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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 in
2、clude: Levels of organization Body symmetry Differentiation of germ layers Formation of body cavities Patterns of embryonic development Segmentation Cephalization Limb formation,Levels of Organization,Animals have specialized cells that are organized into tissues. There are several types of tissues
3、found in animals: Epithelial tissues- cover body surfaces inside and out, are also thin and flat. Example: epithelial tissues line lungs and allow gases to easily diffuse through Muscle tissues Connective tissues Tissues combine during growth and development to form organs and organ systems to carry
4、 out complex functions,Body Symmetry,Bodies of most animals exhibit some sort of symmetry There are two different forms of symmetry Radial 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 i
5、maginary plane divides the body into left and right sides that are mirror images of each other. Animals with bilateral symmetry have the following A definite front: also known as the anterior A definite end: also known as the posterior An upper side: also known as the dorsal side A lower side: also
6、known as the ventral side,Differentiation of Germ Layers,During embryological development the cells of most animal embryos differentiate into 3 germ layers 1. Endoderm: the innermost germ layer, develops into linings of the digestive tract and much of the respiratory system 2. Mesoderm: the middle l
7、ayer, gives rise to the muscles and much of the circulatory, reproductive, and excretory organ systems 3. 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 di
8、gestive tract and body wall Body cavities provide space for internal organs to suspend and room for organs to grow Most complex animal phyla have a true coelom- a body cavity that develops within the mesoderm and is completely lined with tissue derived from the mesoderm The coelom wraps around the g
9、ut and internal organs are suspended in it Animals with a coelom allows the animals to move without damaging the internal organs or interfering with the organs function Acoelomates are invertebrates that lack a coelom The are of an acoelomates body wall and gut is completely filled with tissues Some
10、 invertebrate groups have a pseudocoelom, which is only partially 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
11、development a zygote forms a blastula, which is a hollow ball of cells like an inflated balloon The blastula develops into the digestive tract by folding in on itself and developing a long elongated tube that runs from one end to the other In the beginning the digestive tract has only one opening, c
12、alled the blastopore,Patterns of Embryological Development,An efficient 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 e
13、nd of the tube Examples: flatworms, earthworms, snails, clams, spiders, and insects Deuterotomes: the blastopore becomes the anus, and the mouth is formed from the second opening that develops Chordates and echinoderms (sea stars) are deuterotomes, which indicates that echinoderms are closely relate
14、d to chordates,Segmentation: Repeating Parts,Segmentation occurs as many bilateral 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 rep
15、eat on each side of the body The most successful animals, including humans, have bilateral symmetry and segmentation,Cephalization: Head Formation,Animals with bilateral symmetry typical exhibit cephalization- the concentration of sense organs and nerve cells at their anterior end The most successfu
16、l animals including arthropods and vertebrates exhibit pronounced cephalization Insect and vertebrate 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 i
17、n the head, such as the eyes Nerve cells that process information and “decide” what an animal should do are also found in the head Animals 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
18、 Formation: Legs, Flippers, and Wings,Segmented, bilaterally symmetrical animals typically have appendages on both sides of the body. The types of appendages vary depending on the animal. Examples: Bristles in worms * Flippers in dolphins Jointed legs in spiders * Wings in dragonflies These differen
19、t kinds of appendages have evolved several times, and have been lost several times, in various animal groups Limb formation 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 *Cn
20、idarians Flatworms *Roundworms Annelids *Mollusks Arthropods *Echinoderms Chordates,25.2 Body Plans and Evolution Vocabulary,Radial 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 b
21、ody into left and right sides that are mirror images of each other. Endoderm: the innermost germ layer, develops into linings of the digestive tract and much of the respiratory system Mesoderm: the middle layer, gives rise to the muscles and much of the circulatory, reproductive, and excretory organ
22、 systems Ectoderm: the outermost layer, produces sense organs, nerves, and the outer layer of skin Coelom: a body cavity that develops within the mesoderm and is completely lined with tissue derived from the mesoderm,25.2 Body Plans and Evolution Vocabulary,Pseudocoelom: which is only partially line
23、d with mesoderm Zygote: a fertilized egg Blastula: a hollow ball of cells like an inflated balloon that develops into the digestive tract by folding in on itself and developing a long elongated tube that runs from end to the other Protostomes: the blastopore becomes the mouth and the anus becomes th
24、e second opening, which develops at the opposite end of the tube Deuterostomes: the blastopore becomes the anus, and the mouth is formed from the second opening that develops Cephalization: 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.,