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 early relation of the elephant, was. With its long tusks it must have been a frightening sight. The woolly rhino was almost as big. It looked a 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 group called megafauna (which means “big animals”). But despite looking scary, these animals only used their horns to defend themselves and, 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 animals lived 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 have found the remains of another plant deep in the permanently frozen soil. With modern DNA testing, they worked out that the most common thing growing in the area was not grass, but leafy protein-rich plants called forbs. These would make much better food for a 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 Hemisphere during 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 the death 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. But where does energy come from?

Plants get their energy from sunlight. Via a special process called photosynthesis, plants are able to turn the energy they receive from the Sun into glucose, a form of sugar, which they can then use to grow. Because plants produce their own food they are called 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 its energy. 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 is called 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 fungi and bacteria. Detritus is an important member of many food chains as you are about to see.

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Video credit: Ted Ed / YouTube. Question 3 Question 4

Recall: Over 30% of plant matter across the globe is eaten while Recall: Most organisms in an ecosystem are directly or indirectly it's still alive. nourished by dead matter, or detritus.

True True

False 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 the flow of energy between the organisms below to create a food web. Use green arrows to show green food chains, brown arrows to show 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 on to 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 will be passed on to the secondary consumer?

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

Video credit: Ted Ed / YouTube.

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 into Yellowstone National Park? Question 4

Recall: Rewilding is the process of restoring ecosystems to their natural state (for example, restoring farmland into the forests that were 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 was caused by humans would it change how we treat endangered animals today? Many organisations want governments to do more to help endangered animals. To do this they need to raise awareness among the general public and encourage people to contact a government representative to plead their case. The more people that contact the government the more likely the government is to take notice.

Question 1

Create: Write a letter or design a presentation that could be sent to a government representative outlining your concerns about the extinction 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 and why the population in decline) Think about whether or not you can reference the death of the megafauna in your letter or presentation to strengthen your argument. 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 evolutionary mysteries that have stumped the world for decades.

Alan grew up in New Zealand, where as a child he would roam the wilderness with his father, a palaeontologist, and his mother, a botanist. They would hunt for fossils, explore caves, study plants, and talk about the geology of the landscape. It was during a caving expedition that he found bones from the now extinct moa – a large flightless bird similar to the emu. The discovery helped him realise that he could combine his love for caving with scientific research. Today, Alan analyses DNA extracted from ancient bones, teeth, leaves, seeds and faeces aged 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 age mammoths – elephant-like animals with shaggy hair that weighed up to 8,000 kg. Mammoths moved into the Arctic about two million years ago and had to adapt to the cold. Using DNA from mammoth bones, Alan cultivated mammoth haemoglobin, the protein in blood that carries oxygen around the body. Haemoglobin normally gets 'sticky' at cold temperatures and doesn't release oxygen to the body's tissues easily. But Alan found that mammoth haemoglobin had special adaptations that allowed it to function at colder temperatures, which would have been critical for the mammoths' survival.

Alan does a lot of his work from his lab at Adelaide University in Image credit: University of Adelaide / Randy Larcombe. South Australia. However, his search for specimens takes him travelling around the world, particularly to cold places "because that’s where bones are preserved the best". He doesn't unearth all specimens in the field, though - he says "you’d be surprised what you can find in the back room of a museum!". For Alan, the joy of his job as an evolutionary biologist lies in studying "amazing animals and amazing things that have happened and using DNA to get a completely new way of looking at them”. 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 enjoy in 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 Condie Art director: Robyn Adderly Profile author: Edwina Berry ​Lesson authors: Nicola Miller and Daniel Pikler