Adaptations to the Environment

Transcription

1 Adaptations to the Environment MODULE 07: ADAPTATIONS TO THE ENVIRONMENT UNIT 1: ENVIRONMENT Objectives At the end of this series of lectures you should be able to: Define terms. Discuss the concept of scale. Describe the different ways that heat is transferred Discuss the different ways that organisms can regulate their temperatures. Explain water potential and how water moves through plants. Discuss the different challenges faced by saltwater and freshwater organisms and their different strategies and adaptations for overcoming those challenges. Discuss the challenges faced by terrestrial organisms in regards to water regulation and adaptations that they can use to overcome those challenges. Distinguish between energy and nutrients. Describe and distinguish between different photosynthetic pathways. 1

2 Defining Scale Scale spatial or temporal dimension of an object or process Example (I am going to measure. Do I bring ocular micrometer, calipers, ruler, meter stick, chain, wheel Differs from the level of organization in the ecological hierarchy Scale is not used consistently Ecological vs. Cartographic/Geographic scale (Small vs. Large) Fine vs. broad Scale The answer to a question depends on the scale it is investigated at. Changing the size of the quadrat or study area yields different results. The spatial and temporal scales important to humans are not necessarily the scale that are relevant to other organisms or ecological processes. 2

3 Defining Scale Scale is characterized by: Grain finest spatial resolution within a given data set. Extent The overall size of the study area. Grain and extent are practically correlated as the area of interest increases the grain size increases, but if the area interest is small we need to use a small grain. 3

4 Response to Environmental Variation The physical environment influences organisms in two ways: Availability of energy and resources impacts growth and reproduction. Extreme conditions can exceed tolerance limits and impact survival. 4

5 Heat Heat moves from regions of warmth to regions to cooler regions: Conduction Convection Radiation 5

6 Organism Performance Environment influences the physiology and behavior of organisms. Environment Light Temperature Water Performance How fast they grow How many offspring they produce How fast they run, fly, or swim How well they avoid predation Organism Performance Most organisms performance best over a narrow range of environmental conditions. Physiological processes have optimal conditions for functioning. Stress: Decreased rates of physiological processes because of suboptimal environmental conditions. Decreases survival, growth, or reproduction. 6

7 Response to Environmental Variation Acclimation: Adjusting to stress through behavior or physiology. It is usually a short-term, reversible process. Adaptation: The result of natural selection to environmental stress. Increased fitness of individuals with traits that enable them to cope with stress. Alleles for coping with stress become more common in the population. 7

8 Regulating Body Temperature Poikilotherms (cold-blooded) Do not regulate body temperature. Ectotherms Regulate body temperature using external sources of energy. Endotherms Regulate body temperature using internal metabolic heat. Homeotherms (warm-blooded) Endotherms that maintain a relatively constant body temperature. Variation in Temperature An organismʼs temperature is determined: Heat gained from the environment. Heat lost to the environment. An organism can modify its temperature (change the heat it gains or losses) by changing its: Physiology Morphology Behavior 8

9 Regulating Temperature Organisms regulate body temperature by manipulating heat gain and loss. Hs Heat stored in body Hm Heat from metabolism Hcd Heat gained or lost through conduction Hcv Heat gained or lost through convection Hr Heat gained or lost through radiation He Heat lost through evaporation Temperature Regulation in Plants Desert Plants Challenge: Reduce heat storage Adaptations for altering heat exchange: Leaves relatively high above ground decreases conductive heating. Small leaves and open growth form increases surface to area ratio which increases convective cooling. Reflective surfaces hairy white surfaces which decreases radiative heating. Change the orientation of leaves and stems -- decreases radiative heating. 9

10 Temperature Regulation in Plants Arctic or Alpine Plants Challenge: Increase heat storage Adaptations for altering heat exchange Leaves close to ground minimize convective loss and maximize conductive heating. Cushion growth form decreases surface area to volume ratio which decreases convective cooling. Dark surfaces increases radiative heating. Change the orientation of leaves and stems -- increases radiative heating. 10

