Plant Systematics Questions and Answers

Answer: A

Phylogenetic relationships are commonly shown as a Cladogram.

A cladogram is a branching diagram built from shared derived characters (synapomorphies). Its branch points represent the splitting of lineages from common ancestors, so it is the standard way of presenting an estimate of evolutionary relationships among taxa.

An idiogram is a diagram of a karyotype, showing the chromosomes arranged by size and banding pattern. A phenogram groups taxa by overall similarity, without asking whether the similarity reflects common descent. A dendrogram is any tree diagram from a clustering analysis, so it is a general term rather than the specific phylogenetic estimate.

Answer: B

The incorrect statements are P, R.

P is incorrect: stamens attached to petals are epipetalous. 'Epiphyllous' is used for stamens attached to the perianth (tepals), as in lilies, where petals and sepals are not distinct. R is incorrect because it reverses the definition: in syngenesious stamens the anthers are united into a tube while the filaments stay free, as in the sunflower family. Filaments united into a bundle with free anthers is the adelphous condition.

Q is correct: in Calotropis the stamens fuse with the stigma to form a gynostegium. S is correct: in synandrous stamens, as in Cucurbita, both filaments and anthers are fused.

Answer: A

Apple belongs to the Rosaceae.

The rose family includes many fruit trees: apple (Malus), pear, plum, cherry, peach, almond and strawberry. The apple is a pome, a false fruit in which the fleshy part develops largely from the floral tube around the ovary, typical of one subfamily of the Rosaceae.

Rutaceae is the citrus family, Rubiaceae the coffee family, and Ranunculaceae the buttercup family; none contains apple.

Answer: A

The correct match is P-4; Q-3; R-2; S-1.

• John Hutchinson wrote The Families of Flowering Plants, the basis of his phylogenetic system dividing dicots into woody and herbaceous lines.
• Adolf Engler and Karl Prantl edited Die Naturlichen Pflanzenfamilien, the multi-volume German work presenting the Engler system.
• Arthur Cronquist wrote The Evolution and Classification of Flowering Plants, setting out his widely used system of angiosperm classification.
• Alfred Barton Rendle wrote The Classification of Flowering Plants, a two-volume work following the Engler arrangement.

The other options give Hutchinson the Rendle or Cronquist title, or give Engler and Prantl an English title, when theirs is the only German work in the list.

Answer: A

The family is Lamiaceae.

A gynobasic style arises from the base of the ovary, between its lobes, instead of from the top. In the mint family the bicarpellary ovary is deeply four-lobed (each carpel split by a false septum), and the single style rises from the depression in the middle where the lobes meet. The same feature also marks the related family Boraginaceae.

Euphorbiaceae has a superior, usually tricarpellary ovary with terminal styles. Malvaceae has a terminal style passing up through the staminal tube of its monadelphous stamens. Poaceae has a one-celled ovary topped by two feathery stigmas. None of them has a gynobasic style.

Answer: C

The partial stem parasite is Viscum, the mistletoe; it is the only option the key accepts in this multiple-select question.

Viscum grows on the branches of host trees. It has green leaves and makes its own sugars, so it is only a partial (hemi-) parasite, but its haustoria tap the host's xylem for water and minerals.

Striga (witchweed) is also green and a partial parasite, but it attacks the roots of cereals, so it is a root parasite. Orobanche (broomrape) lacks chlorophyll and is a total root parasite. Cuscuta (dodder) twines round stems but has almost no chlorophyll, so it is a total stem parasite.

Answer: A

Tendu belongs to the family Ebenaceae.

Diospyros melanoxylon, the tendu or East Indian ebony, is in the ebony family Ebenaceae, along with the true ebonies of the same genus. Its leaves are collected for wrapping bidis, an important source of income for forest dwellers in Madhya Pradesh.

Dipterocarpaceae is the family of sal, and Combretaceae that of arjun, harra and baheda. 'Diospyraceae' is not a recognised family.

Answer: C

The correct sequence is Division, class, order, family, genus, species.

In the botanical hierarchy, a division (phylum) is divided into classes, a class into orders, an order into families, a family into genera, and a genus into species. Each rank is more inclusive than the one below it.

The other options put genus above order or family, or species above family, which reverses parts of the hierarchy.

Answer: D

Budding is the chief mode of reproduction in duckweeds.

Duckweeds (Lemna, Spirodela, Wolffia) are tiny floating flowering plants that rarely flower. They multiply mainly by vegetative budding: new fronds grow out from pouches at the base of the parent frond and break away, letting a population double in a few days.

Pipeworts (Eriocaulon), stoneworts (the green alga Chara) and bladderworts (Utricularia), spelt with '-warts' in the paper, reproduce mainly by seeds, oospores or fragmentation and are not known for budding.

Answer: B

Some traits are considered more important than others in cladistics.

Cladistics groups organisms only by shared derived characters (synapomorphies). Characters are therefore not equal: a shared derived trait counts as evidence of common ancestry, while a shared primitive trait (symplesiomorphy) or a convergent one is discounted.

Phenetics is the opposite approach: numerical taxonomy weights all characters equally and groups organisms by overall similarity. Taxonomy and systematics are the general fields within which both approaches work, so they do not name the weighting approach the stem describes.