Populations and Communities

(IB Topic C4.1)

Essential Idea(s): Populations and communities are dynamic systems shaped by intra- and inter-specific interactions, resource limitations, and environmental factors. They are studied through various sampling methods, statistical analyses, and ecological modeling.

Unit Length: 6 Lessons (No AHL for this unit)

Guiding Questions

◊ How do interactions between organisms regulate sizes of populations in a community?

◊ What interactions within a community make its populations interdependent?

Materials:

Self-Teaching Slides	Quizlet Vocab Set
Teaching Slides	Notes Template

IB Statement(s) and Objective(s)
C4.1.1: Populations as interacting groups of organisms of the same species living in an area Define population State what isolates one population from another population of the same species C4.1.2: Estimation of population size by random sampling Define population sample 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 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 Give a real-life example of a negative feedback loop regulating population size control C4.1.7: Population growth curves Outline conditions in which populations can grow exponentially Explain the reasons for the pattern of sigmoid population growth curve C4.1.8: Modelling of the sigmoid population growth curve (See activities at right!) Collect data regarding population growth C4.1.9: Competition versus cooperation in intraspecific relationships Define intraspecific relationship List examples of cooperation in animal populations List examples of competition in animal populations List examples of competition in plant populations List examples of cooperation in plant 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 Define interspecific relationships Outline the ecological interactions within biological communities, including mutualistic (++), competition (–), predation (+-), herbivory (+-), parasitic and pathogenic interactions (+-) Distinguish between predation, parasitism, and pathogenicity State examples of the various types of ecological interactions listed above 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 Outline experimental approaches that can be used to determine interspecific competition C4.1.15: Use of the chi-squared test for association between two species Explain the methodology and limitations of using a chi-square test to assess presence of interspecific competition in a community Use chi-squared to test for association between two species State the null and alternative hypothesis of the chi-square test of association Calculate a chi-square statistic based on observed values from fieldwork 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

IB Statement(s) and Objective(s)

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

Define population
State what isolates one population from another population of the same species

C4.1.2: Estimation of population size by random sampling

Define population sample
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
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
Give a real-life example of a negative feedback loop regulating population size control

C4.1.7: Population growth curves

Outline conditions in which populations can grow exponentially
Explain the reasons for the pattern of sigmoid population growth curve

C4.1.8: Modelling of the sigmoid population growth curve

(See activities at right!) Collect data regarding population growth

C4.1.9: Competition versus cooperation in intraspecific relationships

Define intraspecific relationship
List examples of cooperation in animal populations
List examples of competition in animal populations
List examples of competition in plant populations
List examples of cooperation in plant 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

Define interspecific relationships
Outline the ecological interactions within biological communities, including mutualistic (++), competition (–), predation (+-), herbivory (+-), parasitic and pathogenic interactions (+-)
Distinguish between predation, parasitism, and pathogenicity
State examples of the various types of ecological interactions listed above

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

Outline experimental approaches that can be used to determine interspecific competition

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

Explain the methodology and limitations of using a chi-square test to assess presence of interspecific competition in a community
Use chi-squared to test for association between two species
State the null and alternative hypothesis of the chi-square test of association
Calculate a chi-square statistic based on observed values from fieldwork

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


Activities: ⓟ = podcast / ⍰ = inquiry 5 / ⓦ = Write it / Ӕ = The academy / Ⓡ = Read it
*You have several options for virtual / simulation labs for this unit:* Ⓛ: Modeling Population Growth in Yeast (💁/👭 max 2) Use this guide to design an investigation on how the size of a population of yeast changes over time in response to different factors such as amount of food, amount of space, and the initial size of the population. Ⓛ: Population Sampling with Beans (💁/👭 max 2) A simple cup of beans goes a long way in this lab: explore how ecologists estimate species abundance using three dynamic sampling methods: quadrat, transect, and mark-recapture. Instead of counting every single organism, you’ll master techniques that let you accurately estimate population sizes with just a sample. Grab some beans and some paper and follow the directions in this guide. Post your answers as a podcast or a written paper to G. Classroom. Ⓛ: Simulation Lab: Estimating Frog Population Sizes Using Mark-Recapture (💁/👭 max 2) This virtual simulation could, in theory, actually work as an IA. For a step-by-step guide, follow the instructions on this website, or alternatively, just use the simulation to come up with your own research question and experimental design. Submit your data analysis to G. Classroom, complete with a data table, graph, and conclusion. Ⓛ: Virtual Lab: Sampling Sea Star + Barnacle Populations on USA’s West Coast (💁/👭 max 2) On the shores of Washington state in the USA is an interesting coastal area, home to sea stars, anemones, various crab species, and more. Follow in the footsteps of previous IB students completing their EEs to get an idea of how population sampling of these species is actually done. Thankfully, they’ve done all the data collection for you, so you are simply seeing what their data actually showed. Complete the virtual lab and submit the answers to each of the questions on the slides, either as a podcast or a written activity. Ⓛ: Virtual Lab: How Well to Mollusks Tolerate Each Other on the Coast? (💁/👭 max 2) Do snails and other shelled mollusks found near the ocean, like chitons, periwinkles, whelks and limpets, also like to live on large, stable substrates? At the end of this lab, you’ll be able to find out the answer to those kinds of questions on your own. Here’s another virtual lab to follow in the footsteps of students who have actually ventured out to the beach to collect data on population sizes. Complete all the questions and graphs and submit to G. Classroom. Ⓛ: Virtual Simulation Lab on Population Growth: Why Death is the Key to Life (💁/👭 max 2) This virtual lab will work you through a simple question that every budding ecologist learns to appreciate: What happens if all the offspring that are born survive? Compare both exponential and logistical growth models to get an appreciation of how nature has evolved to find the right balance between life and death so that life and thrive and evolve. Answer the questions on the student worksheet (as either a podcast or written exercise), then submit to G. Classroom. Ⓛ: Simulation Lab: How Populations Grow and Collapse (💁/👭 max 2) Here’s another simulation to virtually explore how populations grow and collapse. Use this guide if you need If you need some help getting the simulation running. Once you do, use it to design your own experiment, focusing on the following: A good, clear research question Clearly defined variables and hypothesis Properly formatted data tables, graphs, and a conclusion This is another simulation that in effect can function as a mini-IA. Do it well and you should breeze through yours!