1. Predation Great White Shark and Fur Seal

2. 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

3. Eurasian Jay with Acorn

4. Masting

6. Fagus sylvaticus – European Beech Often masts in years following hot summer, but not in years following cool summer

7. Dipterocarp distribution

8. Dipterocarp trees Dipterocarps usually mast during El Nino years

9. Beech seeds and boring moth

10. Lyme’s disease life cycle

11. Masting and Human Health - Lyme’s Disease

12. 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

13. Impact of Herbivores Is Not Uniformly Experienced

14. Aphids attacking Alfalfa Spotted Alfalfa Aphid

15. Induced defenses in Birch Trees

18. Rubus prickles

19. Acacia depanolobium

20. 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

21. Pine beetle infestation – British Columbia

22. Serengeti Grazing System

24. Grazing facilitation Grazing facilitation occurs when the feeding activity of one herbivore species improves the food supply for a second species

25. Opuntia stricta – prickly pear

26. Prickly pear infestation in Australia

27. Area infested with prickly pear before biocontrol

28. Same area after biocontrol

29. Biocontrol Agent – Cactoblastis cactorum