Symbiosis. Biology.

Transcription

1 Biology Symbiosis Cuckoos lay their eggs in the nests of other bird species and so avoid the hard work involved in raising chicks. This is just one of the diverse ways that different species live together. 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

2 Introduction: Symbiosis Cuckoos are unusual among birds for not building their own nests. Instead, a female cuckoo swoops down on another bird's nest, knocks out one of the eggs and lays one of her own to replace it. The host returns to ᎅ nd the same number of eggs and often fails to notice the swap. Scientists have just discovered how cuckoos have been getting away with this for so long. It seems the crafty birds do provide something useful in return for the free childcare. While studying crows breeding habits in Spain, scientists observed lots of cuckoos laying eggs in the nests of crows and magpies. If the magpies noticed the deception, they fought back and threw out the cuckoo eggs. But the crows allowed the eggs to stay, let them hatch and then fed the cuckoo chicks as they grew. Curious, the scientists investigated, taking note of how well the crows with cuckoos did compared to those without. They discovered that when they handled the cuckoo chicks, the little birds released a foul-smelling substance that predators wouldn t eat. So by having the baby cuckoos in their nests the crow parents could leave their own chicks while they went o䂟 in search of food, knowing that the cuckoos would protect them. It s a great example of two species helping each other out. Read the full Cosmos Magazine article here. Left: Cuckoo chicks release a foul-smelling slime that seems to drive some predators away. Right: Sea anemones sometimes hitchhike on the back of hermit crabs. 1

3 Question 1 Identify: Describe at least ᎅ ve interactions with other organisms that you frequently have in your life. These do not necessarily have to be interactions with other humans and they do not have to all be positive interactions. Place a positive [+] sign next to the individuals that are beneᎅ ting from the relationship, a negative [ ] sign next to the individuals that are being harmed by the relationship, and a neutral [0] sign next to the individuals that are una 䂟 ected by the relationship. For example: I [+] like to interact with my dog [+]. He helps me to feel happy and I teach him new things. Hint: To share your answer with your class, ask your teacher to open the discussion board at the bottom of this page and write your answer there as well. 2

4 Gather: Symbiosis Di erent types of symbiosis All organisms are dependent on other organisms in some way. For example, during its lifetime, an animal such as a kangaroo is likely to interact with millions of other organisms including microbes, parasites, mates, predators and food. In contrast with predator prey relationships, where the predator attacks the prey with the intention of killing and eating it, symbiotic relationships occur where diϲerent species interact and live side by side with each other. Symbiosis refers to a long-term ecological interaction between diϲerent species that live close together, where one or more of the species bene ts. Think back to the answers you gave to the question in the Introduction section. You may now recognize that each of the interactions you described can be classi ed as symbiotic. There are, in fact, three diϲerent categories of symbiotic relationships: 1. Parasitism 2. Commensalism 3. Mutualism 3

5 0:00 / 5:16 Credit: Symbiosis: Mutualism, Commensalism, and Parasitism by Untamed Science (YouTube). Question 1 Notes: Use this space to take notes for the video. Note: This is not a question and is optional, but we recommend taking notes they will help you remember the main points of the video and also help if you need to come back to answer a question or review the lesson. Question 2 Recall: A commensalistic relationship is when one species bene ts and the other species is harmed. True False Question 3 Recall: Clown sh are protected from predators by living among anemones. They also chase away animals that might harm the anemones. What sort of symbiotic relationship is this? Parasitism Commensalism Mutualism 4

6 Question 4 Select: When you eat yoghurt, you ingest bacteria that take up residence in your gut. Who bene ts from this relationship? You, because the bacteria help you digest food The bacteria, because your body provides them with a place to live Neither you nor the bacteria Question 5 Explain: Lions hunt gazelles for food. Why is this not an example of a symbiotic relationship? In a symbiotic relationship both species must bene t Symbiotic relationships are always between members of the same species Symbiosis only applies to certain species, such as sh and bacteria Symbiotic relationships require species living together this is a predator prey relationship Question 6 Classify: Oryxes, shown on the right, eat grass and produce lots of dung. Dung beetles eat the dung and the females lay their eggs in it. What type of relationship is this? Parasitism Commensalism Mutualism Not symbiotic Question 7 Identify: Which of the following are examples of symbiotic relationships that might be found in a typical home? Fleas living on a dog Pet gold sh in a shbowl that the owner enjoys watching Fungus living on the skin of gold sh, damaging their health Human parents caring for their children Fungus living on the skin of humans but not causing any harm 5

