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AP BIOLOGY

Ecology

www.njctl.org

March 2013

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Table of Contents

· Intro to Ecology

· Population Ecology

· Community Ecology

Click on the topic to go to that section

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Intro to Ecology

Click to return to the Table of Contents

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Ecology

Ecology is the study of how organisms interact with each other and their environments.

Clownfish interact with sea anemones in a manner that is positive to both. The sea anemone provides protection and nutrients to the

clownfish. In return, clownfish fecal matter provides nutrients to the sea anemone.

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Biotic vs Abiotic

Factors that ecologists study can be either biotic or abiotic.

Biotic factors of this coral reef include fish, corals, sea anemones, and plankton.

Abiotic factors of this coral reef include water temperature, water salinity, nutrient availability and sunlight.

Use this information to define the parameters of

biotic and abiotic factors.

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Biotic vs Abiotic

Biotic Factors Abiotic Factors

Living factors in an environment.

Nonliving factors in an environment.

· Animals· Plants· Fungi· Bacteria

· Sunlight· Water· Temperature· Nutrients· Soil

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The salt marsh ecosystem is composed of land that is submerged by ocean water during high tide and is dry during low tide. Organisms that live in a salt marsh need to have the ability to survive in both wet/dry conditions and in high/low salinity conditions. Plants are composed of grasses and shrubs. Common animals include crabs, mussels and a variety of birds. Many fish use salt marshes as hatcheries.

Salt Marsh

Describe three biotic and three abiotic factors that affect the salt marsh.

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Community

Levels of Biological Organization

Ecosystem

SMALLEST LEVEL

Population

Organism

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Organism:

Any individual that has all the characteristics of life.

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Population:

A group of organisms of the same species that live in the same geographic area.

Remember: What are the characteristics of a species?

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Population:

A group of organisms of the same species that live in the same geographic area.

Remember: What are the characteristics of a species?

[This object is a pull tab]

Ans

wer

A species is a group of organisms that can interbreed to produce

fertile, viable offspring.

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Community:

All of the populations that live in the

same geographic area.

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Ecosystem:

All of the living organisms (communities) and the nonliving components of a geographic area.

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1 Groups of different species living together and interacting in the same environment are referred to as a

A Organism

B Community

C Ecosystem

D Population

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1 Groups of different species living together and interacting in the same environment are referred to as a

A Organism

B Community

C Ecosystem

D Population


Ans

wer

B


2 All of the following are abiotic factors EXCEPT:

A Algae

B pH

C Temperature

D Nutrients

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2 All of the following are abiotic factors EXCEPT:

A Algae

B pH

C Temperature

D Nutrients


Ans

wer

A


3 Which of the following levels of biological organization includes both abiotic and biotic factors?

A Species

B Population

C Community

D Ecosystem

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3 Which of the following levels of biological organization includes both abiotic and biotic factors?

A Species

B Population

C Community

D Ecosystem


Ans

wer

D


Habitat

The term habitat describes the specific area - including biotic and abiotic factors - where an organism lives within an ecosystem.

A habitat is like an organism's home within an ecosystem.

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Ecological Niches

An organism's niche is a description of the role it plays in its habitat. A niche includes all aspects of where and how an organism lives including: * the type of food it eats * how it obtains food * where it lives in its environment (tree, nest, hive, etc.) * when and how it reproduces

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Komodo Dragon Niche

Komodo dragons live in the Indonesian Islands. They hunt and ambush invertebrates, birds and mammals. They lay up to 20 eggs at a time in self-dug holes. The eggs incubate for eight months. Komodo dragons take nine years to mature and can live up to 30 years.

Ecological Niches

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Ecological Niches

A population's habitat answers the question

"Where do you live?".

A population's niche answers the question

"How do you make a living?".

Click this picture to watch a video about niches in the North African river plains.

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Ecological NichesNo two species can occupy the same niche in the same environment at the same time. This is called niche overlap. When this occurs, competition for resources will displace one of the species. The figure below shows three different species of warblers that have established different niches in the same tree.

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Ecological NichesNiche overlap leads to a fundamental niche and a realized niche for a species.

Fundamental niche - the optimal niche of a species, in the absence of limiting factors

Realized niche - the actual niche of a species, as a result of competition

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4 Traditionally, a polar bear's diet consists mainly of seals that it hunts from the edges of sea ice. As the sea ice melts and humans encroach on the existing habitat, polar bears are now known to hunt through human trash for nutrition. Describe the difference between the polar bear's fundamental niche and realized niche.

