Flashcards · 0680 · Topic 5

Ecosystems, biodiversity and fieldwork flashcards

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

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What is an ecosystem?: A community of living organisms interacting with each other and with the non-living (abiotic) environment in a particular area.
Producer vs consumer vs decomposer: Producer: makes its own food by photosynthesis, usually a green plant. Consumer: gets energy by eating other organisms. Decomposer: bacteria and fungi that break down dead material and return nutrients to the soil.
Why do food chains rarely have more than four or five trophic levels?: Only about 10% of energy is passed to the next level; the rest is lost as heat from respiration, in movement, in waste and in uneaten parts, so little is left for higher levels.
How does energy flow differ from nutrient cycling?: Energy flows one way through an ecosystem and is lost as heat. Nutrients are recycled: decomposers return them to the soil and plants absorb them again.

What are the layers of a tropical rainforest?: Emergent trees, canopy, understorey and forest floor.
Why does a rainforest recover poorly after clearance?: Most nutrients are held in the living vegetation and leaf litter, not the thin soil, so clearing the trees removes the nutrients and the exposed soil erodes.
What are the causes of deforestation?: Clearance for farming, cattle ranching and plantations such as palm oil; commercial logging; mining, roads and settlement; and fuelwood collection.
What are the impacts of deforestation?: Habitat and biodiversity loss, soil erosion and more flooding, less carbon dioxide absorbed and more released if trees are burned, and loss of livelihoods for forest communities.
How can forests be managed sustainably?: Selective logging with replanting, protected reserves, agroforestry, timber certification, ecotourism, and alternatives that give local people an income.

What is biodiversity, and why does it matter?: The variety of living things in an area, including the number of species and genetic variety within them. It makes ecosystems more resilient and provides food, medicines and materials.
What are the main threats to biodiversity?: Habitat loss, overharvesting and hunting, invasive species, pollution and climate change.
Captive breeding vs seed banks: Captive breeding: breeding rare species in zoos for release; saves very rare species but is expensive and needs the habitat to survive. Seed banks: store seeds in cold storage; preserve genetic variety cheaply but do not protect wild habitats.
What are the strengths and limitations of protected areas?: Strength: they protect whole habitats and all the species in them. Limitation: they need funding and enforcement, and can exclude local people who depend on the land.
What is CITES?: The Convention on International Trade in Endangered Species, an international agreement that controls trade in endangered species. It reduces illegal trade but is hard to police.

Quadrat vs transect: Quadrat: a square frame placed on the ground to count organisms in a known area. Transect: a line along which samples are taken at regular intervals, used where conditions change gradually.
Random vs systematic sampling: Random sampling (for example using random number tables) avoids bias in where samples are placed. Systematic sampling at fixed intervals suits a gradient, such as along a transect.
How do you measure abiotic factors in fieldwork?: With a light meter for light intensity, a moisture meter for soil moisture, a thermometer for temperature, and pH paper or a probe for soil or water pH. Repeat readings and calculate means.
How can a fieldwork investigation be made more reliable?: Take more samples, place quadrats randomly, repeat the study at different times or seasons, and use calibrated equipment.
Five quadrats contain 3, 4, 2, 5 and 1 plants. What is the mean per quadrat?: Total = 3 + 4 + 2 + 5 + 1 = 15. Mean = 15 ÷ 5 = 3 plants per quadrat.