Lecture 9: Microbial Population Ecology Flashcards
Explain the biological species concept.
Members of a population that interbreed & produce fertile offspring
- Based on sexual reproduction
Explain the ecology species concept.
Set of individuals that are identical in terms of ecology
What is the most common OTU definition used to describe microbial species?
A. 97% whole genome hybridization
B. 70% 16S rRNA sequence identity
C. 97% 16S rRNA sequence identity
D. 100% plasmid compatibility test
A. 97% whole genome hybridization B. 70% 16S rRNA sequence identity
C. 97% 16S rRNA sequence identity
D. 100% plasmid compatibility test
Define operation taxonomic unit (OTU).
Clusters of organisms grouped by DNA sequence similarity of a specific taxonomic marker gene
Explain the genetic species concept.
A genetic species is a group of genetically compatible organisms
- Focuses on genetic isolation (as opposed to reproductive isolation)
Why is it difficult to categorize bacterial species?
Horizontal gene transfer
- Results in the blurring of distinctions between microbial organisms
What does chimeric mean? What are core genomes vs. accessory genomes?
- Chimeric:
- Core genome: gene set shared by almost all clade members (conserved)
- Accessory genome: more mobile elements of the genome (may be shared with only a few other strains)
Explain what happens in resource partitioning and utilization.
- Through time and natural selection, the two species diverge in their use of the resource
- A new species arrives, and further competition leads to a narrower range of resource use for all three species
Define niche.
The role an organism plays in a community
- Encompasses both physical and environmental conditions and interactions with other species
What is the ecological niche concept?
The range of conditions under which an organism can survive and reproduce
What are fundamental vs. realized niches?
- Fundamental: full range of conditions that an organism could use
- Realized: portion of the fundamental niche actually occupied by that species
Which of the following determine the “size” of a population’s niche?
A. Tolerance for abiotic conditions
B. Competition
C. Overlap in resource utilization
D. Both A & B
E. All of the above
A. Tolerance for abiotic conditions
B. Competition
C. Overlap in resource utilization
D. Both A & B
E. All of the above
Define competition.
Interaction between populations in which growth rates decrease for both
What is competitive exclusion?
If there is significant niche overlap and limited resources, one population will drive the other to extinction
Explain intraspecific competition. Why would a population level out?
- Competition within a population
- Carrying capacity (K) = max population size the environment can sustain
- S shaped curve - As pop gets closer to K, growth slows and eventually levels out
How well do these populations fit the logistic growth model?
- Lab populations of some small animals and microorganisms fit an S-shaped curve if resources are limited
- Constant environment lacking predators and competitors
What are r-selected vs. K-selected populations?
- r-selected: high growth rate, poor competitors, good dispersal
- K-selected: slow growth, good competitors
What are the equivalent terms for growth types in soil vs. aquatic vs. overall ecology?
Explain zymogenous vs. autochthonous soil bacteria.
- Zymogenous: require an easily oxidizable external sources of energy that causes the population to fluctuate with nutrients
- Autochthonous: doesn’t fluctuate in response to nutrient availability
- Found in soil with limited resources
According to the logistic model, what would happen if the 2 species were competing for the same nutrient?
The Lotka-Volterra model of interspecific competition is able to generate a range of possible outcomes. What are they?
- The predictable exclusion of one species by another
- Exclusion dependent on initial densities
- Stable coexistence
What does coexistence of 2 species occur?
When interspecific competition is weaker than intraspecific competition
- Even so, the final or equilibrium density of each species is lower than its carrying capacity
Niche partitioning _____ competition (increases/decreases).
decreases
Define succession.
Directional, continuous pattern of colonization and extinction of a site by populations
