Module 9S1 Ecological Interactions

Module 9S1 - Ecological Interactions

Introduction

In Module 9: Section 1, you will analyze complex ecosystems to identify the relationships between community members. You will see that each organism belongs to a given trophic level and has a role to play within the community. You will consider both interspecific and intraspecific competition for scarce resources. You will learn that individual organisms with alleles that allow the organism to compete better than others live to reproduce, thereby improving the population gene pool within that environment.
 
You will learn about predator/prey or producer/consumer interactions in a community’s food chain. You will learn how predators act as selecting agents, removing those with less successful alleles and leaving those whom are more genetically fit. You will come to understand that predators and prey cycle together through time as the populations of one control the numbers of the other. You will also see that prey species and producers have evolved many chemical, structural, and behavioral defences that protect them from consumption.
 
You will look at how an organism filling its niche in the food chain may have positive or negative effects on those it lives with. You will study mutualistic, commensal, and parasitic relationships among organisms.

You will study the changes that occur in communities as a geographical area ages. You will learn about succession and see how pioneer species invade a barren habitat and change the environment to the extent that the pioneer species can no longer survive there. Having prepared the environment, the pioneer species will be replaced by a more suitable species. As producer species change through succession, the consumer species who rely on them change as well. Does the changing cast of characters in successions indicate a problem?

In This Module

Section 1: Lesson 1—Species Interactions and Symbiotic Relationships

In this lesson you will learn to identify various interactions between species and explain the types of symbiotic relationships that exist between species.

The focusing questions being addressed in this lesson are:

• What are the relationships that exist between species and ecosystems?
• What is the effect these interactions have on population changes?

Section 1: Lesson 2—Role of Defense

In this lesson you will examine how organisms compete in every day relationships and how they protect themselves from members of other species.

The focusing question being addressed in this lesson is:

• What are the defence mechanisms within predation and competition?

Section 1: Lesson 3—Populations and Communities Changing Over Time—Succession

In this lesson you will explore the features and types of succession that are at work and constantly changing the environment.

The focusing question being addressed in this lesson is:

• How do communities and their populations change or remain stable over time?

Big Picture

Humans live with other humans. For the most part, our interactions with other species are limited to the family pet, or to food from the grocery store. Organisms in the wild, however, live in complex communities comprised of many species of different trophic levels, interacting daily in positive, negative, and competitive relationships. We have little understanding of the instinctive and learned behaviors that allow organisms to live (and die) together while competing for the same scarce resources. Over the millennia, successful ‘partnerships’ have developed between species. As long as these relationships improve survival, the alleles that govern them will remain in the population. Chemical, physical, and behavioral defenses that improve survival have been selected for in the same way. The species make-up of a community changes over time – not due to evolution, but due to natural successions that see new producer and consumer players filling niches as habitats age and change.

You will explore the following essential questions:

• What are the living relationships that exist between individuals that ensure survival?
• What mechanisms protect individuals in a population from individuals in other populations?
• How can the various populations that make up a community change over time, or remain as a climax community?

Lesson 4.9.1S1

Lesson 1: Species Interactions and Symbiotic Relationships

Get Focused

Banff National Park was created in order to preserve the ecosystems of a pristine wilderness in Alberta’s Rocky Mountains. If you spend time hiking in the backcountry of the park today, you have a good chance of encountering several species of organisms in their natural habitats.

Although you may see grizzly bear, moose and lichen, you may not see the grizzly bear upturning rotting logs looking for a meal of larvae and roots, nor the moose being swarmed by mosquitoes drawing blood in order to feed their eggs, nor the algae and fungi that work cooperatively to form the lichen that the caribou feed on in the winter.

All organisms are part of ecological communities made up of food webs specific to a defined area. Each species has a role to play (niche) and this interdependence can cause communities to collapse if even only one species is severely affected.

The interactions and relationships that we see occurring between organisms are coded in DNA, and the alleles responsible for these behaviors are favored as long as they give the organism a selective advantage within their specific environment.

By the end of this lesson you should be able to answer the following questions:

• What relationships exist between species and ecosystems?
• What effect do these interactions have on population changes?

Module 9: Section 1—Lesson 1 Assignment

 Once you have completed all of the learning activities for this lesson, you can complete the online assignment.

Bio 30 4.9.1S1 online assignment

In addition to your lesson work as listed below, any summary notes, diagrams, charts or tables should be stored in the course folder for your teacher’s feedback and study as you prepare for exams.

