1. CONDITIONS & RESOURCES Chapter 3: Organismal Ecology

2. Environmental Factors Factors which vary in space and time, and to which organisms are differentially responsive

3. Conditions (abiotic factors) Physicochemical features of the environment that may be altered by the activities of living organisms, but not consumed Temperature Relative humidity pH Salinity Current velocity Soil structure Pollutant concentration

4. Resources Quantities of something that can reduced by the activities of a living organism during its growth and development Made less available or unavailable to other organisms Solar radiation Inorganic materials - CO 2, water, oxygen, mineral nutrients (macro-, micronutrients) Food Space

5. Effects of conditions For each species, there is some level/concentration/intensity of a factor at which it does best - its optimum for that factor Optimum conditions result in individuals with the highest fitness Higher or lower levels of a factor result in reduced fitness or non-survival

6. Example of a condition Temperature - one of the most important factors because of its influence on metabolism

7. Temperature Homeotherms - maintain constant body temp. as environmental temp. varies Poikilotherms - body temp. varies with environmental temp. Endotherms - regulate body temp. by internal heat production Ectotherms - depend on external heat sources

8. Endotherms Regulate body temperature by internal heat production (birds, mammals) Regulators - 35-40°C Constancy of performance over wide range of temperatures Large expenditure of energy to maintain internal heat (large food requirements) (cost) At higher temps., they alter insulation, shunt blood flow to surface, pant, seek out cool habitats

9. Ectotherms Depend on external heat sources Conformers Can moderate or modify heat exchange with environment by: Developing various body coverings (reflective) Simple or complex behaviors Complex physiological process (bee shivering)

10. Body temp. still varies with environment because… Regulatory powers limited (esp. plants) Dependent on external source of heat (not always available) Costs associated with temp. regulation (energy, predator exposure) - benefits must outway costs

11. Ectotherms Changes in body temperature result in changes in rates at which physiological processes occur Temperature coefficient = Q 10

12. Q 10 rule For every 10°C increase in temperature, a reaction rate (e.g., metabolism, development) increases two times Q 10 = 2 May be higher or lower in some organisms for some reactions

13. Other effects of temperature on ectotherms Can become acclimatized to different temperature regimes Some physiological processes adjust over time to different temperatures Temperature may serve as stimulus to begin some process Initiate development in some plants Diapause

14. Other effects of temperature on ectotherms High temperatures can… Inactivate/denature enzymes Greatly increase energy expenditures Dehydrate (most important for terrestrials)

15. Other effects of temperature on ectotherms Low temperatures can… Reduce energy expenditures (also cease maintenance, repair activities) Induce “hardening” in plants (acclimatization to low temps.) Produce chilling injury - disruption of membrane structure that interferes with water uptake or retention Produce freezing injury/death - ice crystal formation within cells

16. Temperature can affect distributions Organisms generally found where temperatures are optimum for survival, growth, reproduction

17. Temperature can affect distributions - continued Lethal high or low temperatures can limit distributions, but only need to occur infrequently to do so

18. Saguaro cactus distribution Distribution limited to regions where freezing temps. last <36 hours

19. Temperature can affect distributions - continued Distributions most often limited by sub- optimal temperatures that reduce growth, reproduction, or increase mortality

20. Crayfish distribution Growth limited below 15°C Toward edge of distribution, organisms occupy microhabitat patches where temperatures are nearest optimal

21. Temperature can affect distributions - continued Sub-optimal temperatures may affect distributions by altering competitive interactions between species, or by interacting with other factors (i.e., O 2 ) that more strongly affect organisms

22. Trout distributions Warmer temperatures produce lower dissolved O 2 levels

23. Temperature can affect distributions - continued Effects of suboptimal temperatures can be moderated by evolution, behavior, physiology

24. Allen’s rule Endotherms in cold climates have shorter extremities than those in warm climates

25. Bergmann’s rule Mammals with wide distribution are larger in colder climates - less surface area per unit volume

26. Other conditions Relative humidity Rate of water loss from evaporation and respiration by terrestrials is dependent on relative humidity Higher humiditylower rate of loss Organisms differ in abilities to reduce or counteract losses Require different relative humidities Often difficult to separate from temperature and wind speed

27. pH Altered pH can: Upset osmoregulation and other processes Alter availability of nutrients, minerals, toxic metals Aluminum at pH < 4.0 Alter quality/range of available food resources Different organisms have different requirements/tolerances

28. Salinity Organisms possess different requirements/tolerances of salinity - osmoregulation Stenohaline - narrow limits Euryhaline - broad limits

29. Current velocity Different requirements of body shape/attachment under different flow regimes Low-profile, streamlining, encrusting forms in higher velocities

30. Current velocity - continued Low-profile - boundary layer e.g., mayfly nymphs

31. Current velocity - continued Streamlining

32. Soil structure Coarse versus fine Smooth versus rough

33. Pollutants Differing tolerances to various pollutants Concentration Percent survival 100 0 Species ASpecies B

34. Ecological Niche Description of the various environmental limits within which a given species can: Survive Grow Reproduce Maintain a viable population n-dimensional hypervolume

