Flashcards · 5014 · Topic 5

Ecosystems, biodiversity and fieldwork flashcards

18 cards on Topic 5, subtopics 5.1 to 5.4. Pick a subtopic or study them all.

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Define an ecosystem: A community of organisms interacting with each other and with the non-living environment in an area.
Food chain vs food web: A food chain shows one feeding pathway. A food web shows how many food chains link together.
What is a trophic level?: A feeding position in a food chain: producers, primary consumers, secondary consumers and so on.
Why can eating plants feed more people per hectare than eating animals?: About 90% of energy is lost at each trophic level, so eating producers directly uses far more of the energy captured by crops.

Describe the climate of a tropical rainforest: High rainfall and steady warm temperatures all year, which support very high biodiversity.
Where are most nutrients stored in a tropical rainforest?: In the living vegetation and leaf litter, not the soil, which is often thin.
Give four causes of deforestation: Clearance for farmland and plantations such as palm oil, commercial logging, mining and road building, and fuelwood collection.
How does deforestation contribute to climate change?: Fewer trees absorb carbon dioxide, and burning cleared trees releases more of it.
What are selective logging and agroforestry?: Selective logging: removing only some trees, with replanting, so the forest survives. Agroforestry: growing crops among trees.

Define biodiversity: The variety of living things in an area, including the number of species and the genetic variety within each species.
Why is high biodiversity valuable?: Ecosystems with more species are usually more resilient, and species provide food, medicines and materials. Many people also value nature for its own sake.
Give one strength and one limitation of captive breeding: Strength: can save very rare species from extinction. Limitation: expensive, and released animals need a surviving habitat.
Why do community schemes help conservation?: When local people share the benefits, such as ecotourism jobs, they support conservation in the long term, though results are slow.

What is a quadrat used for?: Counting organisms or estimating plant cover in a known area of ground, so samples can be compared.
When should a transect be used instead of random quadrats?: When conditions change gradually along a line, such as inland from a shore or away from a footpath.
What are the stages of a fieldwork investigation?: State an aim or hypothesis, plan the method, collect data, present it, analyse it and evaluate it.
Why may one field visit give unreliable results?: Populations and conditions change with season and time of day, so a single visit can miss this variation.
Six quadrats contain 2, 6, 4, 3, 5 and 4 limpets. What is the mean?: Total = 24. Mean = 24 ÷ 6 = 4 limpets per quadrat.