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Organisms and Their Environment Biology 2009 Environment and Ecology Everything that surrounds a living thing makes up its environment. Living things are affected by their environments, and also have an impact on their environments. The study of the interaction between organisms and their environment is called ecology. Ecosystem An ecosystem is composed of all living and nonliving things in a particular location. Examples: Forest Pond Meadow Any place where living things interact with the nonliving environment. Biotic Factors The living things are called biotic factors (bio = living) Examples: Microorganisms Plants Animals Abiotic Factors The nonliving things are called abiotic factors. Examples: Climate Soil Rocks Wind Rain Species A biological species is a group of organisms having a genetic makeup that is similar enough that they can mate and produce fertile offspring. Populations A population is made up of all members of a particular species living in a particular area at the same time. Example: All of the deer living on Kennesaw Mountain Another Example: All the ducks of a certain species living in a pond would be a population. Within that population, individual ducks may vary in many traits, such as size. However, most members of the duck population could be described by an average size. Community All of the populations living in the same area make up a community. It includes all the different kinds of living things, which all live together. Example: The frogs, lizards, birds, ducks, spiders, mosquitoes, flies, etc., that live in your backyard. Habitat A habitat is the physical surroundings, or the place, in which an organism lives. Niche A niche includes all aspects of an animal’s lifestyle, especially its feeding patterns. A niche also refers to the job or role that each organism has in the community/ Animals that live in the same place, but do not feed in the same way, do not fill the same niche and do not compete with each other. Biosphere The biosphere is the part of the Earth where life exists. It consists of the thin envelope around the Earth made up of atmosphere, land and water. The biosphere has elements that are constantly used and reused in the ecosystems. The Elements The elements used and reused in the biosphere are Carbon, Hydrogen, Oxygen and Nitrogen. They are provided in cycles so they can be used and then reformed to keep the elements constant in our environment. Water Cycle The water cycle provides water which is necessary for organisms to live. Water evaporates from the surface of Earth, whether from water sources or moist land. As much as 2/3 of all precipitation evaporates into the atmosphere. Water vapor condenses and clouds form. Precipitation in the form of snow, ice, or rain falls to the Earth. Eventually that precipitation will again evaporate. Water Cycle Nitrogen Cycle The nitrogen cycle is needed to supply amino acids which are the building blocks of proteins. Nitrogen gas is 80% of our atmosphere. Some organisms can only use nitrogen in the form of ammonia. When nitrogen in the air is converted to ammonia it is called Nitrogen Fixation. Some bacteria convert nitrogen on plant roots so that nitrogen is eaten in the plant and the consumers use it to make protein. Nitrogen is also found in our waste products and in decaying matter. When organisms die, decomposers return nitrogen to the soil. Nitrogen Cycle Carbon Cycle The carbon cycle provides carbon, an element present in every living organism. Carbon is in our atmosphere in the form of carbon dioxide. In organisms carbon dioxide is breathed out in respiration and is released in the decomposition of matter. Plants use carbon dioxide in photosynthesis and make sugars and oxygen. Carbon Cycle Biomes of North America Biomes are parts of the biosphere characterized by large regions that can be identified by the types of plants and animals that live there. Biomes: Tundra Desert Grassland Tropical Rain Forest Temperate (Deciduous) Forest Taiga (Coniferous Forest) Biomes A number of climatic factors interact in creating a biome. Temperature Precipitation Length of growing season Tundra Regions – Arctic/Antarctic areas Plant life – grass and wildflowers Animal life – reindeer, caribou Description – thin soil, permafrost Taiga Regions – Northern forests Plant life – Conifers Animal life – Wolves, rabbits, elk Description – Long, cold winters Deciduous Forest Regions – NE/mideastern US; Western Europe Plant life – Deciduous trees Animal life – deer, birds, small animals, bears Description – Avg. precipitation, warm summers, cold winters Grassland Regions – Mid-western US; Eurasia, Africa Plant life – Grasses Animal life – Prairie dogs, ferrets, snakes Description – Hot summers, cold winters, rainfall unpredictable Desert Regions – Western US; N. and SW Africa Plant life – Cacti, succulents Animal life – Jackrabbits, lizards, rats Description – Arid; extreme daily temperatures Tropical Rainforest Regions – Central America, Central Africa, SE Asia Plant life – Diverse plants Animal life – monkeys, leopards Description – High rainfall and temperature Changes in Populations Ecological Succession Populations of species found in certain habitats change over time. This concept, called ecological succession or environmental variation. Primary Succession Primary succession consists of a sequence of communities developing in a newly exposed habitat devoid of life. Examples: Succession on a bare rock Newly deposited sand New land from cooled lava Secondary Succession Secondary succession consists of communities taking place on sites that have already supported life. Examples: Old field succession Clearcut forests Burned areas **Difference between primary and secondary succession is that secondary starts with soil. Pioneer Community The original plant forms that colonize an area are called the pioneer community. These must be a strong group, able to withstand the forces of mother nature. **Bare rock would be an unwelcome habitat for most plants, but lichens are up to the challenge. Blown there by the wind, lichens attach to the rock and begin the process of breaking it down as it carries on its life functions. As soil accumulates, a bare field forms. This eventually becomes the home of grasses and flowers. The Progression 1. Rock 2. Lichen 3. Soil 4. Grasses 8. Hardwood Forest 5. Flowers 7. Pine Forest 6. Shrubs Climax Community A hardwood forest of trees like oak, beech, and maple trees, grows in the final stage of development. This final stage is called the climax community. The climax community does not change much, as long as no disasters strike, like wild fires, tornadoes, or humans needing a parking lot! Animals The animals that live in the habitat change as the plants change. Small animals like mice and rabbits, prefer the open field. More Animals Deer and bear prefer the cover of wooded environments. Ponds Pioneer communities may sometimes be ponds that develop underwater plants, then cattails. As the pond fills with sediment, grasses may begin to grow