Students type their answers here

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4 Traditionally, a polar bear's diet consists mainly of seals that it hunts from the edges of sea ice. As the sea ice melts and humans encroach on the existing habitat, polar bears are now known to hunt through human trash for nutrition. Describe the difference between the polar bear's fundamental niche and realized niche.



Ans

wer The fundamental niche is hunting

for seals from the edges of sea ice. The realized niche is hunting

for food in human trash.


Population Ecology


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Populations

Factors that affect populations can be density dependent or density independent.

Population ecology studies the interactions between populations and their environments.

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Density dependent factors affect populations based on the density of that population. Examples include predation, competition and disease.

Density Dependent Factors

A low density population will suffer more from heavy predation than a high density population.

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Density Independent FactorsDensity independent factors affect a population, regardless of population density. Examples include weather and natural disasters.

Severe weather that causes flooding will destroy both high density and low density populations.

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5 In 2005, hurricane Katrina deposited over 5 cm of sediment on the coastal wetland ecosystem of the Gulf of Mexico, destroying 100 km2 of wetland. Did hurricane Katrina have density dependent or density independent effects?

A Density dependent

B Density independent

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5 In 2005, hurricane Katrina deposited over 5 cm of sediment on the coastal wetland ecosystem of the Gulf of Mexico, destroying 100 km2 of wetland. Did hurricane Katrina have density dependent or density independent effects?

A Density dependent



Ans

wer

B


6 In a field of wildflowers, population size is limited by available nutrients in the soil. When the density of flowers reaches a certain level, the death rate increases due to lack of nutrients. Is this population affected by density dependent or density independent factors?

A Density dependent


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6 In a field of wildflowers, population size is limited by available nutrients in the soil. When the density of flowers reaches a certain level, the death rate increases due to lack of nutrients. Is this population affected by density dependent or density independent factors?

A Density dependent



Ans

wer

A


Leaving Entering

Population Size

Population size is positively correlated with birth rate and immigration and negatively correlated with death rate and emigration.

Draw two graphs illustrating the relationship between population size and 1) birth rate/immigration and 2) death rate/emigration.

Ans

wer

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Exponential Population Growth

When a population has access to unlimited resources, it experiences exponential growth.


dN dt

= r N

where r = growth rate

and N = population size

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After elephants in Kruger National Park, South Africa, were protected from hunting, the population grew exponentially for 60 years. When population size threatened to destroy habitat and food supply, park managers implemented elephant birth control and exportation.

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Logistic Population Growth

Most populations do not have unlimited resources.

When a population becomes too large, it exhausts food supply, water supply and shelter. At this point, intraspecific competition causes the population to decrease.

Intraspecific competition - competition among members of the same species. These two lions are competing for the same prey.

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The population size that can be maintained with a given amount of resources is called the carrying capacity.

Populations that are limited in resources experience logistic growth.

In logistic growth, the rate of increase approaches zero as the carrying capacity is reached.

Logistic Population Growth

Source: Nature.com

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Case Study: Red Tail HawkConsider a new population of red tail hawks that have been released by conservationists into a woodland in upstate New York.

Six years ago scientists released 50 hawks into a 900 acre woodland.

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Consider a new population of red tail hawks that have been released by conservationists into a woodland in upstate New York.

Since the hawks had no natural predators and plenty of prey in the environment, they showed exponential population growth.

Case Study: Red Tail Hawk

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This year scientists believe the population has reached a peak population growth rate.


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As an example, we will look at a new population of red tail hawks that have been released by conservationists into a woodland in upstate New York.

Over the coming years growth will slow because the hawks have been consuming most of the prey. Their food source is becoming a limiting resource.


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They estimate that after six additional years the population will reach the carrying capacity of the woodland.

In other words, death and emigration rate will equal birth rate.

What is the immigration rate of this population?


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Human PopulationThe advent of new technologies has allowed human populations to grow exponentially. Food and energy have recently been made more abundant for the human species, leading to a surge in growth.

7,000,000,0002011 world population

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Human PopulationThe current population growth rate for humans is about 1.1% population increase per year.

This rate has been decreasing which means that growth is slowing, but the population is still increasing.

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Human PopulationMany models predict that by 2040, the human population will exceed 10,000,000,000. This will effect the planet in a variety of negative ways.

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Agriculture is a human technology that transforms natural ecosystems into areas devoted to the production of food and fuel. The current size of the human population was made possible by the advancements in this technology.

Without the huge increase in edible biomass created by agricultural systems, there would simply not be enough to feed the 7,000,000,000 humans on Earth.

