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1. DIscussion QuestionConsider humanity as the ultimate predator. Many, if not most of us, particularly in the United States, are quite comfortable with the harvesting of organisms like tuna, deer, ducks, or rabbits. Other countries and cultures; however, value species for food that rarely, if ever, find their way to the North American dinner plate. What are your thoughts on the harvesting of organisms such as whales, dolphins, seals, etc.? Is hunting the only major issue that might threaten the existence of these organisms? Should we limit ourselves to eating only certain organisms? Why, or why not? Feel free to do some independent research.Please be original….No references….Response can be one or two paragraphs ______________________________________________________________________________________________2. Please give a response to the below response from my peer. In a way I feel biased because I eat meat like chicken, steak, beef, etc. but when it comes to things like dolphins, whales and seals, I feel like it is a horrible thing. Us as humans make it our priority to survive, I get it but I think we should use our resources more wisely. We are all aware pf the animal chain. When one kind of animal goes completely extinct, it affects the entire chain. Hunting is NOT the only issue when it comes to animals existence. Us as humans have the ability and power to change an environment. Some of these animals are dying due to the inability to survive their own habitat because of things like pollution and lack of food. I don’t think we should limit ourselves to eating only certain organisms but instead, we need to spread our resources out because our population is only going to evolve more and more. If humans begin to overpower our available resources, this can be a real problem and a threat to humans. Please be original….No references….Response can be one or two paragraphs
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UnitIII_LessonPresentation
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Slide 1
Unit III, Species Interactions, Humans as Predators, and Maximum Sustainable Yield
Unit Learning Outcomes
2.1 Explain how predation and competition affect population growth.
3.1 Compare the symbiotic relationships of parasitism, mutualism, and commensalism.
3.2 Identify how humans act as predators, and explain the concept of maximum sustainable yield.
Course Learning Outcome
2. Describe the various factors that affect population-growth regulation.
3. Identify the various ways in which organisms interact with their environment.
Slide 2
Species Interactions
In Unit II, we touched on the concepts of intraspecific and interspecific interactions. Unit III will
focus on interspecific interactions and the effects of those interactions on each species involved.
Heterotrophic organisms are those that must feed on other organisms for survival. At the lowest
point of the trophic hierarchy, there are the photosynthetic organisms (known as autotrophs) that
can feed themselves with water, a nutritious substrate, and sunlight. These organisms, known as
producers, may be plants, algae, and photosynthetic bacteria. Primary consumers are organisms
that feed on producers. Examples of primary consumers would be animals such as deer, mice, or
rabbits. Secondary consumers are organisms that feed on primary consumers. Examples of
secondary consumers would be foxes, hawks, and most sharks.
The relationships between species can generally be defined by the effects of the relationship on
each of the species involved in the interaction. Competition, listed by the affect they have on each
partner as ( – , – ), is a term that even those new to the study of ecology are usually familiar with.
This interaction results in a negative effect (-) on both of the species in the relationship. Two
species competing for food, habitat, water, or other resources will prevent one another from
reaching their maximum reproductive capacity. As stated, “-” indicates a negative effect on one
organism in the relationship, “+” represents a beneficial effect, and “0” indicates no effect.
Somewhat related to competition is the concept of amensalism ( – , 0 ). With amensalism, one
species may negatively affect another but will not be affected positively or negatively. The most
common example of this relationship is large tree shading smaller plants. The smaller plants are
negatively affected in not receiving sufficient light, yet nothing changes for the tree.
When one organism feeds on another, this is a predator-prey ( – , + ) relationship. A wolf eating a
rabbit or an owl eating a mouse would be examples of a predator-prey interaction. This definition
would not include scavengers and decomposers, which feed on organisms that are already dead.
With predation, one of the two parties involved will be affected negatively. While we tend to think
of carnivorous organisms, such as wolves and owls, as exemplary predators, the definition can
be broader. Herbivores (organisms that feed solely on plants) and omnivores (organisms that
feed on both plant and animal material) may be considered predators as well. Often, the term true
predator is used to describe an organism that kills its prey and consumes it immediately.
