1. Community Interactions Chapter 40

2. Habitat  Place where you would normally find an organism. It is characterized by the temperature, physical features, chemical features, and other species living in it.  Directly or indirectly all of the species in one will associate with one another as a community.

3. Community  Each organism within a community has a sum of activities and relationships in which it engages to secure and use the resources necessary for survival and reproduction.  This is an organism’s niche.

4. Species Interactions  Neutral relationships – where organisms do not affect each other directly. Indirectly they may affect each other. Example: Canadian lynx and grass.  Commensalism – directly helps one organism without affecting the other. Example: Birds use trees for roosting.

5. Species Interactions cont…  Mutualism – interacting species both benefit from the association.  Example: Flowering plants and pollinators.  Obligatory – individuals of one species cannot grow or reproduce without the other.  Example: Yucca plants cannot be pollinated by anything besides a yucca moth.

6. Competition  Disadvantages flow both ways between species.  While one organism may be the winner of the competition, it will still be injured in the process.

7. Predation  Where one animal feeds upon another. Predators feed on prey, but do not take up residence on or in them.  1. Many predator and prey relationships arose by coevolution, where two species exert selection pressures on each other because of close ecological interaction.  2. These relationships depend on carrying capacity, the maximum number of individuals that resources can maintain indefinitely.

8. Parasitism  One organism takes up residence in or on another living organism called the host.  The parasite will feed upon the tissues of the host, and may or may not cause death. Parasites drain hosts of nutrients causing a weakened condition.

9.  This weakened condition can make the host an appealing candidate for predation, but a less than appealing candidate for reproduction.  Natural selection tends to favor a parasitic relationship that does not kill the host, and allows the parasite to reproduce.

10. Types of Parasites  Ectoparasites – live on host’s surface.  Endoparasites – live inside a body.  Microparasites – small parasites such as bacteria, viruses, protozoans, and sporozoans.  Macroparasites – large parasites such as flatworms, roundworms, fleas, and ticks.

11. Competitive Interactions  Intraspecific – competition of organisms within a species.  Interspecific – competitions among different species.  Competitive Exclusion – two species requiring identical resources cannot coexist indefinitely.  Resource partitioning – subdividing of resources that let species coexist

12. Defense Mechanisms  Camouflage – adaptations in form, coloring, pattern, or behavior that help organisms blend in to their surroundings.

13. Warning Coloration  Conspicuous patterns that warn predators to stay away.  Example: Skunks.

14. Mimicry  Many prey bear resemblance to dangerous organisms. One species serves as a mimic to the other, more dangerous species.  Viceroy on left, Monarch on right

15. Ecological Succession  A community develops in sequence, from pioneer species (opportunistic colonizers of vacant habitats) to an end array of species that remain in equilibrium over some region.  More competitive species will replace the beginning species until the array of species stabilizes and results in the climax community.

16. Primary Succession  When pioneer species colonize a barren habitat.  Generally, these species are small plants with brief life cycles. Once established, the pioneers improve the conditions of the area and replacement species can enter.

17. Secondary Succession  A disturbed area in a community recovers and moves toward the climax state.

18. Instability  An outcome of forces that lead to an uneasy balance is called community stability.  If these forces are disturbed, it can hurt the growth of some populations.

19.  If the instability is great enough, the community can change in ways to help its survival.  If a species cannot adapt, it may become extinct.

20. Works Cited  www.naturalsciences.org/ images/skunk.jpg  static.howstuffworks.com/ gif/animal- camouflag  www.ci.san-luis-obispo.ca.us/ naturalresources