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