Slide 3
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The relationships between species can generally be defined by what?
Fill in the circle of the correct answer:
 A) The effects of the relationship on each of the species involved in the interaction
 B) Secondary consumers’ organisms that feed on primary consumers
 C) Population size and density
 D) The effects of the relationship on only one species
Knowledge Check
Slide 4
As we know, a species’ interaction with its physical environment drives its evolution. However,
just as importantly, the interaction with other species does as well. As two species interact with
one another over long spans of time, each can develop adaptations in response to the other. This
is called coevolution, and there are countless examples of it throughout the plant and animal
kingdoms. An interesting example of this can be seen in the toxicity of the rough-skinned newt,
which is found along the West Coast of the United States. These newts produce tetrodotoxin,
which is a neurotoxin. The potency of the toxin produced by the rough-skinned newt is enough to
kill 10-12 humans. Scientists wonder why such a small animal would need to produce such an
incredibly potent toxin. Researchers eventually discovered that the newt’s only known predator,
the common garter snake, is resistant to this toxin. Currently, the common garter snake is the
only animal known that can consume a rough-skinned newt and survive. What is happening
between these two organisms is an excellent example of coevolution. It is a biological “arms race”
with one species’ defense countering the other’s offense resulting in a more toxic newt and a
more resistant snake.
Take a look at the video segment about the rough-skinned newt on the next slide. Please note
that you will need to use your myCSU login and password
in order to access the video.
Slide 5
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440&fHeight=365
Slide 6
Check for Learning
A species’ interaction with its physical environment drives its __________.
Fill in the circle of the correct answer:
 A) survivability
 B) growth
 C) evolution
 D) defense mechanisms
Knowledge Check
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Slide 7
Another type of species interaction where one of the individuals is positively affected to the
detriment of the other is known as parasitism ( – , + ). Parasitism involves two individuals of
different species – the parasite taking the benefit from the relationship and the host of the parasite
is harmed. A parasite may use its host for food, as a habitat, and as a means for passing the next
generation to another host. Parasitism can take a variety of forms, and parasites come in a wide
range of sizes and complexity. Microparasites are, as the name implies, very small and typically
microscopic. This category would include viruses, bacteria, and single-celled eukaryotic
organisms such as a amoebae or euglenoids. Macroparasites are large and can be seen with the
naked eye. Examples of organisms that fall into this category are roundworms (Ascaris),
tapeworms, ticks, fleas, lice, and fungi. Even birds can engage in a form of parasitism known as
brood parasitism. An example of this would be the brown-headed cowbird, a common North
American species. Cowbirds are obligate brood parasites, which means that they reproduce by
finding a nest of another, usually smaller species that already contains eggs. The cowbird will
destroy or remove one of those eggs and replace it with one of its own. Cowbirds have a short
incubation period relative to that of most of the birds they parasitize, and the young grow very
quickly. In turn, the parents of the parasitized nest will spend more energy feeding the large and
fast-growing cowbird chick, much to the
detriment of its own offspring.
Slide 8
Coevolution can work in the parasite-host relationship as well. Moth larvae generally tend to
cause considerable damage to their host plants, often resulting in the demise of the host.
However, one moth species has found an equilibrium with its only host plant, the soapweed
yucca. The moth is colloquially called the yucca moth (Tegeticulla yuccasella) and, due to an
unusual behavior, it is able to help its host plant while providing resources for its future offspring.
