Plant Systematics Questions and Answers

Answer: C

The system is phenetic classification.

Phenetic classification (numerical taxonomy, developed by Sokal and Sneath) groups organisms by their overall similarity in as many observable characters as possible, each given equal weight, without trying to reconstruct evolutionary history.

Phylogenetic and evolutionary classifications are built expressly on lines of descent. 'Natural classification' in the historical sense (as of Bentham and Hooker) used many characters to show natural affinity and later came to be read in evolutionary terms, so the system defined by ignoring phylogeny is the phenetic one.

Answer: C

The key credits the binomial system to Caspar Baubin, that is, the Swiss botanist Caspar (Gaspard) Bauhin.

In his Pinax Theatri Botanici (1623) Bauhin often named plants with a genus name followed by a single descriptive word, the first systematic use of two-word names, which is why textbooks describe him as having introduced binomial nomenclature. Linnaeus later applied the method consistently to all plants in Species Plantarum (1753) and all animals in Systema Naturae (1758), so he is the one credited with establishing it, but the key follows the textbook account of who first devised the binomial name.

Augustin Pyramus de Candolle introduced the term taxonomy, and his son Alphonse de Candolle drafted the first code of botanical nomenclature (1867); neither devised the binomial name.

Answer: B

Guttiferae (spelt Gutliferae in the paper) is the conserved alternative name of family Clusiaceae.

The botanical code allows eight long-used family names that do not end in a genus name plus -aceae to stand as conserved alternatives: Guttiferae (Clusiaceae), Leguminosae (Fabaceae), Palmae (Arecaceae), Umbelliferae (Apiaceae), Compositae (Asteraceae), Cruciferae (Brassicaceae), Gramineae (Poaceae) and Labiatae (Lamiaceae). Clusiaceae is based on the genus Clusia, and Guttiferae refers to the gum or latex these plants yield.

The distractors are the type-based names of three other conserved pairs: Fabaceae is the alternative of Leguminosae, Arecaceae of Palmae and Apiaceae of Umbelliferae.

Answer: C

Bentham and Hooker's system covers all seed plants.

Their Genera Plantarum (1862-1883) classified only the seed-bearing plants, which they divided into three classes: Dicotyledons, Gymnospermae (placed between the dicots and monocots) and Monocotyledons. Cryptogams were not included.

Angiosperms is too narrow, since the system also includes gymnosperms. Embryophytes is too broad, because that group also takes in bryophytes and pteridophytes, which the system leaves out. Thallophytes (algae and fungi) are not covered at all.

Answer: A

It is the principle of the APG system.

The Angiosperm Phylogeny Group's first classification (1998) opens with the statement that the family is central in flowering plant systematics, and it is built on families (and the orders that group them) defined as monophyletic from molecular, chiefly DNA sequence, evidence. Later versions (APG II to APG IV) keep the same emphasis.

Bentham and Hooker and Engler and Prantl were nineteenth-century systems based on morphology, the first a natural and the second an early phylogenetic system. Armen Takhtajan's system is a phylogenetic scheme built on morphology and organised around subclasses and superorders. None of them is associated with this statement.

Answer: B

The association of algae and fungi, as in a lichen, is called symbiotism (symbiosis).

In a lichen the fungal partner (mycobiont) provides shelter, water and minerals, and the algal or cyanobacterial partner (photobiont) supplies carbohydrates by photosynthesis. Both benefit, so the association is a mutualistic symbiosis, and together they can colonise bare rock and bark that neither could occupy alone.

Parasitism benefits one partner at the other's cost. Helotism is an older, master-and-slave interpretation of the lichen, holding that the fungus enslaves the alga; it is not the accepted name for the association. Heterothallism is a mating system in fungi and algae that needs two compatible strains, not an association between organisms.

Answer: C

The seed plants that retain flagellated sperm are Cycas and Ginkgo, so the answer is (i) and (v).

In cycads and Ginkgo the pollen tube is mainly a haustorial structure, and it releases large multiflagellate sperm that swim a short distance to the archegonium. This is a primitive feature that links them with the ferns, and the sperm of Cycas are among the largest in the plant kingdom.

Gnetum and Welwitschia are gymnosperms of the Gnetales, whose male gametes are non-motile and are carried to the egg by the pollen tube (siphonogamy). Casuarina (spelt Casurina in the paper) is a flowering plant, also with non-motile gametes. Every option containing (ii), (iii) or (iv) is therefore wrong.

Answer: D

Archegonia are absent in Gnetum.

In most gymnosperms the female gametophyte inside the ovule bears archegonia, flask-shaped organs that each hold an egg. Gnetum (with Welwitschia) is the exception: its female gametophyte forms no archegonia, and free nuclei in its micropylar part act directly as eggs. This reduction is one of the features that link the Gnetales with the angiosperms.

Cycas, Taxus and Pinus all produce archegonia at the micropylar end of the female gametophyte, so they are the distractors.

Answer: A

Nori comes from Porphyra.

Porphyra (now partly placed in Pyropia) is a red alga that grows on rocky shores. In Japan its thin blades are pressed and dried into the dark sheets called nori, used to wrap sushi; it is also eaten as laver in Wales and as gim in Korea.

Polytrichum is a moss, Potamogeton is a pondweed (a flowering plant) and Pteridium is bracken fern. None of them is the source of nori.

Answer: D

For an analysis of species the OTUs are Populations.

In numerical taxonomy the operational taxonomic units (OTUs) are the basic units whose characters are scored and compared. They are always the level just below the groups being studied, so that the analysis can show how they cluster into those groups.

To delimit or analyse species, the units compared must lie below the species level, which in practice are populations (or individual specimens). Families and genera are ranks above the species, and species are the OTUs only when genera are being analysed.