introduction to animal evolution chapter 32. animals 1 st appeared in precambrian in waters, spread...
TRANSCRIPT
Introduction To Animal Evolution
Chapter 32
• Animals 1st appeared in Precambrian in waters, spread to land.
• 5 criteria that define animal:• 1Animals multicellular, must get
food through ingesting other organisms or organic material.
http://www.biology.wustl.edu/plant/simplealgalsystems1.jpg
• 2Animals do not have cell walls.• 3Animals have nervous tissue to
conduct impulses and muscle tissue for movement.
• 4Most animals reproduce sexually with diploid stage being dominant.
• 5Animals have special regulatory genes (Hox genes) help zygote form into animal.
Branching of evolutionary tree
• 1st branch point splits Parazoa (lack true tissues) from Eumetazoa (true tissues).
• Parazoa include sponges.• Eumetazoans divided into 2
major branches, partly based on body symmetry.
http://www.sciencedaily.com/images/2007/07/070705153000.jpg
• Radial symmetry - phylum Cnidaria and phylum Ctenophora.
• Bilateral symmetry (left and right side) - rest of phyla.
• Bilateral symmetry - cephalization, - concentration of sensory equipment towards head.
• Difference between 2 groups - presence of germ layers - layers of embryonic tissue that form various tissues and organs.
http://www.guam.net/pub/sshs/depart/science/mancuso/apbiolecture/27_Animalia/Annelida/Image11.gif
• Bilaterally symmetric animals - 3 germ endoderm (innermost), mesoderm (middle) ectoderm (outermost).
• Bilateral animals split according to presence of body cavity (fluid-filled space separating digestive tract from outer body wall) and what cavity looks like.
http://universe-review.ca/I10-13-layers.jpg
• Acoelomates (phylum Platyhelminthes) have solid body, lack body cavity.
• Some organisms - body cavity - not completely lined by mesoderm.
• Pseudocoelomates include rotifers (phylum Rotifera), roundworms (phylum Nematoda).
• Coelomates organisms with true coelom, (fluid-filled body cavity completely lined by mesoderm).
• Body cavity has many purposes including cushioning organs, allowing them more room to grow.
• Coelomate phyla divided based on differences in development.
• Many protostomes (mollusks, annelids, arthropods) undergo spiral cleavage.
• In many protosomes, blastopore develops into mouth; 2nd opening at opposite end of gastrula develops into anus.
http://chsweb.lr.k12.nj.us/mstanley/outlines/animals/antax/image51.gif
• Zygotes of many deuterostomes undergo radial cleavage.
• Deuterostomes - blastopore usually develops into anus, mouth derived from 2nd opening.