carrying capacity of ecosystems tip group #1 nancy lennon, robin daham, jennifer polignone

Carrying Capacity of Ecosystems

Tip Group #1

Nancy Lennon, Robin Daham, Jennifer Polignone

Unit Objective

Students will be able to describe the factors that affect the carrying capacity of environments.

Unit Components

This unit will run over the course of 4 days, 84 minute classes (block schedule).

Unit will consist of lecture/notes, discussion, “clicker” activities, and outside reading.

Day One

Populations within Ecosystems

Populations (group of organisms of a single species living in a given area) within ecosystems grow, shrink, or stay the same based on the how many are born (birth rate), die (death rate), join (immigration), and leave (emigration) over time.

Exponential Population Growth

Exponential growth occurs when resources are unlimited and environmental conditions are ideal.

Birth Rate >>> Death Rate

J-shaped curve results when number of organisms over time is graphed

Exponential Growth Curve

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are needed to see this picture.

However, in most ecosystems….

Resources are NOT unlimited….limiting factors slow population growth by increasing death rate and decreasing birth rate.

Is demonstrated in the Logistic Model of Population Growth which incorporated limiting factors and recognizes a carrying capacity in each ecosystem.

Results in an S-shaped curve (Sigmoid) when number of individuals over time is graphed.

Logistic Model of Growth…..



Carrying Capacity (K)

What is meant by the carrying capacity of an ecosystem?











Carrying Capacity is….

The total number of individuals the environment can support over an indefinite period of time.









Carrying Capacity (K) is reflected in the Logistic Model for Population Growth……



What determines the carrying capacity?

Limiting factors control the growth of populations.Some limiting factors are density-dependent and others density-independent.Ecosystem composition of plants and animals is determined by various abiotic factors, as well as biotic factors that act as limiting factors to growth.Disruptions of any of these factors shift the carrying capacity of ecosystems.

How do limiting factors work?

Population Size

Competition

Predation

Parasitism and disease

Unusual weather

Natural disaster

can be limited by

Abiotic Factors…..

The physical components of an ecosystem.

Any nonliving part of the environment.

Example:A bullfrog is affected by water availability, temperature, and humidity.

Abiotic Factors that influence carrying capacity…

TemperaturePrecipitationSoil compositionpHHumiditySalinityAmount of sunlightAvailability of nitrogen





•The importance of each factor varies from environment to environment.

•Abiotic factors vary from region to region and over time.

•For example, temperature varies from hour to hour, from day to day, from season to season, and from place to place.

•Subtle differences (i.e. from shade to full sun) makes a tremendous difference in terms of plant composition.





Abiotic Factors as Density-Independent Limiting Factors…

Density-Independent limiting factors limit population growth in similar ways no matter how dense the population is at the time.Unusual weather (hurricanes, drought, floods) and natural disasters (wildfires) act in this way.These factors often result in a population “crash.”

Biotic factors…..The biological influences on organisms.

Any living part of the environment with which an organism may interact.

Example:Bullfrogs may be affected by the algae it ate as a tadpole, insects it eats as an adult, herons that eat bullfrogs, and other species it competes with for food and space.

Biotic Factors that influence carrying capacity….All biological aspects of an ecosystem

fall into this category. Vegetation composition often determines what species will be attracted to a given area due to food availability.Scientists note that competition, predator-prey relations, mutualism, and host-pathogen interactions are critical to consider when accessing carrying capacity.

Concept Check

You will have 2 minutes to discuss the following question with the person sitting next to you and formulate a logical response.Write your response on a piece of paper or on your white boards (provided by your teacher).

Compare abiotic factors with biotic factors and give two examples of each.



End of Lecture for Day 1

Students will spend the rest of class on the activity explained on the next slide.

Day 1 Activity…..

“How many raccoons can live in the forest?” Activity

Tonight’s homework……

You will read several sections in the text, define vocabulary, and answer review questions. This assignment will be due on Day 4.

Day Two

Form a hypothesis to the following….

What factors might cause the carrying capacity of a population to change?

You have 2 minutes to construct your response.

Write your hypothesis in your notebook.

Biotic Factors in greater detail..

Competition for resources

Symbiotic Relationships

Predator/Prey interactions

How does competition shape communities and affect carrying capacity of ecosystems?

Competition for Resources

Interspecific Competition= an interaction in which two or more species use the same resource.

Examples: when lions and hyenas compete for zebras,and when different plants in a forest compete for soil and sunlight.

Often competition results in the reduction or complete elimination of one species from the area due to competitive exclusion.

