HL IB Biology Populations & Communities

These flashcards cover key concepts, definitions, and methodologies in population ecology, essential for understanding populations and communities in ecosystems.

What is a population in ecology?

A group of organisms of the same species living in an area at one time.

What does reproductive isolation refer to?

Two populations of the same species that are separate and not interbreeding.

What methods are used to estimate population size?

Random Quadrat Sampling and Capture-mark-release-recapture.

What is the ACFOR scale used for?

To measure species abundance in a quadrat.

What is carrying capacity?

The maximum number of individuals of a species that an ecosystem can support.

What are density-dependent factors?

Factors that have different effects on a population at different population densities.

How does the predator-prey cycle affect populations?

The size of predator and prey populations rise and fall in a cycle, affecting each other's populations.

What types of interactions occur in intraspecific relationships?

Cooperation, where both benefit, and competition, where one outcompetes the other.

What is mutualism?

An interaction where organisms of different species work together for mutual benefit.

What is the chi-squared test used for in ecology?

To determine whether there is a significant association between the distributions of two species.

What are invasive species?

Non-native species that cause harm to the environment where they have been introduced.

What is competitive exclusion?

The process by which one species outcompetes another for resources, possibly leading to the latter's extinction.

How can you determine if competition is present between two species?

By observing changes in species distribution upon the removal of a competing species.

What defines a community in an ecosystem?

Multiple populations of different species living and interacting in the same area.

What does allelopathy refer to?

A strategy used by plants to secrete harmful chemicals into the environment to outcompete other species.

What is the fundamental niche?

The ideal niche for a species in an ecosystem.

What role do abiotic factors play in determining carrying capacity?

They are non-living parts of an ecosystem, such as light and temperature, that can limit population size.

What factors are involved in top-down population control?

Predation, where predators limit the populations of their prey species.

What is the difference between random and systematic sampling?

Random sampling selects sites at random, while systematic sampling uses fixed intervals.

What is the significance of the Lincoln index?

It is a statistical measure used to estimate population size through the capture-mark-release-recapture method.

What effects do parasites have on their hosts?

Parasites live on or in a host, causing it harm, and obtaining nutrients at the host's expense.

What is the plateau phase in a population growth curve?

The phase where the death rate equals the birth rate and population growth stops at carrying capacity.

How does a chi-squared test compare observed and expected values?

It assesses whether the difference is due to chance or indicates a significant relationship.

What is pathogen-induced pathogenicity?

When an infectious microorganism causes disease in a host organism.

What is the main cause of population fluctuation around carrying capacity?

Density-dependent factors that regulate population size.