Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 25 An Introduction to Animal Diversity

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Characteristics: 1) Animals are heterotrophs that ingest their food 2) Animals are multicellular eukaryotes 3) Their cells lack cell walls 4) Their bodies are held together by structural proteins such as collagen 5)Nervous tissue and muscle tissue are unique to animals 6)Most reproduce sexually

LE 32-2_3 Zygote Eight-cell stage Cleavage Blastula Cross section of blastula Cleavage Blastocoel Endoderm Ectoderm Gastrula Blastopore Gastrulation

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Many animals have at least one larval stage A larva is sexually immature and distinct from the adult; it eventually undergoes metamorphosis Ex: pine beetle and its maggot

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Symmetry Animals can be categorized according to the symmetry of their bodies, or lack of it Some animals have radial symmetry, the form found in a flower pot

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The two-sided symmetry seen in a shovel is an example of bilateral symmetry

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Bilaterally symmetrical animals have: – A dorsal (top) side and a ventral (bottom) side – A right and left side – Anterior (head) and posterior (tail) ends – Cephalization, the development of a head

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Assymetrical - No symmetry at all! A sponge is one of the few good examples

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Terms to know: Zygote – the first cell formed from the union of sperm and egg. Embryo – from the 1 st cell division to birth. In humans it’s until 8 weeks – then called a fetus.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Animal embryos have ringed layers called germ layers that form tissues and organs Ectoderm is the germ layer covering the embryo’s surface (out – skin, nerves) Endoderm (endo = in)is the innermost germ layer like lining of digestive tract.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mesoderm – meso means middle. Makes muscles

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Body Cavities A true body cavity is called a coelom and is made from mesoderm. It is an area that holds organs in place.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Protostome and Deuterostome Development Based on early development, many animals can be categorized as having protostome or deuterostome development In protostome development, the blastopore becomes the mouth In deuterostome development, the blastopore becomes the anus

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Inverts/Verts Two broad categories – Invertebrates 95% of animal species No backbone, vertebral column Examples: bugs, giant squid (over 20 meters long) – Vertebrates 5% of animal species Have backbone, vertebral column