Lecture 3 Hope organisms cope （应对） with their environment

1. Lecture 3Hope organisms cope（应对） with their environment Principles of EcologyEbenGoodaleCollege of Forestry, Guangxi University

2. Last week’s comprehension test and some thoughts • Rather than read lecture notes after class, let’s read them before. • By Thursday / Sunday afternoon, lecture notes will be available on web. • Still working on readings; eventually these may replace the lecture notes. • Tuesday March 30, I am away; my wife will fill in. • Apr 4 we will have another comprehension test, this time worth participation points.

3. Today’s class • How do organisms cope with variation（变化） in the environment? Species’ responses and ranges • Species responses to variation in • Temperature • Water • How species obtain energy

4. Review of last time • Biomes（生物群落） are broad categories of communities that allow us to understand the diversity of climates and vegetation in a simple way. • We “toured” the diversity of biomes. • How do organisms live in some of these extreme environments? • The case of the frozen frogs.

5. The organism’s range • An organism has two solutions to coping with difficult conditions: to “tolerate（忍受）” or to move. • The non-solution: to die!

6. The organism’s range • So each species has a range of（范围） environmental conditions over which it can live. • It’s realized range 实际范围(where it actually occurs) might be different from its fundamental range 理论范围(where it could occur)

7. How does an organize cope with its environment? • An individual can acclimatize（适应）during its lifetime. Example: people getting used to high altitudes. • Or a population can adapt（适应） through natural selection: • Some individuals have a trait that makes them better suited than others to the environment. They survive and reproduce better. • This trait is hereditable, and over time comes to spread in the population. • Note that an individual doesn’t adapt.

8. Temperature • Temperature is an important determinant of an organism’s survival and reproduction. • Enzymes work at a certain range of temperatures and denature when overheated. • Freezing can disrupt and puncture cells.

9. Gaining and losing heat • Conduction: heat moves from colder to warmer body by direct contact. • Convection: the water or air moves across the surface of a body (occurs in a fluid). • Radiation: transfer of heat through electromagnetic waves. • Evaporation: change in the state of water from fluid to gas reduces (uses) heat. • In living things, heat can also be made through metabolism (break down of food) Tea cup gets hot. Loss of heat from tea to air Micowave tea. Water turns to steam. Hs = Hm ± Hcd ± Hcv + Hr - He

10. For plants • Plants mostly lose heat by being able to lose water through their leaves (specialized type of evaporation called transpiration) • Have special cells in the bottom of their leaves called stomates（气孔） that allow water out. • But with loss of heat comes loss of water. Hs = Hm ± Hcd ± Hcv + Hr - He

11. Desert and artic plants Hs = Hm ± Hcd ± Hcv + Hr - He For deserts Plant trying to lose heat without losing water Hs = Hcd - Hcv + Hr Away from ground decreases conduction Textbook gives example of pubescence (little white hairs) increasing reflectance in desert plant. Open structure increases convection Leaves are reflective to decrease radiation Dark or light pigment? Leaves are parallel to sunlight to decrease radiation

12. Desert and artic plants Hs = Hm ± Hcd ± Hcv + Hr - He For artic plants Plants trying to gain heat Hs = Hcd - Hcv + Hr Close to ground increases conduction Low surface area decreases convection Leaves are absorptive to increase radiation dark or light pigment? Leaves are perpendicular to light

13. For animals • Some animals are endoderms（内胚层） and regulate temperature through internal heat generation. • Rest of animals are ectotherms（变温动物）, regulate body temp through energy exchange with environment Hs = Hm ± Hcd ± Hcv + Hr - He Which animals?

14. 6 m2 1 1 24 m2 3 = 6 = m m 1 m3 8 m3 For animals Small animals have large surface-area-to-volume ratio 1 m 24 m2 Surface area: 2 m 8 m3 Volume: Surface area to volume: Surface area: 6 m2 So do you expect endotherms to be big or large? 1 m3 Volume: What other adaptations do endotherms have to retain heat? Surface area to volume:

15. Some endothermic animals undergo torpor（麻木） or hibernate • Especially important for small animals like rodents and hummingbirds.

