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ABBOTTS COLLEGE

PAGE 73. ABBOTTS COLLEGE. Organisms are descended from common ancestors This theory guides scientists in their search for order in the astounding diversity of animal life on earth The science of taxonomy names and classifies different species to illustrate this order. PAGE 73.

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ABBOTTS COLLEGE

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  1. PAGE 73 ABBOTTS COLLEGE

  2. Organisms are descended from common ancestors • This theory guides scientists in their search for order in the astounding diversity of animal life on earth • The science of taxonomy names and classifies different species to illustrate this order

  3. PAGE 73 • Animals can be grouped into phyla according to similarities in various features of their basic structure(body plan) • This makes it possible to understand the evolutionary development of the group Body plan = the general similarities in development, form and function among members of a particular phylum

  4. The term phylum is one of seven major categories that are used to classify organisms. In order of broad to specific, these seven categories are: Kingdom, Phylum, Class, Order, Family, Genus, and Species. CarolusLinnaeus developed this system of classification in the 18th century

  5. Body Symmetry • Number of tissue layers developed from the embryo • The number of openings in the gut • The presence or absence of a coelom (body cavity) and blood systems

  6. PAGE 73 The body plans of multicellular organisms are either asymmetrical, radially symmetry or bilaterally symmetrical Asymmetry: Having no symmetry Sponges

  7. PAGE 73 Having no symmetry Sponges

  8. the body parts are arranged around a central axis and can be divided into mirror images by an imaginary line through any vertical plane

  9. Tubular, vase or bowled shaped animals that have a mouth at one end are usually radial symmetrical • Radial symmetry is common in sessile, free-floating or weakly swimming animals. • They need to interact with their surroundings equally well on all sides

  10. the body can only be divided into mirror images by an imaginary line through one plane • If cut lengthwise, the y form left and right halves (mirror images) • Also have a top and a bottom • And a front and a back • This type of symmetry is suited to animals that move about

  11. They show cephalization which allows them to become aware of the environments around them as they move forward • This increases their chance of finding food or predators Cephalisation = concentration of sense organs, feeding appendages and nervous tissue near the anterior end of the animal

  12. CEPHALIZATION

  13. Germ layers formed from developed embryo(zygote) Upper layer (ectoderm) forms the epithelium of the body surface (skin) and the nervous system Lower layer (endoderm) forms the wall of the digestive system (gut) Mesoderm is formed by an interaction between the ectoderm and endoderm

  14. Diploblastic animals only have two layers of tissues Ectoderm and endoderm Triploblastic animals have three layers of ttissues Ectoderm, mesoderm and endoderm

  15. The development of the mesoderm was a tremendous evolutionary advancement • Mesoderm plays a role in the formation of tissueseg connective tissue, cartilage, bone • and organseg reproductive organs • and systemseg blood and lymph sytems Page 74

  16. Single opening • Two openings PAGE 74 Gut = The alimentary canal or a portion thereof, especially the intestine or stomach.

  17. Single opening • Primitive animals • Sac like digestive cavity • Take in food and expel waste out of the same opening • Not an efficient system Porifera and Cnidarians

  18. Two openings • It allows food to be continually taken through the mouth, digested and the waste released from the anus • This body plan allows specialization of parts along the tube, such as a stomach, intestine, etc.

  19. PAGE 74 A coelom is an internal fluid filled body cavity that develops in the mesoderm of triploblastic animals The coelom separates the digestive tract from the body wall Diploblastic animals do not have a coelom In triploblastic animals we distinguish between: acoelomate, pseudocoelomate and coelomate animals

  20. These animals have no coelom (body cavity) in the mesoderm • Can be diploblastic or triploblastic

  21. NOT IN TEXTBOOK ADD TO WORKBOOK • Have a body cavity, • Not seen as a true coelom because it is not completely in the mesoderm

  22. Have a body cavity in the mesoderm • They are more advanced than acoelomate animals

  23. PAGE 75

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