 You should also watch the tutorial video from this lesson and submit a summary.  Bio30 tut#4.9.1S1 Population and communities

The other questions in this lesson are not marked by the teacher; however, you should still answer these questions. The Self-Check and Try This questions are placed in this lesson to help you review important information and build key concepts that may be applied in future lessons.

After a discussion with your teacher, you must decide what to do with the questions that are not part of your assignment. For example, you may decide to submit to your teacher the responses to Try This questions that are not marked. You should record the answers to all of the questions in this lesson and place those answers in your course folder.

4.9.1S1 page 2

Explore

Predator-Prey Relationships

The success of the predator means the death of the prey. Predators are selecting agents on prey populations because they’re more likely to kill the sick or poorly adapted prey individuals, removing those deleterious alleles from the prey gene pool, leaving superior alleles and improving the quality of the gene pool.

Predators also control prey population numbers so that they can not exceed the capacity of the environment. When rabbits were introduced into Australia, there were no predators to keep rabbit populations in check. Rabbits are now considered a nuisance and threat to native species in Australia.

The population numbers of predators and prey follow each other in predictable cycles. Because more successful predators select for more successful prey, the two species co-evolve.

High predators → low prey → low predators → high prey

Producer-Consumer relationships follow the same patterns as predator-prey. When rabbits were introduced to Australia in the absence of predators, their unhindered reproduction resulted in many habitats being completely denuded of grasses.

Scarcity leads to competition, and competition leads to natural selection of the fittest phenotype/genotype. A plant that is a better competitor than its neighbors of the same species may make do with less water, cast its seeds further from the mother plant, or produce more seeds per seed pod. This intraspecific competition favors one phenotype at the expense of the other and thus reduces diversity. At the same time that a lynx is competing with others in its own species, it is also competing with coyotes and hawks in interspecific competition. If two species with the same niche (are competing for the same resources, in the same place, using the same methods), typically only one species survives – a principle called competitive exclusion.

In symbiotic relationships, the lives of two species are locked together in co-evolution; success of one limits the success of the other. Like human relationships, symbiotic relationships can be defined by the effect on each participant species:

1. + - One species benefits at the other’s expense.
2. + + Both species benefit.
3. + 0 One species benefits but the other is unaffected.

Mutualism ( + + ) increases survival of both species;the products of one, provide the needs of the other. The same cannot be said for commensalism (+ -), where one species unwittingly boosts the survival of another without obtaining any benefit. Parasitism ( - - ) allows one species to expend very few resources in staying alive, but at the expense of its host.

To further explore these concepts:

Read

Read p 717-4 of your text.

Watch and Listen

Parasitism, Mutualism, Commensalism.

Predator, Prey Relationships

Self-Check 1

SC 1. Re-read the Explore section on predator-prey relationships. Although we can argue that the relationship is positive for the predator and negative for the prey, support the argument that predator/prey relationships are in fact +  + relationships when we consider populations rather than individual organisms.

SC 2. Scientists have found that the number of predators in a stream influences the natural selection of guppies.

Conduct the on-line simulation of evolution in guppy populations at

1. Guppy Simulation
2. In what ways do the populations change over time?

SC 3. Fill in the empty boxes in the table using examples from your text.

4.9.1S1 page 3

Self-Check 2

SC 1. Complete this Self-Check activity.

Try This

TR 1. Check out the typical predator/prey cycle graph in Figure 20.12 on p. 721. 

1. If you were not shown the legend, how would you know which line represents predator, and which represents prey? Hints:
    
   • Which would always have the highest numbers? (think food pyramid)
   • How long would it take for an excess of prey to translate to an excess of predator? (High food supply expresses itself as more babies being born the following season)
2. What is the length of the lynx-hare cycle in years?

Discuss

Deer and moose hunters pride themselves on the size of the animal taken and the # of tines on the antlers (# of tines increases with the age and size of the buck). Both hunters and predators keep the prey population in check. However, hunters tend to have a negative effect on the prey gene pool whereas predators have a positive effect.

Prepare reasons for this distinction. What kind of hunting regulations would correct this problem? Post your work on the discussion board, and discuss the work of other students. Summarize the thoughts of the group and put the summary in your course folder.

Module 9: Section 1—Lesson 1 Assignment

Submit your completed Module 9: Section 1—Lesson 1 Assignment to your teacher for assessment.

