Local ecosystems

Classify these ecosystems as terrestrial or aquatic: a lagoon, a beech forest, a salt marsh, a grassland, a reef, and a shrubland.

State whether these ecosystems are freshwater or marine: the Mississippi River, the Gulf of Mexico, a mountain lake, a pond, and the Atlantic Ocean.

Point out two differences between a freshwater ecosystem and a marine ecosystem and explain why most fish cannot move from one environment to the other.

Name two terrestrial ecosystems characteristic of the Iberian Peninsula and one specific to the Canary or Balearic Islands, mentioning a typical species from each.

Name two characteristic species of the Mediterranean forest and two of the Atlantic forest of the Iberian Peninsula.

In the Canary Islands, there are species, such as the El Hierro giant lizard, that live nowhere else in the world (endemic species). Explain the role island isolation plays in the occurrence of endemic species.

Beside a river that crosses an area of live oak woodland, poplars, aspens, and willows grow, forming riverside woodland. Explain which abiotic factor makes this woodland, so different from the one surrounding it, possible.

In the mountains, above a certain altitude, trees disappear (the tree line). Name two abiotic factors that prevent their growth on the summits and explain how one of them acts.

Few species live on coastal dunes, but they are highly adapted. Name two harsh conditions of this environment (shifting sand, salinity, wind, scarcity of fresh water) and explain one adaptation of dune plants.

A saltwater aquarium and a freshwater aquarium need very different care. Relate these differences to the conditions of the natural environment of each type of fish.

An amateur environmental group proposes restocking a river estuary by introducing brown trout specimens caught in the upper course of that same river, arguing that "since it is the same river basin, the species will acclimate without any issues." Refute the ecological and physiological viability of this proposal by analyzing how three abiotic factors vary (current velocity, temperature and dissolved oxygen concentration, and salinity) between both sections. Justify why the adaptations of these resident trout, moved without prior acclimation, would make their survival in the river mouth very unlikely.

Following the reintroduction of beavers into a mountain river, their dams reduce current velocity from 1.4 m/s to 0.1 m/s, promote silt deposition on the bed, increase summer temperature by 3 °C, and lower dissolved oxygen. As a result, trout and fast-water macroinvertebrates disappear from the stretch, but amphibians, riparian birds, and aquatic plants that did not previously exist in the valley settle in. Interpret these data: justify why the new abiotic conditions exclude the original fish and predict the impact that this animal, as an "ecosystem engineer," has on biodiversity at the landscape scale.

A native fish species inhabits the lower reach of a river, adapted to slow-flowing, turbid, and warm waters (22 °C in summer), where it spawns on muddy bottoms and camouflages itself from predators. A dam is built upstream that traps sediment (clearing the water) and periodically releases hypolimnetic bottom flows at 11 °C. Predict and justify how these abiotic modifications will affect the viability of this fish population regarding reproduction, predation, and the potential invasion of alien species from cold, clear waters.

You want to compare the biodiversity of a plantation pine forest with that of a nearby live oak woodland. Design a simple study: state what you would observe or count, how you would make the measurements comparable, and what result you would expect to get.

Describe the ecosystem closest to your local area: state whether it is terrestrial or aquatic, name three living things that inhabit it, and mention an important abiotic factor in it.

Explain in your own words the difference between a natural ecosystem and one transformed by humans, and give an example of each.

What is an urban ecosystem? Name three living things that live in your local area and one abiotic factor characteristic of that environment.

A dehesa is a holm oak or cork oak woodland cleared by humans to be used as pasture and farmland. Explain why it is considered a human-modified ecosystem while also being an example of sustainable land use with high biodiversity.

The plant biodiversity of three 500 m² plots in a Mediterranean ecosystem is analyzed: a mature holm oak forest (24 species), a reforested pine forest (9 species), and a commercial eucalyptus plantation (5 species). After a period of extreme drought and a defoliating insect outbreak, the eucalyptus plantation lost 65% of its leaf mass, whereas the holm oak forest was barely affected (less than 8% damage). Interpret these results by relating species diversity, vertical vegetation stratification (herbs, shrubs, trees), and ecological niches to the resilience and self-regulation capacity of each ecosystem.

Topic Challenge. Become an ecological consultant for your city and assess the health of a nearby urban ecosystem (a park, a garden, or a vacant lot). Follow these steps:

1. Biotope and climate: Go to the National Weather Service website and record the average temperature (for example, $T = 16.4\text{ }^\circ\text{C}$) and the precipitation for the last month in your town. Also, write down two abiotic factors observed on-site (soil type, hours of sunshine, or humidity).

2. Biocenosis and interactions: Identify at least $5$ living things present (classifying them into producers, consumers, and decomposers). Describe two observable ecological relationships between them (such as plant-insect mutualism or competition for space).

3. Food web and proposal: Design a diagram showing the observed trophic relationships and draft two realistic measures to promote biodiversity and mitigate human impact in that area.

As a final product, prepare a brief one-page report with your data, the food web, and your proposal.

Evaluation criteria:

• Accuracy in collecting and interpreting climatic data from the National Weather Service and biotope factors.

• Conceptual correctness in trophic classification and relationships between living things.

• Ecological coherence and feasibility of the proposed improvement measures.