Human Population

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The land, water, and energy resources required to support this level of food production are vast. Agriculture represents a major way in which humans impact ecosystems.

Human Population

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Agriculture can be particularly damaging when chemicals are used to stop pests from eating crops. It may have unintended consequences.

For example, DDT, a chemical used to control insects, nearly caused the extinction of the American Bald Eagle via biomagnification.

Biomagnification is the process by which the concentration of a substance increases substantially as it moves up the food chain.

Source: US Fish & Wildlife

Human Population

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The lifestyle of an average citizen in a developed country requires enormous amounts of energy to power modern technology.

As populations grow the environmental impact will grow exponentially.

Human Population

In what other ways will an increasing human population affect the planet?

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7 When the collared dove first colonized Great Britain, the population grew exponentially. Twenty years later, the population size was smaller than predicted by the exponential model. Which of the following is not a conclusion that can be made from this information?

A The rate of population growth had slowed.

B The population had unlimited resources.

C The population was approaching its carrying capacity.

D Competition was decreasing population size.

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7 When the collared dove first colonized Great Britain, the population grew exponentially. Twenty years later, the population size was smaller than predicted by the exponential model. Which of the following is not a conclusion that can be made from this information?

A The rate of population growth had slowed.

B The population had unlimited resources.

C The population was approaching its carrying capacity.

D Competition was decreasing population size.[This object is a pull tab]

Ans

wer

B


8 Which of the following is not a situation in which exponential growth could occur?

A Bacteria growing in a petri dish.

B Pine trees rebounding after a forest fire.

C A population of snowshoe hares after the lynx population is decimated by disease.

D A species of fish colonizing a new marine environment.

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8 Which of the following is not a situation in which exponential growth could occur?

A Bacteria growing in a petri dish.

B Pine trees rebounding after a forest fire.

C A population of snowshoe hares after the lynx population is decimated by disease.

D A species of fish colonizing a new marine environment.


Ans

wer

A


The red squirrel inhabits forests of Asia and Europe. When populations are high, competition for habitat results in some females obtaining low quality territory. This, in turn, results in low fecundity (reproductive success) for those females and the growth rate of the population decreases.

Case Study: Red Squirrels

Read the description of red squirrels and answer the questions that follow.

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9 List one biotic and one abiotic factor that affects the red squirrel population.


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10 What is the limiting factor for the red squirrel population?

A Food

B Predation

C Habitat

D Water

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10 What is the limiting factor for the red squirrel population?

A Food

B Predation

C Habitat

D Water[This object is a pull tab]

Ans

wer

C


11 Is red squirrel population size being affected by density dependent or density independent factors?

A Density dependent


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11 Is red squirrel population size being affected by density dependent or density independent factors?

A Density dependent



Ans

wer

A


12 As the population growth rate slows in response to habitat availability, what is the population nearing?

A Extinction

B Speciation

C Carrying Capacity

D Exponential growth

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12 As the population growth rate slows in response to habitat availability, what is the population nearing?

A Extinction

B Speciation

C Carrying Capacity

D Exponential growth


Ans

wer

C


Reproduction vs SurvivalSurvivorship is a population's expectation for average death rates at a given yearly age.

Survivorship curves show how many individuals are alive after a certain period of time. There are three survivorship strategies.

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Humans are an example of type I. Young humans are likely to survive well, but death rates increase exponentially as the years pass.

Reproduction vs Survival

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Birds are an example of type II. As the linear line shows, each year a bird is just as likely to die as they were the previous years. Young or old has no bearing on survivorship.


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Frogs are an example of type III. They are very like to die at a young age but if they survive their youth, then they are likely to live a long time.


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Type I Survivorship Characteristics:

- Stable environment- Larger size- Long life expectancy- High level of parental care- Few offspring


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Type III Survivorship Characteristics:

- Unstable environment- Early Maturity- Little parental care- High number of offspring- Short lifetime


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r/K Selection TheorySurvivorship strategies are a trade off between quantity and quality of offspring. One strategy is not more successful than another. Environmental conditions dictate which strategy will be favored.

r and K selection theory relates parental investment with quantity and quality of offspring.

vs

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The theory gets its name from the algebraic expression of ecological population dynamics.

r is the maximum growth rate of the population (N).K is the carrying capacity of its local environment.

r/K Selection Theory

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r/K Selection Theoryr-selection predominantes in unstable or unpredictable environments in which the ability to reproduce quickly is crucial. There is little advantage in adaptations that permit successful competition with other organisms, because the environment is likely to change again. Population size changes drastically.

r-selection characteristics· high fecundity· small body size· early maturation· short lifespan

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K-selection predominates in stable or predictable environments in which the ability to compete for limited resources is crucial. Populations sizes of K-selected organisms typically are constant and close to the maximum that the environment can accommodate.