7 Question 8 Match: With the help of the information in the media clip above, drag and drop the labels and descriptions to identify the type of symbiotic relationship shown in each picture. Question 9 Complete: Select one of the examples in the question above and assign a number to each species to complete the following table. Example selected Species 1 Species 2 Describe what you think would happen to the population of species 1 if species 2 was no longer present Describe what you think would happen to the population of species 2 if species 1 was no longer present 6

8 Below are three sets of graphs showing the populations of two species over time, living separately and together. Within each set, let's call the species represented by the red line species 1 and the species represented by the blue line species 2. Question 10 Describe: Each set of graphs represents one of the three types of symbiosis. Analyze the graphs to identify the type of symbiotic relationship represented by each set and brie y explain your choices. Set Type of symbiotic relationship Explanation A B C 7

9 Process: Symbiosis A closer look at parasitism If your pet has ever had Ȫeas then you've already witnessed parasitism in action. Parasites can bene떠t from the relationship with their hosts in a number of ways: by obtaining nutrients from them, by gaining protection from predators, and by being given free transport. Parasites are adapted to living either inside their hosts or on their outer surfaces. They can only survive by reproducing oȫspring that are capable of 떠nding new hosts. Question 1 Question 2 Recall: The only way that parasites bene떠t from their Apply: Mistletoe is a plant that grows up around a hosts is by obtaining nutrients. tree and derives water and nutrients from it. True False Which two features make this a case of parasitism? The mistletoe bene떠ts by obtaining nutrients from its host The mistletoe is harmed by having its sunlight blocked by the host tree The host tree is neither bene떠ted nor harmed The host tree is harmed by losing nutrients to the mistletoe 8

10 Left: Fleas live symbiotically with cats. What kind of symbiotic relationship is it? Right: Scanning electron micrograph of a cat Ȫea (Ctenocephalides felis). Although a parasite harms its host, by de떠nition, the relationship ideally doesn't lead to the host's death. If that happened, the parasite would have to 떠nd another home. However, some parasites are more destructive than others and can have unusual eȫects on the behaviour of their hosts... 0:00 / 1:23 Credit: Zombie Animals that Exist in Nature Zombie Attack by Howcast (YouTube). Question 3 Notes: Use this space to take notes for the video. Note: This is not a question and is optional. 9

11 Question 4 Explain: The parasites responsible for creating "zombie animals" manipulate their hosts' behaviour so that they can spread to new hosts. Use the information provided in the video to summarize the eȫects on the hosts' behaviour and propose explanations for how this helps the parasites spread. Host organism Image Description of how the parasite changes the behaviour of its host Proposed explanation of how this helps the parasite spread Snail Ant Cricket Many parasites have complex "life histories" with multiple stages involving more than one host species. The following video shows the life cycle of the dog and cat tapeworm which provides an example of how this works. Credit: Dipylidium Caninum The Life Cycle of the Dog & Cat Tapeworm by Michael Sims/Sally Cantle (YouTube). 10

12 Question 5 Notes: Use this space to take notes for the video. Note: This is not a question and is optional. Question 6 Complete: Drag the terms into their correct locations on the following life cycle diagram of the dog and cat tapeworm. Question 7 Suggest: Dog and cat tapeworms are much smaller, and develop much faster, than their hosts. This is also true of the cuckoo chicks described in the Cosmos Magazine article, which are smaller and develop much faster than the crow chicks they share a nest with. Suggest some advantages that small size and quick development might give a parasite. 11