After mating, the female yucca moth first finds a yucca flower and collects pollen using modified
antennae, which she carries under her head. She then finds another yucca flower, creates a hole
in the ovary, and lays her eggs. The larvae will eat the developing seeds. After laying her eggs,
the moth does something that is highly unusual. She then crawls to the top of the ovary and
pollenates it so that the seeds will develop. Lastly, she marks the flower with a pheromone to
indicate to other moths that the flower is taken. Other moths will either lay fewer or no eggs at the
marked flower. Seeds of the soapweed yucca always outnumber the larvae, so there are plenty of
seeds to consume and still provide a sufficient number for the plant to reproduce. This species of
yucca is dependent on this moth for reproduction, and the moth is dependent on soapweed yucca
for its reproduction. So, they have developed a relationship over time that benefits the both. This
type of species interaction is called mutualism ( + , + ).
Lastly, there is commensalism ( + , 0 ). Commensalism is a relationship where one species may
use another for habitat or food without causing harm or benefit. Orchids are an excellent example
of commensalism. Many orchids are epiphytes and grow on the branches of trees, high in the
canopy. The orchid does not use the tree for nutrients, only as a suitable habitat where it can
receive more light and avoid predation from potential ground-dwelling predators. The orchid is
benefitted, and its host tree is not affected positively or negatively.
Take a look at the video segment on the next slide about the cuckoo bird and brood parasitism.
Note that you will need to use your myCSU login and password to access the video.
Slide 9
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580&fHeight=365
Slide 10
Another type of species interaction where one of the individuals is positively affected to the
detriment of the other is known as __________.
Fill in the circle of the correct answer:
 A) coevolution
 B) parasitism
 C) amensalism
 D) commensalism
Knowledge Check
Slide 11
Humans as Predators
Before the advent of agriculture around 10,000 years ago, humans existed as hunter-gatherers.
Even as agriculture became the primary source of human sustenance, our intelligence allowed us
to continue to sharpen our abilities as predators through our technology and creativity. To this
day, humans draw heavily from the wild to feed our rapidly growing populations around the
planet. We are in a class of our own in terms of predatory abilities, and over the millennia, we
have, often inadvertently, driven wild populations of land animals to extinction. Our effect on other
organisms does not just apply to animals that we eat. We have hunted animals for their fur and, in
the process, taken out would-be competitors for certain prey species. We also cut down trees for
timber and have cleared entire forests that took thousands of years to become established.
Today, most of us rely on agriculture in the form of farming and the raising of livestock to obtain
the bulk of our nutritional needs. Even in many less-developed countries, meat that is raised
instead of hunted is relatively easy to come by. Seafood, at least for now, is largely a different
story. While some seafood is farmed, more than 80% of it is taken from wild populations of fish
and shellfish found in our oceans, lakes, and rivers. The effect of this massive harvest has been
catastrophic to certain populations of marine life. An example is the Atlantic cod that has been
harvested off the rocky coast of Newfoundland since the 1500s. The abundance of this fish was,
at one time, a marvel. Historically, this species of cod was in such abundance that fishing vessels
were slowed as they moved into the waters where these fish congregated. Cod fishing in this
area was very stable for hundreds of years due to the fact that catches were taken by small fleets
only periodically. The Atlantic cod fishery was seemingly inexhaustible. However, after World War
II, fishing techniques changed. To keep up with increasing demand, industrial fishing fleets were
employed that used larger, deeper nets and other modern technology to take unprecedented
numbers of cod. In the late 1960s, the yearly catch tonnage numbers began to plummet, and
regulations were put in place to protect the fishery in the 1970s. In spite of that effort, by the early
1990s, the North Atlantic cod fishery had collapsed, and it has yet to rebound.
Without some restraint, thoughtful harvesting, and more sustainably farmed seafood, wild fish and
shellfish populations are destined to go the way of the many terrestrial prey species that we have
hunted to extinction already.
Slide 12
Check for Learning
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During the 1960s and 1970s, the highest amount of Atlantic cod harvested was just over how
much?