K-selection characteristics· low fecundity· large body size· late maturation· long lifespan· extensive parental care

r/K Selection Theory

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13 A turtle lays a large clutch of eggs on a beach. However, there is no parental support for the offspring and only a few will make it back to the ocean before being eaten by predators.

A Type III survivorship

B Type II survivorship

C Type III survivorship

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13 A turtle lays a large clutch of eggs on a beach. However, there is no parental support for the offspring and only a few will make it back to the ocean before being eaten by predators.

A Type III survivorship

B Type II survivorship

C Type III survivorship[This object is a pull tab]

Ans

wer

C


14 Elephants are large mammals that can live to be 80 years old. Gestation lasts about two years with only one to two babies being born at a time. Maturation does not occur until 9 years (females) and 15 years (males).

A r-selection

B K-selection

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14 Elephants are large mammals that can live to be 80 years old. Gestation lasts about two years with only one to two babies being born at a time. Maturation does not occur until 9 years (females) and 15 years (males).

A r-selection

B K-selection


Ans

wer

B


15 Which of the following is correctly paired?

A r selection / Type I survivorship

B K selection / Type I survivorship

C r-K selection / Type II survivorship

D K selection / Type III survivorship

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15 Which of the following is correctly paired?

A r selection / Type I survivorship

B K selection / Type I survivorship

C r-K selection / Type II survivorship

D K selection / Type III survivorship


Ans

wer

B


16 Which graph shows a population using

r-selection strategies?

A B

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16 Which graph shows a population using

r-selection strategies?

A B


Ans

wer

A


Community Ecology


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CommunitiesCommunity ecology studies the interactions between

different populations and their environments.

Populations in a community interact with each other in a variety of ways.

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Predation

Predation is an interaction in which one species (predator) kills and eats the other (prey).

The whale shark is the largest extant (living) fish species, growing up to 14 meters in length. Despite this intimidating size, they are

filter feeders, preying on algae, plankton and krill.

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PredationPredation leads to the evolution of adaptations that enable

predators to capture prey and prey to elude predators.

Predator adaptations Prey adaptations

· claws· fangs· stingers· poison

· cryptic coloration· herding· toxins· mechanical (spines)

Can you find the frog in this

picture?

This snake's hollow fangs

secrete venom.

Source: livescience.com

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Competition

Competition occurs when individuals vie for a limiting resource.

Intraspecific competition occurs when individuals of the same species compete.

Interspecific competition occurs when individual of different species compete.

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Competitive Exclusion

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SymbiosisSymbiosis is any long term interaction between species.

In obligate symbiosis, species cannot survive without each other.

In facultative symbiosis, species can survive without each other.

A lichen is composed of a fungi and algae living as obligate symbiotes. The algae creates food via photosynthesis while the fungi offers protection and minerals.

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SymbiosisCommensalism is an interaction that benefits one species while the other species is neither benefited nor harmed.

Remoras are fish that attach to larger marine animals, such as sharks.

Remoras eat leftover food from the shark. The shark is not affected in the

process.

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SymbiosisParasitism is an interaction that benefits one species while

harming another species.

Ticks are arachnids that attach to other animals and ingest their blood. The tick (parasite) gains nutrition from this relationship while the animal (host) experiences reduced health and possibly death.

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SymbiosisMutualism is an interaction between species in which all

species benefit.

Pollination illustrates mutualism between

flowering plants and their animal pollinators.

Pollinators receive nutrition while the plants receive

help with dispersal.

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Interaction Species #1 Species #2Predation

Competition

Commensalism

Mutualism

Parasitism

Interactions

In the table above, indicate whether each species in the interaction experiences a positive (+), negative (-) or neutral (0) effect.

Ans

wer

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17 Oxpeckers are birds that perch on the backs of rhinos. They eat ticks and other parasitic bugs.

A Predation

B Competition

C Commensalism

D Mutualism

E Parasitism

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17 Oxpeckers are birds that perch on the backs of rhinos. They eat ticks and other parasitic bugs.

A Predation

B Competition

C Commensalism

D Mutualism

E Parasitism[This object is a pull tab]

Ans

wer

D


18 Parrot fish and yellow tang fish both eat algae on the same coral reef.

A Predation

B Competition

C Commensalism

D Mutualism

E Parasitism

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18 Parrot fish and yellow tang fish both eat algae on the same coral reef.

