IB Biology: C4.1 Populations and communities

What defines a population in an ecological context?

• A group of different species living in the same area

• A group of organisms of the same species that interact and reproduce in a specific area

• A collection of individuals that do not breed with each other

• A set of species that share the same habitat and compete for resources

Why is random sampling used to estimate population size instead of counting every individual?

• Counting every individual is more accurate but unnecessary

• Random sampling allows for estimation while reducing time and effort

• Whole population counts are always inaccurate

• Random sampling eliminates all errors in data collection

Which method is best for estimating the population size of sessile organisms?

• Capture–mark–release–recapture

• Random quadrat sampling

• Direct observation of all individuals

• Satellite imaging

The Lincoln index is used to estimate population size of motile organisms. What assumption must be true for it to be accurate?

• Marked individuals mix randomly with the population

• All marked individuals remain in the same location

• Marking an individual increases its chance of survival

• The population is decreasing at a constant rate

What is carrying capacity?

• The number of individuals that can be supported indefinitely in a given environment

• The number of species found in a community

• The maximum speed at which a population can grow

• The amount of food available for a population

Which of the following is an example of a density-dependent factor that controls population size?

• Earthquakes

• Wildfires

• Spread of disease in crowded populations

• Seasonal temperature fluctuations

What does a sigmoid population growth curve represent?

• Unrestricted exponential growth

• Initial slow growth followed by rapid increase and stabilization at carrying capacity

• Continuous decline in population numbers

• Random fluctuations in population size over time

In ecological communities, which of the following describes mutualism?

• One species benefits while the other is harmed

• Both species benefit from the interaction

• One species is unaffected while the other benefits

• Both species compete for the same resources

What ecological interaction occurs between an invasive species and an endemic species when they compete for the same resources?

• Mutualism

• Commensalism

• Interspecific competition

• Allelopathy

Which of the following best describes top-down control in a community?

• Predator populations regulating prey populations

• Producers determining the structure of the food web

• Abiotic factors controlling population sizes

• Competition among prey species limiting population size