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Name: Date:Biology 11E: Population Ecology

Chapter: 53.1-53.6, *Population Formulae Sheet

Big Ideas:

Big Idea Chapters Illustrative Examples2. Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. Essential knowledge2.a.1 All living systems require constant input of free energy

53.3, 53.4 Life-history strategy (biennial plants, reproductive diapause)• Change in the producer level can affect the number and size of other trophic levels• Change in energy resources levels such as sunlight can affect the number and size of the trophic levels

4.a.5: Communities are composed of populations of organisms that interact in complex ways.

53.1, 53.2, 53.3, 53.5, 53.654.1, 54.2

• Predator/prey relationships spreadsheet model• Symbiotic relationship• Graphical representation of field data• Introduction of species• Global climate change models

AP Biology: Chapter 53 Population Ecology guided notes

Population Ecology: Chapter 53-Circle the diagram below that illustrates a population. Explain your answer below.

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-What is Population Ecology?

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Population Characteristics

1. Density and Dispersion

-Two important characteristics of populations are the distribution (dispersion) and density of

organisms. (Page 724). The diagram below illustrates both of these concepts, differentiate

density and dispersion and define these two terms.

a) Density __________________________________________

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b) Dispersion ________________________________________

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-Describe the three main patterns

of dispersal within a population.

a) Clumped ___________________________________________

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b) Uniform ___________________________________________

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c) Random ____________________________________________

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Techniques for Estimating Population Density

1. Sample Plot Method counts the number of organisms of the study species in plots of known

size. The data found is then used to estimate the entire population size.

a) With what type of organisms is this method appropriate?

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b) The formula used in the Sample Plot Method is:

Population Density = Number of Individuals in Sample Plots Total Area of all Sample Plots

c) Your Sample Plot Analysis (show all your calculations!)

Location:

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Sample Plot Area:

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Species of Study:

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Individuals Counted:

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Estimated Population Density:

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d) After conducting this study, brainstorm some of the limitations of the Sample Plot Method.

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2. Mark-Recapture Method uses two trapping events to estimate the size of a population. First,

the study area is determined and a trap is set. All animals caught in this trap are marked and

released. Later, the traps are set again and the proportion of marked to unmarked animals

captured in the second trapping provides an estimate of the number of individuals in a population.

a) With what type of organisms is this method appropriate?

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b) The formula used in the Mark-Recapture Method is:

Population Density = M x C R

M= Total number of animals captured and marked in the first trapping eventC= Total number of animals captured in the second trapping eventR= Number of animals captured in the first trap that were recaptured in the second trapping eventc) Your Sample Plot Analysis (show all your calculations!)

Location:

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Sample Plot Area:

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Species of Study:

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Individuals Counted in First Trap:

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Individuals Counted in Second Trap:

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Individual Recaptured in the Second Trap:

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Estimated Population Density:

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d) After conducting this study, brainstorm some of the limitations of the Sample Plot Method.

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2. Demographics

-The study of vital statistics that affect population size is called ____________________

-Additions to the population are caused by ____________________________ and

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Deletions from the population are caused by ______________________________ and

_____________________________.

a) Life Tables

-A life table is an age-specific summary of the survival pattern of a population.

-The best way to construct a life table is to follow the fate of a cohort, a group of individuals of

the same age, from birth throughout their lifetimes until all are dead.

-To build a life table, researchers need to determine the number of individuals that die in each age

group and calculate the proportion of the cohort surviving from one age to the next.

-Examine table 53.1

b) Survivorship Curves

-A graphic way of representing the data in a life table is a survivorship curve, a plot of the numbers or proportion of individuals in a cohort of 1,000 individuals still alive at each age.-A survivorship curve is a plot of the proportion or numbers of a cohort still alive at each age. Compare Type I, II and III survivorship curves. Each type of organism has a particular survivorship curve.

-Take your own notes about the three different survivorship curves.

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-What do we mean by the life history of an organism? ___________________________

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Concept 53.2: Population Growth-The size of a population continually changes due to various factors that will affect the

density of a population. The numbers in a population will either increase or decrease

depending on the following population parameters.


Change in population size = _________________________________________________

-Using mathematical notation, we can express this relationship more concisely:

-If N represents population size and t represents time, then N is the change in population size and t is the time interval.-We can rewrite the verbal equation as: N/t = B − D where B is the number of births during the time interval and D is the number of deaths. ( if we ignore immigrants and emmigrants)

-The per capita birth rate is the number of offspring produced per unit time by an average member of the population.

Calculate:-If there are 34 births per year in a population of 1,000 individuals, the annual per capita birth rate is: ____________________________________________________________________________ -If we know the annual per capita birth rate (expressed as b), we can use the formula B = bN to calculate the expected number of births per unit time in a population of any size.-Similarly, knowing the per capita death rate (symbolized by m for mortality) allows us to calculate the expected number of deaths per unit time in a population of any size using the formula:_______________________________________________________________________ -If m = 0.016 per year , we would expect 16 deaths per year in a population of 1,000 individuals.-If the mortality rate of a population is 0.05 per year. How many deaths can be expected in a population of 1 million people? ____________________________________________________

-Now we can revise the population growth equation, using per capita birth and death rates:

N/t = bN − mN

-Population ecologists are most interested in the difference between the per capita birth rate and the per capita death rate.

-This difference is the per capita rate of increase, or r:

r = b − m

-The value of r indicates whether a population is growing (r > 0) or declining (r < 0).-When r = 0, there is zero population growth (ZPG).-Births and deaths still occur, but they balance exactly.

