IB Environmental systems and societies 2.2 Energy and Biomass in Ecosystems Questionbank

Table 1 displays various ecological characteristics measured at three different stages (A, B, and C) of a primary succession on a newly formed volcanic island.

Table 1: Ecological characteristics of three stages in a primary succession

(a) Identify which stage in Table 1 represents a pioneer community.

(b) State one human activity that could arrest an ecological succession, preventing it from reaching Stage C.

Explain how energy flows through an ecosystem, from sunlight to top predators.

Explain how climate change can affect ecosystem structure and function.

(c) Outline two reasons why species diversity typically increases as a site progresses from Stage A to Stage B.

(d) Explain how the relationship between Gross Primary Productivity ($GPP$) and total community Respiration ($R$) changes as an ecosystem reaches the climax stage (Stage C).

Figure 1: Fact file on North American beavers

• Typically, one family per square kilometer of river habitat.
• Live in family groups consisting of two adults and up to three kits, born annually between April and June.
• Experience high mortality rates due to harsh weather, limited suitable habitats, and predation.
• North American beaver population:
• Estimated at 250 million before the fur trade.
• Currently around 9 million.
• Primarily feed on tree bark.
• Build lodges using wood and mud, which serve as:
• Safe spaces for eating, sleeping, and raising young.
• Winter shelters where they remain during the colder months.
• Defended structures to keep other beavers out.
• Beavers are being reintroduced in Europe to aid in wetland restoration.

Source: adapted from www.sbaa.ca, www.ecology.info, www.tobyhemenway.com and http://acs7.cortland.edu

Figure 2: Algonquin wolf pack territories and protected areas

Source: https://www.researchgate.net/publication/222046620_Protection_from_harvesting_restores_the_natural_social_structure_of_eastern_wolf_packs

(a) With reference to Figure 1, outline one reason why there are more beaver remains in wolf faeces during summer.

(b) The number of wolves in Algonquin Provincial Park is estimated to be between 250 and 1000. Outline two reasons why it is so difficult to estimate the number of wolves accurately.

(c) With reference to Figure 2, explain the threats to the future existence of a small and sustainable population of wolves as a result of their protection in limited area.