Slide 1 of 34 Copyright Pearson Prentice Hall Biology

Slide 2 of 34 Copyright Pearson Prentice Hall 29–1 Invertebrate Evolution

Slide 3 of 34 Copyright Pearson Prentice Hall Origin of Invertebrates Invertebrate fossils, dating between 575 and 543 million years ago, were discovered in the Ediacara Hills of Australia and in Chengjiang, China. The Ediacaran fossils include some of the earliest and most primitive animals known.

29–1 Invertebrate Evolution Slide 4 of 34 Copyright Pearson Prentice Hall The fossils: were flat and plate shaped were segmented had bilateral symmetry lived on the bottom of shallow seas were made of soft tissues absorbed nutrients from the surrounding water Origin of Invertebrates

29–1 Invertebrate Evolution Slide 5 of 34 Copyright Pearson Prentice Hall Some of these animals may have had photosynthetic algae living within their bodies. Some may have been related to soft-bodied invertebrates. They were probably simple and had little internal specialization. Origin of Invertebrates

29–1 Invertebrate Evolution Slide 6 of 34 Copyright Pearson Prentice Hall Origin of Invertebrates Beginnings of Invertebrate Diversity By the Cambrian Period, 544 million years ago, some animals had evolved shells, skeletons, and other hard body parts. One of the best-known sites of Cambrian fossils is the Burgess Shale of Canada.

29–1 Invertebrate Evolution Slide 7 of 34 Copyright Pearson Prentice Hall By the Cambrian period, animals had acquired specialized cells, tissues, and organs. During that time, the ancestors of most modern animal phyla first appeared in the fossil record. Origin of Invertebrates

29–1 Invertebrate Evolution Slide 8 of 34 Copyright Pearson Prentice Hall The animals of the Burgess Shale had many of the characteristics of modern day invertebrates including: body symmetry segmentation a skeleton a front and a back end appendages adapted for many functions Origin of Invertebrates

29–1 Invertebrate Evolution Slide 9 of 34 Copyright Pearson Prentice Hall Invertebrate Phylogeny Many features of modern invertebrates evolved during the Cambrian period such as: tissues and organs patterns of early development body symmetry cephalization segmentation formation of three germ layers and a coelom Invertebrate Phylogeny

29–1 Invertebrate Evolution Slide 10 of 34 Copyright Pearson Prentice Hall Invertebrate Evolutionary Relationships Invertebrate Phylogeny

29–1 Invertebrate Evolution Slide 11 of 34 Copyright Pearson Prentice Hall Unicellular ancestor Sponges Cnidarians Flatworms Roundworms Invertebrate Phylogeny

29–1 Invertebrate Evolution Slide 12 of 34 Copyright Pearson Prentice Hall Invertebrate Phylogeny

29–1 Invertebrate Evolution Slide 13 of 34 Copyright Pearson Prentice Hall Invertebrate Phylogeny

29–1 Invertebrate Evolution Slide 14 of 34 Copyright Pearson Prentice Hall What are the major trends in invertebrate evolution? Invertebrate Phylogeny

29–1 Invertebrate Evolution Slide 15 of 34 Copyright Pearson Prentice Hall Evolutionary Trends The appearance of each phylum in the fossil record represents the evolution of a successful and unique body plan. Features of this body plan typically change over time, leading to the formation of many new traits. Evolutionary Trends

29–1 Invertebrate Evolution Slide 16 of 34 Copyright Pearson Prentice Hall Evolutionary Trends

29–1 Invertebrate Evolution Slide 17 of 34 Copyright Pearson Prentice Hall Evolutionary Trends

29–1 Invertebrate Evolution Slide 18 of 34 Copyright Pearson Prentice Hall Specialized Cells, Tissues, and Organs As larger and more complex animals evolved, specialized cells joined together to form tissues, organs, and organ systems that work together to carry out complex functions. Flatworms have simple organs for digestion, excretion, response, and reproduction. More complex animals, such as mollusks and arthropods, have organ systems. Evolutionary Trends

Slide 19 of 34 29–1 Invertebrate Evolution Copyright Pearson Prentice Hall Evolutionary Trends Body Symmetry All invertebrates, except sponges, exhibit some type of body symmetry.

