bio lab 2. Population Growth and Competition

intraspecific competition

competition within the same species

- happens in the absence of another species

interspecific competition

competition between individuals from different species

- happens in the presence of another species

fundamental niche

range of habitat that can theoretically sustain a viable population in absence of interspecific competition

realized niche

constricted and decreased habitat resulting from the interspecific competition

- equal or smaller than fundamental niche

G. F. Gause

ecologist who conducted experience with protozoa species and studied the concept of niche.

He proposed the competitive exclusion principle

niche

Full range of environmental conditions in which an organism lives and the way in which the organism uses those conditions

2 protozoa species that Gause grew

Paramecium aurelia, Paramecium caudatum

food for the protozoans Gause used

bacteria and yeasts

food for the bacteria and yeasts Gause used

oatmeal

growth pattern observed by the protozoans when cultured alone

logistic growth curve, with exponential increase at the start due to abundant resource (bacteria/yeast) and high reproductive success of protozoan, and cycling above and below the carrying capacity at the end (overexploitation / replenishment of nutrients)

logistic growth curve

growth observed by the population within an environment with limited resource. S shape

carrying capacity

K: maximum number of individuals a set of resources can support in a given environment

growth pattern observed when two protozoans (P. aurelia & P. caudatum) were cultured together

P. aurelia always survived & P. caudatum always went extinct

which protozoan was the better competitior?

P. aurelia

Competitive exclusion principle

two species competing for the same limiting resources cannot coexist in the same local niche indefinitely.

result of Gause's experiement

realized niche of P. caudatum is substantially smaller than its fundamental niche; P. caudatum wasn't able to sustain a viable population when a better competitor was present

2 protozoans studied in our lab

Paramecium digitus and paramecium utensilius

difference between P. digitus and P. utensilius

P. digitus' mouth part resembles human hand, while P. utensilius' mouth part resembles a fork --> only difference

feeding method of P. digitus

use dominant hand to capture food & collect food in the same hand

feeding method of P. utensilius

use non-dominant hand & fork to capture food and hold food in the other hand

environment of P. digitus and P. utensilius

creek with fixed amount of nutrients replenished from the nutrient rich upstream as water flows through the habitat

how are streams marked in the simulation?

separated rectangle with size of 3x4m.

how many streams are in the simulation?

3

what are significance of 3 bags of 200 kidney beans?

200 unit of food in one stream area

what is the significance of bag with 40 kidney beans?

40 unit of food brought by the flow of water after every generation of protozoa feeding

how long does each generation of feeding last?

30 seconds

simulating intraspecific competition

single individual of paramecium colonize the area. After 30 seconds, count the nutrients. 5 nutrients needed for survival, additional 5 nutrients = offspring. Scatter 40 kidney beans again for the next round of feeding.

simulating interspecific competition

single individuals from both paramecium species each colonize 1 area of 200 beans (stream). Repeat the steps the same as intraspecific competition.

maximum life for each paramecium

3 rounds (generations)

environment of 2 protozoans Gause used

liquid medium

number of generations simulated in each experiment

15; or when instructor tells to stop

type of competition simulated in the first and second simulation

intraspecific competition

type of competitions simulated in the third simulation

intra and interspecific competition

x and y axis of the graph

generation over number of individuals