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Community Ecology Chapter 19 Part B Community An association of all the populations of species that occupy the same habitat Habitat: Physical and chemical features of an area where a species normally lives. Niche: The specific resources a species needs for survival and reproduction Community Directly or indirectly species in a habitat affect each other as part of the community structure. Five factors shape community structure Community Structure Climate and Topography Temperature, rainfall, soil types, etc Kinds and amounts of food and other resources Nutrient poor or extreme habitats don’t support very many species Community Structure Adaptive traits Allow them to survive and exploit specific resources Population sizes and history Interactions between species Questions Match the following to Habitat or Niche Many organisms share “Profession” of organism Area where the organism lives Only one species Overlap results in competition for resources All the biotic (living) and abiotic (non-living) factors Questions How does climate influence community structure? How would poor soil affect community structure? How would population size influence community structure? Species Interactions Interactions among species can be grouped by their effects on both participants Indirect Commensalism Mutualism Competition Exploitation Species 1 None Helpful Helpful Harmful Helpful Species 2 None None Helpful Harmful Harmful Indirect Interactions No direct effect on each other Songbird and tree Bird eats caterpillar, indirectly benefitting the tree Grass and Canadian lynx Rabbits eat grass, which are in turn eaten by lynx Good grass plenty of rabbits food for the lynx Commensalism Helps one species, but does not affect the other Birds build a nest in a tree Commensal ferns attach to the trunk of a tree More access to sunlight Mutualism Both species benefit Insects and plants Insect transfer pollen between plants Plant provides nectar Birds and plants Bird disperses seeds Plant provides fruit •Sea anemone provides shelter •Pink anemone fish chases off butterfly fishes (bite off anemone’s tentacles) p.704b Mutualism Faculative Mutualism Either species can survive without the other Obligate Mutualism Both species cannot survive without the other Yucca plant and the yucca moth Fig. 40-3a, p.707 Competitive Interactions Disadvantage to both organisms Occurs when niches are similar and overlap between two species Limits the resources available to either species Competitive Interactions Competition takes two forms Interference competition one species actively prevents another from accessing some resource Exploitative competition Each species reduces the amount of resources available to the other by using that resource Competitive Interactions Effects of competition Competitive exclusion One species will outcompete the other when they require identical or very similar resources Paramecium caudatum Paramecium aurelia Competitive Interactions Effects of competition Resource partitioning Species become adapted in different ways to subdivide similar resources Allows competing species to co-exist Essentially reduces each species’ niche Alpine chipmunk Alpine zone Lodge pole pine chipmunk lodge pole zone Least chipmunk Forest zone Merriam’s chipmunk Base of mountain Sierra Nevada: competition keeps nine species of chipmunks in different habitats Exploitation One species benefits at the cost of the other Predation One organism feeds on another, but does not live in or on them Interaction between predator and prey influences both species’ population size PREY POPULATION PREDATOR POPULATION Fig. 42.7, p. 724 Lynx - - - Hare Exploitation Predation Interactions between predators and prey have led to co-evolution Each population exerts selective pressure on the other Prey needs to escape Predator needs dinner Traits that confer an advantage for survival will be selected Exploitation Predation Prey adaptations Difficult to eat Hard, sharp parts Chemicals that taste bad Warning colorations Conspicuous color pattern Poison dart frogs Skunk Wasp’s black and yellow stripes Exploitation Predation Prey adaptations Mimicry Wasp stings (warning coloration) Close resemblance in form or behavior to a dangerous organism Non-stinging insects which mimic the wasp’s coloration: non-stinging wasp, beetle, and a fly Exploitation Predation Prey adaptations Last chance trick Look larger and more intimidating: hissing, puff up, eyeshaped spots Play dead Squirt irritating chemicals Exploitation Predation Prey adaptations Camouflage Form, patterning, color, or behavior blend with the surroundings Lithops Exploitation Predation Predator adaptations Stealth Camouflage Traps Avoid repellents Grasshopper mice plunge the chemical-spraying tail end of the beetle into the ground and feast on the head end Exploitation Herbivory Animal eats a plant or plant parts Plant adaptations Recover quickly Prairie grasses Deterrents: thorns, tough leaves, bad tastes Exploitation Parasitism A parasite feeds on the host without immediately killing it Many live in or on the host Endoparasite lives inside the host (tape worm) Ectoparasite feeds while attached to external parts of the host (tick) Strangleweed Fig. 40-14a, p.714 Roundworms in pig intestines Fig. 40-15, p.714 Exploitation Types of parasitism Brood parasites Female lays eggs in a different species’ nest The foster parent then pays the cost of caring for the young Parasitoid Insects that lay their eggs in other insects The larvae hatch, develop, and eat the host’s body Questions For the following pictures indicate what type(s) of species interaction is involved Yucca plant can only be pollinated by a yucca moth Yucca moth can only lay eggs in yucca plant Whistling Thorn Acacia provides protection for ant larvae and honey-like secretions used by the ants as food. Ants provide protection against herbivores by swarming out as soon as the tree is touched. Canadian Lynx Grass Preying mantis Remains of insect Tree Bird builds nest in tree Human feet Fungus Fig. 40-17a, p.715 Community “Stability” Not always very stable actually an uneasy balance Community “Stability” Climax community Typical array of plants under prevailing habitat conditions Forest: trees Prairie: grasses “Stable” community Community “Stability” Disturbance Disrupts the climax community Fire, volcano, empty farm field, tidal wave, etc The type of disturbance influences species richness (biodiversity) Number of different species within a community Community “Stability” Community Succession Disturbed area develops through a sequence of predictable stages to a final “stable” array of species Community “Stability” Community Succession As each stage grows they change the environment Changed environment is favorable for the next stage New stage then out-competes previous array of species Community “Stability” Community Succession Pioneer species Lichens, moss, fireweed Stages of temporary species (seres) Typically each stage increases in height Wild flowers, grass Bushes/shrubs Trees Climax species Barren land Pioneer Species Climax community Temporary Stage May 1980 6-9 years later Pioneer species 12 years later Seedlings of the dominant climax community species: Douglas firs Community Stability Keystone species Major effect on community stability Removal of a keystone species can dramatically change the diversity of species in that habitat Sea stars are the keystone species in this example. Grazing periwinkles affect the number of algal species in different ways in tide pools and on rocks Periwinkles graze on Enteromorpha the dominant alga in tide pools, promoting the survival of less competitive algal species Periwinkles find Chondrus, which is the dominant alga on rocks, to be tough so they eat other less competitive algal species reducing diversity Community Stability Species introductions Exotic invaders Non-native species Invasive Out compete natives Community Stability Species introductions Kudzu in the South Rabbits in Australia Caulerpa taxifolia Gypsy moth Kudzu in the South Caulerpa taxifolia Rabbits in Australia Questions Describe the community succession of a Missouri farm field if it was left alone. Questions Missouri Bare soil Annuals, legumes, grasses Herbaceous perennials Shrubs Intolerant trees (shade) Mid-tolerant trees Tolerant trees (woodland climax) Summary Community Habitat Niche Community structure Species interactions Community stability