Biology

Food Chains: Death of the Arctic megafauna

This lesson will investigate how species in an ecosystem are linked.

We will look at questions such as:

• What are food chains and food webs?

• What is a brown food chain?

• How much energy is transferred through food chains?

• How are species in a food web linked?

• What can we do to help endangered species?

Hop into a time machine and go back 10,000 years to see what we can learn from the death of the megafauna.

This is a print version of an interactive online lesson. To sign up for the real thing or for curriculum details about the lesson go to www.cosmosforschools.com

Introduction: Food chains (P1)

Imagine an animal three times as tall as you are that weighs as much as five cars. That’s how big a woolly mammoth, an earlyrelation of the elephant, was. With its long tusks it must have been a frightening sight. The woolly rhino was almost as big. It lookeda bit like a modern rhinoceros but its horn was even longer.

Both animals lived in the icy Arctic region during the Pleistocene epoch, more than 10,000 years ago. They belonged to a groupcalled megafauna (which means “big animals”). But despite looking scary, these animals only used their horns to defend themselvesand, like modern rhinos and elephants, were vegetarians.

Scientists have found lots of fossilised grass pollen in soil from that time and, until now, thought this was what the huge animalslived on. But it looks as if the scientists may have missed a key piece of the puzzle.

Grass produces more pollen than other types of plants and so it looked like that was all that was there. But now scientists havefound the remains of another plant deep in the permanently frozen soil. With modern DNA testing, they worked out that the mostcommon thing growing in the area was not grass, but leafy protein-rich plants called forbs. These would make much better food fora big beast than grass.

And there is other evidence that these forbs might have been the animals' main diet. The forbs died out about 10,000 years ago –about the same time as many megafauna.

Read the full Cosmos Magazine article here

Woolly mammoths and woolly rhinos are just a couple of the now extinct species that roamed the Northern Hemisphereduring the Pleistocene epoch. Image credit: Mauricio Antón / Wikipedia.

Question 1

Propose: It is likely that a number of causes contributed to the extinction of the megafauna. What causes can you suggest for thedeath of the Arctic megafauna?

Hint: The above introduction suggests one possible cause.

Gather: Food chains (P1)

All living things need energy to survive. It helps grass grow, enables lions to roar and is even helping you read this right now. Butwhere does energy come from?

Plants get their energy from sunlight. Via a special process called photosynthesis, plants are able to turn the energy they receivefrom the Sun into glucose, a form of sugar, which they can then use to grow. Because plants produce their own food they arecalled producers.

Animals get their energy from the food they eat and are called consumers. An antelope is a consumer because it eats grass to get itsenergy. Similarly, a lion is a consumer because it eats antelope to get its energy.

Question 1

Identify: Label each of the organisms in the sketchpad below as either a producer or a consumer.

A food chain shows the flow of energy from organism to organism in an ecosystem. A simple example of a food chain is:

grass → antelope → lion

As in the above example, food chains typically start with a producer, in this case grass. The consumer that eats the producer iscalled a primary consumer (in this case the antelope), and the consumer that eats the primary consumer is called a secondary

consumer (in this case the lion).

Question 2

Identify: Label the Pleistocene food chain below with the terms producer, primary consumer and secondary consumer.

When plants and animals die they return to the earth and become detritus, which is eventually consumed by decomposers like fungiand bacteria. Detritus is an important member of many food chains as you are about to see.

Video credit: Ted Ed / YouTube.

Loading

Question 3

Recall: Over 30% of plant matter across the globe is eaten whileit's still alive.

True

False

Question 4

Recall: Most organisms in an ecosystem are directly or indirectlynourished by dead matter, or detritus.

True

False

Question 5

Recall: What is the difference between a green food chain and a brown food chain?

Question 6

Draw: The above video showed how multiple food chains can be joined together make a food web. Use the arrow tool to show theflow of energy between the organisms below to create a food web. Use green arrows to show green food chains, brown arrows toshow brown food chains and red arrows to show the flow of energy to generate the detritus.

Process: Food chains (P1)

Image credit: Getty Images.

The arrows in a food chain show how energy is transferred in an ecosystem. Only about 10% of an organism's energy is passed onto the organism that consumes it. The rest is used up in growth, reproduction, repair, and movement, to name a few.

