such as cattle and horses, often stir up insects as they graze on grass in fields and pastures. Birds known as cattle egrets often follow behind the grazing herbivores and eat the insects that have been displaced. Since the cattle egret benefits by being able to find food easily and the grazing herbivores are not affected by the presence of the egrets, their interaction is an example of commensalism. Parasitism This mosquito is receives nourishment, while the human is harmed. This is an example of parasitism. Image is courtesy of the CDC. One organism benefits and the other is harmed in a parasitic relationship. The organism that receives a benefit is known as a parasite. The organism that is harmed by the relationship is known as the host. The host species is usually impaired slowly over a long period of time. Parasites are usually smaller than the host species, but not always, and can live either inside the body of their host or externally. Common external parasites include fleas and mosquitoes which feed on the blood of their hosts. Internal parasites, such as tapeworms, live inside the body of their host and absorb nutrients from the host's body. In both cases, the parasite receives nutrients at the expense of the host and the host can no longer use these nutrients for its own life processes. Predation Predation is a type of interaction in which a predator hunts, kills, and eats its prey. Predators use the prey as a source of food. Predation is different from parasitism because the prey is killed immediately for consumption. During parasitism, the host is kept alive for a long period of time so that the parasite can continue to receive nutrients from the host. An example of predation is a wolf pack hunting, killing, and consuming a deer. Lions kill and eat zebra. Lions are predators. Zebras are prey. Competition Since there are limited amounts of resources in an ecosystem, if one organism gets a particular resource, another does not. This leads to competition as two organisms try to access the same resources. Food, water, sunlight, and space are examples of resources that organisms compete for. Plants and animals of the same species may compete for resources such as food, water, shelter, and space. Populations of different species will also compete with one other if their needs are the same as the needs of another population in that ecosystem. For example, trees in a forest compete for sunlight. As one tree grows taller, the shorter trees are shaded by it, and they receive less sunlight. The shorter trees may die as a result. The tall tree and the shorter trees in this picture are competing for sunlight. Cooperation Cooperation is a type of interaction in which organisms work together. Many species exhibit cooperative behavior, including horses, dolphins, lions, and ants. Animals that exhibit cooperative behavior often live, travel, and/or hunt in herds or groups. Living in these groups can provide protection for the animals and a higher success rate during hunts. Groups of organisms that live together cooperatively are usually part of a hierarchy of leadership. Some members of the group have a higher status than other members of the group. Dominant members determine what the group will do and subordinate members follow their lead. This helps to eliminate aggression between group members and allows the group to work together for the benefit of all. An example of an animal that lives in a cooperative group is the wolf. Wolves live in packs that usually include six or seven members. There are two leaders within the group, the alpha male and the alpha female, and these two pack members determine when the pack hunts, moves location, or stays in an area. The leaders of the pack are usually the pack members with the most experience in hunting and defending territory. The other pack members have roles within this pack to help the pack work effectively.