PLANT KINGDOM · Comparison Tables

1. Artificial vs Natural vs Phylogenetic Classification

System	Basis	Key point
Artificial	A few superficial, often morphological characters	May separate closely related species; Linnaeus used vegetative characters and androecium.
Natural	External and internal features, including anatomy and embryology	Reflects natural affinities better; Bentham and Hooker proposed a natural system for flowering plants.
Phylogenetic	Evolutionary relationships and common ancestry	Modern accepted approach; supported by evidence from many sources.
Numerical / cyto / chemo taxonomy	Observable characters / chromosomes / chemical constituents	Tools used to resolve classification difficulties.

2. Green vs Brown vs Red Algae

Feature	Chlorophyceae	Phaeophyceae	Rhodophyceae
Common name / pigments	Green algae; chlorophyll a, b	Brown algae; chlorophyll a, c and fucoxanthin	Red algae; chlorophyll a, d and r-phycoerythrin
Reserve food	Starch, often in pyrenoids	Laminarin and mannitol	Floridean starch
Motile cells	2-8 equal, apical flagella	Two unequal, lateral flagella	No flagellated stages
Habit / body	Unicellular, colonial or filamentous	Often holdfast, stipe and frond	Mostly marine; can occur at greater depths
Examples	Chlamydomonas, Volvox, Ulothrix, Spirogyra, Chara	Ectocarpus, Dictyota, Laminaria, Sargassum, Fucus	Polysiphonia, Porphyra, Gracilaria, Gelidium

Commercial products Brown algae yield algin; red algae yield carrageen, and Gelidium/Gracilaria yield agar.

3. Liverworts vs Mosses

Feature	Liverworts	Mosses
Plant body	Thalloid, dorsiventral and closely appressed to substrate	Two stages: protonema then leafy stage
Rhizoids	Unicellular	Multicellular and branched
Asexual reproduction	Fragmentation or gemmae in gemma cups	Fragmentation and budding in secondary protonema
Sporophyte	Foot, seta and capsule	Foot, seta and a more elaborate capsule
Examples	Marchantia, Riccia	Funaria, Polytrichum, Sphagnum

Shared feature Bryophytes are amphibians of the plant kingdom: they live on soil but need water for sexual reproduction. Their sporophyte remains attached to the gametophyte.

4. Major Plant Groups at a Glance

Feature	Algae	Bryophytes	Pteridophytes	Gymnosperms	Angiosperms
Plant body	Thalloid	Rhizoids; root-/stem-/leaf-like parts	True roots, stem and leaves	Woody sporophyte, usually evergreen	Flowering plants
Vascular tissue	Absent	Absent	Present; first vascular cryptogams	Present	Present
Dominant phase	Variable by life cycle	Gametophyte	Sporophyte	Sporophyte	Sporophyte
Seeds / fruits	Absent	Absent	Absent	Naked seeds; fruits absent	Seeds enclosed in fruits
Water needed for fertilisation	Generally yes	Yes	Yes	No external water needed	No external water needed

5. Homospory vs Heterospory and Gymnosperms vs Angiosperms

Feature	Homosporous pteridophytes	Heterosporous pteridophytes
Spore types	One kind	Microspores and megaspores
Examples	Most pteridophytes	Selaginella, Salvinia
Evolutionary significance	Free-living gametophyte	Female gametophyte retained; precursor of seed habit

Feature	Gymnosperms	Angiosperms
Ovules / seeds	Naked; not enclosed by ovary wall	Ovules enclosed in ovary; seeds enclosed in fruit
Reproductive structures	Male and female cones (strobili)	Flowers
Gametophytes	Highly reduced and retained within sporangia	Pollen grain and embryo sac
Special point	Cycas has coralloid roots; Pinus bears cones	Double fertilisation; monocots and dicots

6. Haplontic vs Diplontic vs Haplo-diplontic Life Cycles

Life cycle	Dominant multicellular phase	Key feature / examples
Haplontic	Haploid gametophyte	Zygote is the only diploid stage; seen in many algae such as Volvox, Spirogyra and Chlamydomonas.
Diplontic	Diploid sporophyte	Gametophyte highly reduced; seed plants show this pattern. Fucus is an algal example.
Haplo-diplontic	Both phases multicellular	Bryophytes: dominant gametophyte and dependent sporophyte; pteridophytes: dominant sporophyte and independent gametophyte.