and over many years, the succession eventually results in a deciduous forest for that area. Succession vs. Evolution **Ecological succession should not be confused with evolution. Succession involves organisms moving into and out of an area over a period of time as a result of environmental change. Evolution involves changes in genetic makeup of a species over generations, which may adapt the animal to a particular environment. Survival of the Fittest One of the basic concepts of evolution is that organisms compete for the available resources in their environments: food, shelter, or mates. Organisms that are more fit will be able to win this competition. An animal that outperforms others, such as running faster, locating food better, or surviving more fights, will be more likely to reach maturity and eventually produce offspring. These traits will then be passed on to succeeding generations. This is known as survival of the fittest. Geographic Isolation Changes in population can also result from geographic isolation. Geographic isolation occurs when a population becomes separated by changes in the environment. In order for a species to exist in a changing environment, members must adapt in order to survive and reproduce. If this does not occur, the species will become extinct. Responses and Behavior One very important life function is that of response. Response characteristics of cells enable organisms to react to stimuli in their environment. A group of complex responses is called a behavior. A reflex is an involuntary response to environmental stimuli. An instinct is a genetically controlled behavior. Examples Reflex: A person’s eye blinks as an object flies past it. A dog sneezes when it inhales pepper. Instinct: Birds respond to changes in season by migrating. A bee develops into a drone. Tropism Tropisms are examples of responses to environmental change. A tropism is an involuntary response of an organism involving orientation toward or away from external stimuli. Geotropism Plants respond to gravity by sending roots “down.” It is called geotropism. Phototropism Phototropism adjusts plants exposure to light. Thigmotropism Thigmotropism is a plant’s response to touch. Adaptation Organisms which do not, or cannot respond to changes in the environment reduce their chances for surviving. This may mean death for the individual organism and, in extreme cases, extinction of the species if too many die before they are able to reproduce. Response to the environment is, therefore, closely related to adaptation. Adaptations Adaptations allow one kind of organism to live in conditions where other organisms cannot. Examples: A cactus has special adaptations which allow it to live in a dry, hot environment. Polar bears have adaptations which allow them to live in very cold environments. **The polar bear could not survive in the desert and the cactus could not live in the Arctic. Homeostasis All organisms must have life functions which work together to produce and maintain a stable internal environment. This is the principle of homeostasis. Adaptations are made to produce homeostasis. Adaptation Example Certain rabbits turn from brown to white in the winter so they can be camouflaged with the snow. Since rabbits with dark coats were more easily seen, they were more likely eaten. Gradually, the proportion of winter-white rabbits to winter-dark rabbits would increase until there were no dark rabbits left. **This is known as survival of the fittest. Human Example In areas where there is a higher incidence of malaria, there is also a higher incidence of sickle cell anemia. This is because the sickle shaped cells cannot be infected with malaria. Over time, the people in the area with sickle shaped red blood cells survived because they were not catching malaria and people with normally shaped red blood cells were dying. Food Chains and Food Webs Predator and Prey Relationships One important interaction in the ecosystem is between predators and their prey. Predators are organisms which hunt and feed on other organisms. The living things that are eaten are referred to as prey. **To maintain balance in the ecosystem, the interaction between predator and prey should not be disturbed. Example In parts of the South, one natural predator of the white-tailed deer, the mountain lion, has been reduced in number. Because there are fewer mountain lions to prey on the deer, the deer population in some regions has risen tremendously. Food Chain A food chain is the relationship of organisms that depend on each other for energy or food. It is a straight line relationship such as algae is food for fish which are food for squid which are food for sharks. Food Web A food web is more complex and is a food chain with the interrelated chain of organisms that depend on each other for food. If one organism is removed, other organisms may be endangered or possibly die out. Food Web Carrying Capacity Carrying capacity is the number of individuals in a population that the resources can support. This provides for a balanced ecosystem. Trophic Levels The living things in an ecosystem can be divided into four levels. Each step in a food chain or food web is called a trophic level. Producers are the first step. Consumers are the next steps. Each step depends on the step below it for food and to provide its energy. Producers Producers are the green plants and some bacteria and alga that are able to make their own food from water, the sun, carbon dioxide in the air, and minerals in the soil. **Remember when plants make their own food they use sunlight and it is called photosynthesis. Consumers Consumers are the animals that rely on other organisms for food. This group can be further divided into three groups: Primary consumers are herbivores, or plant eaters. Examples – certain insects, deer, or mice. Secondary consumers are carnivores, or flesh eaters. They feed on herbivores. Examples – snakes and coyotes Tertiary consumers can be carnivores or omnivores, which eat both plants and animals. Example – hawks and humans Scavengers Scavengers feed on dead organisms. They include earthworms, ants and vultures. Decomposers Decomposers are organisms that break down dead organic matter. This decomposition produces many of the raw materials that are used by the producers in photosynthesis. Decomposers include bacteria and fungi. Ecological Pyramids Ecological pyramids are diagrams that show each trophic level in a biome. There are three types: Energy pyramid Biomass pyramid Numbers pyramid Energy Pyramid Energy pyramid – the energy pyramid shows the transfer of energy from one level to the next. The bottom of the food chain shows the largest amount of energy which comes from the sun then as you move up energy is used but also lost in the form of heat energy. Energy Pyramid Biomass Pyramid Biomass pyramid – the biomass pyramid is based on the mass of organic material at each level. Numbers Pyramid Numbers pyramid – it shows the relative numbers of organic material at each level. 1 organism 10 organisms 100 organisms 1000 organisms