-Using the per capita rate of increase, we rewrite the equation for the change in population size as:

N/t = rN

-Ecologists use differential calculus to express population growth instantaneously, as the growth rate at a particular instant in time:

dN/dt = rinstNwhere rinst is the instantaneous per capita rate of increase.

-Population growth under ideal conditions is called exponential population growth.-Under these conditions, we may assume the maximum growth rate for the population (rmax), called the intrinsic rate of increase.

-The equation for exponential population growth is

dN/dt = rmaxN


a) Exponential model of population growth (J-curve)

This type of growth pattern can occur when a population is small and resources are unlimited. ________________________________________

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The recovery of the whooping crane population illustrates exponential population growth

*Do concept check 53.2 # 3.

Concept 53.3: Logistic Growth


-The logistic growth model describes how a population grows more slowly as it nears its carrying capacity.-The logistic model of population growth incorporates the concept of carrying capacity.

-What is ‘carrying capacity’? ________________________________________________

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-This model incorporates the idea that the growth rate of the population slows down as the population size reaches the carrying capacity of the environment (K):

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-Logistic growth gives a ‘J-shaped’ growth curve:


-Few populations actually follow the logistic growth pattern exactly, but it is used as a starting point for analyzing population growth. Here are some examples:

-The logistic growth model can be used to analyze various types of life histories.

-What type of life history traits are favoured in crowded conditions (high density) where the population is near the carrying capacity of the environment?________________________________________________________________________

*Do concept check 53.3 #2

Concept 53.4: Life history traits are products of natural selection.-Natural selection favors traits that improve an organism’s chances of survival and reproductive success.

-In every species, there are trade-offs between survival and traits such as frequency of reproduction, number of offspring produced, and investment in parental care.

-The traits that affect an organism’s schedule of reproduction and survival make up its life history.

*Read and understand the Inquiry in Figure 53.13


-Selection for life history traits that are sensitive to population density is known as ____selection,

or density-_______________ selection.

-K-selection tends to maximize population size and operates in populations living at a density near K, where competition between individuals is strong.

-Mature trees growing in an old-growth forest are an example of K-selected organisms.

*Review Fig. 53.17, page 1183 to 1184.

-Selection for life history traits that maximize reproductive successes at low densities is know as

_____ selection, or density- _______________ selection.

-r-selection tends to maximize r, the per capita rate of increase.

-This occurs in environments in which population densities fluctuate well below K or when individuals face little competition.

-Such conditions are often found in disturbed habitats, such as weeds growing in an abandoned agricultural field.

-What type of life history traits are favoured in less dense environments?

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-Why do we say these traits are a result of r-selection?

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-Complete the following table of the Two Life Strategies.

Characteristics r-strategists K-strategists

# of Offspring

Level of Parenting

Young Maturation

Young Size

Annual Reproductive

Rate

Examples


Population Limiting Factors

Limiting factors are those factors that limit population growth. They are divided into two categories:

1. Density – dependent factors are those factors that increase directly as the population increases. They include competition for food, the buildup of wastes, predation and disease.

2. Density – independent factors are those whose occurrence is unrelated to population density. For example earthquakes, storms, and naturally occurring fires and floods.

-How do the rates of birth, death, immigration and emigration change as population density rises?

-Population equilibrium is reached when the birth rate equals the death rate (assuming no immigration or emigration).

-What is the difference between a ‘density dependent’ and a ‘density-independent’ birth or death rate?________________________________________________________________________________________________________________________________________________

-Density independent birth or death rates do not change regardless of population density. Analyze the graphs below:

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Negative feedback prevents unlimited population growth: ________________________________________________________________________________________________________________________________________________________________________


-What does population dynamics explain? ________________________________________________________________________________________________________________________________________________________________________________________________________________________

-Some populations have regular ‘boom-and-bust’ cycles

What could account for the regular fluctuations in the snowshoe hare and lynx populations? There are three main hypothesis:

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-The availability of prey is the major factor influencing population changes for predators such as lynx, great-horned owls, and weasels, which depend heavily on a single prey species.

-When prey become scarce, predators often turn on one another. -Coyotes kill both foxes and lynx, and great-horned owls kill smaller birds of prey as well as weasels, thus accelerating the collapse of the predator populations.

-Immigration and emigration also influence populations: When a population becomes crowded and resource competition increases, emigration often increases.


Concept 53.6 The human population is no longer growing exponentially, but it is still increasing rapidly.

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Activity: Human Population Growth

-To maintain population stability, a regional human population can exist in one of two configurations:

a) Zero population growth = High birth rates − High death ratesb) Zero population growth = Low birth rates – Low death rates

-The movement from the first toward the second state is called the demographic transition.

-As countries go through the ‘demographic transition’, their population growth rate can be very high because the death rate is much lower than the birth rate:


-The age structure of the population in a given country determines to some extent its future population growth pattern:

Activity: Analyzing Age-Structure Pyramids

How are age structure diagrams useful? ________________________________________________________________________ ________________________________________________________________________________________________________________________________________________

Which country in the diagrams above represents a developing nation? ______________

What determines our human footprint? ________________________________________________________________________________________________________________________________________________

-Calculate your own Ecological Footprint at

http://www.royalsaskmuseum.ca/gallery/life_sciences/footprint_mx_2005.sw f

-How do you compare with people:

a) In Canada? _________________________________________

b) The World? ________________________________________

-How many Earths would be required to support the human population if everyone lived

like you? _____


http://www.royalsaskmuseum.ca/gallery/life_sciences/footprint_mx_2005.swf

-What can you do to reduce your ecological footprint?

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