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February 2nd

by: Sierra

February 2nd Biol 28600


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Notes from February 2nd
Introduction to Ecology and Evolution
Joshua Springer
Class Notes
Ecology, evolution, Biology
25 ?




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This 48 page Class Notes was uploaded by Sierra on Thursday February 11, 2016. The Class Notes belongs to Biol 28600 at Purdue University taught by Joshua Springer in Spring 2016. Since its upload, it has received 63 views. For similar materials see Introduction to Ecology and Evolution in Biology at Purdue University.


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Date Created: 02/11/16
Exam I • On Monday, February 15, 8—10pm; more details coming soon • Continue to email me or the TAs if you have questions • Homework 1 is now available and will be due on Sunday, Feb 7, at 11:59pm iClicker (polling question: 1 point for answering) Where do plants obtain the Carbon they need? A) Soil B) Atmosphere C) Water Plant Adaptations •Photosynthesis and respiration •Environmental controls on photosynthesis •Plant adaptations to: –High and low light –Water limitation –Nutrient availability Conditions and Resources • Conditions are physical / chemical features of the environment – e.g. Temperature, humidity, pH, etc.  Not consumed by living organisms (but may still be important to them) • Resources are consumed – Once used, they are unavailable to other organisms (in that original form) – Plants: sunlight, water, mineral nutrients, … – Animals: prey organisms, nesting sites, … Plant Resources • Plants are autotrophs - make their own organic carbon form inorganic nutrients – Need light, ions, inorganic molecules • Plants are sessile (do not move once established—but seeds…) – Grow towards nutrients • Or in environments with the most appropriate nutrients PHOTOSYNTHESIS Conversion of carbon dioxide into simple sugars LIGHT 6CO +212H O  2 H O + 6O 126H6O 2 2 RESPIRATION C 6 O12 66  6CO2+ 6H O + 2TP 2 Photosynthesis involves gas exchange Controls on photosynthesis •Light •Water •Nutrients •Temperature Tradeoff • Shade plants grow better in the sun plant than in the shade, • but sun plants grow faster than shade Sun plants in direct sun plant Tradeoff • Shade plants Shade survive well in either plant sun or shade • Sun plants cannot tolerate shade Sun plant Phenotypic plasticity • Sun and shade leaves can and do exist within the same tree More deeply lobed --> More rapid heat Sun leaf • thicker • more cell layers • more chloroplasts Shade leaf • flat • thin • larger surface area / unit weight Sun leaves Shade leaves •Leaves at many angles •Horizontal leaves, single layer •High saturation point •Low saturation point •High compensation point •Low compensation point •High respiration •Low respiration •Less chlorophyll •More chlorophyll •Enzymes limit •Light availability limits photosynthesis (limit to how photosynthesis rate much can be produced) Strategies for drought i. Avoiders • Short lifespan • Wet season • Seeds survive drought • Drought deciduous species – Leaves shed in dry season Strategies for drought ii. Tolerators • Leaves transpire slowly • Change orientation of leaves • Sunken stomata (gas exchange organs) – E.g. pines • More efficient photosynthesis • E.g. C4 --> reduces photorespiration • E.g. CAM --> stomata open at night • (Details in Text) Water absorption • Root hairs increase surface area Nutrients • Macronutrients – needed in large amounts (e.g. C, H, O, … N, P , K, Ca, Mg, S) • Micronutrients – trace elements (e.g. Fe, Mn, B) • Micro/macro refer to the quantity needed Evergreen leaves • Plants adapted to nutrient-poor conditions tend to have evergreen leaves Effects of temperature Increase temperature --> increase biochemical reaction rate • At high temperature, enzymes denature --> death Leaf temperature • > 95% of sunlight absorbed by a leaf becomes heat • Cooling of leaves: 1. Transpiration 2. Convection (movement of cool air around a leaf) Keep a microclimate around leaves Response to cold Chilling injury - near, > 0 C - cell membranes rupture o Freezing - < 0 C - ice inside cells = death - ice outside cells = dehydration (may survive) -may kill juveniles only Saguaro cacti (S.W. United States) store large amounts of water; they can tolerate short periods of freezing temperatures CLOSER TO HOME •Freeze-tolerant plants: frost hardening •When T decreases – plants synthesize