Lesson 2: Build Your Own Ocean Food Web! - CCE LTERcce.lternet.edu/sites/default/files/Food Web Lesson Plan...1 Lesson 2: Build Your Own Ocean Food Web! Focus Question What are the

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Lesson 2: Build Your Own Ocean Food Web!

Focus Question

What are the roles played by plants, animals, and other organisms in marine food webs off the California coast?

Grade Levels

6-8 Number of Participants

All students (no minimum or maximum) Objectives

Upon completion of this lesson plan, students should be able to:

1. Discuss different roles that animals, plants, and other organisms play in ocean food webs.

2. Understand the difference between a food chain and a food web.

3. Describe how changes in the abundance of one species can affect other species in a food web.

Science Content Standards for California Public Schools

Grade 6: Ecology 5a. Students know energy entering

ecosystems as sunlight is transferred by producers into chemical energy through photosynthesis and then from organism to organism through food webs.

5b. Students know matter is transferred over time from one organism to others in the food web and between organisms and the physical environment.

5c. Students know populations of organisms can be categorized by the functions they serve in an ecosystem.

5d. Students know different kinds of organisms may play similar ecological roles in similar biomes.

Materials

1. String cut into pieces. There should be ~5 pieces of string per student. Each piece should be about 5-10 feet long.

2. Marine species cards (provided) 3. PowerPoint file and PDF showing

examples of roles played by different organisms in a food web (provided)

4. Pictures demonstrating the difference between a food chain and a food web (provided)

5. Safety pins (optional) Background Information for Educators

One way of classifying different organisms that live in an ecosystem is based on what they eat. Organisms that generate their own energy through photosynthesis are referred to as primary producers. In marine ecosystems, examples of primary producers include plants (e.g., seagrasses, mangroves), multicellular algae (e.g., kelp and other seaweeds), single-celled algae (e.g., diatoms), and photosynthetic bacteria (e.g., blue-green algae or cyanobacteria). Some marine ecosystems also include organisms that produce energy through chemical reactions in a process known as chemosynthesis. Chemosynthetic organisms are another type of primary producer.

Primary producers are eaten by organisms known as primary consumers. Primary consumers can either be herbivores (e.g., plant eaters) or planktivores (e.g., plankton eaters). In coastal ecosystems off California, examples of herbivores include sea urchins and kelp crabs, which both consume kelp.

Photosynthetic plankton, or phytoplankton, are eaten by a large variety of organisms in pelagic (open-water) ecosystems. Larger-sized plankton that eat

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phytoplankton are collectively referred to as zooplankton. Different species of zooplankton may prefer to eat either large phytoplankton, such as diatoms, or small phytoplankton, such as cyanobacteria. To give you a sense of the size of these phytoplankton, about 7 of the larger diatoms could fit on the head of a pin, whereas 750 small cyanobacteria could be crammed onto the same pinhead.

Copepods and krill are both planktonic crustaceans that prefer large-sized phytoplankton. In contrast, small phytoplankton may be eaten by ciliates, which are a type of protist (a single-celled eukaryotic organism). Some phytoplankton are also eaten by animals that live on the sea floor, such as mussels.

Primary consumers are eaten by secondary consumers. Many small fishes found in marine ecosystems, such as sardine, anchovy, and lanternfish, are secondary consumers. In benthic (or sea floor) ecosystems, sea stars are an example of a secondary consumer. Other types of secondary consumers found in pelagic ecosystems include squid, jellyfish, and some species of whales. In pelagic ecosystems, some secondary consumers may occasionally eat both phytoplankton and zooplankton. This is an example of omnivory. Since sardine and jellyfish mainly consume zooplankton, but occasionally eat diatoms, they can be considered omnivorous species.

Tertiary consumers that eat secondary consumers are also common in ocean ecosystems. Sometimes it is ambiguous whether a species is a tertiary or quaternary consumer in a marine ecosystem because a food chain can include many steps where one planktonic organism is eaten by another planktonic organism. For simplicity, in this lesson plan we use the term carnivore to refer to all organisms at the level of tertiary consumption or above. Examples of marine

carnivores include fishes, sharks, seabirds, seals, sea lions, dolphins, and some whales.

