Biology - An Illustrated Guide to Science (794127), страница 18
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However, they all haveflowers that produce seeds.● Angiosperms generally have a centralstem bearing side branches with leavesthat tend to be smaller than the largefronds of ferns, and flatter and widerthan the needles of pines. Roots tendto be well developed, and waterconducting tissues in angiosperms aremore advanced than in any other plantgroup.●rootlateral rootVertical section through flowerstamenantherfilamentpetalpistil(carpel)stigmaReproductionsepalovuleovaryflower stalkReproduction depends on flowers,which contain the sex organs of theangiosperm. The stam en , the maleportion of the flower, produces andstores pollen , microspores containingmale gam etes.
The stamen consists ofan thers (containing two pollen sacs)posted on stalks called filaments. Thepistil or carpel, the femalereproductive organ of the flower,consists of: the stigm a, the style, theovary, and the ovule.● The male gamete tends to leave theflower when it is produced, while thefemale gametes are retained in theovule for the whole of their life cycle.Angiosperms also produce fruits thataid in the dispersal of seeds.●© Diagram Visual Information Ltd.style10 4DIVERSITYKey wordsdiploidgametophytehaploidmeiosismitosissporophytezygoteKingdom Plantae:Angiospermae: life cycleAngiosperm life cycleh Seedling sporophytea FlowerFlowers●The Angiospermae are the only groupof plants with fully-developed flowers.They also produce specializedstructures to support dispersal andgermination of the seeds produced.The sporophyte generationAs with all plants there are sporophyteand gam etophyte generations. Inangiosperms, the sporophytegeneration is the visible plant and it isdiploid; i.e.
When mature, thesporophyte generation produceshaploid gametes by m eiosis. Thegametes fuse during fertilization andthe diploid number is then restored.● The male gametes (the pollen grains)are produced by meiosis inanthers (b, c). These are released atmaturity (d) and pass to the stigma ofthe ovule. The ovule contains thefemale gamete.●The gametophytegenerationAngiosperms are unique in that theyundergo double fertilization. Followingpollination, the pollen graingerminates on the stigma of a flowerof the same species, and the pollentube grows down through the style toan ovule in the ovary (e). Two spermnuclei enter the embryo sac.
Onefuses with the egg nucleus, leading tothe formation of a zygote, while theother fuses with the two polar nucleiin the center to produce anendosperm nucleus (f). Mitosis thenleads to the formation of the embryoand cotyledons.● Another pollen grain nucleus fuseswith other nuclei in the egg sac toform a storage tissue calledendosperm (g).● The seed is diploid and produces thelarger sporophyte generation (h).© Diagram Visual Information Ltd.●g Seed with embryotestab Antherendospermembryohf Fertilizationnucleiagbfcedpolarnucleic Anther: transverse sectioneggnucleuspollen grains(microspores)e Pollinationpollen grain(microspore)nucleitubenucleuspollen tubed Pollen grains releasedovary wallpolarnucleieggnucleusovulepollen grains(microspores)10 5Kingdom Animalia:classificationDIVERSITYKey wordsabdomenexoskeletoninvertebratethoraxvertebrateTree diagram of AnimaliaAnimaliaBackboneAnimals are classified at the first levelby the presence of a backbone: thosewith backbones are called vertebratesthose without are in vertebrates.● Most of the lower animals areinvertebrates and include a range ofsoft-bodied animals ranging fromplantlike Porifera and worms throughthrough “spiny-skinned”Echinodermata to Arthropoda.●NematodaMolluscaEchinodermataPlatyhelminthesAnnelidaCoelenterataThe ArthropodaPorifera●ArthropodaThe arthropods do not possess bonesbut do have a hard structuresurrounding their bodies called anexoskeleton .
The most successfulgroup of arthropods are the insects,which have three pairs of jointed legsand a segmented body divided intothree parts: head, thorax, andabdom en .The vertebratesAlmost all large animals are vertebratesand have a well-developed backboneand a complex nervous system.Vertebrates are also called Chordata.● The most primitive chordates are thecartilaginous fish (theChondrichthyes), which do notpossess true bone but rely on toughcartilage. The most well-known speciesin this group are the various types ofshark.● Mammals are the most successfulgroup and are warm-blooded, possessfur, give birth to live young, and feedthem on milk produced by themammary glands.ArachnidaInsectaChilopodaand DiplopodaChordataChondrichthyesAvesAmphibiaOsteichthyesReptiliaMammalia© Diagram Visual Information Ltd.●Crustacea10 6DIVERSITYKey wordsciliumgametelife cycleosculumsubstrateKingdom Animalia:PoriferaTypical poriferanColony of ascon-type sponges: external viewInvertebrates●osculumThe Porifera or sponges are a primitivegroup of invertebrates.
In many waysthey look like plants in that theycannot move themselves and spendmost of their life cycle attached to afirm su bstrate. There is somedifferentiation within the body,although they do not show the rangeof cell types present in higher animalsAscon-type sponge: partially sectionedosculumspiculechoanocyteBody structureThe outer surfaces of Porifera arecovered with thin, flattened cells calledpinacocytes. Porocytes (cells withpores) located all over the body allowwater into the sponge. Because theirbodies are hollow, their structure issupported by a soft network of fiberscalled spongin and/or by hard particlescalled spicule, which protect theanimal. Between the outer body andthe spongocoel (the central cavity) is agelatinous layer called the mesohyal.● Within the sponge, choanocytes, cellsfringed with cilia, force water throughthe spongocoel, bringing in nutrientsand removing waste.