Lesson Summary

In this lesson you have studied the following concepts:

• What are the relationships that exist between species and ecosystems?
• What is the effect these interactions have on population changes: 

You should now have come to appreciate the many types of living relationships that can help, harm, or have little effect on interacting species.

Lesson 4.9.2S1

Lesson 2—The Role of Defense

Get Focused

On your hike into the backcountry of Banff National Park, remember that each species you see is a winner; a species that has out-competed all others that have attempted to share its niche. The grizzly bear’s behavioral defenses are easy to spot: Standing up on the hind legs and hair standing up on end make it appear larger and more fearsome. Baring of teeth, growling, laying back of ears and mock-charging all indicate danger to would-be competitors or predators. What other kinds of defenses do organisms use to protect themselves from other competitors or from being consumed, thus protecting their alleles from elimination?

By the end of this lesson you should be able to answer the following focusing question:

• What are the defense mechanisms within predation and competition?

Module 9: Section 1—Lesson 2 Assignment

Once you have completed all of the learning activities for this lesson, you can complete the online assignment.

Bio30 4.9.2S1 online assignment

You must decide what to do with the questions that are not marked by the teacher. Remember that these questions provide you with the practice and feedback that you need to successfully complete this course. You should record the answers to all of the questions and place those answers in your course folder.

4.9.2S1 page 2

Explore

Although venom is a commonly used defense in reptiles and insects, producers have also evolved chemical defenses against consumers. Some plants produce chemical toxins that simply taste bad or can poison consumers who eat them. The roots of some plants secrete toxins that inhibit growth of their neighbors, reducing inter or intraspecific competition. Behavioral defenses are fascinating: the arched back of a cat produces the same large, threatening silhouette as a bear standing on its hind legs or a dog with its hair standing on end. Markings and coloration usually provide a distinct selective advantage. Cryptic coloration allows prey organisms to evade predators, and allows predators to sneak up on prey. Protective coloration is ensured when bright colors signal clear warnings to would-be predators. Looking dangerous is one strategy, but mimicry of dangerous species may be just as effective. Your text offers good examples.

Read

Read pages 722-724 in the textbook.

Try This

TR 1. Read the following 2 statements. Although both of these indicate chemical defenses, what is the difference between them?

1. Some species of plants produce toxins that prevent them from being eaten by herbivores.
2. Some species of plants secrete chemicals into the ground that prevent other plants of its own species from growing near it.

Self-Check

SR 1. Describe the following as being either: (a) chemical defense, (b) cryptic coloration, (c) protective coloration, (d) mimicry

1. When elephants begin to eat the leaves of the Thorn tree, the tree releases a bitter tasting substance into the leaves that prevents elephants from consuming the whole tree.
2. The beautiful red, blue, and yellow tree frogs of Costa Rica produce some of the poisonous venoms of the natural world.
3. The dusty, golden-brown coyote is difficult to spot against the dry grasses of the prairie.
4. A harmless sea snake has almost the identical bright markings as the highly venous coral snake.

Guppy Predator Simulation

Scientists have found that the number and type of predators in a stream influence the natural selection of guppies. Conduct online research about evolution in guppy populations.

Retrieve your copy of Module 9: Section 1—Lesson 2 Assignment that you saved to your computer earlier in this lesson. Complete the assignment. Save your completed assignment in your course folder. You will receive instructions later in this lesson on when to submit your assignment to your teacher.

Watch and Listen

Watch the following video that shows the use of thermal defenses in bees.

Module 9: Section 1—Lesson 2 Assignment

Submit your completed Module 9: Section 1—Lesson 2 Assignment to your teacher for assessment.

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Lesson Summary

All species rely on defenses of some kind to reduce their chances of becoming a meal for another species. These can take the form of structural characteristics (thorns, claws), chemical characteristics (plant toxins, venoms) behaviors (territoriality, barking), or coloration (protective coloration, mimicry, and cryptic coloration). These defenses allow organisms from one species to protect themselves and to compete interspecifically with species that share the same trophic level. Slight variations in defenses between individuals of the same species (intraspecific competition) allow some individuals to compete better than their neighbors, changing allele frequencies in their favor. The greater the scarcity in a habitat, the more competition there is, thus the faster evolution occurs.

