Populations Growth and Interactions

Comprehensive practice flashcards covering population ecology, growth patterns, species interactions, and ecological succession based on Chapter 20 lecture notes.

Population

All individuals of a specific species living in a specific area at a specific place in time.

Community

All species that occupy an area at one given time.

Ecosystem

Includes all biotic and a-biotic factors of a specific area at a particular time.

Habitat

The physical area where a species usually lives.

Geographic Range

The total defined area where a species could be found.

Population Size ($N$)

The number of individuals of the same species living in the same place at the same time.

Population Density ($D_p$)

The number of individuals in a given space at a given time, defined by the formula $D_p = \frac{N}{A}$ or $D_p = \frac{N}{V}$.

Random Distribution

Occurs when resources are very abundant and individuals do not have to compete or group together to survive; this pattern is rare in nature.

Clumped Distribution

The most common form of distribution where individuals gather where food, water, or shelter are abundant; also provides safety in numbers and social interaction.

Regular/Uniform Distribution

Pattern where individuals are evenly distributed in a defined area, often characteristic of territorial organisms like Golden eagles ($\text{Aquila chrysaetos}$).

Natality

The number of births in a population.

Immigration

The movement of individuals into an area.

Mortality

The number of deaths in a population.

Emigration

The movement of individuals out of an area.

Change in Population Size ($\triangle N$)

Calculated as $\triangle N = (\text{Natality} + \text{Immigration}) - (\text{Mortality} + \text{Emigration})$.

Growth Rate ($g_r$)

The change in number of individuals in a population over a specified period of time ($g_r = \frac{\triangle N}{\triangle t}$).

Per Capita Growth Rate ($cgr$)

The change in population number in a specific time period relative to the original population size ($cgr = \frac{\triangle N}{N}$).

Carrying Capacity ($K$)

The maximum number of individuals of a population that can be sustained by the resources found within a specific area.

Biotic Potential ($R_{max}$)

The maximum number of offspring that can be produced by a species in a specific time period, determined by factors like offspring surviving to reproduce and reproductive cycles per year.

Environmental Resistance

All limiting factors in the environment, such as resource availability, competition, predators, and disease, that reduce population numbers or limit growth.

Intra-specific Competition

Competition for resources between individuals of the same species.

Inter-specific Competition

Competition for resources between individuals of different species.

Lag Phase

The initial adjustment period when a population is introduced to a new environment and births are low.

Growth / Log Phase

A period of dramatic increase in population as young individuals are actively reproducing and births are high.

Stationary Phase

Phase where the carrying capacity is approached, births equal deaths, and resources become depleted.

Death Phase

Phase where deaths exceed births because the population has exceeded its carrying capacity and resources are lacking.

r-selected species

Species adapted to unstable environments that reproduce at a young age, have many offspring, and exhibit J-shaped growth curves (e.g., insects, microorganisms).

k-selected species

Species adapted to stable conditions with long lifespans, few offspring, and population sizes that stabilize near carrying capacity (e.g., mammals, birds).

Closed Populations

Confined populations where individuals cannot leave or move in, meaning density changes are due only to mortality and natality.

Open Populations

Populations where individuals can move in or out, allowing density changes via mortality, natality, immigration, and emigration.

Density dependent limiting factors

Biotic factors that influence survivability based on the size of the population, such as competition, disease, and predation.

Density independent limiting factors

Abiotic factors that influence survivability regardless of population size, such as weather, climate change, and natural disasters.

Law of Minimums

States that the substance required for population growth that is present in the smallest amount is the controlling factor.

Shelford’s Law of Tolerance

States that too much or too little of any factor can be harmful, and populations with a wider range of tolerance are more likely to survive.

Gause’s Principle of Competitive Exclusion

States that no two species can occupy the same niche at the same time.

Resource Partitioning

When individuals of different species reduce competition by occupying slightly different niches.

Mimicry

Development of color patterns, behaviors, or physical characteristics that provide an organism with a survival advantage.

Camouflage

The development of color patterns or shapes that allow organisms to blend in with their environment to avoid predators.

Symbiosis

A close relationship between two individuals of different species.

Parasitism

A relationship where one species lives in or on another (the host) and obtains food while harming the host.

Commensalism

A relationship where one species benefits and the other is unaffected.

Mutualism

A relationship where both species benefit from living in close association.

Ecological Succession

The gradual and orderly change of a community as it is either developed from bare land or replaced by another community.

Pioneer Community

The first species to appear during ecological succession.

Climax Community

The final stable community that results at the end of ecological succession.

Seral Stages

The specific ordered stages of succession marked by specific types of species.

Primary Succession

The establishment of plant life in an area that was completely barren, soil-less, and undeveloped.

Secondary Succession

The re-establishment of a community that was partially or completely destroyed, but where the soil remains.

Sustainability

Living in a way that meets current needs without compromising the health of future generations or the planet.

Population Histograms

Graphs showing the composition of a population by age and gender at a specific time, also known as population pyramids.