T4 Exploring Trophic Cascades

Exploring Trophic Cascades

• Go to EdPuzzle & watch “How Wolves Change Rivers.” Use you class code to access the video. When complete, progress to next slide.

  • 1st period: oviomie

  • 4th period: rachifa

  • 7th period: dujohic

Part 1: How Wolves Change Rivers

Open Ended

Record your Edpuzzle score here, then continue to the next slide.

Multiple Choice

What is a trophic cascade?

• A waterfall in a tropical forest.

• 
  A series of changes in an ecosystem that occur when a new species is introduced.

• A series of secondary extinctions triggered by the primary extinction of a key species in an ecosystem.

• A process where predators at the top of the food chain affect the density and behavior of their prey and plants below.

Multiple Choice

Which species has experienced directly, an increase in consumption by wolves since their reintroduction?

• Rough-legged hawk

• Beavers

• Elk

• Mice

Multiple Choice

Based on the diagram, how do wolves have an indirect impact on grasses?

• Wolves eat grasses, reducing their abundance

• Wolves have no indirect impact on grasses

• Wolves increase the abundance of grasses by controlling herbivore populations

• Wolves trample grasses, leading to their decrease

Multiple Choice

What can you infer about the relationship between wolves and rough-legged hawks?

• Wolves prey on rough-legged hawks

• 
  Rough-legged hawks and wolves compete for the same prey

• The reduction in mice due to wolf activity decreases the food available for rough-legged hawks

• Rough-legged hawks benefit because more vegetation provides shelter increasing mouse populations

Open Ended

According to the graphic, The elk and mule deer populations decreased in number because of an increase in Wolf Predators. What other population was adversely affected by the reintroduction of wolves? Explain how they were negatively affected and why.

STOP! Do not continue until you have accessed the HHMI website and split your screen.
Part 2: Exploring Trophic Cascades

You will now go to the HHMI Biointeractive website and explore an aquatic trophic cascade. Click the following link, and click "start interactive" and the "Introduction" to complete the following slide.
CLICK HERE!!!!
(the answers are in the above link!!) CLICK IT!

Split your screen so it looks like this

Dropdown

Ecosystems are comprised of a ​

Select answer

of organisms and their physical environment. Ecologists study the ​

Select answer

among these organisms and the factors that affect organisms’ distribution. The structure of an ecosystem can be represented by a pyramid made up of ​

Select answer

such that ​

Select answer

are on the bottom, followed by primary consumers, secondary consumers, and so on.

​Click "Educator Resources" at the bottom of the interactive to complete the following slides.

Dropdown

​

Select answer

are a central concept in ​

Select answer

and focus on the interactions between species and how the effects of those interactions are transmitted through the ​

Select answer

.

Categorize

Options (10)

plants

soil

water

nutrients

sunlight

climate

animals

pathogens

predators

decomposers

Organize these options into the right categories

biotic factors

abiotic factors

Drag and Drop

Organisms can have both direct and indirect effects on other members of their ecosystem.

​

Placeholder

effects occur when organisms ​

Placeholder

close relationship such as predation, competition, or mutualism.

​

Placeholder

effects occur when an organism affects other members of the ecosystem with which they ​

Placeholder

a close relationship.

Effects can be either positive or negative. For example, a predator has a ​

Placeholder

effect on its prey species because the more predators you have, the fewer prey.

Drag these tiles and drop them in the correct blank above

Direct

have a

Indirect

do not have

negative

positive

Return to the Introduction

Then click on the arrow button on the right of the interactive. Watch the short video, then answer the questions that follow.

Multiple Choice

This scientist went to two different locations to observe the effects the presence or absence of otters had on sea urchin populations and kelp forests. Which of the following would be an appropriate hypothesis for this experiment?

• Effects of sea otters on kelp growth

• Effects of Kelp on sea otter growth

• Effects of sea urchins on sea otters

• Effects of kelp growth on sea urchins

Multiple Select

James Estes found that when there were a lot of sea urchins, there were (choose two)...

• very few kelp

• very few sea otters

• an abundance of kelp

• a large population of sea otters

Drag and Drop

According to James Estes, "Trophic cascade Is when you have a(n) ​

Placeholder

controlling the distribution of ​

Placeholder

leading to a cascade of ​

Placeholder

effects, lots and lots of indirect effects."

Drag these tiles and drop them in the correct blank above

apex predator

producer

decomposer

resources

populations

indirect

direct

Categorize

Options (4)

urchins

birds

otters

invertebrates

Organize these options into the right categories

feed on the kelp

feed on the urchins

Progress through the interactive, then answer the questions that follow.

Click on KELP EXAMPLE

note the difference between DIRECT EFFECTS and INDIRECT EFFECTS on trophic levels in the cascade.

Watch the animation

Click on the arrow button

Match

Match the following

• Represents a direct effect

• Represents a negative effect

• Represents an indirect effect

• Represents a positive effect

A solid line

A minus (-) sign

A dotted line

A plus (-) sign

• A solid line

• A minus (-) sign

• A dotted line

• A plus (-) sign

Hotspot

Click the hotspot that shows an indirect positive effect on kelp growth.

Hotspot

Click the hotspot that shows a direct negative effect on kelp growth.

Multiple Choice

Glaucous-winged gulls are common seabirds along the northwest Pacific coast of North America. They are omnivores that primarily consume fish and marine invertebrates. However, with the absence of otters, gull diets shifted from mainly fish to mainly invertebrates. What would be the most likely explanation for this?

• The kelp forests were more important for fish populations than invertebrate populations therefore in the absence of otters there were still some invertebrates present for the gulls to eat.

• Without the kelp forests to absorb excess toxins released by the sea urchins, the fish died off leaving only invertebrates as food for the gulls.

• Invertebrates are likely more nutritious than fish and are the preferred food for the gulls.

Reorder

When sea otters are removed, a trophic cascade occurs. Put the trophic cascade in the order in which it occurs.

• sea urchin populations rise dramatically

• kelp forests decline and disappear because they are eaten by sea urchins

• fish populations decline because they lose food and shelter with the disappearance of the kelp

• sea gulls shift to eating small invertebrates more than fish because the fish have declined

• bald eagles shift to eating sea gulls because there are less fish and the gulls are their most direct competition for the remaining fish

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