rMf AOAPTATION Of ANI^AAli TO JHl INVIHONMINl 795 



liigli .111(1 low II. Ic 111.11 ks; CJ) ihc shallow ioa, ilic ic|.>,i<)ii lynif.; ovci ilic 

 COlilmciil.il shell .iiul cMciidiiifj; oiil (o ;i dcplli oj .iIxmM .')()() led; (:i) ili< 



pelagic zono, iIk <)|>c cm <\i( ndni); .lowii ;i.s I. it .is Miiili^lil i.iii 



|)c'iu'li.ilr (M.mc '.(Id (.. KlOO ic.i); m.! (j) ij,,' ahyttal zono, ilic (.<(.iii 

 beyond the ( onliiiciii.d slicll imd bciicidi iIk ikI.i^k /one. 



I he 111. nine ()i).;;inisnis ;ii<' (hissed ec oIo^^k .illy ;is plankton, <»i).;.in 

 isnis lli.ii llo.il .111(1 ;iie moved passivfly hy die (iiiieiils. wind, .md w;ives, 

 nekton, .1111111. iK di.ii swim .k lively; :iiid benthot, ilir Ixdiom dwell«-is 

 lh;it (i;ivvl over, hiiiiow iiilo. 01 ,im- . hi. k lied lo die 1)0110111. I lie id. ink 

 loii are generally very small -pioio/oa, alga*-, small laiv.d l<»iiii'. ol .1 

 variety ol animals, and a lew woims. The ncklon iiuliide llie )ellylisli, 

 squid, lisli, (miles, seals and whales. .Some ol die heiidiic animals, <ial>s, 

 snails, slaifisli and some worms, crawl over die siibsitate; (lams and 

 worms hiiiiow iiilo llie sand, mud 01 io(k ol die se.i holloiii, .iiid .1 lliitd 

 group, including sponges, sea .iiieinoiies, (r»i;i|s, htyo/oans, (iiiioidH, 

 oysters, barnacles and luni(ales, aic alladied lo rlie subsUale. 



llie tidal /one is one ol the most lavoiablc ol all llie liabilali ol 

 the woild, with an abundaiue ol light, oxygen, (aibon dM>xi<|e and 

 minerals to foster a rich growth ol plants, and die |>laiiis, providing 

 food and shelter, make it an ex(ellenl habitat \t>t animals. I lie pi. mi 

 life is laigely composetl ol algae, wiih only a lew grawen in addiiK^n, 

 There is keen competition atnong the plants lot space and am(;ng the 

 animals for space and lood, so the lojms living lictc have had to evolve 

 special adaptatic>ns to survive. 



The iniertidal zone is exposed Kj tlie air twicer daily and its in- 

 habitants have had to develop some sort ol protection against desicca- 

 tion. .Some animals avoid this by burrowing luio the cl;imp sand ot r'xkh 

 until the tide returns; others liave evolved shells wfiich can be r |f>sec| 

 to retain a supply of water within them. .Many plants contain jelly like 

 substances such as agar which absorb and retain large cjuantitieo of 

 water. One of the outstanding characteristics c^l this region, ol (ourse, 

 is the ever-present action of the waves, and the organisms in adapting 

 to life here have evolved ways of resisting wave action. Ifie many sea 

 weeds have tough pliable bcjdies, able to fjend witfi the waves without 

 breaking, while the animals are either encased in hard calc,areou<> sheIN, 

 such as those of molluscs, bryozoa, starfish, Ijarnatles and (.r'd\)S, or a/* 

 covered by a strong leathery skin that can fxrnd without fjreaking, sucft 

 as that of the sea anemone and octopus. 



The shallow sea region, just h>eyond the intertidal /one, is alw 

 thicklv populated, for it has plenty of Hght and an abuncJance of rrtin- 

 erals and other nutrients for plant growth. The absence of the j^ericxJjc 

 exposure to air and the lesser wave action permit many plant* and ani- 

 mals to live here which could not survive in the interticbl /one. 



The pelagic region, distinguished by the presence of sunligfit and 

 the absence of" a substrate, is populated by plankton and neku..n. There 

 are no large seaweeds, except occasional pieces torn from their anchw- 

 age in die shallow sea, and fewer microscopic algae, generally, than m 

 the shallow sea. There are protozoa such as foraminifera and radio- 

 laria, small Crustacea and many larval forms. The larger amniaU in- 



