Physical conditions and availability of resources

1. Chapter 3 Physical conditions and availability of resources

2. What is the difference between a resource and a condition? An environmental condition is… A resource is consumed by organisms for growth and reproduction Thus: organisms may compete with each other for a share of a limited resource Resources vs conditions

3. What is a ‘harsh’ or ‘benign’ or ‘extreme’ environment? Temperature, relative humidity, and other physicochemical conditions induce a range of physiological responses in organisms – which determine whether the physical environment is habitable or not to them Three basic types of ‘response curve’ Environmental Conditions

4. (a) extreme conditions are lethal but between the two extremes is a continuum of more favorable conditions. Notice range of growth and reproduction (b) condition lethal only at high intensities. (eg: poisons) (c) conditions required by organisms at low [ ] but toxic at high [ ] (eg: copper and sodium chloride) Environmental Conditions

5. most life processes occur within the temperature range of liquid water, 0o-100oC • few living things survive temperatures in excess of 45oC • freezing is generally harmful to cells and tissues Temperature limits the occurrence of life.

6. Most life processes are dependent on water in its liquid state (0-100oC). • Typical upper limit for plants and animals is 45oC (some cyanobacteria survive to 75oC and some archaebacteria survive to 110oC). • Good: high temp -> organisms develop quicker • The bad: High temperatures: • denature proteins • accelerate chemical processes • affect properties of lipids (including membranes) Tolerance of Heat

7. Temperature and Metabolism • High temperature increases speed of molecular movement • High temperature speeds up chemical reactions • For each 10C rise in temperature – rate of biological processes often roughly doubles • Effects on rates of growth or development or on final body size? Metabolic Effectiveness

8. Oxygen consumption increases as a function of temperature

9. Rate of oxygen consumption of the Colorado beetle – increases non-linearly with temperature Doubles for every 10C rise up to 20C - increases less fast at higher temperatures

10. Linear relationships between rates of growth and development and temperature for protist

11. Temperature has consistent effects on a range of processes important to ecology and evolution (Univ of New Mexico ecologists) • Rates of metabolism • Rates of development of individuals • Productivity of ecosystems • Rates of genetic mutation • Rates of evolutionary change • Rates of species formation Metabolic theory of ecology

12. Temperature has consistent effects on a range of processes important to ecology and evolution (Univ of New Mexico ecologists) • Rates of metabolism • Rates of development of individuals • Productivity of ecosystems • Rates of genetic mutation • Rates of evolutionary change • Rates of species formation Metabolic theory of ecology

13. Increasingly: ecologists are asked to predict consequences of say – a 2C rise in temperature What about cold temperatures? Chilling injury: organisms may be forced into extended periods of inactivity and cell membranes of sensitive species may begin to break down; affects many tropical fruits

14. What about freezing temperatures?

15. Temperatures rarely exceed 50 degrees C (except….) • Note: water can supercool to temperatures as low as -40C w/o forming ice • Sudden shock allows ice to form within plant cells  this is lethal • If temperatures fall slowly – ice can form between cells  dehydrated cells  impact to cell like high-temperature drought Freezing temperatures…

16. Freezing disrupts life processes and ice crystals can damage delicate cell structures. • Adaptations among organisms vary: • maintain internal temperature well above freezing • activate mechanisms that resist freezing • glycerol or glycoproteins lower freezing point effectively (the “antifreeze” solution) • glycoproteins can also impede the development of ice crystals, permitting “supercooling” • activate mechanisms that tolerate freezing Tolerance of Freezing

17. Note: absolute temperature is important Also important: timing and duration of temperature extremes Remember: an individual need only be killed once Tolerance of cold

18. Environmental Conditions as stimuli

19. Proximate factors (day length, for example) – an organism can assess the state of the environment but these factors do not directly affect its fitness • Ultimate factors (food supplies, for example) – environmental features that have direct consequences on the fitness of the organism • Photoperiod: the length of daylight: proximate factor to virtually all organisms • Winter  day shortens  bears and other mammals develop a thick coat; insects enter dormant phase (diapause) What are the stimuli for change

20. Insects may speed up development as daylength decreases (winter); and speed up development as daylength increases (spring) Effect of daylength on larval development time in the butterfly photoperiod

21. … may trigger an altered response to the same or even more extreme conditions Eg: exposure to relatively low temperatures may lead to an increased rate of metabolism at such temperatures and/or to an increased tolerance of even lower temperatures - acclimatization Environmental conditions…

22.  a shfit in an individual’s range of physiological tolerances  generally useful in response to seasonal and other persistent changes in conditions  reversible But – increased tolerance of one extreme often brings reduced tolerance of another extreme acclimatization

23. Photosynthetic rate as a function of leaf temperature is shown for 3 species of plants. • Blue = 20C; • Red = 45C • A species’ capacity for acclimatization may reflect the range of conditions in its environment

24. Acclimation to low temperatures Samples of the Antarctic springtail were taken from field sites in the summer (5C) on a number of days and their supercooling point (pt of freezing) determined; blue circles = control; brown circles = acclimation

25. One way increased tolerance is achieved: forming chemicals that as antifreeze compounds • Prevent ice from forming within the cells and protect their membrane if ice does form

