1 / 35

Living Planet 2010

Living Planet 2010. Responses by sedentary organisms. Plants, aquatic invertebrates In all (except equatorial environments), physical conditions follow a seasonal cycle Morphological and physiological characteristics must change accordingly. Animal responses to environmental temperatures.

szuniga
Download Presentation

Living Planet 2010

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Living Planet 2010

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

  3. Animal responses to environmental temperatures • Most species of animals are, like plants, ectotherms: rely on external sources of heat to determine their pace of metabolism • Fish, amphibians and lizards • Others – endotherms: regulate their body temperature by producing heat within their body • Mainly birds and mammals

  4. Organisms maintain a constant internal environment. • An organism’s ability to maintain constant internal conditions in the face of a varying environment is called homeostasis: • homeostatic systems consist of sensors, effectors, and a condition maintained constant • all homeostatic systems employ negative feedback -- when the system deviates from set point, various responses are activated to return system to set point

  5. Negative feedback system

  6. Temperature Regulation: an Example of Homeostasis • Principal classes of regulation: • homeotherms (warm-blooded animals) - maintain relatively constant internal temperatures • poikilotherms (cold-blooded animals) - tend to conform to external temperatures • some poikilotherms can regulate internal temperatures behaviorally, and are thus considered ectotherms, while homeotherms are endotherms

  7. Homeostasis is costly. • As the difference between internal and external conditions increases, the cost of maintaining constant internal conditions increases dramatically: • in homeotherms, the metabolic rate required to maintain temperature is directly proportional to the difference between ambient and internal temperatures

  8. Limits to Homeothermy • Homeotherms are limited in the extent to which they can maintain conditions different from those in their surroundings: • beyond some level of difference between ambient and internal, organism’s capacity to return internal conditions to norm is exceeded • available energy may also be limiting, because regulation requires substantial energy output

  9. Partial Homeostasis • Some animals (and plants!) may only be homeothermic at certain times or in certain tissues… • pythons maintain high temperatures when incubating eggs • large fish may warm muscles or brain • some moths and bees undergo pre-flight warm-up • hummingbirds may reduce body temperature at night (torpor)

  10. Hummingbirds maintain a constant low body temp when in torpor

  11. Plant resources

  12. Resources may be either biotic or abiotic components of the environment • Organisms that are fixed and ‘rooted’ in position cannot search for food; must grow toward their resources – like a shoot or a root – or catch resources that move to them • Green plants depend on: • Energy that radiates to them • Atmospheric carbon dioxide that diffuses to them • Mineral cations that they obtain from soil colloids in exchange for hydrogen ions • Water and dissolved anions that the roots absorb from the soil

  13. Solar radiation • Green plants use only ~ 44% of that narrow part of the spectrum of solar radiation that is visible to us between infrared and ultraviolet • Rate of photosynthesis increases with intensity of radiation that a leaf receives – but with diminishing returns. What does that mean?

  14. Response of photosynthesis by leaves of various types of green plants

  15. Solar radiation • Sun and shade plants and sun and shade leaves • Photoinhibition of photosynthesis – rate of fixation of carbon decreases with increasing radiation intensity • High radiation  overheating • Solar radiation – dynamic • Angle and intensity change – diurnally; cloud cover; leaf shadowing

  16. water • Most plant parts are largely composed of water; as much as 98% of soft leaves; minute fraction of water that passes through plant • Wilting  if rate of uptake falls below rate of release, body of plant starts to dry out; cells lose turgidity; plant wilts

  17. Moving Water from Roots to Leaves • 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)

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

  19. Plants and water • Species of green plants differ in who they survive dry environments • Avoiders: desert annuals, annual weeds, and most crop plants • Short lifespan; photosynethetic activity [ ] during periods when + balance; otherwise dormant as seeds or shed their leaves • Tolerators: produce long-lived leaves that transpire slowly • Tolerate drought; slower photosynthesis

  20. Adaptations to Arid Environments • 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

  21. Adaptations to Arid Environments • 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

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

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

  24. Leaves of desert plants: adaptations These 3 species from the Sonoran Desert in Arizona all have adaptations that help them cope w/ hot, dry conditions

  25. Plants and heat • Evaporation of water lowers temperature of body • If plants are prevented from transpiring – they may overheat; die from heat • Example: desert honeysweet – grows strongly; leaves killed if temp reaches 50C; • Transpiration cools leaf surface to a 40-45C • How?

  26. Water and Salt Balance in Terrestrial Plants • Plants take up excessive salts along with water, especially in saline soils. • plants must actively pump salts back into soil • In coastal mudflats, mangroves must acquire water while excluding salts. They: • establish high root osmotic concentrations to maintain water movement into root • exclude salts at the roots and also excrete excessive salts from specialized leaf glands

  27. Mangrove plants have adaptations for coping with a high salt load. (a) roots immersed in salt water at high tide; (b) specialized glands in the leaves excrete salt

  28. Plants and Mineral nutrients • Roots: extract water and minerals from soil • N, P, S, K, Ca, Mg, and Fe • Traces of Mn, Zn, Cu, and B • All from the soil • Root architecture • Foraging efficiency

  29. Plants and carbon dioxide • Variations beneath a canopy • Carbon dioxide [ ] is highest very close to the ground in the summer – where it is released rapidly from decomposing organic matter in the soil • Daytime photosynthesizing plants: actively remove CO2 from the air; night [ ] increase as plants respire • Winter: low temperatures  rates of photosynthesis, respiration, and decomposition – all slow • Aquatic environments: variations in CO [ ] highest when water mixing is limited • Summer: layers of warm water towards the surface and colder, carbon-dioxide rich layers beneath

  30. Carbon cycle

More Related