Fill in the circle of the correct answer:
 A) 500,000 tons
 B) 600,000 tons
 C) 700,000 tons
 D) 800,000 tons
Knowledge Check
Slide 13
The intelligence that afforded humans an unparalleled capacity to deplete or extinguish
populations of prey, competing organisms, and other biological resources can also be used to
manage and maintain those populations. As we learned in Unit II, we have developed methods
for estimating population size in organisms that are highly mobile by using these and other
science-based techniques so populations of wild organisms that we rely on for food can be
monitored. Policy can be enacted based on the analysis of the data collected, and, provided all
interested parties participate, prey populations can be maintained for future harvesting. Yield is
the amount of a resource that is harvested in a given unit of time. A sustainable yield allows
humans to harvest resources but allows the population of prey to rebound to a level close to that
of the carrying capacity of the ecosystem in which those populations live. Previously, we looked
at the concept of carrying capacity and the S-shaped growth curve. Prey populations rebound
quickest when they are harvested to a point at which the population is at half the amount of its
carrying capacity. This is known as maximum sustainable yield. Estimating this halfway point is
very difficult and perhaps not realistic, particularly for animals that move rapidly over large
geographic areas. However, as an ideal, aiming for the maximum sustainable yield appears to
best serve both humans and prey alike in the long-term.
Slide 14
Check for Learning
A sustainable yield allows humans to harvest resources but allows the population of prey to
rebound to a level close to that of the carrying capacity of the ecosystem in which those
populations live.
Fill in the circle of the correct answer:
 A) True
 B) False
Knowledge Check
Slide 15
References
Cressler, A. (n.d.). Yucca moths on a yucca flower [Photograph]. Retrieved from
https://www.fs.fed.us/wildflowers/pollinators/pollinator-of-themonth/images/yuccamoth/yucca_moth1_lg.jpg
Dpatdfci. (2013). Elephants Tanazania safari [Photograph]. Retrieved from
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https://pixabay.com/en/elephant-elephants-tanzania-safari-289134/
Jeffkins, H., & Choudhury, S. (Directors). (2014). Curious imposters: Attenborough’s natural
curiosities, series 2 [Video file].
Retrieved from
https://libraryresources.columbiasouthern.edu/login?auth=CAS&url=https://fod.infobase.com/Port
alPlaylists.aspx?wID=273866&xtid=60422
Pimentel, G. (Executive Producer). (2010). Freaks on land: World’s weirdest [Video file].
Retrieved from
https://libraryresources.columbiasouthern.edu/login?auth=CAS&url=http://fod.infobase.com/Portal
Playlists.aspx?wID=273866&xtid=49723&loid=449935
Reid, W. V., Mooney, H. A., Cropper, A., Capistrano, D., Carpenter, S. R., Chopra, K.,…Zurek, M.
B. (2005). Ecosystems and
human well-being: Synthesis. Retrieved form
http://www.millenniumassessment.org/documents/document.356.aspx.pdf
Skeeze. (2006). Red spotted newt [Photograph]. Retrieved from https://pixabay.com/en/redspotted-newt-newt-reptile-590542/
U.S. Forest Service. (n.d.). Yucca moth [Photograph]. Retrieved from
https://www.fs.fed.us/wildflowers/pollinators/pollinator-of-themonth/images/yuccamoth/yucca_moth1_lg.jpg
Yap, L. K. (2006). Molothrus bonariensis [Photograph]. Retrieved from
https://commons.wikimedia.org/wiki/File:060408_shiny_cowbird_female_ER.jpg
Slide 16
Answer Key
Slide 4:
The relationships between species can generally be defined by what?
: A) The effects of the relationship on each of the species involved in the interaction
Slide 7:
A species’ interaction with its physical environment drives its __________.
: C) evolution
Slide 11:
Another type of species interaction where one of the individuals is positively affected
to the detriment of the other is known as __________.
: B) parasitism
Slide 13:
During the 1960s and 1970s, the highest amount of Atlantic cod harvested was just
over how much?
: D) 800,000 tons
Slide 15:
A sustainable yield allows humans to harvest resources but allows the population of
prey to rebound to a level close to that of the carrying capacity of the ecosystem in
which those populations live.
: A) True
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