Community Interactions APBio


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  • Nightjar bird was an excellent example.
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  • Good day :) In slide ten, you said that 'predators tend to be larger and more numerous than their prey' is true they are usually larger, but are you sure they are more numerous? I was taught that predators only increase population sizes because their prey have increased drastically as well, or they are experiencing exponential growth at which point there would eventually start to die off because their numbers have exceeded their food source/ prey. Though, most animal species (herbivores included) tend to be kept in check by the abundance of their food source (except deer and moose (herbivores whose natural predators have been greatly reduced (by man particularly) and have great adaptability to different environments' vegetation that allows them to overtake other species residing in the same habitats). If I am misunderstanding you point, please feel free to respond. Thanks.
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  • Community Interactions APBio

    1. 1. Community Interactions
    2. 2. Exotic Species <ul><li>Zebra mussels (left) </li></ul><ul><li>Brown tree snakes in Hawaii </li></ul><ul><li>Kudzu </li></ul><ul><li>Fire ants </li></ul>
    3. 3. Why Are Exotic Populations Out of Control? <ul><li>Native populations within communities have evolved together </li></ul><ul><li>Community persists in a delicate balance between populations </li></ul><ul><li>Introduction of an &quot;exotic&quot; species destroys the balance </li></ul><ul><li>Lack of coevolution </li></ul><ul><ul><li>Two interacting species interacting over time </li></ul></ul><ul><ul><li>Act as agents of natural selection on one another </li></ul></ul>
    4. 4. Ecological Niche <ul><li>Encompasses all aspects of a species’ way of life, including </li></ul><ul><ul><li>Physical home or habitat </li></ul></ul><ul><ul><li>Physical and chemical environmental factors necessary for survival </li></ul></ul><ul><ul><li>How the species acquires its energy and materials </li></ul></ul><ul><ul><li>All the other species with which it interacts </li></ul></ul>
    5. 5. Community Interactions <ul><li>Ecological niche </li></ul><ul><ul><li>No two species ever occupy exactly the same niche </li></ul></ul><ul><ul><li>Niches of different species will overlap </li></ul></ul><ul><li>Effects on balance of community of species </li></ul><ul><ul><li>Competition </li></ul></ul><ul><ul><li>Predation </li></ul></ul><ul><ul><li>Symbiosis </li></ul></ul><ul><li>Competition </li></ul><ul><ul><li>Interspecific competition helps control population size </li></ul></ul><ul><ul><li>Competitive exclusion </li></ul></ul><ul><ul><li>Resource partitioning—develops during the course of coevolution </li></ul></ul>
    6. 6. Reduction of Niche Overlap <ul><li>The competitive exclusion principle states that if two species occupy exactly the same niche, one will eliminate the other </li></ul>
    7. 7. Competitive Exclusion: The Ciliate Paramecium over 24 d Grown in Separate Flasks Grown in the Same Flask
    8. 8. Reduction of Niche Overlap <ul><li>When species with largely overlapping niches are allowed to compete, their niches may focus on a different part of the resource spectrum </li></ul><ul><ul><li>This is called resource partitioning </li></ul></ul><ul><ul><li>This reduces interspecific competition </li></ul></ul><ul><ul><li>Example: North American warblers </li></ul></ul>
    9. 9. Resource Partitioning
    10. 10. Predator-Prey Interactions <ul><li>Predators kill and eat other organisms </li></ul><ul><ul><li>Broadly defined, predators include herbivorous as well as carnivorous organisms, including cows, pika, and bats hunting moths </li></ul></ul><ul><li>Predators tend to be larger and more numerous than their prey </li></ul>
    11. 11. Evolutionary Adaptations <ul><li>Predators have evolved characteristics that increase their chances of catching prey </li></ul><ul><ul><li>Examples: tearing claws of mountain lions and keen eyesight of hawks </li></ul></ul><ul><li>Prey have evolved characteristics that decrease the chances of being eaten </li></ul><ul><ul><li>Examples: dappling spots and motionless behavior of deer fawns </li></ul></ul>
