Communities biodiversity, issues keystone species habitats, niches Interactions: competition, predation, mutualism

1. Communities biodiversity, issues keystone species habitats, niches Interactions: competition, predation, mutualism, commensalism co-evolution

2. Dining In • Waspsand Pieris caterpillars form a food chain • Wasp eggs layed inside caterpillar • Caterpillar eaten up by larvae

3. and will deposit her own eggs inside of the first wasp’s larvae • A second wasp can detect wasp larvae inside these caterpillars

4. Finally, yet another wasp, a chalcid, may lay its eggs inside the second wasp’s larvae • Only the chalcid wasp’s larvae emerge from the caterpillar carcass

5. Community • = All the organisms in a particular area • Description includes: • Trophic structure (feeding relationships) -- Vegetation -- Biodiversity -- Response to disturbances Figure 36.1

6. TROPHIC LEVEL Quaternaryconsumers What’s for lunch? Carnivore Carnivore Tertiaryconsumers Carnivore Carnivore Secondaryconsumers Carnivore Carnivore Primaryconsumers Herbivore Zooplankton Producers Plant Phytoplankton Figure 36.9A A TERRESTRIAL FOOD CHAIN AN AQUATIC FOOD CHAIN

7. Wastes anddead organisms Tertiaryandsecondaryconsumers Food webs often more real than food chains Food webs reveal the flow of energy Secondaryandprimaryconsumers Primaryconsumers Producers Detritivores (Plants, algae,phytoplankton) (Prokaryotes, fungi,certain animals) Figure 36.10

8. Energy supply limits the length of food chains • 170 billion tons of biomass per year Avg. 10% conversion of biomass to next level Tertiaryconsumers 10 kcal Secondaryconsumers 100 kcal Primaryconsumers 1,000kcal Endothermic animals convert only 2% Producers 10,000 kcal Plants convert 30-85% 1,000,000 kcal of sunlight Figure 36.11

9. Consequences: • Low density of large carnivores • a field of corn can support more vegetarians than carnivores. TROPHIC LEVEL Secondaryconsumers Humanmeat-eaters Cattle Primaryconsumers Humanvegetarians Corn Corn Producers Figure 36.12

10. DDT concentration:increase of10 million times DDT infish-eating birds25 ppm • Chemicals are concentrated in food chains by biological magnification DDT inlarge fish2 ppm DDT insmall fish0.5 ppm DDT inzooplankton0.04 ppm DDT in water0.000003 ppm Figure 38.3B

11. Components: • Species variety: total number of different species in the community • relative abundance of different species • Genetic variation within each species • Biodiversity is the variety of organisms that make up a community

12. Biodiversity - current issues • Another mass extinction in progress? • Wildlife preserves - do they work? • Biodiversity hot spots: Should conservation efforts focus only on areas of high biodiversity? 4. Alien species

13. Communities • Habitat is the environment in which an organism lives. • A population's niche is its role in the community • How it uses the biotic and abiotic resources of its habitat

14. Community interactions • There are four main types of relationships among species within communities • Competition • Parasitism, predation • Commensalism • Mutualism

15. Community interactions Interspecific competition occurs between two populations if they both require the same limited resource

16. Populations of two species cannot coexist in a community if their niches are nearly identical • The competitive exclusion principle Hightide Chthamalus Balanus Ocean Lowtide Figure 36.2

17. One population will eventually eliminate the other • Natural selection may lead to resource partitioning (division) • Competition between species with identical niches has two possible outcomes

18. Predation is an interaction where one species eats another • consumer = predator • food species = prey • Parasitism is a form of predation • Parasite, host • Not immediately lethal

19. Other modes of nutrition for plants: • Some plants have evolved parasitic ways of obtaining food from other plants • Dodder taps into the host’s vascular tissue Figure 32.12A

20. Mistletoe siphons sap from vascular tissue of its host plants Figure 32.12B

21. This reciprocal adaptation = coevolution • Example: Heliconius and the passionflower vine • As predators adapt to prey, natural selection also shapes the prey's defenses. Eggs Sugardeposits Figure 36.3A

22. Sundew and Venus flytrap use insects as a source of minerals • enables them to thrive in highly acidic soil • Carnivorous plants obtain nutrients from animal tissues Figure 32.12C, D

23. 1. Mechanical defenses, such as the quills of a porcupine • Prey gain protection against predators through a variety of defense mechanisms

24. Animals are often brightly colored to warn predators • Example: the poison-arrow frog 2. Chemical defenses Figure 36.3B

25. 3. Camouflage Figure 36.3C

26. mimicry can involve behavior • hawkmoth larva puffs up its head to mimic the head of a snake 4. Batesian mimicry occurs when a harmless species mimics a harmful one Figure 36.3D

27. What are effects of predation? • Eliminates weaker individuals • keystone predator maintains diversity by reducing numbers of the strongest competitors in a community - Ex. sea star is a keystone predator Figure 36.4A

28. Predation by killer whales on sea otters, allowing sea urchins to overgraze on kelp • Sea otters represent the keystone species Figure 36.4B

29. Commensalism - one partner benefits and the other is unaffected • Examples - Algae that grow on the shells of sea turtles • Barnacles that attach to whales • Birds that feed on insects flushed out of the grass by grazing cattle

30. Mutualism: both partners benefit Example: • Acacia trees and the ants of the genus Pseudomyrmex Figure 36.5B

31. Mutualism • mycorrhizae • fungal threads increase plant's absorption of nutrients and water • fungus receives nutrients from the plant Figure 32.11

32. Legumes and certain other plants house nitrogen-fixing bacteria Shoot • nodules in the plant roots contain bacteria that convert N2 gas to soluble NO3-, NH4+ Nodules Roots Figure 32.14A

33. Nitrogen-fixing bacteria and legumes ATMOSPHERE N2 Aminoacids Nitrogen-fixingbacteria N2 NH4+ NH4+(ammonium) NO3–(nitrate) Soil Nitrifyingbacteria Ammonifyingbacteria Organicmaterial Root Figure 32.13

34. Disturbance is a prominent feature of most communities • Disturbances include events such as storms, fires, floods, droughts, overgrazing, and human activities • damage biological communities • remove organisms • alter the availability of resources Figure 36.6