Unit 8: Ecology: Ecosystems and Communities

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1 Unit 8: Ecology: Ecosystems and Communities An ecosystem consists of all the plants and animals that interact with the nonliving things in an area. Biosphere = area on Earth where living things are found Biosphere is divided into biomes that have different types of plants, animals and climate conditions. Climate Matters! Weather is the day-to-day conditions in a particular time and place. Climate is the average year-to-year conditions of both temperature and precipitation. Climate determines the types of plant species that live in an area which then determines the types of animals that will live there! Our atmosphere acts like an insulating blanket to keep the temperature relatively stable in the biosphere. CO2, methane (CH4) and H 2O vapor trap heat energy to help maintain the temperature. This blanket keeps the Earth about 30ºC warmer than it would be without the atmosphere. Greenhouse Effect The gases in the atmosphere act like windows in a greenhouse: Biomes The temperature, amount of sunlight and precipitation determine the plants and animals that live in an area.

2 The more species that live in an area, the higher the biodiversity (or variation!) The higher the biodiversity, the healthier the ecosystem. Marine = high biodiversity Tropical Rainforest = high biodiversity Savannah = medium biodiversity Desert = low biodiversity Temperate Grassland = medium biodiversity Temperate Deciduous Forest = high biodiversity Coniferous Forest (Taiga) = medium biodiversity Tundra = low biodiversity Biotic and Abiotic Factors Biotic = all the living things in an ecosystem. ( plants, animals, fungi, decomposers ) Abiotic = all the nonliving things in an ecosystem. ( climate, precipitation, temperature, nutrients ) Habitats and Niches A habitat is the area where an organism lives. A niche is the role an organism plays in the ecosystem the physical and biological conditions in which an organism lives and how it uses those conditions. Producer = use the sun s energy to do photosynthesis and make their food. (Also called autotrophs...) Consumer = can t harness the sun s energy directly, so they must consume ( eat ) other organisms for food. (Also called heterotrophs...) Herbivores eat only plant material Carnivores eat only animal material Omnivores eat both plant and animal material Detritovores eat only dead matter Decomposers are the bacteria and fungi that break down dead material and return nutrients to the ecosystem! An organism s niche can include: Range of temperatures needed for survival Food the organism eats Reproductive cycle No two species can share the same niche in the same _habitat at the same time. Ever. Similar yes the SAME NO!!!

3 Levels of Organization Smallest unit is the individual. All the members of the same species in an area is called a population. All the populations living in an area is called a community. All the biotic and abiotic factors in an area is the ecosystem. Community Interactions: 1. Competition occurs when organisms of the same or different species attempt to use the same limited resources. ( food, water, space, shelter.) The more similar the organisms, the more competition between them and there is ALWAYS a winner and a loser. 2. Predation occurs when one organism catches and eats another for food. The predator eats the prey is eaten. **Generally the predator has adaptations to catch, while the prey species has adaptations to escape or hide!*** 3. Symbiosis is a relationship between 2 species that live closely together. Mutualism = both species benefit from the arrangement. Examples: Lichens, Ants and their aphid livestock, bees pollinating flowers. Commensalism = one species is helped and the other is neither helped nor harmed. Example: barnacles that ride on whales or clown fish and anemones. Parasitism = one species is helped while the other is harmed. Examples: fleas, ticks and lice. Population Dynamics Population Density = the number of individuals per unit area. Example: people per square mile

4 Population Growth = affected by birth and death rates, individuals entering or leaving population. If births are greater than deaths, population will grow. If births are equal to deaths, population is stable. If births are less than deaths, population will decrease. Immigration = organisms entering population Emigration = organisms leaving population Methods of Growth Exponential Growth: only found in populations with ideal conditions and unlimited resources. (**Not realistic.) When graphed, is called a J curve. Logistic Growth: a realistic model as resources become less available, growth slows or stops -- following a period of exponential growth. When graphed, is called an S _ curve. Population grows until it reaches a maximum number of individuals that can be supported by the available resources. The growth rate stops and the population will maintain this number -- called the carrying capacity. Carrying capacity may be exceeded temporarily -- but some will die from lack of resources -- so the total population will remain close to the carrying capacity.) A limiting factor causes population growth to decrease. Density-Dependent Factors: These become limiting only when population density reaches a certain level. Competition : for limited resources Predation : the predator / prey relationship maintains balance

5 Parasitism or disease : similar to predation, but the parasite depends on the host for survival. Density-Independent Factors: affect ALL populations, regardless of population size. Weather, natural disasters, seasonal cycles, human activities ( damming rivers, clear-cutting forests) Populations usually show a dramatic crash, but MAY eventually recover. Human Population Growth: Developed countries (like the U.S.) usually show slow growth patterns. But developing countries can have birth rates as high as 3 people/second!) Humans have almost an exponential growth curve, and we haven t hit our carrying capacity yet. It is estimated that by 2050, world population will reach 9 billion! Why so high? (*THINK*) Advances in medicine, agriculture and sanitation have allowed more people to survive and live longer. Humans CANNOT maintain this growth rate indefinitely -- even humans Demographics have a carrying capacity. Demographics is the scientific study of human populations. Scientists look at birth and death rates, as well as the age structure of the population. This information helps scientists make predictions about the growth of that population.

6 Growing quickly! Birth rates much _greater than death rates child-bearing population very large. Growing slowly Birth rates slightly greater than death rates. Little to no growth. Birth rates equal to death rates.