Exercises: The kingdoms of living things

Name the six kingdoms of living things and give an example of an organism for each of them.

Classify these organisms into their kingdom: a holm oak, an amoeba, a mushroom, an eagle, and yoghurt bacteria. Justify each choice using a characteristic of the corresponding kingdom.

The diagram shows the classification tree of living things according to the five-kingdom model, but one kingdom is missing, marked with "?". Identify which kingdom it is and explain the characteristics (cell type, number of cells, and mode of nutrition) that define it.

Which kingdom groups bacteria together? State which type of cell they have and give two examples of bacteria present in your daily life.

Classify these organisms into their kingdom, justifying each case with one characteristic: a microscopic alga, bread mould, a louse, an oak tree, and a lactobacillus from yoghurt.

Which kingdom brings together multicellular living things that make their own food thanks to light? Name the cell organelle that makes this possible and give two examples of organisms from that kingdom.

Summarise four characteristics of the Animal kingdom: cell type, number of cells, how they obtain food, and what they usually do to get it.

The Fungi kingdom is closer to your life than you think. Name three fungi (or products made thanks to fungi) from your daily life and explain the role of each one.

Create a table showing the five kingdoms of the traditional classification (Whittaker-Margulis), specifying for each: cell type (prokaryotic or eukaryotic), whether its organisms are unicellular or multicellular, and its type of nutrition.

For centuries, mushrooms were considered plants. Explain at least two reasons why fungi are today classified in their own kingdom, separate from the plant kingdom.

A microscopic organism is unicellular, has eukaryotic cells, and moves actively in search of food. Which kingdom does it belong to? Explain why it cannot be either an animal or a bacterium.

The yeast that makes bread rise is a unicellular fungus. Explain why it is not a bacterium, even though both are microscopic and single-celled, looking at the cell type of each one.

Algae carry out photosynthesis like plants, but in the five-kingdom model they are classified in the kingdom Protista. Explain how their organisation differs from that of plants (they do not form true tissues or organs such as roots, stems, and leaves: they have a thallus) and reason why the criterion "carries out photosynthesis" is not enough to classify a living thing.

The amoeba and the paramecium move around and capture their food, as an animal would. Reason why they do not belong to the Animal kingdom and place them in the correct kingdom.

Cyanobacteria, formerly called "blue-green algae", carry out photosynthesis. Explain why they stopped being considered algae and are classified in the kingdom Monera, stating which characteristic carries more weight than the way of feeding when classifying them.

Order these organisms from the simplest to the most complex and explain the criterion you have used: a fungus, a bacterium, an oak tree, an amoeba, and a seagull.

A single-celled organism with a nucleus is discovered in a pond. It has chlorophyll when light is available, but in the dark, it engulfs food particles. Discuss which kingdom you would classify it into and what problem cases like this pose for kingdom classification.

A student observes a lichen on a bare limestone rock and states: “It is a simple plant, because it is green and performs photosynthesis.” Refute their statement by explaining the true biological composition of a lichen and which kingdoms its components belong to. Then, predict what would happen to each of these two organisms if you separated them and left them isolated on that same sunny rock with no soil, justifying your answer based on the type of nutrition of each one.

Compare two organisms belonging to the kingdom Protoctista: the Paramecium (unicellular, heterotrophic, and with cilia to move) and the giant Kelp (multicellular, over 20 meters long, and photosynthetic autotroph).

1. a) Justify why including both in the same kingdom creates contradictions when compared with the criteria that define Plants and Animals.
2. b) Explain why, despite their similarities to them, the paramecium is not classified as an animal nor kelp as a true plant.

Mini-investigation: place two slices of bread in closed bags, one slightly moistened and one dry, and observe them for a week without opening them. Write the hypothesis, predict in which one mould will appear first, explain which kingdom mould belongs to, and reason why the bags must not be opened during the practical.

A space probe takes a dust sample on Mars containing microscopic particles made up only of a protein coat and an RNA molecule inside. In the laboratory, they show neither energy expenditure nor growth, but when placed in contact with a culture of living bacteria, they enter them and multiply rapidly, destroying the host cells. A newspaper headline announces: “First alien bacteria discovered!”. Refute this headline by explaining why this agent cannot be a bacterium nor be classified into any of the five kingdoms of living things.

A farmer decides to completely sterilize the soil of his fields with a powerful bactericide to “kill all bacteria and prevent his crops from getting sick.” Predict two serious problems his crops will suffer in the medium term as a result of this action, and justify your answer by explaining the vital functions that soil bacteria perform in relation to plants and the matter cycle.

An experimental forest plot is periodically sprayed with a product that eliminates all decomposing fungi without harming other living beings. After one year, it is observed that fallen logs and leaf litter accumulate intact, but the forest trees begin to wither from malnutrition. Justify the relationship between the accumulation of dead wood and the malnutrition of living trees, and predict what would happen to life on the planet if all decomposers disappeared.

On an expedition, three new organisms are discovered and the following data are collected in the laboratory:

• Organism 1: Unicellular, without a nuclear membrane, capable of producing its own organic matter from sulfur and volcanic gases.

• Organism 2: Multicellular, with eukaryotic cells surrounded by a cell wall, a heterotroph that absorbs decomposing organic matter after carrying out external digestion.

• Organism 3: Multicellular, formed by photosynthetic eukaryotic cells with chloroplasts, but without differentiated tissues or organs (thallus-type organization).

Apply the criteria for classifying kingdoms (cell type, level of organization, and type of nutrition) to assign each organism to its corresponding kingdom with reasoned arguments, indicating in each case why it does not fit into the kingdoms with which it shares any characteristic.