1. Predation Great White Shark and Fur Seal

2. Predator-Prey Interactions

4. Food Preferences A preference exists if the proportion of a type of food is higher in the animal’s diet than it is in its proportion in the environment Ranked preference – predator preferentially eats prey which is most valuable (usually in terms of calories) Balanced preference – predator eats prey items that provide integral parts of a balanced and mixed diet (usually in terms of nutrients and vitamins)

5. Pied Wagtail

7. Caribou feeding in winter

8. Preferences Fixed preference – predator eats certain items regardless of what else is available – can be fixed in terms of species consumed or energy consumed

9. Edible mussel – Mytilus edulis

10. Shore crab and edible mussels

13. Backswimmers

14. Asellus aquaticus – prey for backswimmers

15. Guppy as predator

16. Guppy prey – tubificid worms and fly larvae

17. Eurasian oystercatcher

18. Search image – this image has dashes arranged as L, as T, and plus signs – can you find the Ts?

19. Bluegill sunfish

21. Effects on populations Population regulation refers to the tendency of a population to decrease in size when above a particular level, and to increase in size when below that level. Population regulation can only occur as a result of one or more density dependent processes acting on birth or death rates. Population abundance is determined by the combined effects of all factors and processes that influence population size, whether they are density dependent or density independent.

22. Predator effect on individual prey

23. Mink Muskrat

24. Arctic Ground Squirrel – Predator population is self-limited

25. Red Grouse in Heather – Predator population is self-limited

26. Tawny Owl Bank vole Predator Switching Regulates Prey Population

28. Cinnabar Moth and Caterpillar on Ragwort Tansy

29. Snowshoe hare and Lynx

32. Lynx Ruffed GrouseSnowshoe hare

33. Sea Otter

34. Sea Urchin

35. Kelp Forest

36. Sea Otter eating Sea Urchin in Kelp Forest

37. Comparison of kelp and urchin biomass with and without sea otters

38. Sea Urchin Barren

39. Kelp forest ecsystems with and without sea otters

40. Plant Resource Defense Qualitative defense - highly toxic substances, small doses of which can kill predators high nutrient environment/fast growth (high turnover in plants) - use toxins (plant secondary compounds) that often require N, expensive to make (must be replaced often), but can be made rapidly - cyanide compounds, cardiac glycosides, alkaloids - small molecules

41. Plant Resource Defense Quantitative defense - substances that gradually build up inside an herbivore as it eats and prevent digestion of food low nutrient environment/slow growth (low turnover in plants) - primarily use carbon structures - wood, cellulose, lignin, tannins - large molecules - makes plant hard or unpleasant to eat (woodiness, silica), but plants are slow to make these defenses

42. Evolutionary “Arms” Races Monarch and milkweed

43. Evolutionary “Arms” Races

44. California garter snakePacific newt

45. Other Plant Defenses Include: mechanical defenses - plant thorns and spines deter many vertebrate herbivores, but may not help much against invertebrate herbivores failure to attract predators - plants somehow avoid making chemicals which attract predators reproductive inhibition - some plants such as firs (Abies) have insect hormone derivatives which if digested, prevent successful metamorphosis of insect juveniles masting - the synchronous production of very large numbers of progeny (seeds) by trees of one species in certain years

46. Eurasian Jay with Acorn

47. Masting

49. Fagus sylvaticus – European Beech

50. Dipterocarp distribution

51. Dipterocarp trees

52. Beech seeds and boring moth

53. Lyme’s disease life cycle

54. Masting and Human Health - Lyme’s Disease

55. Induced Defenses Another aspect of plant defenses is that plants do not always have tissues loaded with defensive chemicals - in many plants, defensive chemicals are only produced when they are needed, usually after the plant has experienced some herbivory - this is an induced defense

56. Impact of Herbivores Is Not Uniformly Experienced

57. Aphids attacking Alfalfa Spotted Alfalfa Aphid

58. Induced defenses in Birch Trees

61. Rubus prickles

62. Acacia depanolobium

63. Plant defenses are developed at a cost to fitness when: 1. Organisms evolve more defenses if they are exposed to much damage and fewer defenses if cost of defense is high 2. More defenses are allocated within an organism to valuable tissues that are at risk 3. Defense mechanisms are reduced when enemies are absent and increased when plants are attacked - mostly true for chemicals not structures 4. Defense mechanisms are costly and cannot be maintained if plants are severely stressed by environmental factors