Question 1

Calculate: Energy is measured in joules. If the primary producer in a food chain has 13,500 joules of energy how much energy willbe passed on to the secondary consumer?

Hint: first work out how much would be passed on to the primary consumer.

Video credit: Ted Ed / YouTube.

Loading

Question 2

Describe: What impact did reintroducing wolves into Yellowstone National Park have on its ecosystem?

Left: Wolf in the Yellowstone National Park. Right: Yellowstone National Park on a world map. Image credit: Wikipedia.

Question 3

Reflect: What can we learn about the relationship between species in a food web from the reintroduction of wolves intoYellowstone National Park?

Question 4

Recall: Rewilding is the process of restoring ecosystems to their natural state (for example, restoring farmland into the forests thatwere originally cut down to create the farmland). Why can't rewilding bring back the megafauna?

Apply: Food chains (P2)

Saving endangered animals

The Tasmanian devil, bilby and corroboree frog are all endangered Australian species. Image credits: iStock, Gallo Images/ Getty Images & National Geographic / Getty Images.

Is it worthwhile discovering the causes behind the extinction of the megafauna? If scientists can prove that their extinction wascaused by humans would it change how we treat endangered animals today? Many organisations want governments to do more tohelp endangered animals. To do this they need to raise awareness among the general public and encourage people to contact agovernment representative to plead their case. The more people that contact the government the more likely the government is totake notice.

Question 1

Create: Write a letter or design a presentation that could be sent to a government representative outlining your concerns about theextinction of a local endangered animal. The following checklist will guide you in writing your letter or presentation:

Choose an local endangered animal. (The EPBC Act List of Threatened Fauna website may help you)

Choose an appropriate government representative.

Find out the postal address of your chosen government representative.

Research information about your endangered species (such as how many individuals of this species are currently alive andwhy the population in decline)

Think about whether or not you can reference the death of the megafauna in your letter or presentation to strengthen yourargument.

Think about what you want the government to do and be explicit about this in your letter or presentation.

Use a formal style of writing and do your best to convince your government to take action!

Career: Food chains (P2)

Professor Alan Cooper is an evolutionary biologist who loves to play detective. He uses ancient DNA to solve evolutionarymysteries that have stumped the world for decades.

Alan grew up in New Zealand, where as a child he would roamthe wilderness with his father, a palaeontologist, and hismother, a botanist. They would hunt for fossils, explore caves,study plants, and talk about the geology of the landscape. It wasduring a caving expedition that he found bones from the nowextinct moa – a large flightless bird similar to the emu. Thediscovery helped him realise that he could combine his love forcaving with scientific research. Today, Alan analyses DNAextracted from ancient bones, teeth, leaves, seeds and faecesaged anywhere from 100 to 300,000 years old. Using this DNA,he reveals long-lost details about extinct animals and humans.

In one of his studies, Alan looked back into the lives of ice agemammoths – elephant-like animals with shaggy hair thatweighed up to 8,000 kg. Mammoths moved into the Arctic abouttwo million years ago and had to adapt to the cold. Using DNAfrom mammoth bones, Alan cultivated mammoth haemoglobin,the protein in blood that carries oxygen around the body.Haemoglobin normally gets 'sticky' at cold temperatures anddoesn't release oxygen to the body's tissues easily. But Alanfound that mammoth haemoglobin had special adaptations thatallowed it to function at colder temperatures, which would havebeen critical for the mammoths' survival.

Alan does a lot of his work from his lab at Adelaide University inSouth Australia. However, his search for specimens takes himtravelling around the world, particularly to cold places "becausethat’s where bones are preserved the best". He doesn't unearthall specimens in the field, though - he says "you’d be surprisedwhat you can find in the back room of a museum!". For Alan, thejoy of his job as an evolutionary biologist lies in studying"amazing animals and amazing things that have happened andusing DNA to get a completely new way of looking at them”.

Image credit: University of Adelaide / Randy Larcombe.

Question 1

Research: Alan's passion for caving as a boy helped lead him into a career as an evolutionary biologist. What activities do you enjoyin your spare time? What career in science do you think best matches your passion with work?

Hint: If you are unable to think of many different careers in science, the career lists on the science buddies website may help you.

Cosmos Lessons team

Education Editor: Bill CondieArt director: Robyn AdderlyProfile author: Edwina BerryLesson authors: Nicola Miller and Daniel Pikler