Identifying species

Define the concept of species and give an example of two different species that look very similar.

Using the fertile offspring criterion, discuss whether these pairs belong to the same species: (a) two dogs of different breeds that have puppies; (b) two sparrows with slightly different plumage that interbreed and have chicks; (c) an Iberian lynx and a domestic cat, which do not interbreed in nature.

The cross between a horse and a donkey produces a mule, which is almost always sterile. Explain what this fact says about whether the horse and the donkey are the same species, even though they can have offspring.

Two frog populations of different colours live in ponds separated by a road and never interbreed in nature. Explain the difficulty in deciding whether they belong to the same species and what test could help resolve the doubt.

In a school debate on biodiversity, someone claims: "A 1.5 kg Chihuahua and a 70.0 kg Great Dane cannot mate naturally due to their enormous anatomical difference; therefore, according to the biological species concept, they should already be officially classified as two distinct species".

1. a) Refute or qualify this statement using the biological species concept: justify why both belong to the same species (Canis lupus familiaris) considering genetic compatibility and gene flow through intermediate-sized breeds.
2. b) Explain what mechanism has made it possible to generate so much morphological diversity in dogs in just a few thousand years compared to the millions of years that comparable diversification by natural selection usually takes in the wild.
3. c) Predict what would happen to the size, morphology, and variety of dogs if a mixed population of all breeds remained isolated on an island without human intervention for 40 generations.

The dichotomous key in the diagram is used to identify four animals. Follow it and write down the complete path (the questions and chosen answers) leading to the lizard.

Using the following dichotomous key:

1. a) Has legs .................................................... 2

b) Does not have legs ................................................. Earthworm

1. a) Has wings ..................................................... Beetle

b) Does not have wings .................................................. Rat

Identify: (a) a beetle, which has legs and wings; (b) a rat; (c) a snake. What problem arises when classifying the snake? Propose an improvement to the key to resolve it.

Construct a three-question dichotomous key to distinguish between these four living things: a dog, a palm tree, a button mushroom, and a trout. Check that it works by following it with two of them.

Construct a two-question dichotomous key that distinguishes a pine, an oak, and a geranium, and check that it works by following it with each of the three plants.

In the school playground you have found five different animals: a snail, a bee, a spider, a sparrow, and a mouse. Create a complete dichotomous key to identify all five and check that it works by following it with two of them.

A classmate has created the following identification card to help identify an animal observed in the schoolyard:

• Name: Black bird.

• Features to identify it: "It is medium-sized, quite dark, very skittish, and sings nicely in the mornings".

• Where it lives: "In trees and on the ground where there is food".

1. a) Critically evaluate the card: justify why these traits are subjective and ambiguous, explaining why they would not help another person differentiate that individual from other similar species such as a starling or a jackdaw.
2. b) Rewrite the identification card for the common blackbird applying scientific criteria: include its scientific binomial name correctly written (Turdus merula), its taxonomic group, at least two objective and observable morphological features (such as sexual dimorphism in plumage and beak color), and its habitat with precision.
3. c) Justify why it is mandatory in international science to use binomial nomenclature in Latin instead of local common names.

On a field trip to the mountains, you observe two adult lizards with brownish backs and about 13.5 cm in length. A student tries to use a school-level dichotomous key based only on "elongated body", "four legs", and "brownish or greenish color", but finds that both lead to the same final box and states: "If the key does not separate them, it is definitive proof that they belong to the same species".

1. a) Refute the student's conclusion by justifying the limitations of dichotomous keys based solely on general macroscopic characters.
2. b) In that area, the Iberian wall lizard (Podarcis hispanicus) and the Iberian rock lizard (Iberolacerta monticola) coexist. Design a strategy with three levels of increasing observation precision (from detailed examination with a hand lens to laboratory techniques) that allows you to break the tie and rigorously confirm the species of each individual.

Correct the writing of these scientific names and explain the three rules you have applied: "quercus ilex", "Homo Sapiens", and "CANIS LUPUS".

The scientific name of the Aleppo pine is Pinus halepensis. Explain what each of the two words indicates, who devised this system of nomenclature, and what advantages using scientific names in Latin has over common names.

Explain what a dichotomous key is and what it is used for, indicating how the questions making it up should be phrased for it to work properly. Also name two other tools that help identify living things in the field, such as a field guide or a mobile identification app, and state one advantage of each compared to a dichotomous key.

Explain what a field guide is and what information it usually offers for each species (photograph or drawing, description, size, where it lives...). Why is it advisable to take one on a field trip?

Explain in your own words what biodiversity is and give two reasons why scientists are interested in knowing which species live in a particular place.

Explain what an extinct species is, give a well-known example, and name one possible cause of an extinction.

A mobile phone app identifies plants from a photo. Explain two advantages of these tools and one risk of trusting them, and describe what you would do to confirm a doubtful identification.

In a stretch of a local river, freshwater bivalves have appeared attached to the rocks. The maintenance supervisor proposes applying a chemical disinfectant discharge along the entire bank to quickly eradicate all mollusks, claiming that "there is no need to waste time identifying them with a magnifying glass because all river bivalves do the same thing."

Two similar-looking species coexist in that river: the native freshwater mussel (Unio mancus), which is protected and endangered, and the zebra mussel (Dreissena polymorpha), an invasive alien species.

1. a) Refute the supervisor's proposal: justify why accurate biological identification is essential before intervening and what irreversible ecological impact their plan would cause.
2. b) Explain what biological traits make the zebra mussel a harmful invasive species compared to the balanced ecological role played by the native freshwater mussel.
3. c) Predict what would happen to the food web and the river's water quality if the zebra mussel is not detected in time and massively colonizes the riverbed.

Many animals can be identified without seeing them: by their tracks, droppings, feathers, or food remains. Explain what advantages studying them this way has, also for the animals' welfare, and give an example of a trace and the information it provides.

On a field trip you find a plant you do not know. Detail which four pieces of information you would note down (or photograph) to identify it later at home, and explain why you must not pull it up to take it with you.

A research team wants to study the feeding habits of birds around the school and proposes two methods:

• Method A: Capture individuals with mist nets, lock them in individual cages in the laboratory to weigh them, and record how many seeds they consume under continuous artificial light.

• Method B: Install feeders in the trees of the courtyard, place an automatic camera trap, and observe them with binoculars from the windows at 15 meters without interfering.

1. a) Taking into account that birds are sentient beings (capable of experiencing pain, fear, and stress), justify which of the two methods is ethically appropriate.
2. b) Predict what physiological and behavioral consequences the stress of Method A would have on the birds and how it could alter or bias the scientific data obtained about their natural feeding.
3. c) If in the laboratory you need to study the response of earthworms to humidity, design two specific measures in your experimental setup to ensure their welfare and avoid causing them dehydration or harm.

Mini-investigation: design an inventory of the biodiversity of your school playground over one week. Plan which areas you will cover, at what times, what you will record in the table (date, place, species or group, number of individuals), which identification tools you will use, and which rules you will follow so as not to disturb the living things.