Exercises: Components of an ecosystem

Classify the following elements of an ecosystem as biotic or abiotic: sunlight, an oak tree, air temperature, an earthworm, a rock, soil moisture, a mushroom, and wind.

Explain in your own words what an ecosystem is and name two biotic and two abiotic components of a pond.

A woodpecker lives in a pine forest, where it excavates its nest in tree trunks and feeds on insect larvae living under the bark. State its habitat and describe its ecological niche.

Define what an abiotic factor is and give three examples found in a marine ecosystem.

From the following elements of a marine ecosystem, state which are biotic and which are abiotic: the water, an alga, the salinity, a dolphin, a rock on the seabed, and the light passing through the water.

Explain the difference between habitat and ecological niche using the example of a squirrel that lives in an oak wood and feeds on acorns.

Grass, horses, vultures, and fungi live in a grassland. Classify each organism as a producer, a consumer, or a decomposer.

Name two abiotic factors that limit plant life in a desert and explain how one of them acts.

Look at the diagram: two species of birds, A and B, live in the same holm oak tree. Bird A feeds on acorns in the canopy, and bird B feeds on insects living on the trunk. Do they share a habitat? Do they share an ecological niche? Justify your answers based on the diagram.

In a desert, plants are spaced far apart from one another. Identify which abiotic factor you think limits their growth and explain how this factor influences other living things in the ecosystem.

An aquarium with fish, aquatic plants, a filter that oxygenates the water, and a lamp is a small artificial ecosystem. Identify its biotic and abiotic components and describe a relationship that occurs between them.

Some crabs live buried in the wet sand of a beach and come out to feed on organic remains when the tide goes out. State their habitat and their ecological niche, and name one abiotic factor that determines their activity.

A temporary pond dries up every summer. Explain how this abiotic factor affects the living things in the pond and cite one adaptation that one of its plants might show.

On the bare rocks of high mountains, only mosses and lichens grow. Identify two harsh abiotic factors of that environment and reason why these organisms are able to live there.

A gardener overwaters a plant pot and the plant's roots rot because the waterlogged potting mix runs out of oxygen. Identify the altered abiotic factors and explain the chain of effects on the plant.

Compare the abiotic factors that limit life on the deep seafloor with those that limit it at the sea surface, citing at least two differences.

After clear-cutting a forest plot, it is recorded that the average soil temperature has increased by 7,5 °C and surface moisture has decreased by 40 % compared to the adjacent intact area. A technical report states that "these abiotic changes will only affect the felled trees, but not the rest of the living organisms in the soil". a) Refute the report's statement by explaining how the temperature change and desiccation directly affect decomposers (bacteria, fungi, and earthworms). b) Predict the cascading consequences that the loss of these decomposers will have on nutrient recycling and the forest's ability to regenerate naturally.

In a natural park, the Iberian lynx and the red fox coexist in the same Mediterranean scrubland environment. The lynx hunts almost exclusively live rabbits by stalking among dense vegetation, whereas the fox consumes small rodents, carrion, fallen fruit, and insects in both dense and open areas. a) Identify, with reasoning, the habitat of both species and compare their ecological niches, indicating which is a specialist and which is a generalist. b) If an epidemic reduces the rabbit population by 90 %, predict what will happen to the population of each species and justify which one is more likely to survive based on the breadth of its ecological niche.

In a school ground, there is a very shady area where plants grow poorly. Propose a simple experiment to find out whether the limiting factor is light or water, stating what you would keep constant and what you would measure.

A study measures water temperature and the number of amphibians in four ponds: pond 1 (16 °C, 42 individuals), pond 2 (19 °C, 28 individuals), pond 3 (23 °C, 12 individuals), and pond 4 (27 °C, 3 individuals). Describe the relationship shown by the data, reason which abiotic factor could explain it, and state how you would test it.

The construction of a dam permanently floods a scrub-covered river valley, creating a 30-metre-deep reservoir. a) Explain how two essential abiotic factors (sunlight penetration and dissolved oxygen availability) will vary from the surface to the bottom of the reservoir, justifying in which zone aquatic photosynthetic producers will be able to establish themselves. b) During the first two years, submerged terrestrial plant biomass rots at the bottom. Predict the impact this biotic process will have on oxygen concentration in the deep layers and the consequences it will bring for the first fish and benthic organisms that colonise the site.

The tomato plant is a warm-climate plant whose optimal temperature range is between 20 °C and 25 °C; below 10 °C its growth halts and at 0 °C it dies from freezing. In an area where winter records average temperatures of 4,5 °C and night frosts, a farmer installs a greenhouse with heating and drip irrigation. a) Using the concepts of "limiting factor" and "tolerance range", justify why outdoor cultivation is unfeasible and how the greenhouse artificially modifies environmental limits. b) Keeping the temperature at 22,0 °C and water constant, in December the plants do not flower and their stems grow weak and pale. Deduce which abiotic factor is acting as a new limiting factor and propose a technical measure to correct it.

Two neighbouring valleys located at the same altitude and with identical aspect receive the same solar radiation and identical rainfall (950 mm annually). However, in the floor of valley A, a lush beech forest thrives, while in valley B, only a sparse pine forest survives. a) Since the climate and aspect are the same, deduce two soil (edaphic) or relief abiotic factors that could explain why beech trees do not colonise valley B. b) Design a procedure to measure one of these factors in both valleys over a month, specifying what instrument you would use, what variables you would keep controlled, and what result would confirm your hypothesis.

In a large city, asphalt and buildings retain heat and the lack of vegetation reduces evapotranspiration, raising the average temperature by 2,5 °C compared to the surrounding countryside (heat island effect). a) A study reveals that trees in urban parks bud and bloom three weeks earlier than those in the countryside, but pollinating insects emerge at their usual time. Predict the impact this mismatch will have on plant reproduction and on urban insectivorous bird populations. b) A municipal project proposes replacing the trees in a town square with artificial turf to "reduce water consumption and keep the square cool". Scientifically refute this idea by explaining what abiotic function living plants perform that synthetic turf is unable to replicate.