5-Population Ecology 2

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What does the logistic growth model suggest about population growth over time?

Population size will continue to increase indefinitely.

Population growth is solely determined by abiotic factors.

Populations will eventually stabilize around a carrying capacity. (correct)

Populations grow exponentially without limits.

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

Natural disasters

Pollution

Food availability (correct)

Climate change

What best describes population cycling?

A constant population size over time.

Rapid growth followed by immediate decline.

Regular fluctuations between high and low population sizes. (correct)

Irregular fluctuations in population numbers.

Which of the following factors is considered an abiotic factor that can affect population dynamics?

Temperature Signup and view all the answers

What is one implication of the human population growth model being well-approximated by the exponential model?

Human populations are experiencing constant growth without limitations. Signup and view all the answers

In the Logistic Growth Model, what happens to the growth rate when the population size exceeds the carrying capacity (K)?

The growth rate becomes negative Signup and view all the answers

Which of the following is a simplifying assumption of the Logistic Growth Model?

All individuals contribute equally to growth Signup and view all the answers

How do biotic factors typically operate in terms of population density?

They primarily operate in a density-dependent manner Signup and view all the answers

Which of the following is an example of an abiotic factor affecting population size?

Hurricane Signup and view all the answers

In the context of population dynamics, what are 'allee effects'?

Decreased reproductive success at low population densities Signup and view all the answers

Which of the following describes the relationship between carrying capacity (K) and population growth?

Growth rate is zero when population equals K Signup and view all the answers

What is meant by density-independent factors?

Factors that influence population size regardless of density Signup and view all the answers

What is the definition of 'r' in the context of population growth?

The intrinsic growth rate of a population Signup and view all the answers

What does the logistic growth model primarily account for in a population?

Carrying capacity limiting growth Signup and view all the answers

In population ecology, which of the following is an example of a density-dependent factor?

Disease spread among individuals Signup and view all the answers

How is the per capita rate of growth, r, calculated?

Difference between birth and death rates per individual Signup and view all the answers

What term describes factors that affect population size regardless of its density?

Density-independent factors Signup and view all the answers

Which equation accurately represents population change over time according to the basic population growth model?

∆N/∆T = B - M Signup and view all the answers

In a population cycle, which species is known to be affected by fluctuations in populations of snowshoe hares?

Lynx Signup and view all the answers

When considering the population growth equation ∆N/∆T = rN, what does 'r' represent?

Rate of population increase per individual Signup and view all the answers

Why is the growth model considered multiplicative rather than additive?

Because growth depends on the size of the population Signup and view all the answers

Study Notes

Population Ecology 2: Population Regulation and Fluctuation

A world map displays average annual population growth rates (1997-2015).
Projections are based on 1980-1997 fertility rates and 1997 age-sex population structures.
Regions show varying growth rates, from less than 0.0% to over 2.0%.
Data is not available for some areas.

McCarty Woods Restoration

Restoration event scheduled for November 17, 2023, from 9:00 am to 10:30 a.m.
Meeting location: Northeast corner of the parking lot.

McCarty Woods Restoration Project: November 17

Volunteers receive a free t-shirt (first 100).
The logo of the project is recognizable and included.

Population Growth Models

Students need to understand exponential and logistic population growth models and their assumptions.
Using population growth equations to determine future population size is crucial.
It is essential to contrast biotic and abiotic factors controlling population sizes, along with defining and recognizing density-dependent and independent population controls.
Learning about the lynx and snowshoe hare population cycles is vital.

Basic Population Growth Model*

The model ignores migration in and out of a population.
Population size change (ΔN/ΔT) equals birth rate (B) minus death rate (M).

Multiplicative Population Growth

Population growth is not additive; it is multiplicative.
If a population of 100 has 50 females each having 1 baby, and no deaths, the second generation is 150 individuals.

Per Capita Birth Rate

Birth rates are expressed per individual (per capita).
Per capita birth rate (b) = Births (B)/ Population size (N).
Example: If 500 elephants are born in a population of 1000 elephants, then the per capita birth rate is 0.5.

Per Capita Death Rate

Death rates are also expressed per individual (per capita).
Per capita death rate (m) = Deaths (M)/ Population size (N).

Population Growth Rate (r)

Combining birth and death rates results in the population growth rate (r).
Population growth equation (Eq. 1) on a per capita basis is: ΔN/ΔT = bN - mN
Per capita rate of increase (r) = b - m
Population growth equation (Eq. 3) is: ΔN/ΔT = rN

Exponential Population Growth

The exponential model describes population growth in an idealized environment (unlimited resources, no competition).
ΔN/ΔT= rN
Assuming unlimited resources, the growth rate (r_max )is constant, but the number of individuals changes over time.

Can Exponential Growth Go On Forever?

No, exponential growth cannot continue indefinitely.
Resources and competition limit populations and stop growth.
Elephants in Kruger National Park, South Africa, illustrate this phenomenon.

A More Realistic Population Growth Model: Logistic Growth

A more realistic population model limits growth by incorporating carrying capacity (K).
Carrying capacity (K): maximum population size the environment can support.

Logistic Growth Model

Logistic model = exponential model + carrying capacity term
dN/dt = r_maxN * (K-N)/K
The growth rate (r) decreases as the population approaches K.
When N=0, (K-N)/K = 1; when N=K, (K-N)/K = 0.

Logistic Growth Model: Example

A hypothetical example illustrates logistic growth.
Factors influencing population growth (intrinsic rate of increase, population size) and calculations are displayed in the table.

Density Dependence in Biotic Factors

Biotic factors (parasitism, disease, predation, competition), often affect population size based on density.
Birth and/or death rates change with changing density.
Density-dependent examples include clutch sizes of song sparrows and seed production of Sanicula plants.

Density Independence in Abiotic Factors

Abiotic factors (fire, flood, hurricane, drought), often affect population size regardless of density.

Population Fluctuations and Cycles

Many populations fluctuate or cycle, showing regular changes between high and low population sizes.
Examples include the snowshoe hare and lynx population cycles.

Human Population Growth

Well-approximated by the exponential model, unusual compared to other organisms in nature.
Current population is about 8 billion.
Predicted population in 2025 is 8.2 billion.
Although population is growing, the rate of increase is decreasing.

Ecology in the News...

Parasites can affect animal behavior, like the parasite Toxoplasma gondii in rats.
- A common protozoan parasite found in rats.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz covers key concepts in population ecology, focusing on population regulation and fluctuation. Students will explore population growth models, including exponential and logistic growth, and analyze factors that influence population sizes. Prepare to enhance your understanding of ecological dynamics and restoration efforts.