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Forestry
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FRST 200
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Chapter 16: Change in Communities (343-347) Agents of change -subtle like one species aquiring dominance or catastrophic like the death of a whole population -Succession: change in species composition of communities over time and is a result of abiotic and biotic agents of change.  Agents of change can be biotic or abiotic Q: if corals need the symbiotic algae, why don’t we place them there ourselves to help with the process?  Abiotic(temperature, salinity, pH, wind)has two categories: Disturbances: physically injures and creates opportunities for others. Stress: reduces growth or reproduction and creates opportunities for others.  Biotic (competition, disease)  Agents of change vary in their intensity, frequency and extent Chapter 5: Coping with Environmental Variation: Energy (107-127) Sources of Energy -radiant energy: from the sun -kinetic energy: motion of molecules- cold or warm objects -chemical energy: from food that is consumed -autotrophs: use energy from sunlight (photosynthetic, organic) OR use energy from chemical Compounds (chemosynthetic, inorganic) -heterotrophs: use energy from eating other organisms. Include detritovore, parasites, herbivores, predators. -energy is stored in the C-C bonds of the organic compounds that these 2 processes produce Autotrophy  Chemosynthesis harvests energy from inorganic compounds  Calvin cycle occurs in photosynthetic and chemosynthetic organisms and is the biochemical pathway used to fix carbon  Photosynthesis is the powerhouse for life on Earth  Environmental constraints and solutions - Light response curve: relationship between the light level and a plant’s photosynthetic rate - Light compensation point: when CO up2ake = CO loss2by respiration - Photosynthesis limited by availability of light. Curve levels off at light saturation point (start at 112) Chapter 12: Predation and Herbivory (264-271) Predators and Herbivores CONCEPT: most predators have broad diets, whereas a majority of herbivores have narrow diets  Some predators move in search of prey, some sit and wait  some predators forage in their habitat, but there’s also “sit-and-wait predators” that stay in one place and wait for prey (barnacles)  predators concentrate on places with high prey abundance (seasonal migration herds)  Many predators have broad diets  Specialist predators: have a strong preference for one type of prey  Most predators eat prey based on availability (most plentiful) NOT specific species  Many herbivores specialize on particular plant parts  Most specialize on certain part of plant: seeds, internal fluids, stems, roots, leaves with leaves being most eaten because present year round and most nutritious after seeds  By eating photosynthetic tissues it can kill plant or hinder growth, survival and reproduction  Most herbivores have relatively narrow diets  Focus on 1 or 2 types of plants most commonly Adaptation to Exploitative Interactions CONCEPT: Organisms have evolved a wide range of adaptations that help them obtain food and avoid being eaten  Predators and herbivores exert strong selection on their food organisms  Due to strong selection pressure from predators, prey developed defenses otherwise they would die  Herbivores also have defenses Escaping predators:  Physical - big or small size and good body plan (agility, armour) to avoid predators  Toxins - usually bright coloured species (warning/aposematic coloration)  Mimicry – camouflage in surroundings (crypsis)or mimic other more dangerious species  Behaviour - forage less when predators, form defense circle with others  There can be trade-off between physical and behavioural defenses Reducing herbivory  Avoidance – masting: producing lots of seeds one year and few the next , these can be dormant then burst and overwhelm predators. Also, producing leaves when predators gone  Tolerance –compensation: when loss of plant tissues causes more to regrow and replace (clipping beech trees causes increase in leaf production and photosynthesis. This can depend of growing season.  Defenses – tough leaves, thorns, spines, hairs. Induced defenses stimulated by predator presence. Secondary compounds reduce herbivory, are usually toxic and either keep predators away or cause predators of the predators to come  Predators and herbivores have adaptations to overcome the defenses of their food organisms  for most prey defenses, there’s a predator adaptation to counter it Predators:  physical –to find cryptic prey use smell or touch (not sight), body forms(fast, eat big things – snake jaw)  toxins – use toxins to get prey  mimicry – camouflage from prey until it’s too late  detoxification – can handle prey toxins, are immune or tolerant (trade-off) Herbivores:  structural – can tolerate thorns  chemical – have special enzymes that counter prey defenses  behavioural – the way they eat prey is modified in order to avoid their defenses (slowly, eating one part first) Chapter 13: Parasitism (290-293) Parasite-Host Coevolution CONCEPT: Host and parasite populations can evolve together, each in response to selection pressure imposed by the other  coevolution: populations of 2 interaction species evolve together based on selection pressures imposed by the other  Selection can favour a diversity of host and parasite genotypes  Gene-for-gene interactions: specific response that makes certain plant genotypes resistant to certain parasite genotypes  Depends on varieties with different genotypes, rust variety can live one year on wheat varieties, but can’t the next year because different wheat variety and that certain rust isn’t resistant to it  Host defenses and parasite counterdefenses both have costs  Host genotypes that are common decrease in frequency because so many parasites attack them, leaving the rare genotype undisturbed and free to reproduce and take over (cycle begins again)  Traits that improve host’s defenses or parasites counterdefenses have tradeoff with growth, survival or reproduction Chapter 20 (Part 2): Energy Flow and Food Webs (433-438) Energy flow among trophic levels CONCEPT: The amount of energy transferred from one trophic level to the next depends on food quality and consumer abundance and physiology.  Energy flow between trophic levels can be depicted using energy or biomass pyramids  in terrestrial energy and biomass pyramids are usually the same (big on bottom and small on top) but in aquatic the biomass can be small on bottom and big on top because of high consumption rate and short life time of phytoplankton.  A bit of energy is lost between levels (due to things
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