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Ch. 47 and 48 Ted-ed: Making sense of how life fits together Introduction: Video Habitat Game Ecology: the study of interactions of organisms with one another and their physical surroundings Biosphere The part of the Earth where life exists Includes: All the areas of land, air and water on the planet All the life that populates these Extent: From about 8 km above the Earth’s surface to 8 km below the ocean’s surface The distribution of life is not uniform: Few organisms live in the polar regions; many in tropics Ecosystems Consist of : an area’s physical features (abiotic factors) An area’s living organisms (biotic factors) Eg: A Pond Biotic factors Abiotic Factors Fish Water Frogs Sunlight Insects Rocks Worms elevation Snails Rainfall Amebas Temperature Waterlilies Humidity Ecosystem…. Community The organisms living together in an ecosystem Ecosystems are connected by: Living features (pond crayfish are eaten by forest raccoons Non living features (A river in the mountains meanders through forest and grassland on its journey to the sea) Ecological Succession Why do ecosystems change over time? Because every organism affects environmental conditions around it Video Eg: Trees - shade the area below their branches making it cooler and darker Due to these changes we see: Ecological succession – when an existing community of organisms is replaced by a different community over time. Time frame of succession? Can be only a few decades to thousands of years Succession can occur where no living community already exists Example: a volcanic island rising from the sea Pioneer Species Organisms that colonize areas that are devoid of life Lichens – pioneers on bare rock Produce acids that break down rocks Over the years, make a thin soil that supports mosses Mosses further change the soil allowing other plants to grow Changes make it possible for earlier species to continue living there Succession can occur where natural disasters or human activities wipe out existing communities Climax community A fairly stable collection of organisms described by the most obvious species present Determined partly by chance If something happens, it may return to the way it was, or may never be the same again Energy and Nutrients: Building the web of life Flow of Energy The ultimate source of energy is the sun ANIMATION Photosynthesis: Green plants and bacteria use sunlight to assemble carbon dioxide and water into carbohydrates Energy Flow cont… Producers: Photosynthetic organisms that make their own food Primary Consumers Organisms which get their food from producers… also known as herbivores Higher level consumer Organisms which get their food from lower organisms (aka. carnivore) Energy Flow through an Ecosystem Decomposers: Video Organisms that obtain food from non-living organic matter eg: bacteria and fungi Trophic Levels Trophic= food At each higher trophic level, less and less of the original energy is available Energy is used to: Maintain metabolism Power daily activities What is left is changed into new animal biomass About 10% of the energy at one level can be used by animals at the next Ecological Pyramids Show the energy relationships among trophic levels Pyramid of: Shows: Energy Total energy at each level Biomass Total mass of living tissue at each level Numbers Total number of organisms at each level (not species) Population Growth Introduction: A population (def’n): a group of organisms that belong to the same species and live in a given area Exponential Growth! (A baby boom) Given ideal conditions, almost any organism will experience a rapid increase in population The larger it gets, the faster it grows This pattern is called exponential growth curve This doesn’t continue in natural populations for long Sketch an exponential growth curve Logistic Growth: A Step closer to realty Most populations go through a number of phases of growth Sketch and label a logistic growth curve Populations: Grow when the birth rate is greater than the death rate. Growth may slow because: The birth rate slows down The death rate speeds up Both Zero growth occurs when birth rate = death rate; this is also called steady state. Steady state is not really steady because the population rises and falls but it averages out at a certain size This problem represents the carrying capacity of an of an environment for that species Factors that block further growth include: Lack of food Overcrowding Competition among individuals 48.2 Factors that control population growth Density Dependent Limiting Factors Population limiting factors that operate on large populations Occur when a population is large and crowded Competition Predation Parasitism Crowding and stress Competiton: The struggle for food water, space and other life essentials Battle at Kruger Predation: Prey evolve defenses such as: poisons, camouflage, shells Predators evolve: Resistance to poisons Stronger teeth Stronger digestion Keener eyesight As their populations cycle together, As prey population grows, it supports a larger predator population As predators become more numerous, they eat more prey increasing the prey death Predators begin to starve Prey survive better and begin to reproduce more The cycle begins again Animation Without a predator to keep numbers down, introduced animals can quickly become serious pests! Parasitism TED-Ed Parasites Parasites live off their hosts weakening them Crowding helps parasites travel from one host to another Crowding and Stress Space is needed for: Hunting Nesting Territory Many species will fight amongst themselves if overcrowded Stress due to over-crowding can cause hormonal changes in organisms Density Independent Limiting Factors Natural occurrences such as storms and weather changes These can cause a population to boom and bust regardless of its size at the time 48-3 Interactions within and between communities Community: all the populations of organisms lving in a certain area Populations within communities interact with one another in many ways Example within the same species: Plant competition for water (intraspecies) Example between different species: predator compete for prey (interspecific) Symbiosis Video Relationships between organisms Parasitism – one species harmed while the other benefits Eg: disease causing bacteria The bacteria reproduce in the human’s body making the individual sick Commensalism One organism benefits and the other is unharmed Eg: Shrimp live in the tentacles of anemones Shrimp are protected from possible predators Mutualism When both species benefit from a relationship Eg: sea anemones and clownfish Describe the relationship: Clownfish have the same benefit as the shrimp, but also chase away fish who are able to eat the anemone (because they are territorial) Interactions among ecosystems All ecosystems are connected, either directly or indirectly, with other ecosystems Example of a Direct Ecosystem connection: A pond in the woods requires water from the forest, shares organisms with other ecosystems etc… 2. Example of an indirect ecosystem connection: A nitrogen atom from fertilizer may interact with several ecosystems and their communities as it goes through the nitrogen cycle 1. Wind, rivers and ocean currents tie the Earth’s ecosystems together. Invasive Species Also called “Exotic”, “Alien” or “Introduced” Species These are species, through human meddling, have been brought to new habitats The consequences can be negative, inconsequential and even positive (Similar to Symbiosis!). Overview: California Academy of Sciences Video Ted-Ed Video