biol 215 - midterm 2 content

what is a niche?

how an organism makes its living

• eg: carnivore

  • hunts at dusk versus during daylight

  • captures large prey versus small prey

difference between interspecific and intraspecific competition?

interspecific is among species, and infraspecific is within species

who was Justus von Liebig

the first German chemist, he made the first chemistry lab. He also identified nitrogen as the major resource for plants

what is Liebig’s Law of the Minimum?

population numbers can be regulated by a single resource that has the greatest relative scarcity

• eg, watering holes in the desert

there was phytoplankton found in an ocean gyer, what were the two-limiting factors for the phytoplankton to produce chlorophyll?

nitrogen and iron

what did Grinnell and Gause study/discover? what were the results?

they studied interspecific competition between paramecium.

• they gave the paramecium a fixed amount of food, this resulted in one species “losing” and one “winning”

• P. aurelia always outcompeted P. caudatum

what is the difference between ‘Competitive Exclusion Principle’ and ‘Gause’s Law of Competitive Exclusion’?

The competitive exclusion principle states that two species cannot coexist indefinitely if they compete for exactly the same limiting resources in the same ecological niche.

The only difference between the two is that Gause’s is specific to paramecium that he was studying.

if competitive exclusion is true, why are there so many species in the same habitat using the same resources?

• eg, predation on arctic lemmings by foxes and owls

possibilities:

• maybe the competitive exclusion principle is incorrect

• alternatively, maybe the ‘same resources’ are not actually the ‘same resources’

• maybe subtle differences in resource use among species

Eg, Grain beetles

• Changed the temperature of the environment (by 3.2 C). It totally changed/flipped the competitive ability of the different Grain beetle species

Habitat heterogeneity

• Habitats may seem similar to us, but they are slight differences in them that let species do well or not compared to other ones

what evidence is there for interspecific competition in nature? (4)

1. habitat shifts in allopatry and symaptry

2. character displacement and resource partitioning

3. habitat differences and resource partitioning

4. Allelopathy

what is habitat shifts in allopatry and symaptry about?

living together (symaptry) vs not living together (allopatry).

• allopatry may use a broader range of resources because competition is absent

• in sympatry it competition may cause a species to shift their habitat or resource use so they over lap less with other species

what is character displacement and partioning about?