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

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Presentation on theme: "Communities biodiversity, issues keystone species habitats, niches Interactions: competition, predation, mutualism co-evolution."— Presentation transcript:

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

2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Wasps and Pieris caterpillars form an unusual three-step food chain Wasp eggs layed inside caterpillar –Caterpillar eaten up by larvae Dining In

3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A second wasp can detect wasp larvae inside these caterpillars –and will deposit her own eggs inside of the first wasp’s larvae

4 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 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 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings = All the organisms in a particular area Description includes: –Biodiversity -- Vegetation –Response to disturbances –Trophic structure (feeding relationships) Community Figure 36.1

6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 36.9A TROPHIC LEVEL Quaternary consumers Tertiary consumers Carnivore HerbivoreZooplankton PlantPhytoplankton Secondary consumers Primary consumers Producers A TERRESTRIAL FOOD CHAINAN AQUATIC FOOD CHAIN What’s for lunch?

7 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure Tertiary and secondary consumers Secondary and primary consumers Primary consumers Producers (Plants, algae, phytoplankton) Detritivores (Prokaryotes, fungi, certain animals) Wastes and dead organisms Food webs often more real than food chains

8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 170 billion tons of biomass per year Figure Tertiary consumers Secondary consumers Primary consumers Producers 10 kcal 100 kcal 1,000 kcal 10,000 kcal 1,000,000 kcal of sunlight Energy supply limits the length of food chains 10% conversion to biomass at next level

9 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Consequence: a field of corn can support more vegetarians than meat-eaters Figure Secondary consumers Primary consumers Producers Human vegetarians Corn Human meat-eaters Cattle Corn TROPHIC LEVEL

10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Biodiversity is the variety of organisms that make up a community Components: –Species variety: total number of different species in the community –relative abundance of different species –Genetic variation within each species

11 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Biodiversity - current issues 1.Another mass extinction in progress? 2.Wildlife preserves - do they work? 3.Biodiversity hot spots: Should conservation efforts focus only on areas of high biodiversity? 4. Alien species

12 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 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 Communities

13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings There are four main types of relationships among species within communities –Competition –Parasitism, predation –Commensalism –Mutualism Community interactions

14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Community interactions Interspecific competition occurs between two populations if they both require the same limited resource

15 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The competitive exclusion principle –Populations of two species cannot coexist in a community if their niches are nearly identical Figure 36.2 High tide Chthamalus Balanus Low tide Ocean

16 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Competition between species with identical niches has two possible outcomes –One population will eventually eliminate the other –Natural selection may lead to resource partitioning (division)

17 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 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 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings As predators adapt to prey, natural selection also shapes the prey's defenses. This reciprocal adaptation = coevolution –Example: Heliconius and the passionflower vine Figure 36.3A Eggs Sugar deposits

19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Prey gain protection against predators through a variety of defense mechanisms 1. Mechanical defenses, such as the quills of a porcupine

20 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 2. Chemical defenses –Animals are often brightly colored to warn predators –Example: the poison-arrow frog Figure 36.3B

21 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 3. Camouflage –Example: gray tree frog Figure 36.3C

22 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 4. Batesian mimicry occurs when a harmless species mimics a harmful one –mimicry can involve behavior –hawkmoth larva puffs up its head to mimic the head of a snake Figure 36.3D

23 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Eliminates weaker individuals keystone predator maintains diversity by reducing numbers of the strongest competitors in a community - Ex. sea star is a keystone predator What are effects of predation? Figure 36.4A

24 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Predation by killer whales on sea otters, allowing sea urchins to overgraze on kelp –Sea otters represent the keystone species Figure 36.4B

25 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 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 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Mutualism: both partners benefit Examples: - Nitrogen-fixing bacteria and legumes –Acacia trees and the ants of the genus Pseudomyrmex Figure 36.5B

27 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Disturbances include events such as storms, fires, floods, droughts, overgrazing, and human activities –damage biological communities –remove organisms –alter the availability of resources Disturbance is a prominent feature of most communities Figure 36.6


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