Nutrients are recycled in ecosystems by organisms that act as decomposers. Bacteria are the most important type of decomposers in marine ecosystems. Bacteria consume organic matter that is released into the water column by both live and dead phytoplankton. Organic matter, dead organisms, and feces that are not consumed by bacteria will eventually sink out of the water column and reach the sea floor. On the sea floor, this organic matter will be consumed by a variety of scavengers. Many types of shrimp are scavengers. Some marine scavengers are referred to as detritivores, because they feed upon detritus (decaying organic matter) found on the seafloor. Sea cucumbers are an example of a detritivore.

A food web is a schematic that shows how energy and nutrients flow between different organisms in an ecosystem. Food webs are more complicated than a food chain, where energy and nutrients flow in a simplified, linear pathway between primary producers, primary consumers, and secondary consumers. In a food web, animals may eat many types of prey items or may change their preferred type of food as they grow from juveniles to adults. Although they are more complicated, food webs provide a more realistic depiction of how marine ecosystems function. This lesson plan includes diagrams depicting marine food chains and food webs to help you explain this difference to your students.

Changes that affect one species can spread throughout an ecosystem through food webs. For example, an increase in nutrients can cause phytoplankton to reproduce rapidly, resulting in an increase in their abundance. The phytoplankton will provide additional food for zooplankton, such as copepods and krill. This can cause these types of zooplankton to become more

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abundant. In turn, the number of fish that eat zooplankton may increase. When changes in an ecosystem spread from primary producers upward through a food web, this is called bottom-up control.

In contrast, top-down control occurs when the abundance of a carnivore changes affecting the species that are eaten by the carnivore. For example, sea otters were hunted nearly to extinction by the beginning of the 20th century. The reduced number of sea otters caused an increase in the abundance of sea urchins, which are eaten by otters. The sea urchins preyed heavily on kelp, causing the destruction of kelp forests throughout much of the West Coast of North America.

The marine ecosystem off California is sometimes referred to as a wasp-waist ecosystem. In wasp-waist ecosystems, there are a large number of species of primary producers and carnivores, but only a few species of secondary consumers. The important secondary consumers in this ecosystem are small fishes, such as sardine and anchovy. Since there are few other secondary consumers, changes in the abundance of sardine and anchovy can have a large effect on both the organisms that they eat and their predators.

Today humans play a major role in marine food webs, since they catch many organisms for their own consumption. This is why several types of fishermen are included as members of the marine food web that students will construct. Key Words

Primary producer, primary and secondary consumers, herbivore, carnivore, omnivore, scavenger, decomposer, plankton, photosynthesis, food chain, food web, ecosystem

For advanced classes or older grade levels, educators may also want to introduce the following concepts: bottom-up control,

top-down control, and wasp-waist ecosystems.

Activity Summary

In this lesson plan, students will construct an ocean food web that can comprise up to 35 species that live in pelagic and benthic environments off California. Each student will be assigned a role of a different species. These roles are described on the marine species cards included as part of this lesson plan. These cards list the major components of each species’ diet. Students will be given ~5 strings each and will be instructed to find the students playing the roles of the species that their organism eats. Once a student finds these other species, they are given the other end of the student’s string to hold. In this way, the students construct a representation of the marine food web off the coast of California.

Once the food web has been constructed, the teacher will pose a number of questions about what happens if a particular organism increases or decreases in abundance. When an organism increases in abundance, the student playing this organism will raise his/her hand. A decrease in abundance is indicated by a student sitting down at a desk or on the floor. When an organism increases in abundance, its prey will become less abundant and its predators will become more abundant. Students playing the role of prey should sit down to indicate their reduced abundance, while students playing predators should raise their hands. A chain reaction of students sitting or raising their hands will propagate throughout much of the food web, demonstrating the interconnection between organisms in an ecosystem.

To help students master new vocabulary and develop critical thinking skills, this lesson plan also contains a few supplemental activities. Step 2 under Lesson Plan Steps describes several (optional) vocabulary learning activities. Step 7 under Lesson

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Plan Steps includes a homework assignment designed to encourage students to think critically about the role of humans in marine ecosystems and about the impacts of fishing and climate change on ocean food webs. Preparation

The teacher will need to print out the species cards provided at the end of the lesson plan that will be given to each student. To make it easier to see the species that each student is playing, it may be useful to either have students pin the species cards to their clothing or have a string attached to the cards, so that students can wear their card like a necklace. To increase the durability of the species card, they could be (optionally) laminated.

A teacher should cut approximately 5 pieces of string per student. Each piece of string should be ~5-10 feet so that the food web does not become too tangled. Lesson Plan Steps

Step 1: Introduce students to new vocabulary words related to the different roles that species play in food webs.

