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1、1.,2.,3.,4.,5.,6.,7.,Which numbers represent chordates and which numbers represent invertebrates?,25.2 Animal Body Plans and Evolution,Features of Body Plans,Each animal phylum has a unique organization of particular body structures that is often referred to as a body plan.Features of body plans inc
2、lude:Levels of organizationBody symmetryDifferentiation of germ layersFormation of body cavitiesPatterns of embryonic developmentSegmentationCephalizationLimb formation,Levels of Organization,Animals have specialized cells that are organized into tissues.There are several types of tissues found in a
3、nimals:Epithelial tissues-cover body surfaces inside and out,are also thin and flat.Example:epithelial tissues line lungs and allow gases to easily diffuse throughMuscle tissuesConnective tissuesTissues combine during growth and development to form organs and organ systems to carry out complex funct
4、ions,Body Symmetry,Bodies of most animals exhibit some sort of symmetryThere are two different forms of symmetryRadial symmetry:any number of imaginary planes drawn through the center of the body could divide into equal halves.Example:Sea anemone Bilateral symmetry:a single imaginary plane divides t
5、he body into left and right sides that are mirror images of each other.Animals with bilateral symmetry have the followingA definite front:also known as the anteriorA definite end:also known as the posteriorAn upper side:also known as the dorsal sideA lower side:also known as the ventral side,Differe
6、ntiation of Germ Layers,During embryological development the cells of most animal embryos differentiate into 3 germ layers1.Endoderm:the innermost germ layer,develops into linings of the digestive tract and much of the respiratory system2.Mesoderm:the middle layer,gives rise to the muscles and much
7、of the circulatory,reproductive,and excretory organ systems3.Ectoderm:the outermost layer,produces sense organs,nerves,and the outer layer of skin,Formation of a Body Cavity,Most animals have a body cavity,which is a fluid-filled space between the digestive tract and body wallBody cavities provide s
8、pace for internal organs to suspend and room for organs to growMost complex animal phyla have a true coelom-a body cavity that develops within the mesoderm and is completely lined with tissue derived from the mesodermThe coelom wraps around the gut and internal organs are suspended in itAnimals with
9、 a coelom allows the animals to move without damaging the internal organs or interfering with the organs functionAcoelomates are invertebrates that lack a coelomThe are of an acoelomates body wall and gut is completely filled with tissuesSome invertebrate groups have a pseudocoelom,which is only par
10、tially lined with mesoderm This false coelom is filled with liquid that can act like a skeleton and provide support,Patterns of Embryological Development,Every animal that reproduces begins as a zygote(a fertilized egg)At the beginning of development a zygote forms a blastula,which is a hollow ball
11、of cells like an inflated balloonThe blastula develops into the digestive tract by folding in on itself and developing a long elongated tube that runs from one end to the otherIn the beginning the digestive tract has only one opening,called the blastopore,Patterns of Embryological Development,An eff
12、icient digestive system needs two openings:a mouth through which food enters and an anus through which waste exits Protostomes:the blastopore becomes the mouth and the anus becomes the second opening,which develops at the opposite end of the tubeExamples:flatworms,earthworms,snails,clams,spiders,and
13、 insectsDeuterotomes:the blastopore becomes the anus,and the mouth is formed from the second opening that developsChordates and echinoderms(sea stars)are deuterotomes,which indicates that echinoderms are closely related to chordates,Segmentation:Repeating Parts,Segmentation occurs as many bilateral
14、symmetrical animals develop,their bodies become divided into numerous repeated parts,or segments Segmented animals such as worms,insects,and vertebrates have at least some internal and external body parts that repeat on each side of the bodyThe most successful animals,including humans,have bilateral
15、 symmetry and segmentation,Cephalization:Head Formation,Animals with bilateral symmetry typical exhibit cephalization-the concentration of sense organs and nerve cells at their anterior endThe most successful animals including arthropods and vertebrates exhibit pronounced cephalizationInsect and ver
16、tebrate embryos heads are formed by fusion and specialization of several body segments during development As the segments fuse the external and internal parts combine in ways that concentrate sense organs in the head,such as the eyesNerve cells that process information and“decide”what an animal shou
17、ld do are also found in the headAnimals with a head move in a head first direction because this way the concentration of sense organs and nerve cells come in contact with the new environment first,Limb Formation:Legs,Flippers,and Wings,Segmented,bilaterally symmetrical animals typically have appenda
18、ges on both sides of the body.The types of appendages vary depending on the animal.Examples:Bristles in worms*Flippers in dolphinsJointed legs in spiders*Wings in dragonfliesThese different kinds of appendages have evolved several times,and have been lost several times,in various animal groupsLimb f
19、ormation and segmentation have evolved to allow animals to be more flexible and have improved movement,Limb Formation:Legs,Flippers,and Wings,Animals to include on chart:Sponges*CnidariansFlatworms*RoundwormsAnnelids*MollusksArthropods*EchinodermsChordates,25.2 Body Plans and Evolution Vocabulary,Ra
20、dial Symmetry:any number of imaginary planes drawn through the center of the body could divide into equal halves.Bilateral Symmetry:a single imaginary plane divides the body into left and right sides that are mirror images of each other.Endoderm:the innermost germ layer,develops into linings of the
21、digestive tract and much of the respiratory systemMesoderm:the middle layer,gives rise to the muscles and much of the circulatory,reproductive,and excretory organ systemsEctoderm:the outermost layer,produces sense organs,nerves,and the outer layer of skinCoelom:a body cavity that develops within the
22、 mesoderm and is completely lined with tissue derived from the mesoderm,25.2 Body Plans and Evolution Vocabulary,Pseudocoelom:which is only partially lined with mesoderm Zygote:a fertilized eggBlastula:a hollow ball of cells like an inflated balloon that develops into the digestive tract by folding
23、in on itself and developing a long elongated tube that runs from end to the otherProtostomes:the blastopore becomes the mouth and the anus becomes the second opening,which develops at the opposite end of the tubeDeuterostomes:the blastopore becomes the anus,and the mouth is formed from the second op
24、ening that developsCephalization:the concentration of sense organs and nerve cells at their anterior end,25.2 Assessment,1a.List eight features of animal body plans.1b.How is the embryology of echinoderms similar to that of vertebrates?What might this similarity indicate about their evolutionary relationship.,
