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Ch. 4

Ch. 4. Interactions Among Organisms. How does competition affect growth, survival and reproduction of organisms?. When a greater number of organisms competes for the same resources, each organisms is affected. Growth is diminished

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Ch. 4

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  1. Ch. 4 Interactions Among Organisms

  2. How does competition affect growth, survival and reproduction of organisms? • When a greater number of organisms competes for the same resources, each organisms is affected. • Growth is diminished • Interaction –relationship between 2 or more organisms that affects growth, survival and reproduction • Competition-most common interaction, neither organism benefits

  3. More… • When resources are scarce organisms compete for food and space can affect their survival and reproductive ability • Exploitation – occurs when one organisms benefits while another organism is harmed • Mutualism – both organisms benefit from the interaction

  4. Types of Competition • Indirect competition –organisms gathering as much of a shared resource as they can before it runs out • Squirrels/acorns • Fish/mayflies • Shorebires/forage on mudflats • Intraspecific competition- competition among members of the same species • Interspecific competition-competition among different species

  5. What is niche? • Everything that affects a species existence – its way of life and role in an ecosystem. • A species niche includes the range of environmental conditions the species can tolerate, what it needs to grow, survive, and reproduce, and how it interacts with its biotic and abiotic environment

  6. What is the difference between a fundamental and realized niche? • A fundamental niche includes the environmental conditions the species can tolerate the resources it is capable of using in ideal conditions • The realized niche is the portion of the environment the species uses in the presence of other species

  7. Two species can not havce the same niche in an ecosystem • Gause’s Law • When 2 species compete for the same resources, one will be more efficient than the other at gathering those resources • The more efficient species will fill the niche with more of its offspring, eventually leaving no resources for the less efficient species which will die off in time. • Competitive exclusion principle • When species with similar niches use a resource in a slightly different way – resources partioning

  8. Types of Exploitation • 3 types: predation, herbivory, and parasitism • Predation involves one organism, predator, gaining energy by catching, killing and eating the prey • Herbivory – involves one organism, herbivore, gaining energy be eating plants • Parasitism- one organisms, the parasite, gaining energy by feeding on blood, fluids or tissues of a host

  9. Adaptations • Keen senses may help a predator find prey • Adaptations such as claws, venom or ambush techniques may help predators • Avoiding detection or evading capture by use of blending coloration, warning coloration and mimicry • Avoiding capture can include the use of shells or bony plates for protection • Herds, flocks and schools protect the group by having more eyes to detect danger.

  10. More… • Some species use toxic chemicals to discourage predators, as well as scare tactics • Plants use thorns, spikes and chemicals to discourage predators • Herbivores use grinding teeth for tough plant parts • Parasites use sucking mouthparts, hook-like appendages and or elaborate life cycles

  11. Warning coloration • I’m not good to eat! • Batesian mimicry – when a harmless species resembles a dangerous one • Hummingbird moth/bee or wasp • Mullerian mimicry – occurs when dangerous or distasteful species resemble each other • Viceroy /monarch

  12. Commensalism • When two organisms interact but one organism benefits and the other is not affected. • Desmodium (stick-tights)

  13. Mutualism • Interaction where both species benefit • Both can benefit from food and energy efficiency • Can sometimes help one organism reproduce • Can increase the safety of participants • When one organism could not survive without the other (symbiosis) • Mutualism, parasitism and some kinds of commensalism are all types of symbiosis

  14. Interactions maintain balance • When prey species disappear, predators soon decline • Thus predators keep prey species in check and maintain balance in an ecosystem • Loss of mutualistic relationships would ripple through the biosphere until very few organisms remained

  15. Resource Management Topics • 1. Timber Stand Improvement (p.44) • 2. Managing wetlands (p.46) • 3. Cowbird prasitism (p.49)

  16. Questions • Explain what the topic is • Give examples • Why is it important • What are the Benefits • What are the Difficulties

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