11 Temperature Regulation in Plants Other ways plants can influence temperature: Transpiration evaporation Stomate control Deciduous leaves Pubescence Hairs on leaves and stems Air flow conduction/convection Color differences radiation Metabolic heat What does a plant gain from thermoregulating? Ectothermic Animals Use external sources of energy to regulate body temperature. Variation of body size, shape, and pigmentation Greater ability to use behavior to thermoregulate 11

12 Ectothermic Animals Reptile under cool conditions Challenge: Increase heat storage Adaptations for altering heat exchange: Laying flat against ground Reduces convective heat loss Basks on a mat of plant material Reduces heat loss to conduction. Dark pigmentation Increases radiative heat gain. What does a lizard gain from thermoregulating? Ectothermic Animals Mechanisms of altering heat exchange: Morphology and behavior. Laying flat against ground Reduces convective heat loss Basks on a mat of plant material Reduces heat loss to conduction. Dark pigmentation Increases radiative heat gain. What does a lizard gain from thermoregulating? 12

13 Endothermic Animals Use internal sources of energy to regulate body temperature. Increased Hm Variation of body size, shape, and pigmentation Greater ability to use behavior to thermoregulate Greater importance of metabolic heat. Endothermic Animals Thermal neutral zone Low temperatures Increase metabolic rate Increase metabolic heat Shiver Increase metabolic heat High temperatures Move blood to near skin Increase radiative heat loss Sweat Increase evaporative heat loss Salivate or lick Increase evaporative heat loss 13

14 Endothermic Animals Aquatic Endotherms Special challenge High specific heat of water Aquatic endotherms will lose heat to water readily. Conductive and Convective heat loss is much greater in water than in air. Gill-breathing species are exposed directly to cold water. Aquatic birds and mammals Air-breathing no exposure of large respiratory surface to water. Insulating fat layer Countercurrent heat exchange 14

15 Surviving Extremes Inactivity Avoid environmental extremes during the day. Find a microclimate that is suitable and stay there. Reducing metabolic activity Dormancy Torpor Low metabolic rate and lowered body temperature Hibernation During winter, extended lengths of times Estivation During summer, extended lengths of times 15

16 Water and Life Water is closely associated with life. Water content of organisms ranges from 50% -90%. Life is built around a biochemistry which requires water as a solvent. To maintain life an organism must maintain a balance between its internal concentrations of water and solutes. Balance water intake and water losses to the environment. Variation in Water Availability Aquatic environments may be: Hyperosmotic more solutes than an organismʼs cells. Isoosmotic same solutes as an organism s cells. Hypoosmotic less solutes than an organism s cells. Remember these terms are in reference to the environment. Organisms in hypoosomotic and hyperosmotic environments must expend energy to maintain their internal water balance. 16

17 Water and Salt Regulation in Aquatic Organisms Marine Invertebrates Isomotic Energy conservation Sharks, rays, and skates Hyperosmotic Gain water through osmosis Excrete excess salt (sodium) through a specialized gland Salt diffuses into body Teleosts (bony fish) Hyperosomotic Lose water through gills Drink seawater to increase body water Drinking salt water increases salt diffusion through gills Specialized glands and kidneys secrete excess salt Produce concentrated urine "Osmoseragulation Carangoides bartholomaei bw en2" by Kare Kare modified by Biezl translation improved by smartse - Licensed under CC BY-SA 3.0 via Wikipedia - g 17

18 Water in Aquatic Organisms Freshwater Invertebrates Expend energy pump out water Expend energy gathering salt Reduced internal salt concentration decreases gradient Teleosts Hypoosmotic Tend to gain water and lose salts through their gills Gain salt by specialized structures from water and from food Produce large quantities of dilute urine "Bachforelle osmoregulatoin bw en2" by Raver, Duane; modified by Biezl translation improved by User:smartse - NOAA. Transferred from en.wikipedia to Commons by User:Quadell using CommonsHelper.. Licensed under Public Domain via Wikimedia Commons

