Exercises: Major groups of living things

Name the five groups of vertebrates and give an example of an animal for each. Also state the characteristic shared by all vertebrates, which gives the group its name.

State which group each of these living things belongs to and justify each answer with a feature of the corresponding group: a frog, a sardine, a cat, a spider, a fern, and a geranium.

The diagram shows the five groups of vertebrates with a typical trait for each, but one group is missing, marked with "?". State which group it is, describe its defining characteristics, and give two examples of animals from that group.

From this list of animals —dog, ant, spider, earthworm, snail, jellyfish, and trout— first separate the vertebrates from the invertebrates. Then, group the invertebrates into insects, arachnids, worms, molluscs, and jellyfish, stating a feature that helped you decide in each case.

Explain the difference between mosses, ferns, and flowering plants, and give an example of each group that you could find near where you live. What type of habitat does each typically grow in?

Create a table with three columns —group, main feature, and example— and fill it in for these six groups of living things: fish, amphibians, reptiles, birds, mammals, and insects.

An explorer finds an unknown marine animal: it has a streamlined body, lacks hind limbs, moves by means of flippers, and spends its entire life underwater. However, he observes that it periodically surfaces to take in air and that it gives birth to live young which it feeds with milk. The explorer notes in his journal: "Because of its shape and because it always lives in water, it is a new species of fish." Refute his conclusion by justifying why it should be classified as a mammal, and predict what type of reproduction, fertilisation, and thermal regulation (homeothermic or poikilothermic) you would expect to find in this animal.

In a school laboratory, three unknown organisms are analysed and their cellular and nutritional characteristics are recorded:

• Organism A: unicellular, eukaryotic, with chloroplasts and autotrophic nutrition.

• Organism B: multicellular, heterotrophic by absorption, with a cell wall and lacking true tissues.

• Organism C: multicellular, heterotrophic that ingests food, lives attached to a marine rock, and lacks differentiated tissues.

Determine with reasoning which kingdom each organism belongs to based on its cellular and nutritional data. In addition, explain why organism C belongs to the animal kingdom despite living immobile like a plant.

Look at these three animals: the bat, the sparrow, and the dolphin. If we used a classification criterion based exclusively on the medium through which they move, which two animals would you group together? Explain why this criterion is misleading for biologists and justify, by comparing the internal anatomy of their limbs and their mode of reproduction, why the bat is much more closely related to the dolphin than to the sparrow.