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Published byKamryn Widdison Modified over 9 years ago
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2.D: Growth and dynamic homeostasis are influenced by changes in the environment
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Organisms Respond to External Events I.e. taxis or kinesis – Many animals change speed based on light (pillbugs run wild when exposed to light) – Many animals change direction in response to stimuli (sharks swim towards blood) Plants grow towards light (phototropism)
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Biotic vs. Abiotic Factors Biotic = Living Animals Plants Fungi Bacteria/ Archaeans Abiotic = Non-living Sunlight Water Vitamins/ Minerals/ Nutrients Temperature
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Cells Are Affected by Both Biotic/Abiotic Factors i.e. bacterial cells attach to each other to form biofilms Cells shrink/grow depending on water availability Cells stop growing after a certain density (except in the case of cancers)
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Organisms Interact with Biotic/Abiotic Factors Organisms access to nutrients is affected by other factors i.e. symbiosis, predator-prey, nutrient availability etc
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Symbiosis-Two species living together Mutualism-both benefit Commensalism- one benefits, other unaffected Parasitism- one benefits at other’s expense "live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance".
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Abiotic Effects on Growth Better nutrition Taller individuals More sunlight More plant growth
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Evolution of Homeostatic Mechanisms Some mechanisms are conserved- showing common ancestry Others have changed, demonstrating divergent evolution
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i.e. nitrogenous waste removal All animals produce nitrogen byproducts Animals in different environments have evolved different mechanisms for excreting these wastes
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Ammonia Toxic byproduct of protein degradation In dilute concentrations is no big deal, so aquatic organisms can excrete it into water
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Urea Mammals convert ammonia into urea Urea travels through the blood to the kidneys and is excreted with water and other substances as urine
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Solid Uric Acid In birds and reptiles (and some desert mammals) nitrogen waste is excreted as a solid Prevents water loss and buildup of water wastes in the shell of an egg
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Evolution of Circulatory System Shows Common Ancestry and Divergence
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Disruptions at the Molecular/Cellular Level Affect Organisms I.e. viral infection of a cell Allergies Dehydration
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Disruption of One Organisms Affects Others I.e. disrupting the food chain If you break one link of the chain, everyone is affected Toxins in one organism get passed on
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Biomagnification Toxins get concentrated as they move up the food chain So small amounts of mercury can become extremely toxic to polar bears (or humans!)
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Invasive Species Usually have no natural predators and grow uncontrollably Disrupt the food chain and outcompete native species
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