sugars, amino acids, other molecules to act as antifreeze. •Winter – deciduous plants •Lose leaves in autumn •Leaves very efficient in summer – high photosynthesis rate •Leaves can’t survive freezing •Costly in energy, nutrients to rebuild leaves •Chilling breaks seed dormancy for temperate/boreal spp. •Lots of genetic factors here; length of cold season matters for survival/reproduction •Germinates only in spring Endothermy and Ectothermy Effects of extreme temperatures • Cold -- the effects of freezing – the membrane bound structures are destroyed or damaged.f ice; • Heat – inadequate O2 supply for metabolic demands (especially in areas where O2 is low, such as water) • Heat and Cold – reduced activity or denaturation of proteins -- the inactivation of certain proteins with the result that metabolic pathways are distorted. Body Temperature • Law of Tolerance: – for most requirements of life, there is an optimal quantity, above and below which the organism performs poorly • There is much variation in the range of temperatures that a species can tolerate Thermoregulation • maintenance of internal temperature within a range that allows cells to function efficiently • Two main types – ectothermy – endothermy Endothermy versus ectothermy Ectothermy • an animal that relies on external environment for temperature control instead of generating its own body heat • “cold-blooded” • e.g., invertebrates, reptiles, amphibians, and most fish • the majority of animals are ectotherms Metabolism and temperature • ectotherms cannot move very much unless the ambient temperature allows • roughly, for each 10 degree increase in temperature, there is a 2.5 increase in metabolic activity Ectothermy Desert iguanas are active only when ambient temperature is close to optimal for them Ectothermic animals Endothermy • a warm-blooded animal that controls its body temperature by producing its own heat through metabolism • evolved approximately 140 mya • E.g., birds, mammals, marsupial, some active fish like the great white shark and swordfish Endothermic animals Behavioural adaptations for thermoregulation • Animals bathe in water to cool off or bask in the sun to heat up Shivering, sweating, and panting • honeybees survive harsh winters by clustering together and shivering, which generates metabolic heat • Inefficient – 75% of energy is lost in mechanical movement Torpor • metabolism decreases • heart and respiratory system slow down • body temperature decreases • conserves energy when food supplies are low and environmental temps are extreme E.g., hummingbirds on cold nights Hibernation • Long-term torpor • adaptation for winter cold and food scarcity • E.g., ground squirrels Aestivation • summer torpor • adaptation for high temperatures and scarce water supplies • E.g., mud turtles, snails Endothermy and the evolution of sleep? • evolutionary remnant of torpor of our ancestors • the body needs sleep in order to offset the high energy costs of endothermy: – When animals fall asleep their metabolic rates decrease by approximately ten percent Colour and Posture • Change coloration (darker colors absorb more heat) – E.g., lizards, butterflies, crabs • Posture: – Change shape (flatten out to heat up quickly) – Orientation changes Chemical adaptations • Many Canadian butterflies overwinter further south and hibernate • they produce sugar-like substances as antifreeze • E.g., Mourning Cloak butterfly Advantages & Disadvantages of Endothermy • Advantages: – external temperature does not affect their performance – allows them to live in colder habitats – muscles can provide more sustained power – e.g., a horse can move for much longer periods than a crocodile can • Disadvantage: – energy expensive –ectotherm of equivalent sizeat much more than an Where can endotherms thrive? • Higher latitudes and deserts • Terrestrial environments have more variation in daily and seasonal temperature which contributes to more endotherms in terrestrial environments • endotherms (mammals and birds) generally outcompete ectotherms if they are after the same food source Size and thermoregulation • Small mammals (such as mice and shrews) have a greater dependence on internally- generated heat than big mammals (such as elephants and hippos) • leads to: – presence of insulation (fur - large mammals generally have less hair) – voracious appetites of small mammals (a shrew eats more per unit body weight than an elephant does)


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