Step 2: To help students learn this vocabulary, 12 images of plants, animals, and fungi that play different roles in terrestrial (or land) food webs are included in this lesson plan. These terrestrial organisms will likely be more familiar to students than sea creatures. This should allow students to focus more on learning the new vocabulary, instead of learning about what each organism eats. These images can be used in one of three ways to help students master their vocabulary:

1.) The images can be projected overhead and the teacher can lead a class discussion about the role that each organism plays in a food web.

2.) Students can be divided into teams and play a jeopardy-style game where they are quizzed about

whether each image is a primary producer, primary consumer, secondary consumer, carnivore, scavenger, or decomposer.

3.) Images could be placed in various stations throughout the classroom. Students can be broken into groups that travel to each station, where students would discuss the role played by each organism in the food web.

Step 3: Once students have mastered the new vocabulary, the teacher should provide a brief overview of food webs and how they differ from food chains. A PowerPoint file visually demonstrating these differences is provided. A PDF file of these diagrams is also included for instructors who do not have access to PowerPoint software.

Step 4: Students line up to select their species card from a pile and take ~5 pieces of string. 35 roles are available for students to play when building their food web. For smaller-sized classes, some organisms in the food web can be left out. For larger classes, some students can double up and play the same role in the food web.

After choosing their species cards, students stand in a circle where they read off the name of their species and tell the class what their species eats. After reading their cards, students may want to pin their card to their shirt to make it easier for other students to recognize what organism they are playing.

Step 5: Students then use their pieces of string to self assemble the food web. Students whose organism eats less than 5 species will not use all their pieces of string.

Step 6: The teacher describes several scenarios where one organism increases or decreases in abundance. If an organism increases in abundance, the student playing this organism raises their hand. A decrease in abundance is symbolized by a student sitting down. If an organism increases in

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abundance, its prey will become less abundant, which is indicated by the students who play prey species sitting down. Predators of the more abundant species will also increase in abundance. Students playing predators should raise their hand. This chain of reactions will then affect the prey’s prey and the predator’s predators. At the end of each scenario, the majority of students will be either raising their hands or sitting down to indicate how their abundance has changed.

Here is a partial list of scenarios that the class should try acting out. Additional scenarios can also be devised by the teacher.

1.) What happens if an increase in ocean nutrients causes there to be more diatoms?

2.) What happens if hunters kill almost all of the sea otters?

3.) What happens if ocean temperatures become too cold for sardine causing them to decrease in abundance?

4.) What happens if ocean temperatures become too warm for anchovy causing them to decrease in abundance?

5.) What happens if sardines decrease in abundance, while anchovy increases in abundance?

The latter three scenarios reflect historical changes in the ocean ecosystems of California, where during different decades conditions have either been favorable for anchovy or sardine. Future lesson plans in this unit will discuss historical cycles in the abundance of these two fishes. Acting out these scenarios will help preview this subject matter.

Step 7: As a homework assignment, students should write answers to the following questions:

1.) Describe what role your organism played in the marine food web.

2.) Why are humans important to include in the marine food web?

3.) In the 1930s, the largest fishery in California was for sardine. However, during the following decades, sardine became much rarer due to changes in ocean temperature and because too many sardine were caught by fishermen. At the same time that sardine became less abundant, anchovy, another species of small fish, increased in abundance. Based on the activity that you did in class today, how do you think these changes in sardine and anchovy will affect other organisms in the ocean food web?

Questions? Contact Rebecca Asch Ph.D. student, Biological Oceanography Scripps Institution of Oceanography [email protected]

Marine Species Cards

Pacific Sardine • 

Secondary consumer

• Eats copepods, ciliates, and som

e diatoms

• Lives in open-‐w

ater habitats

• Bonus fact: John Steinbeck (a fam

ous writer from

California) has w

ri@en a

book about the fishery for sardine. The Dtle of this book is Cannery Row

.

Marine Species Card 1 of 35

Anchovy • 

Secondary consumer

• Eats copepods


ater habitats that are close to the coast

• Bonus fact: The fishery for anchovy off South Am

erica was once the largest in the

world. At that Dm

e, fisherm

en caught nearly 12 million tons of anchovy

each year.


Lanternfish • 

Secondary consumer

• Eats copepods and krill

• Lives in the deep ocean, but com

es to the surface at night to feed

• Bonus fact: Lanternfish have special cells that produce light. This is w

hy they are named “lanternfish.”