Lesson 4.9.3S1

Lesson 3—Populations and Communities Changing Over Time

Get Focused

You may be surprised to find that a small grassy meadow surrounded by forest that you enjoyed when you were a child had disappeared 5 years later. What you would see in the place of grasses (at least in Central Alberta) would be wild roses and thistles. A few years later, wild rose and thistle would begin to be replaced by wild raspberry bushes, Saskatoon berry bushes, hazelnut bushes, high-bush cranberry, and dogwood shrubs. Several years later you could have returned to the same place and found some chokecherry and pincherry trees nestled amongst a forest of mature aspen trees. If you continued to return year after year, you would find that the aspen forest remained.

In the same way that individuals go through life cycles from young to old, communities age as well, with one species succeeding another. This species changes the environment enough that it can no longer live there, making the environment suitable for a more adapted new occupant.

At the end of this lesson you should be able to answer the following focusing question:

• How do communities and their populations change or remain stable over time?

Module 9: Section 1—Lesson 3 Assignment

Once you have completed all of the learning activities for this lesson, you can complete the online assignment.

Bio30 4.9.1S1 online assignment

You should also watch the tutorial video for this lesson and submit a summary.  Bio30 tut# 4.9.3S1 Succession

In addition to your lesson work as listed below, any summary notes, diagrams, charts or tables should be stored in the course folder for your teacher’s feedback and study as you prepare for exams.

4.9.3S1 page 2

Explore

The changes that a community goes through as it ages are known as succession. For every biome, or micro-climate within a biome, there is a predictable succession of plant and animal species that will play their parts then disappear, from the first pioneer species to the final stable climax species that represents the completed succession. Communities are named by their climax species (e.g. aspen forest, black spruce forest). Why does succession occur? How does one species change the environment resulting in its replacement by another species? How does primary succession differ from secondary succession?

Read

Read p. 725-6 and 728 in the textbook.

Watch and Listen

Succession and Climax Communities

Description of Succession

Primary V.S. Secondary Succession

Self-Check

Alberta has significant forestation. Every year you hear about the forest fire hazard, and where fires are burning out of control. To review the role of fire in the ecosystem and how it affects the succession of communities, try the following self check. You may wish to score your answers, and be sure to add your work to your course folder.

Fire is a force of nature that has positive and negative roles to play in a healthy ecological community. In nature, the source of fire is lightning.

Research the following questions regarding the role of fire.

SC 1. What positive and negative roles do forest fires play in nature?

SC 2. Research and evaluate the practice of ‘controlled burns’ used in National Parks in terms of advantages and disadvantages. If fire terminates an existing succession and causes secondary succession to start over, isn’t a controlled burn interfering with natural processes?

SC 3. In the past, native aboriginal Albertans would purposely set prairie fires in the spring to begin a secondary succession. Why? (Remember what the primary food source was.)

SC 4. One of the first species to colonize burned forest is fireweed. What are some traditional uses of this plant by native aboriginals?

Try This

To review the types and conditions of succession, complete the following table for your course folder.

TR 1. Using your text fill out the following table:

SC 5.

If producer species go through successions, consumer species must as well. As the food source changes, conditions favor the invasion of different animal species. For example, after a fire, the pioneer species of grasses favors the presence of seed eaters like mice and gopher. The lack of overhead cover suits them in that they can burrow to hide from predators overhead like hawks. When the soil is too cool and shady to germinate grasses, shrubs start to appear, and rabbits will tend to replace the mice and gophers.

Continue this central Alberta plant animal succession on the table below. You made need to do some research on Alberta food chains.

Self-Check

Succession and Biodiversity

You will recall the significance of biodiversity from Biology 20, and from Unit D, Module 8. Consider how they might interact by completing the following assignment. There is opportunity to score your answer, but be sure to file your work in your course folder.

How does primary succession affect genetic biodiversity of communities?
Check out "Figure 20.21" on page 726 and answer the following questions.

SC 1. What is the effect of time on biodiversity in a succession? Why does this occur?

SC 2. Why is the number of species that can survive at the beginning of the succession so low?

SC 3. Why does the number of species level off towards the end of the succession?

SC 4. How many years did it take to complete this succession?