13 Project: Symbiosis Design your own parasite These nasty little parasites, shown in yellow, cause a disease in humans called "sleeping sickness". They enter the bloodstream through the bite of a tsetse 㗎 y, causing the host fevers, headaches and sleeping di culties, among other symptoms. This coloured scanning electron microscope image shows them amongst red blood cells. Credit: Eye of Science / SPL Creative / Getty Images. Imagine that you're a scientist at the World Health Organization (WHO). Your main role is to research parasitic diseases and unusual parasite-host interactions. Sometimes you ꛈ nd yourself thinking about what life might be like as a parasite... 0:00 / 2:23 Credit: Thinking like a parasite The Biology Journey by The Fuse School (YouTube). 12

14 Question 1 Notes: Use this space to take notes for the video. Note: This is not a question and is optional. Parasites have adapted to survive best in their host's speciꛈ c environment. These adaptations might be: structural e.g. a mouth with hooks to attach to a host's intestines, physiological e.g. the ability to digest blood to obtain energy, or behavioural e.g. making a cricket jump into water. Question 2 Create: Your challenge in this activity is to design an original, never before discovered, parasite that has adapted to survive in a speciꛈ c host. The following questions will help guide you through the design process of your parasite and its host. Type your answers to the questions in the project space below. 1. What type of organism will your parasite's host be? 2. What environment will the host live in? 3. What will the body size and shape of your parasite be? 4. What methods of travel will your parasite use to reach the host? 5. What part of the host's body either on the inside or the outside will your parasite infect? 6. What strategies will your parasite use to obtain its food? 7. What damage will your parasite do to the host? 8. What evasive or defensive strategies will your parasite use to avoid being killed by the host? Now create a visual representation of your parasite and its host, with labels that describe how each of its features help it survive. Identify these adaptations as structural, physiological or behavioural. You may wish to design your parasite and host on poster paper, photograph it and upload the image below. Give scientiꛈ c names to your parasite and its host. 13

15 Career: Symbiosis Sly tricksters, singing divas, and musical drummers are just a few of the many interesting characters Naomi Langmore meets through her job. But she doesn't work in Hollywood Naomi is a zoologist from the Australian National University who studies the complex and often amusing world of birds. Naomi spent the rst eight years of her life in Papua New Guinea. Although she left the lush rainforests behind, Naomi s love for animals followed her all the way back to Canberra, Australia, where she moved to attend school. Growing up with lots of di erent pets, Naomi learnt she could make a career out of doing what she loved most studying animal behaviour as a behavioural ecologist. She pursued her dream by studying biology and psychology in high school. But Naomi credits her English classes with polishing her writing ability, a skill crucial for a successful career in science. Throughout her career, Naomi has looked at many curious aspects of bird behaviour. She has studied how cuckoos trick other birds into raising their babies, why female birds sing, and even how cockatoos drum out a beat using tree branches. Being able to answer these fascinating questions in biology is incredibly exciting, she says. For Naomi, it s the best job in the world. Much like the birds she studies, Naomi s lifestyle changes drastically with the seasons. In the spring and summer, she gets to watch her birds out in the eld. The life of a bird is a busy one, and Naomi usually has her hands full keeping up to date with the many social dramas in a ock. When autumn and winter roll around, Naomi returns to university to spend the cold months indoors, teaching and writing. Even when she isn t working, Naomi enjoys the wilderness. She loves going camping, bird-watching and bush-walking with her family and her dog, Panda. 14

16 Question 1 Research: Naomi's career as a behavioural ecologist developed out of a love for animals, which she has had since childhood. Think back to when you were a child...which animals did you love? Were you fascinated by worms, beetles or lizards or perhaps even daddy-long-legs spiders? Using the internet, research a parasite-host relationship that your favourite childhood animal is involved in. Identify whether it is playing the role of parasite or host and describe how it bene ts or is harmed by the relationship. As part of your research, locate a country and institution (e.g university) where research about this parasite-host relationship is taking place. Image Credits Introduction: Daniela Canestrari and National Geographic; Gather: ViviSuArt and Biophoto Associates; Getty Images, Adobe Stock 15