    12. 12. Predator–Prey Interactions: Shape Evolutionary Adaptations <ul><li>Camouflage—both predator and prey </li></ul><ul><li>Warning coloration </li></ul><ul><li>Mimicry—prey species &quot;evolve&quot; resemblance to dangerous/poisonous species </li></ul><ul><li>Aggressive mimicry—predators resemble harmless species or objects </li></ul><ul><li>Chemical warfare </li></ul><ul><ul><li>Bombardier beetle </li></ul></ul><ul><ul><li>Plant chemicals, secondary metabolites </li></ul></ul><ul><ul><li>Venoms/poisons </li></ul></ul>
    13. 13. Camouflage <ul><li>Camouflage renders animals inconspicuous even when in plain sight </li></ul><ul><ul><li>May include evolved colors, patterns, and shapes that resemble one’s surroundings </li></ul></ul>
    14. 14. Camouflage by Blending in Sand dab (fish) Nightjar (bird)
    15. 15. Camouflage <ul><li>To avoid detection by predators, some animals have evolved to resemble objects such as bird droppings, leaves, or thorns </li></ul>
    16. 16. Camouflage by Resembling Specific Objects Moth “ poop” Leafy Sea Dragon Treehoppers
    17. 17. Camouflage <ul><li>Some plants have evolved to resemble rocks to avoid detection by herbivores </li></ul>
    18. 18. A Plant That Mimics a Rock Cactus
    19. 19. Camouflage <ul><li>Camouflage also helps predators ambush their prey </li></ul><ul><ul><li>Examples: the cheetah blending with tall grass and the frogfish resembling a rock </li></ul></ul>
    20. 20. Camouflage Assists Predators (a) Cheeta Frogfish (b)
    21. 21. Bright Colors <ul><li>Some animals have evolved bright warning coloration that attracts the attention of potential predators </li></ul><ul><ul><li>Advertises that they are distasteful or poisonous before the predator attacks </li></ul></ul><ul><ul><li>Examples: poison arrow frogs, coral snakes, and yellow jackets </li></ul></ul>
    22. 22. Warning Coloration
    23. 23. Protection Through Mimicry <ul><li>Mimicry refers to a situation in which one species has evolved to resemble another organism </li></ul><ul><li>Two or more distasteful species may each benefit from a shared warning coloration pattern ( M ü llerian mimicry ) </li></ul><ul><ul><li>Predators need only experience one distasteful species to learn to avoid all with that color pattern </li></ul></ul>
    24. 25. Protection Through Mimicry <ul><li>Some harmless organisms can gain a selective advantage by resembling poisonous species (Batesian mimicry) </li></ul><ul><ul><li>Example: harmless hoverfly resembles bee </li></ul></ul><ul><ul><li>Example: harmless mountain king snake resembles the venomous coral snake </li></ul></ul>
    25. 27. Protection Through Mimicry <ul><li>Snowberry flies avoid by jumping spider predation by mimicking them both visually and behaviorally </li></ul>
    26. 28. Visual and Behavioral Mimicry (a) (b)
    27. 29. Protection Through Mimicry <ul><li>Some animals deter predators by employing startle coloration </li></ul><ul><ul><li>Have spots that resemble eyes of a large predator </li></ul></ul>
    28. 30. Startle Coloration Swallowtail butterfly caterpillar Peacock moth
    29. 31. Chemical Warfare <ul><li>Both predators and prey have evolved toxic chemicals for attack and defense </li></ul><ul><li>Spiders and poisonous snakes use venom to paralyze their prey and deter predators </li></ul><ul><li>Many plants have evolved chemicals to deter herbivores </li></ul><ul><li>Bombardier beetle sprays hot chemicals from its abdomen </li></ul>
    30. 32. Chemical Warfare
    31. 33. Coevolutionary Adaptations <ul><li>Plants have evolved a variety of chemicals to deter herbivores </li></ul><ul><ul><li>Example: the toxic and distasteful chemicals in milkweed </li></ul></ul><ul><li>Some animals evolve ways to detoxify these chemicals, allowing them to eat the plants </li></ul><ul><ul><li>Plants may then evolve other toxic substances </li></ul></ul>
    32. 34. The monarch butterfly uses deterrent chemicals of milkweed, acquired by a feeding caterpillar, to make itself distasteful to its predators
    33. 35. Symbiosis—a Close Interaction Between Different Species <ul><li>Parasitism—one benefits, other is harmed </li></ul><ul><ul><li>Parasites smaller, more numerous than hosts </li></ul></ul><ul><ul><li>Parasites with higher reproductive rate </li></ul></ul><ul><li>Commensalism—one benefits, other is neither harmed nor benefits </li></ul><ul><li>Mutualism—relationship benefits both species </li></ul><ul><ul><li>Ruminants </li></ul></ul><ul><ul><li>Nitrogen fixation </li></ul></ul>
