Ch. 53 - Population Ecology Flashcards | Knowt (2024)

Population

a group of individuals of a single species living in the same general area. Often described by their boundary and size (as determined by the researcher)

Ecology

the interaction of organisms with each other and their environment.

Population ecology

explores how biotic and abiotic factors influence density, distribution, size, and age structure of populations.

What is an example of population ecology?

the number of loggerhead turtle hatchlings that survive their first journey to the ocean is affected by both biotic (seagulls, fish, human help) and abiotic factors (lights, weather, tide height).

Density

the number of individuals per unit area or volume.

What can be used to estimate densities and total population sizes?

sampling techniques

What is a sampling technique often used for plants?

quadrat - counting the number of plants in a certain area and applying that average to a larger area.

What is the sampling technique used for animals?

mark-recapture method - mark individuals you see in sample 1, in sample 2 find the proportion of individuals previously captured vs. new individuals

Dispersal

The interplay between processes that add individuals to a population and those that remove individuals.

What are the three different types of dispersal?

What does the acronym “Ions need space” help you remember?

Dispersion

Dispersion

the pattern of spacing among individuals within the boundaries of the population (highly dependent on spatial scale)

What are the three types of dispersion?

Demography

the study of vital statistics of a population and how they change over time

Life table

an age-specific summary of the survival pattern of a population (often put as the probability of survival

Cohort

a group of individuals of the same age

Survivorship curve

a graphic way of representing the data in a life table

What does the y-axis commonly represent in a survivorship curve?

the number of survivors

What does the x-axis sometimes represent in a survivorship curve?

the percentage of maximum life span

What are the three general types of survivorship curves and an example of each?

Idealized growth models

Population growth rate

What does ΔN represent in the population growth rate formula?

change in population size

What does Δt represent in the population growth rate formula?

time interval

What does B represent in the population growth rate formula?

number of births

What does D represent in the population growth rate formula?

number of deaths

Population growth or decline formula

change in population size = births + immigrants - deaths - emigrants

Per capita growth rate

denoted as “r”, symbolizes the average contribution of each individual in the population

Change in population size formula

What will r be if the population is increasing?

r > 0

What will r be if the population is decreasing?

r < 0

What will r be if the population is in zero population growth (ZPG)?

How can some populations grow exponentially/intrinsically?

What is an example of exponential growth in a population?

Elephants in Kruger National Park (South Africa) due to hunting being banned

Logistic growth model

describes how a population grows more slowly as it nears its carrying capacity (K)

Carrying capacity

Symbolized by “K”, it is the maximum population size the environment can support. It can vary depending on the abundance of limiting resources

What declines in the logistic population growth model as carrying capacity is reached?

the per capita rate of increase in population

What is the formula for logistic population growth including carrying capacity?

What does the logistic model start with and how does it differ?

exponential models, but it adds an expression that reduces per capita rate of increase as N approaches K

What curve does the logistic model of population growth produce?

S-shaped

What happens to a population when it overshoots K (carrying capacity)?

It goes through a series of overshooting then dying-back till it settles down to a relatively stable density

What is a boom-and-bust cycle?

populations fluctuate greatly, and K becomes difficult to define. An example of this is rabbits and wolves (predator and prey).

In a density-dependent control of population size, what happens when the population density is low?

the population often grows rapidly

In a density-dependent control of population size, what happens when the population density is high?

the population may grow slowly, remain stable (zero growth), or decline (due to lack of resources, competition, predation, lack of space, and spread of disease)

What factors affect density-dependent controls on population growth?

Life history traits are products of what?

natural selection

What three main variables does life history entail?

What will natural selection favor in any environment?

specific combinations of life history traits that maximize reproductive success

What limits a population at low density?

intrinsic rate of growth (r selection)

What limits a population at high density?

carrying capacity (K selection)

r-selection

a type of selection that favors life history traits that maximize reproduction (environmental factors cause a disturbance which creates low-density conditions and frees resources → independent of density → often display type III survivorship curves)

What adaptations are successful for r-selection conditions?

K-selection

selects for life history traits that are sensitive to population density → density-dependent selection (high density → close to carrying capacity → competition for resources due to lack of space → often display type I survivorship curves)

What adaptations are successful for K-selection conditions?

Do K and r selected species exist together or separate? What is an example of this?

together, because small scale disturbances create space for r-species (colonizers). Example: a downed tree allows for light and nutrients for r-groups

Organisms have finite resources which may lead to what? Example?

trade-offs between survival and reproduction. Example: plants containing many small seeds vs. few large seeds that may have better survival rates.

Semel parity

also known as big-bang reproduction, organisms that reproduce once and die (although mostly seen in plants, this still happens with mayflies, salmon, and groups of squid/octopi)

Intero parity

also known as repeated reproduction, organisms that produce offspring repeatedly

What environments likely favor Semel parity?

highly variable or unpredictable environments

What environments likely favor Intero parity?

dependable environments

Density-independent control of population size

events that cause more deaths or fewer births regardless of population density (example: hurricanes, floods)

On a large scale, what type of curve do humans have regarding population size?

exponential curve reaching ~8.1 billion

Is the human population currently still growing exponentially?

no, but it is still rapidly increasing (the growth rate is still above 1). The rate of growth began to slow during the 1960s

Can any population grow indefinitely?

no

What have population ecologists predicted the global human carrying capacity is?

9-10.6 billion in 2050 based on area of habitable land and food availability (assuming there are no mass catastrophic events) but overall, nobody truly knows.

Ecological footprint

a concept that summarizes the aggregate land and water area needed to sustain the people of a nation (how much do we need vs. how much we use). Used as a measure of how close we are to carrying capacity of Earth.

How can ecological footprints be more useful/beneficial in determining carrying capacity than just population numbers?

other factors contribute other than just the numbers, such as energy use for each country compared to their population size.

What area uses the most energy on average?

western countries

More often than not, do higher populated countries use more or less energy than those that are less populated?

less

How are humans carrying capacity similar to other organisms?

it could potentially be limited by food, space, nonrenewable resources, or buildup of wastes

How are humans carrying capacity dissimilar to other organisms?

it is possible to regulate population growth through social changes (example: countries that start to slow growth rate tend to have increased education particularly in women)

What is an issue declining population can cause?

aging population → more retirees than workers → social security funds decrease due to an age gap

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