Ecosystems：練習問題

A food chain in a woodland consists of:
Oak tree → Caterpillars → Blue tits → Sparrowhawk

The total biomass at the oak tree level is \(15000\text{ kg}\). The efficiency of biomass transfer from the oak tree to the caterpillars is \(12\%\). Calculate the biomass of the caterpillars in kilograms.

Nitrogen-fixing bacteria live in the root nodules of leguminous plants like clover. This relationship is an example of:

A student investigates the rate of decay of biological material. At the start of the experiment, the mass of the organic waste is \(5.0\text{ kg}\). After \(20\) days, the mass has decreased to \(3.2\text{ kg}\).
Calculate the average rate of decay in \(\text{g/day}\).

Microorganisms such as fungi and bacteria play a vital role in ecosystems as decomposers. How do these organisms contribute to the continuous cycling of chemicals?

Which abiotic factor is most likely to cause a decrease in the rate of decomposition in a waterlogged soil environment?

A woodland community consists of bluebells, oak trees, and various insects. Explain the difference between this community and the woodland ecosystem.

A student investigates the rate of decay of compost at different temperatures. Explain, in terms of microbial activity, why the rate of decay increases as temperature rises from \(10^{\circ}C\) to \(40^{\circ}C\).

Explain why the efficiency of biomass transfer between a producer and a primary consumer is typically only around \(10\%\).

A student investigates the rate of decomposition of organic material. They place 500g of fresh compost in a bin and measure the mass remaining over several weeks.
At the start, the mass is 500g. After 4 weeks, the mass is 420g. After 8 weeks, the mass is 360g.

(a) Calculate the percentage of mass lost between week 0 and week 8.
(b) Calculate the average rate of decay in grams per week (\(g/week\)) over the 8-week period.
(c) Explain how temperature and oxygen availability affect the rate of decomposition by microorganisms.

Biotic and abiotic factors affect the distribution of organisms.

(a) List two abiotic factors and two biotic factors that could affect a population of plants in a woodland.
(b) A scientist observes that bluebells grow earlier in the spring than many trees grow their leaves. Explain this observation in terms of competition for light.
(c) Explain how the introduction of a new predator might affect the entire community, not just its direct prey.