Ameobocytestake food to other cells. Water leavesthe sponge through a large pore,usually at the top of the body, calledthe oscu lu m . The mechanism is veryefficient, with some spongesprocessing 20,000 times their ownvolume of water in 24 hours.●Reproduction© Diagram Visual Information Ltd.●Sponges reproduce sexually andasexually. Male gam etes are releasedinto the inner space and pass outthrough the osculum.
Thesesperm are collected by othersponges, and female gametes arefertilized internally. Sponges can alsoreproduce asexually through theproduction of buds.porocytespongocoelpinacocytesmesohyalamebocytepinacocytes10 7Kingdom Animalia:CnidariaDIVERSITYKey wordscolonial polypsepidermisexoskeletongastrodermismesogleaColonial polypstentaclemouthfeeding polyp:external viewInvertebrates●hypostomereproductive polyp:external viewsubstratetentacleCnidaria are invertebrates that can bedivided into two major groups: thecolon ial polyps that live their livesattached to a su bstrate, and the freefloating medusa-like forms that driftaround in the oceans.Body structureColonial polyps are enclosed in atransparent, chitinous exoskeletoncalled the perisarc.
Inside is livingtissue, collectively called thecoenosarc.● Colonial polyps have a body made upof branched tubular structuresspecialized for feeding orreproduction.● The feeding polyp, the hydranth, isenclosed in a thin chitinous cup calledthe hydrotheca.
The mouth is locatedat the opening of the gastric columnatop a low mount called thehypostome. It is surrounded by a ringof ten tacles used to entangle andinject poison into small prey. Food ispushed into the gastrovascular cavity,where it is partially digested anddistributed to all parts of the body.● The reproductive polyp consists of anelongated cylinder called a gonothecaenclosing a blastostyle, a column thatbears small medusa buds producedasexually. These eventually developinto medusae, which when maturebreak free and swim out the apertureof the gonotheca into the sea.● Obelia Medusa, shown bottom left,begins life as a polyp. The polyps,in turn produce medusae, orjellyfish, which reproducesexually and, in turn,produce polyps.gonothecamedusa budfeeding polyp:longitudinalsectionreproductive polyp:longitudinal sectionhydrotheca(cup-shaped)gastrovascularcavityperisarccoenosarcMedusa:subumbrellarviewgonad (ovary)Obelia colony as seenwith naked eyetentacleradial canalmouthgastrovascular cavity© Diagram Visual Information Ltd.●10 8DIVERSITYKey wordsguthermaphroditeparasiteKingdom Animalia:PlatyhelminthesTypical turbellarianDorsal viewanteriorendInvertebrates●The Platyhelminthes or flatworms area group of invertebrate worms thatinclude two significant parasites ofhumans: liver flukes and tapeworms.They show extensive differentiation ofcell types and have relatively complexbodies with a well-developed nervoussystem, including sense organs thatrespond to certain chemicals and light.posterior endheadlateral lobeeyespotcerebral ganglionventral nerve cordBody structureThe flatworms or turbellarians haveflattened bodies that allow diffusion ofoxygen into every cell in the body.Carbon dioxide diffuses easily theother way.
Consequently, they do nothave a functional circulatory system.● The gu t in flatworms is often highlydivided and reaches into the majorityof the body. Again, this is requiredsince they have no circulatory systemto distribute food materials easily. Themouth of the gut also functions as theanus, and waste materials are passedout of it even as fresh foods are beingdrawn in.● Flatworms are herm aphrodite— theyhave both male and female sexorgans— and the parasitic forms liketapeworms and liver flukes have highlyspecialized life cycles, sometimesinvolving two hosts and theproduction of thousands of eggs froma single worm.●Nervous systemposterior gut branchanterior gut branchgut cecummouthpharynxDigestive systemvas deferensyolk sacovaryoviducttestiscopulatory sacpenisgenital chambergenital poreReproductive system© Diagram Visual Information Ltd.flame cellExcretory systemexcretory poreexcretory canal10 9Kingdom Animalia:Platyhelminthes:tapewormDIVERSITYKey wordsfecesguthermaphroditehostparasiteTapeworm life cycleI Primary host(human)fThe intestinal tapeworma Adult tapewormin human intestineThe tapeworm is a parasite that livesinside the human gu t.
It enters the gutwhen meat containing its larvae iseaten. An ingested larva attaches itselfto the gut wall by a sucker and hookson its head. The body, which can reachup to 20 feet (6 m) in length, thendangles down into the gut space,absorbing food materials and releasingwastes.● Most of the body of the tapeworm isdevoted to reproduction as almost allof the other essential physiologicalprocesses are carried out by its host.Tapeworms are herm aphrodite.●proglottidabf Cysticercus evertswhen raw porkis eaten anddevelops intotapewormafb Mature proglottidin feces containingonchospheres(embryos)beLife in the primary host●cdc Onchosphere eaten by pigcapsuleembryophore(envelope)hexacanth( six-hooked) larvae Hexacanth larva migrates to muscleto form inverted cysticercusd Hexacanth larvareleased in pig intestineHumans are the primary hosts fortapeworms. The worm consists of along series of segments calledproglottids, which grow from the head(a).
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