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Unformatted text preview: BIOLOGY OF ANI MALS LIFE 31 31.3; 40.1; Fig. 4.2 31.1 What evidence indicates the animals are monophyletic?-What traits distinguish the animals from the other groups of organisms ? In contrast to the Bacteria, Archaea, and most microbial eukaryotes , all animals are multicellular and have complex patterns of development all animals are heterotrophs (take in nutrients from their environment ) The fungi are also heterotrophs . In contrast to the fungi, however, animals use internal processes to break down materials from their environment into the organic molecules they need most. Most animals can move // have specialized muscle tissues that allow them to move 31.1.1 Animal monophyly is supported by gene sequences and morphology-most convincing evidence that all the organisms considered to be animals share a common ancestor comes from their many shared derived molecular and morphological traits : Many gene sequences, such as the ribosomal RNA genes , support the monophyly of animals Animals display similarities in the organization and function of their Hox genes Animals have unique types of junctions between their cells ( tight junctions , desmosomes , and gap junctions ) Animals have a common set of extracellular matrix molecules , including collagen and proteoglycans-ancestor of the animal clade was probably a colonial flagellated protist similar to existing colonial choanoflagellates 31.1.2 Developmental patterns show evolutionary relationships among animals-The first few cell divisions of a zygote are known as cleavage . In general, the number of cells in the embryo doubles with each cleavage- cleavage patterns are influenced by the configuration of the yolk , the nutritive material that nourishes the growing embryo-in early development of most animals, distinct layers of cells form differentiate into specific organs and organ systems as development continues // embryos of diploblastic animals have an outer ectoderm and an inner endoderm // embryos of t riploblastic animals have a third distinct cell layer, the mesoderm , which lies between the ectoderm and the endoderm-pattern of development after formation of the blastopore has been used to divide the t riploblastic animals into two major groups: (1) protostomes : mouth arises from the blastopore ; the anus forms later [derived condit ion] (2) deuterostomes : blastopore becomes the anus ; the mouth forms later [ancestral] 31.2 What are the features of animal body plans?- body plan : general structure of an animal, the arrangement of its organ systems, and the integrated functioning of its parts // can be seen as variations of 4 features: (1) body symmetry (2) structure of body cavity (3) segmentation of body (4) external appendages that move the body 31.2.1 Most animals are symmetrical-overall shape of an animal can be described by its symmetry-types of symmetry: Spherical symmetry : body parts radiate out from a central point (i.e. unicellular protists)...
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