Review: Evolution of Life

• First life on Earth are prokaryotes (bacteria)

• Endosymbiosis gives rise to eukaryotes (protists)

• Photosynthetic protists give rise to plants

• Aquatic, single-celled flagellated protists give rise to fungus

• Fungus gives rise to animals

KINGDOM ANIMALIAMulticellular eukaryotes that ingest their food

Characteristics of Animals• All animals share certain characteristics:– Multicellular eukaryotes– Heterotrophic ingest their food• Ingestion – take food into body, digest internally• Carnivores, herbivores, omniovores, detritivores

Characteristics of Animals, cont.

• Most reproduce sexually• Development:

How are animals classified?

• Four key characteristics for classification Body Plan

1. Symmetry2. Tissues3. Body cavities4. Pattern of development

1. Symmetry

• 3 types:

2. Tissues

• Presence of true tissues– Group of similar cells that work

together to perform a specific function

• Form from germ layers during development– Ectoderm: covers surface– Endoderm: innermost germ layer– Mesoderm: fills space between

ectoderm and endoderm• Animals can be:

– Diploblastic (“two layered”) or– Triploblastic (“three layered”)

3. Body Cavities

• Coelom = fluid-filled space separating the digestive tract from the outer body wall

DigestiveCavity

BodyCavity

DigestiveTract

OuterBodyWall

3. Body Cavities, cont.

• Three types of body cavities:

1. Acoelomate (“lacking cavity”)– No body cavity solid body,

space filled with mesoderm

2. Pseudocoelomate (“false cavity”)– Cavity forms between

mesoderm and endoderm

3. Coelomate – Cavity forms within the

mesoderm

4. Pattern of Development

• Protostome or deuterostome depending on cell cleavage and fate, coelom formation, and fate of blastophore

Protostome Deuterostome

1. Cell cleavage Spiral Radial

2. Cell fate Determinate Indeterminate

3. Fate of blastophore Mouth Anus

4. Coelom formation Mesoderm splits Mesodermal outpocketings

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=Syq4NWHGxxRUzM&tbnid=Y-1eDjCNFUEZLM:&ved=0CAUQjRw&url=http%3A%2F%2Fwww.baileybio.com%2Fplogger%2F%3Flevel%3Dpicture%26id%3D1490&ei=TsycUpCVEMXYyAHn64HgCg&psig=AFQjCNGWxjOKWEl195Vpg1rpTuqZYV4z-Q&ust=1386093963722077