Section 2 – Species Interactions

1. Section 2 – Species Interactions

2. The Niche and Competition • An organism’s niche is affected by both its tolerance and competitive interactions • Habitat: general place it lives • Niche: an organism’s habitat, resource use, and fundamental role in a community • Habitat • Food Source • How/When it Reproduces • Interactions with other Organisms

4. Tolerance • Tolerance: the ability to survive and reproduce under changing environmental conditions • Specialists: very restricted tolerance ranges • Ex. Panda Bears • Generalists: wide tolerance ranges • Ex. Rats • BOTH may not be able to adapt when conditions change.

6. Competition • Multiple organisms seek the same limited resource. • Food, Light, Water, Space • Direct Competition: physically, for territory • Indirect Competition: flowers, for pollinators • Intraspecific Competition: competitive interactions among members of the same species • Interspecific Competition: competitive interactions among members of two or more different species

8. Competitive Exclusion • Competitive Exclusion: if one species is a very effective competitor, it may exclude another species from resource use entirely • Mussel and Clam Populations in Lake St. Clair • Lake St. Clair connects Lake Erie and Huron • 20 native mussel species • By 1997, they were all gone • When Zebra Mussels attack, shellfish cannot open their shells – they eventually suffocate or starve

10. Fundamental and Realized Niche • Usually, neither competing species fully excludes the other. • Instead, competing species tend to adjust to each other, minimizing competition. • Changing Behavior • Using only a portion of the resources they are capable of using • Fundamental Niche: full niche of a species • Realized Niche: a niche restricted by competition

13. Resource Partitioning • Resource Partitioning: a process that allows different species to share common resources • If 2 bird species eat the same type of seeds • 1 specializes in eating larger seeds • 1 specializes in eating smaller seeds • OR • 1 is active in the morning • 1 is active in the evening

15. Character Displacement • Character Displacement: resource partitioning can lead to the evolution of physical characteristics among the competing species that reflect their specialized role in the environment • Darwin’s Finches – Galapagos Islands • Birds specialize in eating small seeds = small bills • Birds specialize in eating large seeds = large bills

17. Predation, Parasitism, and Herbivory • “0” = relationship in which there is no effect, or the effect is neutral • “-/-” = negative effect on both organisms • Competition • “+/-” = beneficial for one participant, but harmful to the other • Predation • Parasitism • Herbivory

18. Predation and Population Cycles • Predation: the process by which individuals of one species (the predators) hunt, capture, and feed on individuals of another species (the prey) • Population Cycles • INCREASE in Prey Population • INCREASE in Predator Population • DECREASE in Prey Population • DECREASE in Predator Population • and Repeat

21. Predation and Evolution • Natural Selection – evolution of better predators • Predators skilled at capturing prey – more successful • Prey – evolution of Defense Mechanisms • Strong selective pressure – IMMEDIATE DEATH

25. Coevolution and Evolutionary “Arms Race” • Coevolution: the process by which two species evolve in response to changes in each other • Newt develops toxins that kills predators • In response, predators evolve immunity to the toxins • In response, newt evolve stronger toxins • Arms Race: each species develops stronger and stronger “weapons” in response to the other • ALL SPECIES ADAPT TO BETTER SURVIVE AND REPRODUCE IN THEIR ENVIRONMENT.

27. Parasitism • Parasitism: a relationship between two organisms from different species in which one organism (the parasite) depends on the other (the host) for nourishment or some other benefit • Tapeworms • Ticks • Symbiosis: a long term and physically close relationship between two organisms from different species in which at least one organism benefits • Commensalism • Mutualism • Parasitism

29. Herbivory • Herbivory: the act of feeding on a plant • Insects – most common type of herbivore • Hervibory usually doesn’t kill the plant • Affects growth and population • Natural Selection has given plants defenses: • Produce Toxic/Distasteful Chemicals • Thorns, Spines or Irritating Hairs • In response, herbivores evolve ways to overcome.

31. Mutualism • Mutualism: (+/+) a relationship between two organisms from different species in which both organisms benefit • Plant Roots + Fungi = Mycorrhizae • Plant provides energy, fungus assists in nutrient absorption • Pollination • Pollinators enable sexual reproduction in plants • Pollinators receive nectar as a reward

34. Commensalism • Commensalism: (+/0) a relationship between two organisms from different species in which one benefits and the other is unaffected • Example: • Palo Verde trees in the Sonoran Desert • Trees create shade and leaf litter that allow the soil to hold moisture • Soil becomes cooler with more moisture, making it easier for young plants to germinate and grow • Other desert plants grow beneath the “nurse” tree

36. Section 3

37. Section 4