LEC 26 - BIS2C Winter 2009 (Ward) Lecture 26. Animal...

Info iconThis preview shows pages 1–16. Sign up to view the full content.

View Full Document Right Arrow Icon

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

View Full DocumentRight Arrow Icon

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

View Full DocumentRight Arrow Icon

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

View Full DocumentRight Arrow Icon

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

View Full DocumentRight Arrow Icon

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

View Full DocumentRight Arrow Icon

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

View Full DocumentRight Arrow Icon

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

View Full DocumentRight Arrow Icon

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

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: BIS2C Winter 2009 (Ward) Lecture 26. Animal development (contd) & Sponges Todays lecture (25 February) animal development sponges (Porifera) Second Wednesday lecture Cnidaria Radial symmetry : animal in form of cylinder, parts arranged around the long axis, and with multiple imaginary planes that divide the animal into equal halves Organization of animal body plans Symmetry : an animal is symmetrical if at least one plane can divide it into two similar, mirror-image halves Bilateral symmetry : a single plane divides animal into left and right mirror-image halves Organization of animal body plans In bilaterally symmetrical animals: 1. Distinct anterior (front) and posterior (back) ends 2. Cephalization : differentiation of anterior end into a head, with concentration of sensory organs 3. Segmentation : serial repetition of body parts in well-defined segments Animal Development Zygote Blastula Gastrula Cleavage : early stages of cell division after zygote formation, resulting in multiple cells (blastomeres) and establishment of a longitudinal axis (animal-vegetal axis) Animal Development Cleavage : early stages of cell division after zygote formation Patterns of cleavage vary among different animal groups, especially as a function of how much yolk (stored nutrient) is in the egg. In invertebrates we can distinguish two fundamental kinds of cleavage: radial cleavage and spiral cleavage . Animal Development Cleavage : early stages of cell division after zygote formation Radial cleavage : cells divide parallel to, or at 90 to, the animal- vegetal axis, and accumulate in even, symmetrical layers Spiral cleavage : cells divide at an oblique angle to the animal- vegetal axis, and new cells lies in furrows between existing ones Animations available at: http://learning.ucdavis.edu/DevBio/ Animal Development Gastrulation: formation of cell layers by invagination (in-pocketing) of blastula to form gastrula Animal Development Gastrulation: formation of cell layers by invagination (in-pocketing) of blastula to form gastrula Diploblastic animals: two cell layers formed, ectoderm and endoderm Animal Development Animal Development Gastrulation: formation of cell layers by invagination (in-pocketing) of blastula to form gastrula Triploblastic animals: three cell layers formed, ectoderm , endoderm and mesoderm blastula blastula gastrula diploblasty blastula gastrula diploblasty triploblasty Which of the following statements is false ?...
View Full Document

Page1 / 52

LEC 26 - BIS2C Winter 2009 (Ward) Lecture 26. Animal...

This preview shows document pages 1 - 16. Sign up to view the full document.

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