17 Test: Symbiosis Note: There may be more than one correct answer to the multiple-choice questions below. Question 1 (1 mark) In a symbiotic relationship at least one organism always bene២ ts. True False Question 2 (1 mark) Symbiosis always takes place between members of the same species. True False Question 3 (1 mark) Commensalism is when one species bene២ ts from the relationship and the other species: also bene២ ts is harmed neither bene២ ts nor su ers harm Question 4 (1 mark) Which of the following are symbiotic relationships? Parasite and host Predator and prey Parent and o spring Cleaner ២ sh and shark Oxpeckers are birds that live on large animals in Sub- Saharan Africa, such as the bu alo shown on the left. The oxpecker feeds on ticks which in turn feed on the bu alo's blood. The oxpecker bene២ ts by gaining a meal and the bu alo bene២ ts by having the harmful ticks removed. 16

18 Question 5 (1 mark) What type of relationship do the oxpecker and bu alo have? Parasitism Commensalism Mutualism Not symbiotic Question 6 (1 mark) What type of relationship do the tick and bu alo have? Parasitism Commensalism Mutualism Not symbiotic Question 7 (1 mark) The oxpecker eats the ticks. Is this a symbiotic relationship? Yes, because one organism bene២ ts from the other Yes, because any interaction between organisms of di erent species is symbiotic No, because one organism dies straight away so it is a predator prey relationship No, because neither species bene២ ts Question 8 (1 mark) Oxpeckers bene២ t zebras too. As well as feeding on ticks, they often squawk and ២ y o when predators approach, warning the zebras of danger. Sometimes, however, the relationship changes. If a zebra is injured, oxpeckers might drink blood from the wound. This prevents it from healing and leaves it open to infection. How would you classify this new relationship between the zebra and oxpecker? Parasitism Commensalism Mutualism Not symbiotic 17

19 Question 9 (1 mark) Lions kill and eat animals such as zebra and wildebeest and then jackals scavenge on the leftover remains. The jackals bene២ t from the lions without harming or bene២ ting them in return. What type of relationship is this? Parasitism Commensalism Mutualism Not symbiotic Question 10 (1 mark) Clown២ sh make their homes among the stinging tentacles of sea anemones. The clown២ sh gain protection from predators while attracting prey for the anemones to eat. Why is this an example of mutualism? The clown២ sh bene២ t but the anemones are neither bene២ ted nor harmed The anemones bene២ t but the clown២ sh are neither bene២ ted nor harmed The clown២ sh and anemones both bene២ t The anemones are harmed by the clown២ sh The clown២ sh are harmed by the anemones' stinging tentacles Question 11 (1 mark) A commensalistic relationship exists between cattle and certain birds called egrets. When cattle graze, their hooves stir up insects which the egrets then eat. Why is this an example of commensalism? The egrets bene២ t but the cattle are neither bene២ ted nor harmed The cattle bene២ t but the egrets are neither bene២ ted nor harmed The egrets and cattle both bene២ t The cattle are harmed by the egrets The egrets are harmed by the cattle Question 12 (1 mark) Tapeworms obtain all the nutrients they need from the gut of the animal in which they live. Some tapeworms that live in humans can grow to over 10 meters long! What type of animal is a tapeworm? Predator Prey Parasite Scavenger Question 13 (1 mark) What is the term given to the animal in which the tapeworm lives? Human Host Predator Prey 18

20 Question 14 (1 mark) In which of the following ways can parasites bene២ t from their hosts? Nutrients Protection Transport Question 15 (1 mark) Which of the following are examples of parasitic relationships that might be found in a typical home? Fleas living on a cat Pet gold២ sh living in a ២ shbowl Fungus living on the skin of gold២ sh, damaging their health Fungus living on the skin of humans but not causing them any harm Question 16 (1 mark) Learning goal 1: Describe what symbiosis is. Are predator-prey relationships symbiotic? Question 17 (1 mark) Learning goal 2: In all symbiotic relationships, one species bene២ ts. Distinguish between the three types of symbiosis by describing whether the other species bene២ ts or is harmed. Question 18 (1 mark) Learning goal 3: Mistletoe is a parasitic plant that grows up around trees of other species. Tapeworms are parasites that live in the guts of animals such as cats, dogs and humans. Both of these parasites derive nutrients from their hosts. What additional bene២ t(s) do tapeworms obtain compared to mistletoe? Total available marks: 18 19