Gause’s Paramecium Study

To illustrate the principle of competitive exclusion.When Paramecium caudatum and Paramecium aurelia grew in separate test tubes, they thrived.However, when grown together, P.caudatum died out because P.aurelia was a more efficient predator of bacteria.

Connell’s Barnacle Study

An example of resource partitioning was demonstrated by Joseph Connell on barnacles off the coast of Scotland (1960).

Semibalanus balanoides and Chthamalus stellatus live in the intertidal zone, exposed to dessication at regular intervals.

Chthamalus tends to live higher up on rocks than Semibalanus? Why when it can tolerate both regions (high and low on the rock)?

Connell explored this question…

He transplanted a rock covered with Chthamalus to lower zones in the intertidal zone.

Soon, the rock was settled by Semibalanus and they crowded out Chthamalus.

Conclusion: competition restricted Chthamalus range.

Competition as a Density-Dependent Limiting Factor

As population increases, individuals will compete for food, water, space, sunlight, etc. The more crowded an area is, the sooner resources will be used up.Those individuals who are better competitors survive and reproduce, those who aren’t, die out (survival of the fittest).

Review what you have learned….

Take 2 minutes and discuss this question with your neighbor and formulate a response….

What is the relationship between competition and population size?

How do species interactions shape communities and how does that affect their carrying capacities?

Symbiotic Relationships

A symbiotic relationship exists when there is a close, long-term relationship between two organisms.

Parasitism, Mutualism, and Commensalism are all examples.

Disruptions to these relationships can alter the flora and fauna of an area, thereby altering its carrying capacity.

a. ParasitismA symbiotic relationship in which one individual is harmed (the host) while the other benefits (the parasite) (+/-).Unlike predation, the host is not immediately killed.Parasites can be ectoparasites (outside the body) or endoparasites (inside the body).The host and parasite species are in an evolutionary “battle” to evolve better ways to resist infection/infect more.





http://www.funnythreat.com/funny_animals/tongue-eating-parasite.html

Parasitism as a Density-Dependent Limiting Factor

The denser the host population, the more rapidly parasites can spread from host to host.Example, pastures that are grazed upon by too many cattle often result the cattle becoming infested with worms passed from one cow to another.Example, the flu virus spreads rapidly through schools because there are a large number of students in one location.

Review what you have learned…..

Take 2 minutes and respond in your notes to the following question…..

What is a limiting factor and how do they affect the growth of populations in a community?

b. Mutualism

A mutual relationship exists when both individuals benefit (+/+).

Mutual relationships, such as pollinators (ex. Bees) and flowering plants (ex. Lilies), are vital to the stability of some ecosystems.







The marsupial D. gliroides and the mistletoe T. corymbosus have a mutual relationship…the marsupial feeds on the fruits and the mistletoe’s seeds get dispersed.

T.corymbosus is a keystone species in this forest, being the sole nectar producer for hummingbirds in the winter.

c. Commensalism

A relationship in which one organism benefits while the other is neither harmed nor benefits (+/0).

For example, barnacles that are attached to a whale’s skin perform no known service to the whale; however, the barnacle benefits from consuming the food particles that are in the water that flows over the whales body as it swims.



barnacles

Google imagaes

How does predation shape communities and affect carrying capacity?

Predation

Because all animals are not primary producers, they must consume other organisms for energy and nutrients.

The predator-prey relationship is important in shaping communities.

Organisms prey on both plants and animals, so the herbivore-plant relationship is just as important.

Predation…..

An interaction in which one animal (predator) captures and feeds on another (prey).

Predators determine the size of prey populations and determine the places prey can live and feed.

For example,Birds of prey regulate the population sizes of mice, voles, and other small mammals.



Predation as a Density-Dependent Limiting Factor….

Predator and prey populations fluctuate up and down over time.

When prey populations are high (birth rate > death rate), predators have an easier time catching them and have plenty to eat.

This often results in an increase in predator population size (birth rate > death rate).

Prey populations will likely drop as a result of more individuals being caught than are born (death rate > birth rate).As prey populations drop, predators begin to starve, increasing the death rate of the predator population (death rate > birth rate).Populations of herbivores and plants cycle in this same manner.



Cyclical changes of moose and wolf populations over time.

End of Day 2 Notes

Students will work on the activity described in the following slide.

Day 2 Activity……

“Wolves in Yellowstone Park” Activity

Tonight’s homework……

Complete work remaining from today’s activity.

Continue to work on reading assignment due Day 4.

Role of Invasive Species in Carrying Capacity of ecosystems.

What is an Invasive Species?