26. Glycoproteins act as a biological antifreeze in the antarcticcodthe fish’s blood and tissues don’t freeze due to the accumulation of high concentrations of glycoproteins, which lower its freezing point to below the min temp of seawater (-1.8C) and prevent ice crystal formation

27. Another physical solution to freezing • is the process of lowering the temperature of a liquid or gas below its freezing point w/o it becoming a solid • Liquids can cool below the freezing point w/o ice crystals development • Ice generally forms around some object (a seed) • In a seed’s absence, pure water may cool more than 20C below its freezing point w/o freezing • Recorded to -8C in reptiles and to -18 in invertebrates • Glycoproteins in the blood impede ice formation by coating developing crystals supercooling

28. …under a restricted range of temperatures (but of course!) Optimum: narrow range of environmental conditions to which organism x is best suited Temperature! One such example. Put a tropical fish in cold water and it becomes sluggish and soon dies; put an Antarctic fish in temperatures warmer than -5C, and it won’t tolerate it but Many fish species from cold environments swim as actively as fish from the tropics Each organism functions best…

29. Different temperatures result in different enzyme formation (in quantity or in qualitative difference of the enzyme itself) • Rainbow trout: • Low temp in its native habitat during the winter • Higher temp in the summer Enzymes and temperatures and swimming

30. Many organisms accommodate to predictable environmental changes through their ability to “tailor” various attributes to prevailing conditions: • rainbow trout are capable of producing two forms of the enzyme, acetylcholine esterase: • winter form has highest substrate affinity between 0 and 10oC • summer form has highest substrate affinity between 15 and 20oC Compensation is possible.

32. Developmental responses  when conditions persist for long periods – env may influence individual development so as to modify the size or other attributes of the individual for long periods Striking example: the African grasshopper – changes color to match the color of their environment Irreversible developmental responses

33. Most grasshoppers complete their life cycle within a single season So in habitats where this color progression occurs – the pigment systems in the epidermis develop in such a way that the nymphs an adult grasshoppers match the background

34. Reaction norm  observed relationship between the phenotype of an individual and the environment Phenotypic plasticity allows individuals to adapt to environmental change

35. Some reaction norms are a simple consequence of the influence of the physical environment on life (heat energy  accelerates most life processes  certain caterpillars grow faster at higher temperatures … but individuals of the same butterfly species from MI and AL have different relationships between growth rate and temperature…) Phenotypic plasticity allows individuals to adapt to environmental change

36. Reaction norms of populations adapted to different environments may differ

37. Reaction norms may be modified by evolution May diverge when two populations of the same species exist for long periods under different conditions…

39. When the reaction norms of two genotypes cross for some aspect of performance, then individuals with each genotype perform better in one environment and worse in another environment (eg: swallowtail butterfly) This relationship  genetoype – environment interaction because each genotype responds differently to environmental variations How to identify them?  reciprocal transplant experiment (remember?) Genotype – environment interaction

40. Temperature does not act on 1 species alone; also impacts its competitors, its predators, its prey • Conditions may affect availability of a resource (a prey, e.g.) • … conditions  disease • Conditions may favor spread of infection, growth of parasite, or weaken/strengthen defenses of host • …conditions  competition Effects of conditions on interactions between organisms

41. Fungal pathogens of grasshopper in the US develop faster at warmer temperatures – but fail to develop at all at temperatures around 38C and higher Proportion of grasshoppers with observable infection with pathogen drops sharply as grasshoppers spend more of their time at high temperatures Grasshoppers that regularly experience such temperatures effectively escape serious infection

42. Changing temperature reverses outcome of competition. At low temp (6C) (left) S. malma fish out survives; at 12 C (right) S. leucomaenis drives S. malma to extinction; alone, they both can live at either temperature Temperature and condition

43. Plants, aquatic invertebrates In all (except equatorial environments), physical conditions follow a seasonal cycle Morphological and physiological characteristics must change accordingly Responses by sedentary organisms

44. First: what is their relationship with water? How do plants adapt?

45. Once water is in root cells, then what? • water moving to the top of any plant must overcome tremendous forces caused by gravity and friction in conducting elements (xylem): • opposing force is generated by evaporation of water from leaf cells to atmosphere (transpiration) • water potential of air is typically highly negative (potential of dry air at 20 oC is -1,332 atm) • force generated in leaves is transmitted to roots -- water is drawn to the top of the plant (tension-cohesion theory) Moving Water from Roots to Leaves

46. Water potential that moves water from the roots to the leaves of a plant is generated by transpiration

47. Most water exits the plant as water vapor through leaf openings called stomates: • plants of arid regions must conserve limited water while still acquiring CO2 from the atmosphere (also via stomates) - a dilemma! • potential gradient for CO2 entering plant is substantially less than that for water exiting the plant • heat increases the differential between internal and external water potentials, making matters worse Adaptations to Arid Environments

48. Numerous structural adaptations address challenges facing plants of arid regions by: • reducing heat loading: • increase surface area for convective heat dissipation • increase reflectivity and boundary layer effect with dense hairs and spines • reducing evaporative losses: • protect surfaces with thick, waxy cuticle • recess stomates in pits, sometimes also hair-filled Adaptations to Arid Environments

49. Spines and hairs help plants adapt to heat and drought. (a) cross section; (b) surface view of the leaf of the desert perennial herb

50. This drought-resistant plant reduces water loss by placing its stomates in hair-filled pits on the leaf’s undersurface