29–1 Invertebrate Evolution Slide 20 of 34 Copyright Pearson Prentice Hall Evolutionary Trends Cnidarians and echinoderms exhibit radial symmetry where parts extend from the center of the body. Radial symmetry Planes of symmetry

29–1 Invertebrate Evolution Slide 21 of 34 Copyright Pearson Prentice Hall Evolutionary Trends Bilateral symmetry Worms, mollusks, and arthropods exhibit bilateral symmetry, or have mirror-image left and right sides.

Slide 22 of 34 29–1 Invertebrate Evolution Copyright Pearson Prentice Hall Evolutionary Trends Cephalization Cephalization is the concentration of sense organs and nerve cells in the front of the body. Invertebrates with cephalization can respond to the environment in more sophisticated ways than can simpler invertebrates.

29–1 Invertebrate Evolution Slide 23 of 34 Copyright Pearson Prentice Hall Evolutionary Trends In most worms and arthropods, nerve cells are arranged in structures called ganglia. In more complex invertebrates, nerve cells form an organ called a brain.

29–1 Invertebrate Evolution Slide 24 of 34 Copyright Pearson Prentice Hall Segmentation Over the course of evolution, different segments in invertebrates have often become specialized for specific functions. Segmentation allows an animal to increase its size with minimal new genetic material. Evolutionary Trends

29–1 Invertebrate Evolution Slide 25 of 34 Copyright Pearson Prentice Hall Coelom Formation Flatworms are acoelomates. This means they have no coelom, or body cavity, that forms between the germ layers. Digestive cavity Acoelomate Evolutionary Trends Ectoderm Mesoderm Endoderm

29–1 Invertebrate Evolution Slide 26 of 34 Copyright Pearson Prentice Hall Pseudocoelomates have a body cavity lined partially with mesoderm. Evolutionary Trends Pseudocoelomate Pseudocoelom Digestive tract

29–1 Invertebrate Evolution Slide 27 of 34 Copyright Pearson Prentice Hall Most complex animal phyla have a true coelom that is lined completely with tissue derived from mesoderm. Coelom Digestive tract Evolutionary Trends Coelomate

29–1 Invertebrate Evolution Slide 28 of 34 Copyright Pearson Prentice Hall Embryological Development In most invertebrates, the zygote divides to form a blastula—a hollow ball of cells. In protostomes, the blastopore, or the opening of the blastula, develops into a mouth. In deuterostomes, the blastopore forms an anus. Evolutionary Trends

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Slide 30 of 34 Copyright Pearson Prentice Hall 29–1 According to the most recent studies of animal fossils, which of the following is correct? a.Annelids with a true coelom appeared before cnidarians with two germ layers. b.Radial symmetry appears in cnidarians and adult echinoderms. c.Protostome development appears after deuterostome development. d.Bilateral symmetry appears before tissues.

Slide 31 of 34 Copyright Pearson Prentice Hall 29–1 Acoelomates lack a.tissues. b.a coelom. c.radial symmetry. d.specialized cells.

Slide 32 of 34 Copyright Pearson Prentice Hall 29–1 Worms, mollusks, and arthropods exhibit a.bilateral symmetry. b.radial symmetry. c.no internal specialization. d.similar larval forms.

Slide 33 of 34 Copyright Pearson Prentice Hall 29–1 In most invertebrates, the zygote divides repeatedly to form a a.coelom. b.digestive tract. c.blastula. d.mesoderm.

Slide 34 of 34 Copyright Pearson Prentice Hall 29–1 The animal group that has no germ layers, body symmetry, cephalization, or coelom is the a.flatworms. b.annelids. c.sponges. d.cnidarians.

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