4.9.3S1 page 3

Self-Check

1. Which of the following is not an example of symbiosis?
   1. Mutualism
   2. Commensalism
   3. Parasitism
   4. Predator/prey

2. Nemo, the clownfish from Under the Sea successfully lived among the stinging tentacles of the sea anemone. The anemone received nothing in return for protecting the clownfish. This is an example of
   1. commensalism
   2. parasitism
   3. mutualism
   4. predator/prey

3. Which of the following is NOT true of predators
   1. They improve the gene pool of the prey population
   2. They are more likely to attack a weak, sick, or old prey than a strong one
   3. Their population numbers can be larger than the prey’s
   4. Predators control the numbers of prey and prey control the number of predators

4. Interspecific competition
   1. occurs when members of the different species compete for scarce resources
   2. occurs between a coyote and a hawk
   3. can lead to competitive exclusion
   4. occurs between organisms of the same trophic level
   5. All of the above

5. Which is true of a secondary succession?
   1. It starts from bare rock
   2. The pioneer species can be lichen
   3. The climax species is the final species
   4. Could occur after an avalanche or volcanic event

6. Which is NOT true of succession?
   1. is the replacement of one species by another
   2. occurs when one species changes the environment enough that it can no longer survive there
   3. is a natural process wherein communities age
   4. results when competition between two organisms of the same niche leads to the success of one

7. Parasitism
   1. uses the resources of the host to survive
   2. is a more energetically expensive way of living
   3. selects for strong immune systems in the host
   4. a and c

8. Mutualism
   1. benefits one species in the relationship
   2. results in co-evolution of the two species in the relationship
   3. decreases survival of both species
   4. is a type of interspecific competition

Module 9: Section 1—Lesson 3 Assignment

Logging Methods

Retrieve your copy of Module 9: Section 1—Lesson 3 Assignment that you saved to your computer earlier in this lesson. Complete the assignment. Save your completed assignment in your course folder. You will receive instructions later in this lesson on when to submit your assignment to your teacher.

Module 9: Section 1—Lesson 3 Assignment

Submit your completed Module 9: Section 1—Lesson 3 Assignment to your teacher for assessment.

Remember that your Module 9 Section 1 Assessment is due at the end of this lesson. Submit your completed assignment to your instructor before moving into Module 9 Section 2.

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Lesson Summary

Communities change over time in the process of succession. Ecological disturbances (both human-caused and natural) can destroy communities and return them to rock or to soil. Primary succession begins from bare rock, where little life exists, and may be the result of avalanche or glacial melting. Secondary succession begins from soil, where life still exists as roots, seeds, and other organisms in the soil, and occurs after fire has destroyed a community, or when human settlements or agricultural fields are abandoned. In either case, a predictable pattern of invasion and replacement of species will occur, ending in a stable climax community. The first species to invade is the pioneer species, and the last species is the climax species, by which the community is known. Animal species undergo succession as well. As producer species change with the succession, so does the basis for new consumer food chains and food webs.

Module Summary and Assessment

Module Summary—Section 1

The ability to analyze complex ecosystems to identify the relationships between community members is a difficult task. Each organism belongs to a given trophic level and has a role to play within the community. However, organisms within the same trophic level compete with each other in interspecific competition for food (the previous trophic level), water and other scarce resources. Competition between members of the same species (intraspecific competition) happens the same way. Those with alleles that allow the individual to compete better, live to reproduce, improving the population gene pool within that environment.

Predator/prey or producer/consumer interactions describe a community’s food chain. Predators act as selecting agents, removing those with less successful alleles and leaving those more genetically fit. Predators and prey cycle together through time as the populations of one control the numbers of the other. Prey species and producers have evolved many chemical, structural, and behavioral defences that protect them from consumption. The more effective the defense, the more likely the organism is to survive to pass on their genes.

As an organism fills its niche (does its job) in the food chain it may have positive or negative effects on those it lives with. Mutualistic relationships benefit both parties, commensal relationships benefit one and don’t affect the other, and parasitic relationships benefit one organism at the expense of the other.

Succession refers to the changes that occur in communities as a geographical area ages. Whether primary (from rock) or secondary (from soil), pioneer species invade a barren habitat, changing the environment so that they can no longer survive there, creating an environment for a more suitable organism to replace it, terminating in a climax species which remains indefinitely until the succession starts over. As producer species change through succession, the consumer species who rely on them change as well. The changing cast of characters in successions are part of a natural process and do not indicate a problem.

Module Assessment—Section 1

In addition to submitting a tutorial summary for each tutorial video each student should also submit the following assignments

Bio30 4.9.1S1 online assignment

Bio30 4.9.2S1 online assignment

Bio30 4.9.3S1 online assignment