A Predation

B Competition

C Commensalism

D Mutualism


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wer

B


19 Some mites attach themselves to flies. The flies transport the mites to alternate locations while remaining unharmed in the process.

A Predation

B Competition

C Commensalism

D Mutualism

E Parasitism

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19 Some mites attach themselves to flies. The flies transport the mites to alternate locations while remaining unharmed in the process.

A Predation

B Competition

C Commensalism

D Mutualism


Ans

wer

C


20 A fungus grows on the back of insects. Its tendrils penetrate the exoskeleton as it feeds on the inner soft tissue of the bug. It will eventually consume the host insect.

A Predation

B Competition

C Commensalism

D Mutualism

E Parasitism

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20 A fungus grows on the back of insects. Its tendrils penetrate the exoskeleton as it feeds on the inner soft tissue of the bug. It will eventually consume the host insect.

A Predation

B Competition

C Commensalism

D Mutualism


Ans

wer

E


21 Describe how niche overlap can lead to competitive exclusion.


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21 Describe how niche overlap can lead to competitive exclusion.



Ans

wer

When two species occupy the same niche, the species that is

the stronger competitor will exclude the other species from

inhabiting the same area.


Nitrogen is the an essential nutrient required by all organisms to make proteins.

Most nitrogen is found as a gas in the atmosphere; however, organisms are unable to use nitrogen in this form (N2).

Case Study: Nitrogen Cycle

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The cycling of nitrogen through the environment involves many organisms:· Bacteria in soil convert N2 into ammonia

(NH3+) or ammonium (NH4) in a process

called nitrogen fixation.· Other bacteria convert ammonia into

nitrates (NO3-) and nitrates (NO2

-).· Producers use ammonium, nitrates, and

nitrites to make proteins.· Consumers eat producers and reuse the

nitrogen to make their own proteins.· When organisms die, decomposers

release the nitrogen back into the soil or convert the nitrates back into nitrogen gas in a process called denitrification.

Case Study: Nitrogen Cycle

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Case Study: Nitrogen CycleRhizobia are soil bacteria that forms symbiotic relationships with legumes. The bacteria grow inside nodules in the plant roots where they receive nutrients from the plant via photosynthesis. The plant, in turn, receives usable nitrogen from the bacteria via nitrogen fixation.

The nodules of Rhizobia can be seen as bubble-like structures on these roots.

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22 What type of interaction is diplayed between Rhizobia and legume roots?

A Parasitism

B Mutualism

C Predation

D Commensalism

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22 What type of interaction is diplayed between Rhizobia and legume roots?

A Parasitism

B Mutualism

C Predation

D Commensalism


Ans

wer

B


23 Rhizobia cannot survive unless they have a host plant. What type of symbiotic relationship is this?

A Obligate

B Dominant

C Facultative

D Density dependent

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23 Rhizobia cannot survive unless they have a host plant. What type of symbiotic relationship is this?

A Obligate

B Dominant

C Facultative

D Density dependent[This object is a pull tab]

Ans

wer

A


Community Diversity

The diversity of a community is a description of the variety of species that make up the community.

Community diversity has two components:· species richness· relative abundance

Which community is more diverse?

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Species Richness

Species richness is the number of species present in a community.

In these hypothetical forest communities, each different tree species is represented by a different color. Which community is more diverse?

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Relative Abundance

Relative abundance is the proportion that each species represents for the entire community.

Relative abundance values:2/8 = 25%

2/8 = 25%

2/8 = 25%

1/8 = 12.5%

1/8 = 12.5%

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Community Diversity

Community diversity can be calculated using the following equation, called the Shannon diversity:

H = - (pA ln pA + pB ln pB + pC ln pC + ...)

H = - (3 (0.25 ln 0.25) + 2 (0.125 ln 0.125))

H = 1.57

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Community Diversity

Communities that are more diverse:· have increased

productivity· are more stable· are more resilient· are more resistant to

invasive species

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24 Which forest has a higher species richness? Students type their answers here

Forest A Forest B

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24 Which forest has a higher species richness? Students type their answers here

Forest A Forest B


Ans

wer

Forest A


25 Which forest has a higher community diversity? Students type their answers here

Forest A Forest B

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25 Which forest has a higher community diversity? Students type their answers here

Forest A Forest B


Ans

wer

Forest A


26 An invasive fungal disease spreads through both forests. Which forest would be better able to recover from this event?


Forest A Forest B

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26 An invasive fungal disease spreads through both forests. Which forest would be better able to recover from this event?


Forest A Forest B


Ans

wer

Forest A


Ecological Succession

Change is inevitable within communities - older members die, new organisms immigrate, sudden disturbances force change, etc.

