C4.1  Populations and Communities

Theme:  Interaction and Interdependence

Their are physical and biological interactions between organisms in populations and communities.

• Individuals of the same species interact as they compete for limited resources like food, mates, or nesting sites. This interaction is a primary driver of density-dependent population regulation.
• Herbivory is an interaction where a consumer feeds on a producer.
  
• Predation is an interaction between predator and prey. 
  
• Competition occurs when two species interact by vying for the same niche. No two species can interact in the same niche indefinitely; one will eventually outcompete the other.
• When a non-native species enters a community, its interactions (or lack of natural predators) can drastically alter the existing community structure.

The survival of one population is interdependent on the presence and activities of others.

• Mutualism is a type of interdependence where both species benefit and may become unable to survive without the other (e.g., zooxanthellae and coral polyps, or flowering plants and their pollinators).
• Parasitism is an asymmetric interdependence where the parasite depends on the host for nutrients and habitat, often harming the host in the process.
• The community is dependent on the primary producers for nutrients and energy.  
  
• The community structure is dependent on apex predators (keystone species) to prevent lower trophic levels from monopolizing resources.
  
• By specializing in different food sources or active times, species in a community maintain a balance that allows the whole community to persist.

Guiding Questions:  
Guiding questions help students view the content of the syllabus through the conceptual lenses of both the themes and the levels of biological organization.

• How do interactions between organisms regulate sizes of populations in a community?
• What interactions within a community make its populations interdependent?

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​Linking Questions:  
Linking questions strengthen students’ understanding by making connections between topics.  The ideal outcome of the linking questions is networked knowledge.

• What are the benefits of models in studying biology?
• What factors can limit capacity in biological systems?

Key Terms to Know: 

Allelopathy
Antibiotics
Bottom-Up Population Control
Capture-Recapture
Carrying Capacity
Chi-Square Test Of Association
Community
Competition
Cooperation
Density-Dependent Factor
Density-Independent Factor
Endemic Species
Experiment
Exponential Population Growth
Growth Curve
Hard Coral
Herbivory

Interspecific
Intraspecific
Invasive Species
Legume
Limited Resource
Lincoln Index
Logarithmic Scale
Mean
Motile
Mutualism
Mycorrhizae
Negative Feedback
Observation
Orchid
Parasitism
Pathogenicity
Pathogens

Population
Predation
Predator
Prey
Quadrant Sampling
Random Sampling
Reproductive Isolation
Root Nodule
Sampling Error
Scientific Model
Sessile
Sigmoid Population Growth
Species
Standard Deviation
Top-Down Population Control
Zooxanthella

C4.1.1-- Populations as interacting groups of organisms of the same species living in an area.

• Define population. 
• State what isolates populations of the same species.​

​C4.1.2— Estimation of population size by random sampling.

• Define sample.
• Outline the purposes of sampling a population.
• Define sampling error. 
• Describe the need for randomness in sampling procedures. 
• Compare sampling methods for sessile vs motile organisms.

C4.1.3-- Random quadrat sampling to estimate population size for sessile organisms.

• Outline the use of quadrat sampling to estimate the population of a sessile organism.  

C4.1.4— Capture–mark–release–recapture and the Lincoln index to estimate population size for motile organisms.

• Describe the method of capture- mark- release-recapture sampling to estimate the population of a motile organism.  
• List assumptions made about the population when using mark-recapture methods to estimate population size. 
• Outline use of the Lincoln index to estimate population size from mark-recapture data.  ​

​C4.1.5—  Carrying capacity and competition for limited resources. 

• Define carrying capacity.
• List examples of resources that may limit the carrying capacity of a population. ​​

​C4.1.6- Negative feedback control of population size by density-dependent factors.

• Outline population size control as an example of a negative feedback loop. 
• Distinguish between density- dependent and density- independent factors that control population size. 
• List examples of density- dependent factors that maintain population  carrying capacity.
• Outline examples of density- independent factors that maintain population  carrying capacity.

C4.1.7-  Population growth curves.

• State that species have the ability to produce more offspring than the environment can support.
• Outline conditions in which populations can grow exponentially. 
• Explain the reasons for the pattern of sigmoid population growth curve.
• ​Sketch and annotate a graph of the sigmoid and exponential growth curves. 
• Outline the use of a logarithmic scale when plotting change in population over time.

​C4.1.8- Modelling of the sigmoid population growth curve. 

• Outline a method for monitoring the population of yeast or duckweed over time.
• Use data of yeast or duckweed population over time to compare observed and expected population growth curves.
  

C4.1.9- Competition versus cooperation in intraspecific relationships.

• Define intraspecific relationship.
• Outline cause and effect of competition in a population.
• Outline cause and effect of cooperation in a population. 
• List examples of competition and cooperation in plant and animal populations. 

​C4.1.10-  A community as all of the interacting organisms in an ecosystem.

• Define community.
• Give an example of a community of organisms.

C4.1.11- Herbivory, predation, interspecific competition, mutualism, parasitism and pathogenicity as categories of interspecific relationship within communities.

• Outline the ecological interactions within biological communities.  Include mutualistic (++), competition (--), predation (+-), herbivory (+-), parasitic and pathogenic interactions (+-).
• State an example of mutualistic (++), competition (--), predation (+-), herbivory (+-), parasitic and pathogenic interactions (+-).

​​​C4.1.12- Mutualism as an interspecific relationship that benefits both species.

• Outline the mutualistic relationship within root nodules in Fabaceae (legume family).  
• Outline the mutualistic relationship within mycorrhizae in Orchidaceae (orchid family).
• Outline the mutualistic relationship of zooxanthellae in hard corals.

C4.1.13- Resource competition between endemic and invasive species.

• Define endemic and invasive species.  
• Describe the effect of invasive species on the realized niche of an endemic species. 
• Outline the competition for resources in an example of endemic and invasive species.

C4.1.14- Tests for interspecific competition.

• Explain the methodology and limitations of using a chi-square test to assess presence of interspecific competition in a community.
• Explain the use of direct experimentation to assess the presence of interspecific competition in a community.

C4.1.15- Use of the chi-squared test for association between two species.

• State the null and alternative hypothesis of the chi-square test of association between species in a community.
• Use a contingency table to complete a chi-square test of association between species in a community.​

C4.1.16- Predator–prey relationships as an example of density-dependent control of animal populations.

• Explain the typical dynamic equilibrium of populations of predator and prey. 
• Describe an example of an oscillating cycle of predator and prey population sizes.​

C4.1.17- Top-down and bottom-up control of populations in communities.

• Compare and contrast top-down and bottom-up control of populations in communities. ​

​​​​C4.1.18- Allelopathy and secretion of antibiotics.

• Define allelopathy.  
• Outline an example of allelopathy.
• Define antibiotics.
• Outline an example of the natural production and function of antibiotics.  ​