16. Maintaining a water balance • Lack of water clearly a problem for terrestrial organisms. • But maintaining water also difficult as we will see for freshwater animals whose internal fluids have more solutes than the water around them.

17. Water balance in plants • We all know that water flows downhill, away from high gravitational potential energy levels. • Water also flows to where it is less concentrated, away from “high osmotic”, or more generally, “high water” potential. • Such flow explains “turgor pressure（膨压）” of plant cells: water flows in because cell has more solutes, putting pressure on the hard cell walls. How can we tell when a plant has low turgor pressure?

18. Water balance in plants • Remember that plants need to transpire to lose heat. • The water that’s lost makes the water potential of the leaf higher than the air, and this causes water to continue to leave. • This is called “transpirational pull”.

19. Water balance in plants • Water also has the property that molecules stick to each other chemically. • Hence a column of water is pulled out of the leaves from the roots and soil. • Even for a 75 m Sequioa tree (think of pull of gravity that is offset)!

20. Water balance in plants The drier the environment, the more plants invest in roots to extract water.

21. Water balance in animals • Teleost fish (96% of living fish) developed in freshwater. • In freshwater they have the problem of being hyper-osmotic高渗透压(more salt inside than out), and need always to excrete water. • In the ocean, they are hypo-osmotic低渗透压, and need to continually drink water.

22. Anadromous fish have unique problem in moving between fresh and salt water Anadromous fish … live mostly in sea, but travel up rivers to spawn. Young fish are hatch in freshwater, than travel to the sea. Young fish go through dramatic physiological changes as they enter salt water for first time called “smoltification” Physiological changes involve the Na+-K+ ATPase in fish gills, which increases as fish prepare to enter ocean

23. Water balance in animals • Many animals have hard coverings to retain water. • The kangaroo-rat lives in deserts and minimizes water loss: it never drinks!

24. Kangaroo rat C6H12O6 + 6O2 6CO2 + 6 H2O Water balance in animals • It gets water from metabolism. • It has very concentrated urine, as do other animals that conserve water. Respiration + energy (ATP) Why is there a need to have urine at all? One of the products of metabolism is nitrogen, often NH3, a poison.

25. Some organisms can withstand desiccation干燥 (drying out) • Some organisms, both plants (especially seeds) and animals, become dormant with very low levels of water inside them, then recover from dehydration when water is plentiful. • Similar to the idea of torpor in low temperatures.

26. Today’s class • How do organisms cope with variation in the environment? Species’ responses and ranges • Species responses to variation in • Temperature • Water • How species obtain energy

27. Trophic levels • Definition of trophic: • Autotrophic: fix carbon into organic molecules. Can be photosynthetic or chemosynthetic. • Heterotrophic: consume the organic molecules made by autotrophs. Organic molecule consists of more than one carbon atom linked together in a chain or ring. Of or relating to nutrition.

28. Chemical autotrophs • Some organisms make sugars by using energy in inorganic compounds. • For example, some bacteria in deep sea trenches use H2S as source of energy (gives electrons). • Not just in strange places – also in “nitifying” bacteria, which fix nitrogen, and are very important symbionts(mutualistic partners) of plants. Chemosynthetic bacteria In sulfur hot spring

29. Photosynthesis: Intro to Light Light like a wave（波浪） … And also like a particle… What colors does chlorophyll appear to us and why? PAR = Photosynthetically active radiation Wavelengths of light that chlorophyll is capable of absorbing.

30. C6H12O6 + 6O2 6CO2 + 6 H2O Photosynthesis • Overall: So it’s the opposite of metabolism: 6CO2 + 6 H2O + energy (solar) + energy (ATP) C6H12O6 + 6O2 2 types of reactions Light reactions – uses light to make ATP (energy) Dark (light-independent) reactions – uses ATP to fix carbon

31. Light reactions Chloroplasts – organelles with own DNA Light reactions occur inside thylakoid stacks

32. Light reactions The electron transport chain produces a proton gradient across Thylakoid(内囊体) membrane. Protons move across that gradient through ATP synthase, producing ATP. What does this moving down a concentration gradient remind you of?