Ecological succession is the term used to describe the series of expected changes that occur within the community of an ecosystem over time.

The first photo shows a forest one year after a forest fire. The second picture is the same forest two years after the fire.

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Primary Succession

Primary succession refers to the founding of new communities in environments that initially had no living organisms, like rocks or new surfaces formed by volcanic eruptions or the movements of glaciers.

The retreat of a glacier left behind this bare rock that can now undergo primary succession.

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Pioneer SpeciesIn primary ecological succession, the first organisms to populate an uninhabited environment are called the pioneer species.

Lichen is the first organism to grow on the bare rock. It is the pioneer species.

Bare rock leftafter retreat of a glacier.

Time

Lichens, followed by moss, begin growing on the rock. As they die, the decaying matter is added to the rock, producing soil.

Pioneer Species

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Primary Succession


Time

Lichens, followed bymoss, begin growingon the rock. As theydie, the decaying matter is added to the rock, producing soil.

Grasses and small plants start to grow.

Nutrients supplied by decaying organic matter support the growth of grasses and small plants.

These add more organic nutrients, which form deeper more fertile soil.

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Primary Succession

Decaying organic matter create deeper soils that can hold water. This allows shrubs to grow.


Time

Lichens, followed bymoss, grow on the rock. As they die, the decaying matter is added to the rock, producing soil.

Grasses and small plants start to grow. Small shrubs

colonize.

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Climax Communities

Finally, larger trees can grow, and climax communities form. Climax communities are the organisms that remain stable in an ecosystem over time.

Time

Climax communitiesdevelop on mature soils.


Lichens, followed bymoss, grow on the rock. As they die, the decaying matter is added to the rock, producing soil.

Grasses and small plants start to grow.

Small shrubs colonize.

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Secondary SuccessionAfter ecosystems are dramatically altered by fires, floods, disease, or human activity, community interactions often restore ecosystems to their original condition.

The reestablishment of climax communities in an ecosystem is called secondary succession.

Ground is cleared of existing community to grow a single crop.

Ground is abandonedand new species begin to grow.

Small shrubsagain colonize.

New climaxcommunityforms.

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27 How could high and low levels of disturbance reduce species diversity?


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27 How could high and low levels of disturbance reduce species diversity?



Ans

wer

High levels of disturbance can destroy entire species, thereby

reducing diversity.Low levels of disturbance can

allow one species to dominate all others, thereby reducing diversity.


28 During ecological succession, describe one way in which early species can facilitate the presence of later species.


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28 During ecological succession, describe one way in which early species can facilitate the presence of later species.



Ans

wer

Example answer: When early species die, their organic matter is added to the ground. This adds essential

nutrients to soil which allows later species to grow.


Community Ecology: Experimental Design

One way in which scientists study the interactions between populations in a community is to conduct exclusion experiments.

In an exclusion experiment, one species is removed from an area. The area is then observed to see what occurs.

What type of information can be gained from an exclusion experiment?

Source: Government of Bermuda, Dept of Conservation Services

This exclusion experiment attempted to determine the effect of sea turtles on sea grass populations. These cages prevent sea turtles from grazing on these sea grasses.

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In the 1950s, Joseph Connell studied the distribution in the intertidal zone of two different barnacles species: Chthamalus stellatus and Balanus balanoides.

Upper Intertidal Zone

Middle Intertidal Zone

Lower Intertidal Zone

Chthamalus

Balanus

How would you describe the distribution of Chthamalus and Balanus in the intertidal zone?

Slide 108 / 131


In the 1950s, Joseph Connell studied the distribution in the intertidal zone of two different barnacles species: Chthamalus stellatus and Balanus balanoides.

Upper Intertidal Zone

Middle Intertidal Zone

Lower Intertidal Zone

Chthamalus

Balanus

How would you describe the distribution of Chthamalus and Balanus in the intertidal zone?[This object is a pull

tab]

Ans

wer

Chthamalus survives primarily in the upper intertidal zone while Balanus survives in the middle

and lower intertidal zone.



Connell wanted to determine why these barnacle species have these distribution patterns.

He observed the species over a long period of time.

In the spring of 1955, the area experienced very low tides. The portion of the intertidal zone that is normally occupied by both species did not receive any water.

Results: Balanus showed high levels of mortality in the upper intertidal zone but not in the lower intertidal zones (which were covered in water).

What could Connell conclude about the distribution pattern of Balanus in the upper intertidal zone?

Slide 109 / 131


Connell wanted to determine why these barnacle species have these distribution patterns.

