Bio 1109—Chapter 18 9

Bio 1109—Chapter 18 9...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Bio 1109—Chapter 18                            16:31 Prelim = through 18.14 Animals 1.5 million species of organisms known to science, more than 2/3 are animals Humans have a long history of studying animal diversity but classifying an  animal isn’t always easy Animal Evolution and Diversity Animals are eukaryotic, mutlicellular heterotrophs that ingest their food and  usually are capable of movement They lack rigid cell walls and they don’t have alternation of generations Where did they come from? Probably originated from colonial protists Cells in these protists gradually became more specialized and layerd i. Early colony of protists, aggregate of identical cells ii. Hollow sphere  1. Cant be more than one or two cell layers thick, need to be able to have  fluid transfer iii. Beginning of cell specialization iv. Infolding v. Gastrula-like “protoanimal” o What will become part of the digestive cavity—probably a mouth or an  anus
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Most animals are bilaterally symmetrical Animals can be characterized by basic features of their “body plan”—such as  type of symmetry…one on the right has mirror images in terms of its right and  left sides o Radial symmetry—pass a plane through the side of an organism and it  would be symmetrical o Bilateral symmetry—can only pass one plane through the organism such  that you would get mirror images on both sides They also usually have a head with sensory structures and move headfirst  through their environment o Learn the terms on the crustacean Body cavities A fluid-filled space between the digestive tract and the body wall—
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 09/22/2009 for the course BIO G 109 taught by Professor Winkler,d. during the Fall '06 term at Cornell.

Page1 / 9

Bio 1109—Chapter 18 9...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online