plants, but for the animal ecologist the following 

 simplified classification, based on Pound and Clem- 

 ents (1900), is sufficient for general purposes: 



1. Annuals: Passing the winter or dry season in 

 seed or spore form alone, no propagation or 

 accumulation of aerial shoots ; living one year. 



2. Biennials : Passing one unfavorable season in 

 the seed or spore form and the next in a vege- 

 tative stage ; no accumulation of aerial shoots : 

 living two years or parts of two years. 



3. Herbaceous perennials: Passing each unfa- 

 vorable season in both seed or spore and vege- 

 tative form : no accumulation of aerial shoots ; 

 living several to many years. 



a. Broad-leaved herbs : mostly terrestrial 



b. Sod grasses : a continuous turf 



c. Bunch grasses : scattered clumps 



d. Succulents : some broad-stemmed cacti 



e. Water plants: 



( 1 ) Submerged : vegetative body entirely 

 underwater. 



(2) Floating: leaves floating on water sur- 

 face ; water lilies, duckweed. 



(3) Emerging: leaves extending above 

 water surface : cattails, sedges, rushes. 



f. Ferns 



g. Mosses 



h. Liverworts 

 i. Lichens 

 j. Fungi 

 k. Algae 



4. Woody perennials: Passing the unfavorable 

 season as aerial shoots or masses, often as seeds 

 also ; living many years as a rule. 



a. Lianas: vines 



b. Succulents : some tree or barrel cacti 



c. Bushes: much -branched, low growth, sev- 

 eral stems 



d. Shrubs: single stem and tree-like but 

 smaller 



e. Trees: 



(1) Deciduous: shedding leaves during 

 unfavorable season. 



(2) Evergreen: leaves shed irregularly 

 and tree never completely bare. 



(a) Needle-leaved: narrow, usually- 

 elongated leaves. 



(b) Broad-leaved: leaves much as on 

 deciduous trees but shed irregu- 

 larly. 



Life-forms of animals 



Systems to classify the life-forms of animals 

 have been little developed (Remane 1943, 1952). 



The major life-forms of animals more often agree 

 with their taxonomy than do plants, but some life- 

 forms include representatives from several different 

 taxonomic groups. There can be recognized encrust- 

 ing forms such as the fresh-water bryozoa Pliiina- 

 tclla and some sponges : coral forms, including grass, 

 leaf, or shrub forms ; radiate forms, such as coelente- 

 rates and echinoderms generally ; bivalve forms ; snail 

 forms : slug forms ; worm forms ; crustacean forms ; 

 insect forms : fish, snake, bird, and four-footed forms. 

 Each of these major types may be subdivided ; for 

 instance, the four-footed form of mammals (Osburn 

 ct al. 1903) : 



Aquatic (swimming) : seal, whale, walrus 

 Fossorial (burrowing) : mole, shrew, pocket 



gopher 

 Cursorial (running) : deer, antelope, zebra 

 Saltatorial (leaping) : rabbit, kangaroo, jumping 



mouse 

 Arboreal (climbing) : squirrel, opossum, monkey 

 Aerial (flying) : bat 



Adaptations 



Plants and animals of specific life-forms are 

 adaptations to live in particular habitats and to be- 

 have in particular ways (Klaauw 1948). The life- 

 forms listed for mammals are largely adaptations to 

 particular strata (water, subterranean, ground, tree, 

 air) within a community rather than to the habitat 

 as a whole ; for instance, the subterranean adapta- 

 tions of mammals living in the Arctic tundra are 

 similar to the subterranean adaptations of mammals 

 in the tropics. In communities lacking one or more 

 strata (for instance, the tree stratum in grassland), 

 animals specifically adapted to the missing strata are 

 also absent. In communities in which all strata are 

 present, a catholic variety of life-forms occurs. 



In addition to adaptations to stratum and habitat, 

 there occur ecologically significant adaptations for 

 food-getting and metabolism, protection, and repro- 

 duction. The variety of teeth found in mammals and 

 lizards, the variation in shape and size of bills of 

 birds, the different mouth parts of insects, the siphons 

 of clams, the suckers of leeches, the water canal sys- 

 tems of sponges are but a few special anatomical fea- 

 tures especially designed for food-getting. Associated 

 with food-getting is a great diversity in structural 

 adaptations for the digestion of the food, for respira- 

 tion, for circulating food materials and gases through 

 the body, for excreting wastes, for support and move- 

 ment, and for nervous and hormonal regulation. All 

 these internal organs and structures are necessary to 

 the animal for utilizing the energy resources of the 

 environment. 



8 Background 