He observed the species over a long period of time.

In the spring of 1955, the area experienced very low tides. The portion of the intertidal zone that is normally occupied by both species did not receive any water.

Results: Balanus showed high levels of mortality in the upper intertidal zone but not in the lower intertidal zones (which were covered in water).

What could Connell conclude about the distribution pattern of Balanus in the upper intertidal zone?


Ans

wer

Balanus is excluded from the upper intertidal zone because it

cannot survive dessication. Chthamalus can survive in the upper intertidal because it is better adapted to dessication.



The dessication information explained why Balanus was not present in the upper intertidal zone. However, it did not explain why Chthamalus was only found in the upper intertidal zone.

Connell performed an exclusion experiment.· He established several study areas throughout the intertidal zone,

in which he periodically mapped every single barnacle.· He removed Balanus from half of each study site.· He determined which half to exclude Balanus from by flipping a

coin.

Chthamalus

Balanus

Slide 110 / 131

Community Ecology: Experimental DesignResults:· In the absence of Balanus, Chthamalus survived in the middle

intertidal zone.· In the lower intertidal zone, Chthamalus experienced high

mortality rates with or without Balanus.

What conclusions can you make from these results?

Slide 111 / 131


Conclusions:· In the middle intertidal zone,

competitive exlcusion of Balanus over Chthamalus occurs.

· In the lower intertidal zone, predation excludes Chthamalus from growing.

Slide 112 / 131

29 Which barnacle species is better adapted

to survive dessication?

A Chthamalus

B Balanus

Slide 113 / 131

29 Which barnacle species is better adapted

to survive dessication?

A Chthamalus

B Balanus


Ans

wer

A


30 "Competitive exclusion of Balanus over Chthamalus occured in the middle intertidal zone." What does this mean?

A Chthamalus is able to compete for resources better than Balanus.

B Balanus is better able to compete for resources

than Chthamalus.

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30 "Competitive exclusion of Balanus over Chthamalus occured in the middle intertidal zone." What does this mean?

A Chthamalus is able to compete for resources better than Balanus.

B Balanus is better able to compete for resources

than Chthamalus.


Ans

wer

B


31 Why did Connell flip a coin to determine in which half of each study site he would remove Balanus?


Slide 115 / 131

31 Why did Connell flip a coin to determine in which half of each study site he would remove Balanus?



Ans

wer By flipping a coin, he was leaving

the decision up to chance instead of allowing the possibility of unconscious bias on his part.


32 In an exclusion experiment, what is an example of a control group?

A The number of organisms present at the start of the experiment.

B A study site in which nothing has been removed.

C A study site in which the opposite organism has been removed.

D A study site from a previous experiment in which no organisms were removed.

Slide 116 / 131

32 In an exclusion experiment, what is an example of a control group?

A The number of organisms present at the start of the experiment.

B A study site in which nothing has been removed.

C A study site in which the opposite organism has been removed.

D A study site from a previous experiment in which no organisms were removed. [This object is a pull

tab]

Ans

wer

B


Swedish Lake Food Chain

Energy TransferFeeding relationships in communities can be observed via food chains and food webs. These show the pathway of energy transfer in a community.

What is the difference between a food chain and a food web?

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Swedish Lake Food Chain

Energy TransferFeeding relationships in communities can be observed via food chains and food webs. These show the pathway of energy transfer in a community.

What is the difference between a food chain and a food web?[This object is a pull tab]

Ans

wer

A food chain shows one pathway of energy transfer. A food web shows several food chains and

how they interact in a community.


Energy TransferEach organism in a food web/chain occupies a specific trophic level.

Individuals feed on organisms at lower trophic levels.

No matter what position is occupied in a food chain, eventually all organisms become energy for decomposers.

Trophic Levels

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Energy TransferEnergy transfer between food chain trophic levels is not efficient. Only about 10% of the energy/biomass from one trophic level is transferred to the next level. Because of this, food chains are limited in length.

Source: EPA

One of the food chains illustrated in this food web is:

phytoplankton dragonfly salamander bald eagle

If the biomass of phytoplankton in this community is 1000 kg, what biomass of bald eagle can survive?

Slide 119 / 131

Energy TransferEnergy transfer between food chain trophic levels is not efficient. Only about 10% of the energy/biomass from one trophic level is transferred to the next level. Because of this, food chains are limited in length.

Source: EPA

One of the food chains illustrated in this food web is:

phytoplankton dragonfly salamander bald eagle

If the biomass of phytoplankton in this community is 1000 kg, what biomass of bald eagle can survive?


