Embedded Files
How do change in species' functions and interactions influence the balance in an ecosystem?
Outcomes:
Make inferences and draw conclusions
Make connections between feeding relationships
Organise information
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
APPROACHES TO EATING
We have learnt about the roles and functions different species have within an ecosystem. We know that ecosystems are made up of different 'eaters' which, through their feeding habits, help to keep the populations of the organisms they eat under control. These interactions are natural and uncontrollable; the organisms are programmed by their DNA to interact with other organisms in a certain way. These organisms do not choose what to eat in the way that we do. (Elk don't think, 'Hmmm. What do I want for breakfast today? Hey! I think some aspen sapling leaves would be a great treat.') Instead, it is a natural instinct within the animal, coupled with its physical characteristics, that drive what and how they eat.
These pictures show some examples of interactions in ecosystems that are driven by the natural instinct and need for food. Make some notes on the interactions you notice between the names organisms. You will use your notes to construct a table to summarise different types of interactions between species.
In Figure 9.1a, the elk is eating the aspen tree saplings; in other words, the aspen saplings are the food source for elk. (look back at the previous section to see where the elk and the aspen are in the food web.) Elk are herbivore, so this interaction is called herbivory. Similarly in Figure 9.1b, we can see the grey wolves are hunting the elk; we can infer that the wolves will kill and then eat the elk. (look back at the previous section to see where the grey wolves and elk are in the food web.) Grey wolves are predators, so this interaction is called predation.
Until this point, the interactions we have focused on have all been about food. But is everything about eating? Does everything in an ecosystem come down to kill or be killed? Are there any examples of 'I'll scratch your back if you scratch mine' in an ecosystem? Do animals ever help each other out, or is it each one for itself?
In the next activity, you look again at different species in the Yellowstone ecosystem, and read about the different ways in which these species interact. You will use the information to identify trends in the interactions to determine which species benefit from the interactions, and which species are at a disadvantage.
ACTIVITY: Enemies, friends and strangers
AtL
Communication skills: Make inferences and draw conclusions.
For each of the 'snapshots' of species interactions, observe the organisms carefully and read the information. Then, use your observations and the written information to fill in the table of interactions.
Dichanthelium lanuginosum or 'panic grass'
Dichanthelium lanuginosum, or 'panic grass', is a unique plant because it is able to grow in soil temperatures that are much higher than those in which most other plants can grow. In fact, because Yellowstone has geothermal (thermal = hot) soils, the soil temperature where panic grass grows is consistently above 50℃. Panic grass is able to grow in these extreme conditions because of a fungus, Curvularia protuberata, which lives on the grass's roots and helps the grass get access to more water. Curvularia protuberata is a fungus that needs plants as a source of food. In addition, a virus called Curvularia thermal tolerance virus. which is naturally adapted to survive in very hot conditions, lives in and depends on the fungus for a place to live and means to reproduce. In exchange for living and reproducing in the fungus, the virus is able to 'pass on' its ability to survive in extreme heat. As a result, the fungus is able to survive in the extreme heat and the panic grass can tolerate life in the hot soil.
Catbirds
Catbirds are songbirds that make their nests and lay their eggs in trees or shrubs that are covered in many branches or leaves. In Yellowstone, catbirds nest in willow trees, which provide the catbirds with protection and 'camouflage' for their eggs and offspring. Catbirds do not eat the willow trees; they just build their nests there and eat berries from trees and bushes that grow near the willow trees.
Sarcoptes scabiei
In the Yellowstone ecosystem, wolves and coyotes get a skin infection called mange from a mite (small insect) called Sarcoptes scabiei. The mites dig down into the skin cells of the coyotes and wolves, causing them to have itchy, allergic reactions. The coyotes and wolves bite and chew their own skin, causing them to bleed and to be more sensitive to other types of infections. The mites use the coyotes and wolves for a place to live, reproduce, and have access to nutrients; in the process, the mites cause the coyotes and wolves to get sick, weak and sometimes even die.
SYMBIOTIC RELATIONSHIPS
Through the previous activity, we can see that in addition to just eating other organisms for food, living things require different types of interactions with other living things in order to survive. Symbiosis literally means living together, and it is the scientific word to refer to the fact that different species do not live separately or independently from one another, but, instead, have many different types of interactions with other species throughout their lives.
As we have seen from the previous activity, these symbiotic relationships can be harmful or helpful, or somewhere in between. Table 9.1 summarises the different types of symbiotic relationships between living things; use the descriptions and your notes from the activity to complete the 'Example' column.
Complete Table 9.2 by using smiley and sad faces to represent the situation for different species in each of the symbiotic relationships.
In addition to symbiotic and feeding relationships, there are other types of natural interactions between species which we can see in Figure 9.4a and Figure 9.4b below. Look carefully at the pictures. What do you notice about the interactions between the named species? Why do the species interact in these way? What are the results of the interactions? Do any of the species benefit from the interactions? are any of the species harmed from the interactions?
In Figure 9.4a, we see the grey wolves are fighting each other. It is not clear why they are fighting, but in ecosystems where food, water, territory and possible mates are limited, it is necessary for members of the same species to fight for their share. In fact, if the resources are very limited or there are very few possible mates in an ecosystem, the 'losing' individual might die from lack of resources or be killed while fighting for a mate. This type of fighting between individuals in the same species is called intraspecific competition, or competition within one species.
In addition to individuals within the same species fighting for limited resources, we can see in Figure 9.4b that individuals from different species can fight for food, water, and territory, or to protect their young from predators. Here, the brown bear is threatening the grey wolf. This time, we can see why the bear is aggressive towards the wolf, but because the bear and wolf are of different species, we call this type of interaction interspecific competition.
All of the pictures in this section show that some individuals and species can have a powerful influence on the survival of not only other individual organisms, but also on whole species. Use Table 9.5 to help organise and summarise the different types of species interactions you have learnt about.
Citations:
Davis, Andrew, and Patricia Deo. “Biology: MYP by Concept 4 & 5.” Biology: MYP by Concept 4 & 5, Hodder Education, an Hachette UK Company, 2016, pp. 236–240.
Reaching to Eat. 1.bp.blogspot.com/-9Pf5SCsIzR8/UIQmiV4azWI/AAAAAAAAGak/jL4IYSRXS3Y/s1600/Reaching_to_eat.jpg.
In Numbers? for Wolves, Maybe Not. 3c1703fe8d.site.internapcdn.net/newman/gfx/news/hires/2011/danstahlernationalparkservice.jpg.
Heat but No Panic. questiongene.com/heat-but-no-panic/.
Gray Catbird. wildlife.ohiodnr.gov/species-and-habitats/species-guide-index/birds/gray-catbird.
Yellowstone Crowdsources Visitor Photos to Help Study Wolf Disease, Dynamics. www.yellowstonegate.com/2013/02/yellowstone-crowdsources-visitor-photos-help-study-wolf-disease-dynamics/.
“Wolves Fighting over Food.” Tambako The Jaguar, c1.staticflickr.com/8/7420/13930579102_be574c73d0_b.jpg.
Bear vs Wolf. animals.desktopnexus.com/wallpaper/1629547/.
Page updated
Report abuse