Opener – Wed., Jan. 18th:

1. Please write these 2 questions, then I’ll give you the data to use to answer them.  (i) State which nutrient shows the shortest mean residence time in a temperate forest. (1 mark) (ii) Identify the biome in which potassium has the longest mean residence time. (1 mark) Opener – Wed., Jan. 18th:

2. Ecosystems require an input of energy, water and nutrients to maintain themselves. Nutrients may be reused through recycling within ecosystems. Nutrient cycling within an ecosystem has been studied in many biomes. One factor studied is the mean residence time (MRT), which is the amount of time needed for one cycle of decomposition (from absorption by organism to release after death). The table below gives the mean residence time for certain nutrients in four different biomes. In addition, the plant productivity is also shown. (Plant productivity gives an indication of the quantity of biomass potentially available to consumers.)

3. And the winners are... • (i) potassium/K 1 • (ii) sub-arctic forest 1 • On IB markschemes (answer keys)... • “/” = • “;” =

4. “Entangled Bank” –Origin of Species, C. Darwin It is interesting to contemplate an entangled bank, clothed with many plants of many kinds. With birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborate constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us.

5. “Entangled Bank” –Origin of Species, C. Darwin ... There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed laws of gravity, from so simple a beginning endless forms so beautiful and most wonderful have been, and are being, evolved'. (Chapter 14: Recapitulation and Conclusion) Darwin. C (1859) Origin of Species

6. IB “Core” Topics: Ecology5.1 5.25.3

7. 5.1 Communities

9. “Infertile Offspring” • Female horse, male donkey  mule • Female tiger, male lion  liger

10. 5.1.3 Consumers, etc. 5.1.2 Autotroph vs.Heterotroph

11. 5.1.14 Decomposers • Saprotrophic bacteria & fungi recycle nutrients (organic molecules) of dead organisms

12. 5.1.14 Decomposition—how’s it work? • Decomposition: forms soil, recycles nutrients, reduces high energy C cmpds • Begins w/secretion of extra-cellular digestive enzymes produced by sap. Bacteria, fungi • Secreted onto dead organism • Hydrolyze biol. Molecs that made up the dead organism  soluble, so absorbed by sap. • Oxidized, release CO2 & N • Gives energy to the bact/fungi but also returns matter to abiotic envt

15. 5.1.4 Food Chains • Simple linear flow • Who eats whom • ARROWS:Energy & matter flowing through links in chain • Amt energy captured @ each level • Energy lost @ each level? • REAL examples, common names ok • But more specific than “tree”, “fish” • Producer, consumers—no decomp.

17. Who’s the producer? • Primary consumer? • Tertiary consumer?

18. Bushgrass  impala  cheetah  lion • Who’s the producer? • Primary consumer? • Tertiary consumer?

19. Buckwheat  gopher  gopher snake  red tailed kite • WHY are big predators so rare?

20. 5.1.5 Food Webs • Diagram, shows how chains linked • BENEFITS: • More complex interactions b/w species and community/ecosystem • >1 producer supports community • Consumer can have diff food sources @ diff trophic levels

21. 5.1.6 Trophic Level • Defines feeding rel’ship of it to others in food web/chain • Consumer can be in different TLs—depends on who prey is

22. 5.1.8 Construct Food Web

24. Phytoplankton  sea whip  reef shark algae  Diadarma  marine omnivores  groupers Snappers & reef sharks can be either secondary or tertiary consumers (depending on food source)

26. 5.1.7 TL in food chain/web

27. Who’s the most important in the food web?? Producers or Decomposers

29. 5.1.9 Light & Food Chains • Chain/web/community interactions maintained by energy • Sunlight = energy source for most aquatic & terrestrial communities • Chlorophyll = principle trap of sun’s energy • In producers’ chloroplasts • Other communities—chemical energy

31. 5.1.11 Efficiency not 100% • ~ 10-20 % energy @ 1 TL will be assimilated at next higher TL • Model: typical loss of energy from solar radiation through various trophic levels • tapering of the model • volume of 1 layer is 10% of the layer below • in part, this loss of energy  makes food chains ~short

32. 5.1.11 Efficiency not 100% • Extreme environments (arctic) • initial trapping of energy by producers is low • food chains are short • Tropical rainforest • trapping of energy is more efficient • food chains are longer, webs are more complex

33. 5.1.12 Shape of energy pyramids • Flow of energy • Units: energy/unit area/unit time • kJ m-2 yr-1 • Narrowing shape—why? • Gradual loss along chain Solar not shown

34. Energy LOSS...WHY? • Prey’s not 100% eaten  detritivores • Not all that is eaten is digested decomposers • Death before being eaten • Heat energy from respiration rxns • ULTIMATELY...all energy lost as heat

35. 5.1.10 Energy flow in food chain • Not all solar energy comes in contact w/chlorophyll • (not trapped in synthesis of org. cmpds) • Photosynthesis • Consumers feed on producers, pass on energy in food • Need lots producers in food web • Fewer & fewer of higher TLs

36. 5.1.13 Energy vs Nutrients • Energy Flows, Matter Cycles • Energy lost as heat @ each TL; top of pyramid tapers b/c ultimately all lost as heat • Producers convert inorg molecs into organic ones; consumers @ diff levels take it in and use for growth...C, N, Water cycles

38. Why are big predators rare? • Energy, matter lost at each stage • # organisms reduced @ each link in chain • Higher TL organisms  less common • Most chains have 4 TL • Top carnivores must feed over wide area/territory to find food • As population decreases, more vulnerable to ‘catastrophes’ ... • ‘super’ top predators unlikely b/c evolutionary disadvantageous