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Introduction to Animal Diversity. Packet #76 Chapter #32. Animal Diversity. Biologists have identified 1.3 million living species if animals. Estimates put the range much higher 10 – 200 million
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Introduction to Animal Diversity Packet #76 Chapter #32
Animal Diversity • Biologists have identified 1.3 million living species if animals. • Estimates put the range much higher • 10 – 200 million • Evolutionists believe that the chanoflagellates, a colonial flagellated protist, was the start of Kingdom Animalia.
Characteristics Most Common to Animals • Eukaryotic • Multicellular • Heterotrophic • Animals use enzymes to digest their food after they have ingested it. • Stores energy as fat (long term) or as glycogen (short term)
Reproduction—The Obvious • Most animals reproduce sexually and have a diploid stage that is dominant in the life cycle. • Sperm and egg unite to form a zygote • Zygote undergoes cleavage • Multiple cell divisions result in the development of a hollow ball of cells • Blastula • Blastula undergoes gastrulation. • Embryonic tissues are formed • Developmental stage is called the gastrula.
Reproduction—The Sometimes Not So Obvious • Some animals develop directly into adults • After transient stages of maturation • However, life cycle of many animals include larval stages. • Larva • Sexually immature form of an adult • Morphologically distinct • Usually eats different food • Inhabits different areas than the adult • Must undergo metamorphosis to become an adult
Developmental Genes Across Kingdom Animalia • Animals share a unique homeobox • Family of genes • Hox genes • The number of hox genes is correlated with the complexity of the animal’s anatomy.
Categorizing Kingdom Animalia • Animals are classified on major features of animal body plans. • Symmetry • Tissue Complexity • Cephalization • Body Cavities
Body Plans Symmetry
Introduction • There are two types of symmetry • Radial Symmetry • Bilateral Symmetry
Symmetry • Radial Symmetry • Describes how the parts of an animal radiate from the center. • Any imaginary slice through the central axis divides the animal into mirror images. • Sea anemones have a top (oral, mouth) side and a bottom (aboral) side.
Symmetry II • Bilateral Symmetry • Describes a two sided body plan. • Animal has a left side and right side • Imaginary slice can only be placed in one location in order to divide the animal mirror images. • Lobster has a dorsal (top) side, a ventral (bottom) side, a left and right side, an anterior (head) with a mouth and a posterior (tail) end.
Symmetry III • Animals can be categorized according to the symmetry of their bodies or lack of it. • Symmetry Reflects Lifestyle • Radial animals are sessile or planktonic • Bilaterial animals more actively from one place to another • The nervous system enables these organisms to move.
Tissue I • As a young embryo develops, embryonic tissue, called germ layers, are produced via gastrulation. • There are three germ layers • Ectoderm • Endoderm • Mesoderm
Tissue II • Ectoderm • Outer layer • Gives rise to the body covering and the nervous system • Endoderm • Inner layer • Gives rise to the lining of the gut (archenteron) and other digestive organs • Mesoderm • Middle layer • Gives rise to most other body structures. • Including muscle
Diploblastic vs. Triploblastic • Diploblastic • Animals with only two layers • Ectoderm and Endoderm • Jellies • Corals • Comb jellies • Triploblastic • Animals with all three layers • Include all bilaterally symmetric animals.
Functions of Body Cavities • Provides protection to internal organs • Allow organs to grow and move independently of the outer body wall.
Body Cavity I • Triploblastic animals have traditionally been classified as • Acoelomates [ey-see-luh-meyt] • No body cavity • Lack a coelom. [see-luhm] • Pseudocoelomate [soo-doh-see-luh-meyt, -si-loh-mit] • Body cavity not completely lined with mesoderm • Body cavity formed from the blastocoel. • Coelomate • True coelom • Body cavity completely lined with mesoderm. • Cushions the internal organs and protects them.
Formation of the Coelom [see-luhm] • Coeloms can be divided into two categories based on how it is developed. • During gastrulation, developing digestive tube forms the archenteron. • Protostomes • Development of the coelom forms from splits in the mesoderm • Schizocoelous Development • Deuterostomes • Development of the coelom forms from outpocketing of the mesodermal tissue of the archenteron. • Enterocoelous Development
Introduction I • Protostomia • Mollusks • Annelids • Arthropods • Deuterostomia • Enchinoderms • Chordates
Protostomes • Blastopore develops into the mouth • Undergo spiral and determinate cleavage • Spiral cleavage • Describes how the planes of cell division are diagonal to the vertical axis of the embryo. • Smaller cells lie in the grooves between larger, underlying cells • Determinate cleavage • Indicates that the developmental fate of each embryonic cell is determined at fertilization. • If cell is isolated it will form an inviable embryo.
Deuterostomes • Blastopore typically becomes the anus. • Undergo radial and indeterminate cleavage. • Radial cleavage • Cleavage planes are either parallel or perpendicular to the vertical axis of the egg • Indeterminate cleavage • Each cell produced by early cleavage divisions has the capacity to develop into a complete embryo.