19 Water in Terrestrial Animals Animals Acquire water Absorb from air Drink Metabolic water Waterproofing Cuticles of terrestrials insects Dry skin of reptiles, birds, and mammals relative to moist skin of amphibians. Concentrated urine or feces Reclaiming water from breath Restricted activity Variation in Water Availability Marine organisms live in an isoosmotic environment, so water balance is not a problem. Freshwater organisms lose solutes to and gain water from their hypoosmotic environment. Terrestrial organisms lose water to the dry atmosphere. 19

20 Water Potential Pressure potential: Water moves from an area of higher pressure, to lower pressure. Osmotic potential: Water flows from a region of high concentration (low solute concentration) to a region of low concentration (high solute concentration). Matric potential: Water is attracted to surfaces. Adhesion. Water Potential Water potential is the sum of all these potentials: Water always moves from a higher Ψ to lower Ψ. 20

21 Water in Plants Osmotic pressure will depend on the solutes in the soil and the in cells of the plant. Matric pressure will depend on the size of spaces and the composition of the materials (soil and vessel elements). Adhesion Capillary action Evaporation from the stomates of the leaf cause negative pressure (tension) on the water column. Cohesion Hydrogen bonds Water in Plants Water moves from the soil into the roots of the plant. (From high water potential to lower water potential) In the roots, the water joins a column of water extending from the roots to the leaves of the plant. (Cohesion hydrogen bonds) Water molecules that evaporate the from the leaves exert a negative pressure (tension) on the water column moving up lowering the water potential of the roots. As soils dry, their water potential drops and the ability of the plant to gather water also decreases. 21

22 Water in Plants Water Acquisition -- Plants Absorb from air Roots Root systems more elaborate in drier areas Root systems go deeper in drier areas Roots can make up a significant portion of the plants biomass Biomass? Water in Plants Water Conservation Plants Deciduous leaves Thick leaves Reduced number of stomates Modified stomates Stomatal crypts Trichomes Dormancy Alternative pathways for photosynthesis 22

23 Energy and Matter Energy The ability to do work. Work is the moving of matter. Matter Anything that takes up space and has mass. Energy and Nutrients Energy Ability to move matter. Move material in and out of the organism as well as in an organism. Chemical bonds. Nutrients Matter Raw materials that make up the organism 23

24 Energy and Nutrients People frequently use energy and nutrients interchangeably an animal bias we obtain both in the same way. The plant difference Energy Sources Autotrophs Photosynthetic Chemosynthetic Heterotroph 24

25 Photosynthesis Basic photosynthesis Light reaction (photochemical reactions) Requires light, water Produces ATP and NADPH Carbon reaction (biochemical/dark reactions) Does not require light can occur in light or in dark Requires ATP, NADPH, and CO2 Captures the CO2 as carbohydrate Photosynthesis Variation in photosynthetic pathways primarily variation in how the CO2 is processed. C3 C4 CAM 25

26 C3 Photosynthesis Problem with C3 photosynthesis. Opening stomates for CO2 allows water to be lost. The water potential of the air is less that the water potential of the leaf. More water is lost than CO2 is gained steeper water than CO2 gradient in the leaf. This is not a real issue in wet places. RuBP caboxylase has a low affinity for CO2 Other Photosynthetic Pathways In arid environments, other pathways allow for greater water conservation. Separating in time or space the light and dark reactions. Fix CO2 with 4-carbon compounds 26

27 C4 Photosynthesis Separates the light and dark reactions into different types of cells. Concentrates CO2 in bundle sheath cells decreasing concentration in the mesophyll cells (increasing the CO2 gradient from the air to the mesophyll cells CO2 moves more quickly from air to the mesophyll cells. Less stomates have to be open to obtain the same amount of CO2. CAM Photosynthesis In CAM (crassulacean acid metabolism) photosynthesis, carbon is fixed (dark reaction) at night and the light reaction occurs during the day. Temperature is lower and humidity is higher during night decreasing water loss from the stomates. CAM all occurs in the same cell. 27