Diatom

• Diatom

s are a type of microscopic algae.

• Prim

ary producer

• Makes its ow

n food through photosynthesis

• Bonus fact: A diatom

is made of a single cell, but

many diatom

s can join together to form

long chains. These chains look a li@

le like a necklace.

Diatom chain


Copepod • 

Copepods are a type of plankton.

• Prim

ary Consumer

• Eats diatom

s and ciliates

• Bonus fact: Copepods are the m

ost abundant animals

on Earth.


Bacteria • 

Herbivore

• Decom

posers

• Mainly eat dying diatom

s and blue-‐green algae

• Bacteria live in all habitats in the ocean.

• Bonus fact: Did you know

that there are a m

illion bacteria in every drop of seaw

ater?

This is a picture of marine bacteria giving off

fluorescent light. The photo was taken under a

microscope.


Blue-‐green Algae • 

Primary producer

• Make their ow


• Live in the upper part of the ocean so that they have enough light for photosynthesis

• Bonus fact: Despite their nam

e, blue-‐green algae are actually a type of bacteria.


Ciliate • 

These are a very small type

of plankton that belong to a group of organism

s called “proDsts.”

• Prim

ary Consumer

• Eats blue-‐green algae

• Bonus quesDon: Can you spot the algae that the ciliate ate in the picture above?


Yellowfin Tuna

• Carnivore

• Eats sardine, anchovy, lanternfish, and squid


ater habitats

• Bonus fact: Tunas can migrate long distances.

Some types of tuna sw

im

across the whole AtlanDc

Ocean betw

een Europe and the U

nited States.


Brown Pelican

• Carnivore

• Eats anchovy and sardine

• Feeds in areas near the coast

• Bonus fact: Brow

n pelicans were once an endangered

species, but they have now

recovered.


Risso’s Dolphin

• Carnivore

• Eats anchovy, sardine, and squid

• Bonus fact: The N

avy has trained dolphins to help detect underw

ater mines.


Blue Whale

• Secondary consum

er

• Eats krill

• Bonus fact: The blue w

hale is the largest anim

al that has ever lived on Earth. It is bigger than the dinosaurs.


Cormorant

• Carnivore

• Eats sardine and anchovy

• Feeds in areas near the coast

• Bonus fact: Fisherm

en in Japan and China have trained corm

orants to help them

catch fish. These fisherm

en have been pracDcing this tradiDon for 1,300 years.

This cormorant is

diving to catch its food.


Mussel

• Prim

ary Consumer

• Eats diatom

s and blue-‐green algae

• Mussels live a@

ached to the sea floor in shallow

waters.

• Bonus fact: M

ussels help keep the ocean clean by filtering w

ater.


Sea Star


er

• Eats m

ussels

• Lives on the sea floor

• Bonus fact: Sea stars can regrow

legs that are lost through injuries.


Kelp

• Prim

ary producer

• Makes its ow


• Lives a@

ached to the sea floor in coastal areas

• Bonus fact: Kelp can grow

up to 2 feet each day.


Sea Urchin

• Prim

ary Consumer

• Eats kelp


• Bonus fact: The eggs of sea urchins can be m

ade into a type of sushi called uni. Marine Species Card 17 of 35

Sea OGer


er

• Eats sea urchins, m

ussels, and crabs

• Lives near the coast

• Bonus fact: A sea o@

er’s fur is so thick that it has one million hairs on each inch of

its body.


Orca

• Carnivore

• Different groups of orcas eat different things. Som

e eat fish, w

hile other eat marine m

ammals.

• This par>cular orca belongs to a group that eats sea o?

ers.

• Bonus fact: Each group of orcas has a disDnct dialect, or language, that they use to com

municate.


Sea Cucumber

• Scavenger

• Eats decaying m

a?er on the sea

floor. Much of this decaying

ma?

er used to be plankton, such as diatom

s or blue-‐green algae.

• Bonus fact: W

hen threatened by a predator, sea cucum

bers eject their internal organs. This is a decoy that distracts the predator and gives the sea cucum

ber a chance to escape.


Garibaldi

• Carnivore

• Eats m

ussels and crabs

• Lives in kelp forests

• Bonus fact: Garibaldi is the offi

cial state fish of California.


