Animals

challenges faced by early animals in their attempts to colonize land:

• food source

• effect of gravity —> strong muscular system and bones/backbone

• keeping moisture —> osmoregulation rather than simple diffusion

• movement

• gas exchange

  • gills —> lungs

  • need complex circulatory system for the exchange of gases and nutrient circulation due to low surface area to vol ration.

• reproduction —> external to internal fertilization

  • oviparous (lay eggs)- birds/ amphibians

  • ovoviviparous - amphibians

  • viviparous - mammals

Common Characteristics of Animals:

• multicellular

• heterotrophs - diverse modes

• no cell walls = flexibility

• nervous tissue = rapid response

• muscle tissue = movement

• sexual reproduction:

  • small, mobile sperm

  • larger egg

  • diploid from a blastula

• extracellular matrix: collagen

• special clusters of Hot genes: patterns body axis

• similar rRNA

• characteristic cell junctions:

  • anchoring

  • tight

  • gap

Animal Evolution:

1. Cellular Level - Porifera

   • aggregations of cells, groups with specialized functions

   • divisions of labor

2. cell-tissue Level - Cnidaria, Ctenophora

   • Tissue = groups of similar cells arranged in definite patterns or layers with a common function

   • many scattered cells still present

   • types of tissue:

     • epithelial tissue

     • connective tissue

     • muscular tissue

     • nervous tissue

3. Tissue-organ level - Platyhelminthes

   • tissues arranged into organs

   • organs consists of multiple tissue types and has a very specialized function

4. Organ-system level

Body Systems:

• integumentary System

• Muscular System..

• Skeletal System