Communities biodiversity, issues keystone species habitats, niches Interactions:

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

2. Dining In • Waspsand Pieris caterpillars form an unusual three-step 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: • Biodiversity -- Vegetation • Response to disturbances • Trophic structure (feeding relationships) 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 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 10% conversion to biomass at next level Tertiaryconsumers 10 kcal Secondaryconsumers 100 kcal Primaryconsumers 1,000kcal Producers 10,000 kcal 1,000,000 kcal of sunlight Figure 36.11

9. Consequence: a field of corn can support more vegetarians than meat-eaters TROPHIC LEVEL Secondaryconsumers Humanmeat-eaters Cattle Primaryconsumers Humanvegetarians Corn Corn Producers Figure 36.12

10. 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

11. 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

12. 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

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

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

15. 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

16. 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

17. 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

18. 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

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

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

21. Example: gray tree frog 3. Camouflage Figure 36.3C

22. 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

23. 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

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

25. 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

26. Mutualism: both partners benefit Examples: - Nitrogen-fixing bacteria and legumes • Acacia trees and the ants of the genus Pseudomyrmex Figure 36.5B

27. 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