33. Dark reactions: C3 Uses enzyme RuBisCo Low affinity for CO2 Dark reactions occur in stoma Making larger strings of carbons Infact about 1/3 of the time takes O2 instead of CO2 This is called photorespiration （光呼吸); It lowers the efficiency of photosynthesis. RuBP PGA The C3 model Calvin Cycle

34. Different forms of photosynthetic pathway do better in certain environmental conditions • Photorespiration is a major problem for photosynthesis at high temperatures (> 27°C). • One solution of plants is C4 photosynthesis（光合作用） (compared to normal “C3” photosynthesis). • Another solution is known as “CAM pathway（景天酸代谢途径）”.

35. Dark reactions: C4 PEP has high affinity for CO2 CO2 low in mesophyll… Released In bundle sheath PEP Bundle sheath separate, high CO2 environment for Calvin Cycle (in which RuBisCo Involved) RuBP CO2

36. Dark reactions: CAM Runs the dark reactions only at night, so water loss with CO2 uptake is low. Reactions prepare 4 C chain like C4. Water loss: C3: 380-900 g of H2O per g of tissue C4: 250-350 CAM: 50

37. Disadvantages of C4 and CAM C3 is the most efficient process biochemically … It doesn’t waste energy getting the carbon ready for the Calvin Cycle. So when temperatures are low it is more productive.

38. C4 and CAM are examples of convergent evolution What is convergent evolution? Pineapple: CAM Saxaul tree: C4 Corn: C4 C4 and CAM evolved independently in different plant families; C4 may be as many as 30 different times.

39. Heterotrophs • Consume organic compounds already produced by autotrophs. Different kinds: • Herbivores • Parasites • Predators • Detrivores Eat other organism without killing Kill their prey Eat already dead organism Much of ecology is about what you eat and who eats you!

40. Heterotrophs • 3 stages of eating: • Finding and obtaining food • Consuming food • Absorbing the energy in the food. • Tradeoff（平衡） between the quality of the food and how easy it is to find. Bacteria: stays in place and ingests low quality food Cheetah: high quality food, but a lot of energy to catch

41. How do foods differ in their quality? • Plant materials have a high amount of cellulose（纤维素） (kind of fiber) and secondary compounds that make them difficult to ingest. • Carbohydrates and fats high amount of energy • Proteins have important nutrient nitrogen

42. The diversity of tools to consume food Red-crossbill appears to be species in process of speciation (breaking apart into different species) 5 subspecies that differ in beak morphology and eat different cone types

43. The diversity of tools used to absorb food • Some bacteria (single celled organisms) have organelle called vacuole where food is broken down • Multi-cellular organisms vary greatly in their digestive systems. • Because herbivores have low quality food, they have much surface area in digestive systems, and unique ways of re-processing（在加工）. Rabbits eat feces “coprophagy” Cow chews “cud”

44. Some animals even make tools to capture, consume food Chimpanzee termite fishing New Caledonian crow Chapter 5 Case study From Gavin and Hunt 2003 Dolphin with sponge on rostrum

45. The story of New Caledonian crows

46. What is the general idea of this figure? From Rutz et al. 2010

47. What is the general idea of this figure? From Rutz et al. 2010

48. Homework • Review: Lecture 3 notes. • Problem solving: Problem on C3/C4 plants: http://sites.sinauer.com/ecology3e/problem05.html • Primary literature: Benkman 2003. • By Thurday night: • Lecture 4 powerpoint with notes. • Be prepared for quiz on Saturday.

49. Key concepts • Organisms cope with variability in temperature and water by acclimitizing (in individual’s lifetime) or through adaptation (population level), and these factors determine species’ ranges. • Water balance and temperature is maintained by exchange between organism and the external environment. • Autotrophs are organisms that capture energy to make carbon-carbon bonds; photosynthesis is the powerhouse for life on earth. • Heterotrophs eat autotrophs and differ among themselves in how they find, consume and absorb food.