California sheephead

• Carnivore

• Eats urchins, m

ussels, crabs, shrim

p, and sea stars


• Bonus fact: All sheephead start off life as fem

ales, but then change into m

ales as they grow.


Kelp Crab

• Prim

ary Consumer

• Eats kelp


• Bonus fact: As crabs grow

, they get too big for their shells, or carapace. A new

carapace grow

s underneath the old one, w

hich is shed by the crab. This process is called “m

olDng.”

Molt shed by a kelp crab


Leopard Shark

• Carnivore

• Eats crabs, shrim

p, and fish, such as anchovy, rockfish, garibaldi and young California halibut

• Lives on the sea floor in coastal areas

• Bonus fact: U

nlike other fish, sharks do not have bones in their body. Instead, carDlage is used to support their body.


California halibut

• Carnivore

• Eats squid and fish, such as garibaldi, rockfish, and anchovy

• Lives on the sea floor in coastal areas

• Bonus fact: As halibut grow

into adults, one of their eyes m

oves across its head, so that both eyes are on the sam

e side of its head.

California halibut can camouflage w

ell with

sand on the sea floor.


Rockfish

• Carnivore

• Eats shrim

p, crabs, squid, and fish (anchovy, sardine, and lanternfish)

• Lives in shallow

and deep water near the sea floor

• Bonus fact: Som

e rockfishes can live to be 200 years old.


Moon Jellyfish


er

• Eats copepods, ciliates, and diatom

s


ater habitats

• Bonus fact: Jellyfish are very hardy organism

s that can live alm

ost anywhere in the

ocean. They occur in tropical areas and cold regions. They live in very salty w

ater and in ocean waters w

ith li@le salt.


Krill

• Prim

ary Consumer

• Eats diatom

s


ater habitats

• Bonus fact: You can tell krill apart from

shrimp because

krill have their gills on the outside of their body. Gills are a feathery organ that help krill breathe.

A swarm

of krill

Feathery Gills


Market Squid


er

• Eats copepods and krill


ater habitats

• Bonus fact: The largest fishery in California catches market squid.


Shrimp

• Scavenger

• Eats decaying m

a?er on

the sea floor. Much of this

decaying ma?

er used to be plankton, such as diatom

s or blue-‐green algae.


• Bonus fact: W

hile shrimp

are delicious, many of the

ways of catching them

can destroy m

arine habitats.


White Shark

• Carnivore

• Eats dolphins, anchovy, sardine, lanternfish, and squid

• Seals and sea lions are other item

s in the diet of these sharks.

• Bonus fact: You are m

ore likely to be struck by lightning than to be killed by a shark.


Fishermen U

sing a Purse Seine N

et

• Carnivore

• A purse seine net is used to entrap large schools of fish by circling them

with the

net.

• Catches squid, sardine, anchovy, and tuna


Fishermen U

sing Long Lines

• Carnivore

• Long lines can have thousands of hooks for catching fishes

• Catches yellow

fin tuna, dolphins, and w

hite sharks

• Som

eDmes species that the

fishermen do not w

ant to catch get hooked on long lines. These include dolphins and sharks.


Urchin Diver

• Carnivore

• Catches sea urchins

• Bonus fact: M

any of the sea urchins are shipped over to Japan w

here they are made

into sushi.


Fishermen w

ith a Traw

l Net

• Carnivore

• Traw

l nets are dragged along the ocean bo@

om to

catch fish. • 

Catches rockfish and California halibut

• Traw

l nets can also uproot other anim

als that live on the sea floor.


Pictures for Learning Vocabulary Related to the Roles of O

rganisms in Food

Webs

Vocabulary Picture 1 of 12








Mold





Differences between Food

Chains and Food Webs

Food Chain (Open-‐W

ater Habitats)

Phytoplankton (single-‐celled algae that photosynthesizes)

Zooplankton

Fish

Primary producer

Primary consum

er

Secondary consum

er

Energy & nutrients

Energy & nutrients

Food Chain vs. Food Web 1 of 3

Food Chain (Sea Floor Habitat)


Kelp

Sea urchins

Sea oEer

Energy & nutrients

Energy & nutrients

Primary producer

Primary consum

er

Secondary consumer

Food Web for

the Northern

California

Current

Field et al. (2006)


Documents

Lesson 2: Build Your Own Ocean Food Web! - CCE LTERcce.lternet.edu/sites/default/files/Food Web Lesson Plan...1 Lesson 2: Build Your Own Ocean Food Web! Focus Question What are the