35. Two Kinds of Niches Fundamental niche Potential limits of the species Realized niche Actual limits of the species as imposed on it by competitors and predators

36. Resources Consumed or made less available to others Solar radiation CO 2 Water Macronutrients (N, P, S, K, Ca, Mg) Trace elements (e.g., Mn, Zn, Cu) O 2 Food Space

37. Solar Radiation Source of energy used by plants for photosynthesis Not equally distributed worldwide Equator - most Poles - least Results from tilt of earth on axis relative to sun and thickness of atmosphere penetrated by light

38. Solar Radiation cont. Only a portion of light spectrum is useable by plants (380-710 nm) Photosynthetically active radiation (PAR) 44% of total solar radiation

39. Solar Radiation cont. Rate of photosynthesis depends on light intensity Zero in darkness Compensation point - level where photosynthesis equals respiration Saturation - maximal (achieved only if products of photosynthesis are withdrawn rapidly for growth or storage)

40. Solar Radiation cont. Low intensities used more efficiently by “shade” species “Shade” species reach maximum photosynthesis rates at much lower light intensities than do sun species

41. Solar Radiation cont. Light intensity determines optimal leaf area index (LAI) for a plant population LAI is surface area of leaves borne above area of ground High light intensities -> high LAI Low light intensities -> low LAI Most plants have LAI optimal for average light intensity they receive

42. Solar Radiation cont. Angle of leaves have strong effect on rate of photosynthesis Perpendicular to sun, absorb most light Angled to sun, reflect some light Angle changes throughout day, seasons

43. Solar Radiation cont. Efficiency of utilization Maximum lab values < 5% Maximum field values < 3% Tropics 1-3% Temperate 0.6-1.2% Temperate crops 0.6%

44. Water Terrestrial organisms continually lose water to environment Animals replenish it by: Drinking water Obtaining it from their food (metabolism) Availability can limit distribution and abundance

45. Water Plants obtain moisture from ground Constant supply in many locations, limited in others

46. Water Plants mechanisms for reducing water loss Rhythmic opening/closing of stomata Leaf surface to reduce water loss Thicker cuticle, waxy or hairy (lower temp) Modified stomata (reduce water gradient) Different conditions--->different leaf forms Dissociate CO 2 uptake from photosynthesis Increase CO 2 gradient into plant

47. Water Limits placed on plant roots’ abilities to obtain water from soil Field capacity - maximum amount soil can contain (held by soil pores against gravity) Permanent wilting point - minimum amount needed by plants (can’t be extracted by root’s suction force, plant wilts and can’t recover) Suction force causes resource depletion zone in vicinity of root

48. Water Root growth to water Elongate first, then branch (develop laterals) Reduces competition between root hairs for same water Branch more in soils that contain more water, or where water moves less freely Clay versus sand Early pattern of growth determines success Heavy rains, waterlogged soil, drought

49. Macronutrients, trace elements Animals get them from food Plants get them from soil Require the same, but in different quantities or proportions Limits distributions of certain plants to certain soil types Each nutrient enters soil independently of others, has different properties of absorption, diffusion

50. Macronutrients, trace elements Nitrates, calcium, sodium move freely through soil with water Often delivered to roots faster than can be taken up by plant Resource depletion zones may be wide because of ease of movement through soil

51. Macronutrients, trace elements Phosphate and potassium bound on soil colloids by surfaces with calcium, aluminum, ferric ions Rate at which they move to plant depends primarily on how rapidly they are released from colloids (tightly adsorbed) Resource depletion zones usually narrow

52. Food Heterotrophs, consumers Predators - kill and eat part or whole Parasites - eat on living Decomposers - eat on dead Polyphagous - generalists - have preferences but are adaptable Monophagous - specialists - not very adaptable

53. Food Quality Plants - high C:N ratio (40:1-20:1) because of high-C cellulose, other structural materials Heterotrophs - low C:N ratios (10:1-8:1), no structural carbohydrate but lots of protein

54. Food Most organisms lack cellulase to break down cellulose Herbivores physically rupture cell walls to gain access to contents, or use microbes Detritivores may get much nutrition from bacteria, fungi colonizing dead materials

55. Food Herbivores may be selective on certain plant parts Parts often have less cellulose and more: Nitrogen - growing tips Carbohydrate (starch, sugar) - tubers Fats (oils) - seeds

56. Defense Against Being Eaten Behavioral Flight Bluff (threat displays) Startle response (moths) “Playing dead”

57. Defense Against Being Eaten Morphological Crypsis (camouflage) Aposematism (warning coloration) Mimicry (Batesian, Mullerian)

58. Defense Against Being Eaten Plant chemical defense Cyanide, acids, glycosides, tannins, alkaloids Secondary chemicals that play no role in normal plant physiology Released by chewing, make plant taste bad, make organism sick

59. Defense Against Being Eaten Physical Spines Thorns Hard seed capsules

60. Defense Against Being Eaten All defenses reduce likelihood of being consumed One or more “predators” capable of overcoming the defense Defense costs energy that could have been used in other activities

61. Resources Add more dimensions to the ecological niche