An invasive species is a species (plant or animal) that is introduced to an ecosystem, where it did not evolve in originally, and experiences exponential population growth.Invasive species often experience this growth because their new environment lacks predators and other environmental factors that limit their growth in their native environments.

Why are Invasive Species such a problem?

Foreign species often compete with native species for food and habitat, OR they may prey on them.Generally, invasive competitors and predators have a greater negative affect on local species than native competitors or predators.This is often due to the fact that native species have not evolved strategies to “deal” with the invasive species because they have not lived “side by side” with that species over time.

How do Invasive Species infiltrate new ecosystems?

Invasive (exotic) species are introduced into new environments in a variety of ways:

Human introduction (intentionally or unintentionally)

In the ballast of ships and boats

In produce and other shipments from country to country

Unintentional release from aquariums, private owners, etc.

So, what does this mean??

It means that invasive species generally end up affecting the carrying capacity of the ecosystem for the native species that are affected by the invasive species.A few examples of invasive species that have affected the carrying capacity of ecosystems include: the brown tree snake in Guam, the zebra mussel in North America, water hyacinth in Lake Victoria, and the Nile perch in Lake Victoria.

Case Scenario #1

Nile Perch in Lake Victoria, East Africa

Introduced intentionally to Lake Victoria in 1960 in order to increase sport fishing revenues.Nile perch, a voracious predator, found an ample supply of food in the abundant cichlid population native to the lake.By 1980, the Nile perch was the primary fish caught in the lake.

Further Affects…..

Introduction of the perch resulted in increased deforestation for firewood for drying the large perch caught.Soil erosion therefore increased, resulting in decreased clarity (increased turbidity) of the water.As the algae population died off due to decreased light penetration, their decomposition (by aerobic bacteria) resulted in a decrease in dissolved oxygen in the ecosystem.



Google images

Case Scenario #2

Brown Tree Snake in Guam

Boiga irregularis (brown tree snake) probably arrived in Guam on a U.S. Navy ship after the end of WW II.

It found no natural enemies and its populations exploded to over 3 million on the island.

This nocturnal snake feeds on birds, reptiles, and small mammals.

Further affects……..9 of the 12 native rainforest birds are extinct in natureExample, the guam rail, a flightless bird, had a population of ~80,000 in 1968 but was extinct by 1986.The snakes have greatly affected the population size of many of the small reptile and mammals on the island.Snakes get into homes and their venom is mildly poisonous to infants.Snakes increase power outages by climbing on poles and electrical wires.



O-M-G!!!!!!Google Images

You have 2 minutes to discuss the following questions with your partner and formulate a response

What is meant by the term invasive species?

Why are non-native species with invasive traits a threat to local ecosystems?

End of Day 3 Notes

Students will spend the rest of class working on the activity described in the next slide.

Day 3 Activity…..

For Teacher: Have students read “What can be done about Invasive Mussels,” about the zebra and quagga mussels, then apply what they have learned to this issue. Article can be found in Miller and Levine’s 2010 text Biology on pg.136 or in in word document included in lesson resources.

Teacher Notes….

Explain that ships carry water in ballast tanks to maintain buoyancy and stability. The waters are loaded and unloaded as the ship travels from port to port.

Explain that zebra and quagga mussels can be piced up in the ballast water as free-swimming larvae.

Student Instructions….

Read the article “What Can Be Done About Invasive Mussels?”

As you read, apply all that you have learned about populations and invasive species to this issue.

Be prepared to discuss this when everyone is finished reading.

Discussion Questions…..

Why does the population growth of zebra and quagga mussels in Great Lakes ecosystems differ from the population growth of these mussels in their native ecosystems?

How has the geographic range of zebra mussels changed between the mid-1980s and now?

Your homework tonight…..

Research the current status of invasive mussel populations and the approaches being used to prevent the spread of these and other invasive aquatic species. What trends are zebra mussel populations showing?What kinds of natural population controls do you think would manage these invasive mussels most effectively? Why?

Hand in your typed responses to the following questions:

Day 4---You Poured It Where? A Case Study in Invasive Species

The case scenario is only added as an example. Whatever we do here, I think this day should be a lab, movie (?), or group presentation.

References

Miller and Levine. Biology ©2010, Pearson Education, Inc., New Jersey.

Raven and Berg. Environment, 3rd edition, ©2001, Harcourt College Publishers, New York.

www.googleimages.com

http://www.googleimages.com/

carrying capacity of ecosystems tip group #1 nancy lennon, robin daham, jennifer polignone

Documents

factors slow population

various abiotic factors

limited byabiotic factors

capacity of environments

capacity kwhat

logistic model of growth

population growthwhat

population crash