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11. (a) (i) Distinguish between a food chain and a food web - Leaving Cert Biology - Question 11 - 2012
Question 11
11. (a) (i) Distinguish between a food chain and a food web. Include a clear reference to each in your answer. (ii) What do ecologists mean by a pyramid of numbers?... show full transcript
Worked Solution & Example Answer:11. (a) (i) Distinguish between a food chain and a food web - Leaving Cert Biology - Question 11 - 2012
Step 1
(i) Distinguish between a food chain and a food web.
Answer
A food chain represents a linear series of organisms where each is eaten by the next in the chain. For example, in a grassland ecosystem, grass may be eaten by a grasshopper, which in turn is eaten by a frog. A food web, on the other hand, consists of interconnected food chains that show the multiple feeding relationships between organisms. An example of a food web would include various animals that consume the grass, like rabbits or deer, which links multiple food chains into a network.
Step 2
(ii) What do ecologists mean by a pyramid of numbers?
Answer
A pyramid of numbers is a graphical representation that illustrates the number of individual organisms at each trophic level in an ecosystem. It typically shows a broad base of producers, such as plants, decreasing numbers of herbivores at the next level, and even fewer carnivores at the top. This pyramid visually emphasizes the energy transfer and population dynamics within different levels of the food chain.
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(ii) Suggest two reasons why the great majority of attempted introductions have been unsuccessful.
Answer
- The failure often arises from a lack of suitable habitat for the exotic species, which limits their ability to thrive and reproduce.
- Competition with native species can result in the exotic species either being outcompeted and thus failing to establish, or negatively impacting the native organisms, leading to ecological imbalances.
Step 5
(iii) Use your knowledge of the life cycle of flowering plants to suggest how an exotic plant may escape from captivity.
Answer
Exotic plants may escape from captivity through seed dispersal, where seeds are carried by wind, water, or animals to new environments. If these seeds find favorable conditions in a ecosystem, they can germinate and establish a new population.
Step 6
(iv) Use the knowledge that you have gained in your studies of ecology to suggest how the impact of an exotic species may: 1. impact negatively on an existing community.
Answer
An exotic species may introduce new diseases to native populations, causing a decline in their numbers. Additionally, they might compete for resources such as food and space, displacing native species.
Step 7
(iv) Use the knowledge that you have gained in your studies of ecology to suggest how the impact of an exotic species may: 2. impact positively on an existing community.
Answer
An exotic species can enhance biodiversity if it fills an ecological role that is currently vacant. For example, an introduced pollinator can assist in the reproduction of local flora, improving the overall health of the ecosystem.
Step 8
(v) It has been stated that an exotic species has a good chance of becoming established in a new environment if there is a niche vacant. 1. Explain the term 'niche' in this context.
Answer
A niche refers to the role or function of an organism within an ecosystem, including its habitat, resource utilization, and interactions with other species. A vacant niche implies there are available resources or environmental conditions that the exotic species can exploit.
Step 9
(v) It has been stated that an exotic species has a good chance of becoming established in a new environment if there is a niche vacant. 2. Do you agree with the above statement?
Answer
Yes, I agree with the statement as vacant niches can provide opportunities for exotic species to thrive without competition for resources, enabling them to establish new populations.
Step 10
(v) It has been stated that an exotic species has a good chance of becoming established in a new environment if there is a niche vacant. 3. Explain your answer.
Answer
The availability of a vacant niche allows for the introduction of new species without direct competition with native species. This can lead to successful adaptation and establishment, especially if the exotic species is well-suited to the environmental conditions of the new habitat.
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(ii) Name one animal from your named ecosystem and describe how you carried out a quantitative study of that animal.
Answer
I studied the white-tailed deer in the temperate forest. I carried out a quantitative study by observing deer populations during different times of the year, utilizing transect lines to track sightings and assess the distribution and density of the population.
Step 15
(iii) Suggest one way in which marking an animal might endanger it.
Answer
Marking an animal can make it more visible to predators, potentially increasing its risk of being hunted. Additionally, if the marking process involves capture, the stress and handling may negatively impact its health.
Step 16
Ecosystems are subject to changes, both natural and artificial. Mention one of each type of change as it applies to your named ecosystem.
Answer
A natural change in the temperate forest ecosystem could be a wildfire, which can dramatically alter the landscape and species composition. An artificial change could involve deforestation for urban development, leading to habitat loss and fragmentation.