    34. 36. Symbiosis
    35. 37. Keystone Species <ul><li>In some communities a keystone species plays a major role in determining community structure </li></ul><ul><li>Role is out of proportion to its abundance </li></ul><ul><li>Removal of keystone species dramatically alters community </li></ul>
    36. 38. Keystone Species <ul><li>Example: The predatory starfish Pisaster from Washington’s rocky intertidal coast </li></ul><ul><ul><li>When removed from their ecosystem their favored prey, mussels, increase and competitively exclude other invertebrates and algae, simplifying the community </li></ul></ul><ul><li>Example: Destruction of encroaching shrubs and trees by African elephants </li></ul><ul><ul><li>Helps maintain the grass savanna which supports many species </li></ul></ul>
    37. 39. Keystone Species: Starfish
    38. 40. Succession: Predictable Sequence of Community Changes <ul><li>Primary succession—bare rock, barren environments </li></ul><ul><ul><li>No previously established ecosystems </li></ul></ul><ul><ul><li>Occurs over a longer period of time (thousands of years) </li></ul></ul><ul><ul><li>Pioneer species </li></ul></ul><ul><ul><li>Climax community (influenced by environment) </li></ul></ul><ul><li>Secondary succession—occurs in a disturbed, established ecosystem </li></ul><ul><ul><li>Plowed field, timbered forest, etc. </li></ul></ul><ul><ul><li>Occurs over shorter time (hundreds of years) </li></ul></ul>
    39. 41. Succession in Progress Mount St. Helens explosion, 1980 Same view, 20 y later
    40. 42. Succession <ul><li>During succession, most terrestrial communities go through stages </li></ul><ul><ul><li>Succession begins with arrival of a few hardy invaders called pioneers </li></ul></ul><ul><ul><ul><li>They alter the ecosystem in ways that favor other species, which eventually displace the pioneers </li></ul></ul></ul><ul><ul><li>Succession often progresses to a relatively stable and diverse climax community </li></ul></ul><ul><ul><li>Recurring disturbances can set back the progress of succession </li></ul></ul><ul><ul><ul><li>Maintain communities in subclimax stages </li></ul></ul></ul>
    41. 43. Primary Succession <ul><li>Primary succession occurs “from scratch,” where there is no trace of a previous community </li></ul><ul><ul><li>May take thousands or even tens of thousands of years </li></ul></ul><ul><ul><li>Examples: succession starting on bare rock, sand, or in a clear glacial pool </li></ul></ul>
    42. 44. Primary Succession
    43. 45. Secondary Succession <ul><li>Secondary succession occurs after a disturbance changes, but does not obliterate an existing community </li></ul><ul><ul><li>Often takes just hundreds of years </li></ul></ul><ul><ul><li>Example: succession when a disturbance leaves behind soil and seeds </li></ul></ul>
    44. 46. Secondary Succession
    45. 47. Succession in Ponds and Lakes <ul><li>Lakes and ponds form when a disturbance blocks the flow of a river or stream </li></ul><ul><li>Nutrient influx, sediment deposition, and other aquatic processes can convert a body of water into a bog, then to a dry land community </li></ul>
    46. 48. Succession in a Freshwater Pond (a) (b) (c)
    47. 49. Climax Community <ul><li>Unless disturbances intervene, succession usually ends with a relatively stable climax community </li></ul><ul><li>Species in climax communities have narrower niches than pioneer species </li></ul><ul><ul><li>Allows many species to coexist without replacing one another </li></ul></ul>
    48. 50. Climax Community <ul><li>Climax species tend to be larger and longer-lived than pioneer species </li></ul><ul><li>The exact nature of the climax community at a site reflects local geological and climatic conditions </li></ul><ul><ul><li>Examples: type of bedrock, temperature, and rainfall </li></ul></ul>
    49. 51. Subclimax State <ul><li>Frequent disturbances maintain subclimax communities in some ecosystems </li></ul><ul><li>Sub climax community example: Tallgrass prairies that once covered northern Missouri and Illinois </li></ul><ul><ul><li>Periodic fires prevented forest from encroaching </li></ul></ul><ul><li>Suburban lawns </li></ul><ul><ul><li>Mowing and herbicides keep weeds and woody species in check </li></ul></ul><ul><li>Agriculture </li></ul><ul><ul><li>Plowing and pesticides keep competing weeds and shrubs from replacing early successional cereal grains </li></ul></ul>
    50. 52. The End