Ans

wer

1 kg


33 In a forest community, shrubs and grasses are consumed by hares, who are, in turn, consumed by foxes. Insects also consume grasses and are, in turn, consumed by shrews and then foxes. This is an example of a

A food chain.

B food web.

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33 In a forest community, shrubs and grasses are consumed by hares, who are, in turn, consumed by foxes. Insects also consume grasses and are, in turn, consumed by shrews and then foxes. This is an example of a

A food chain.

B food web.


Ans

wer

B


34 Food chains will be longer in communities that have higher

A numbers of tertiary consumers.

B predation.

C photosynthetic production.

D competition.

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34 Food chains will be longer in communities that have higher

A numbers of tertiary consumers.

B predation.

C photosynthetic production.

D competition.[This object is a pull tab]

Ans

wer

C


35 Use this food web to determine the biomass of primary producers necessary to support an osprey biomass of 286 kg.

Slide 122 / 131

35 Use this food web to determine the biomass of primary producers necessary to support an osprey biomass of 286 kg.


Ans

wer

286,000 kg


Dominant Species

A dominant species is one that has a large effect on a community due to high biomass.

Tidal swamps are dominated by mangroves. (Mangroves have the largest biomass in the community.) The mangrove root system traps sediments, dissipates wave energy and provides habitat for oysters. If a mangrove population were eliminated, the entire ecosystem would change drastically.

Slide 123 / 131

Keystone SpeciesIn contrast to a dominant species, a keystone species has a low

biomass but a large effect on community structure.

Consider this simplified food web for Eel River, California:

Algae

Predatory Insects

Roach fry Stickleback fry

Large Roach Steelhead

Larval insects

(fish)

(fish)(fish)

(fish)

Slide 124 / 131

Keystone SpeciesMary Power conducted research in Eel River to determine the effect of fish on food web structure.

Experimental Design:· She set up cages in Eel River that excluded movement of large

fish but allowed movement of insects, stickleback and roach fry.· In 6 cages, she excluded large fish.· In 6 cages, she allowed steelhead and large roach.

What is the control group in this experiment?

Slide 125 / 131

Keystone SpeciesMary Power conducted research in Eel River to determine the effect of fish on food web structure.

Experimental Design:· She set up cages in Eel River that excluded movement of large

fish but allowed movement of insects, stickleback and roach fry.· In 6 cages, she excluded large fish.· In 6 cages, she allowed steelhead and large roach.

What is the control group in this experiment?


Ans

wer

The cages with large fish included.


Keystone Species

Results:· In cages in which large fish were excluded, algal biomass

grew exponentially.· In cages in which large fish were enclosed, algal biomass was

reduced.

Keeping in mind that large fish are at the top of the food chain, what can be concluded from these results?

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Keystone Species

Results:· In cages in which large fish were excluded, algal biomass

grew exponentially.· In cages in which large fish were enclosed, algal biomass was

reduced.

Keeping in mind that large fish are at the top of the food chain, what can be concluded from these results?


Ans

wer Although large fish have a low

biomass, they have a strong effect on the Eel River ecosystem. They

are a keystone species.


36 In the cages where large fish were excluded, what would you predict would happen to the larval insect populations?

A They would increase.

B They would decrease.

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36 In the cages where large fish were excluded, what would you predict would happen to the larval insect populations?

A They would increase.

B They would decrease.


Ans

wer

A


37 If a virus eliminated steelhead and large roach from the Eel River, what would be a possible consequence?

A The river would be overrun by algae.

B Predatory insect populations would crash.

C Algal populations would crash.

D Nutrient levels in the river would increase.

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37 If a virus eliminated steelhead and large roach from the Eel River, what would be a possible consequence?

A The river would be overrun by algae.

B Predatory insect populations would crash.

C Algal populations would crash.

D Nutrient levels in the river would increase.[This object is a pull tab]

Ans

wer

A


38 What do dominant species and keystone species have in common?

A They have large biomass.

B They have minimal impact on community structure.

C They have small biomass.

D They have a large impact on community structure.

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38 What do dominant species and keystone species have in common?

A They have large biomass.

B They have minimal impact on community structure.

C They have small biomass.

D They have a large impact on community structure.


Ans

wer

D


39 Dominant species are usually located where in a food chain?

A tertiary consumer

B decomposer

C primary producer

D primary consumer

Slide 130 / 131

39 Dominant species are usually located where in a food chain?

A tertiary consumer

B decomposer

C primary producer

D primary consumer[This object is a pull tab]

Ans

wer

C


Slide 131 / 131

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