divided into phyla according to obvious differences in their body plan.
groups of animals according to differences in body plans. 30 different phyla among living animals. ex- chordates, anthropods, sponges, etc.
make up the vast majority of earth's animals. sources of animal protein for humans. contribute to crop pests and disease vectors.
represents 5% of living animals. human's phylum.
important trend of animal evolution. ability to move- most important factor driving evolution of animal body plan.
7 major innovations for locomotion
1. bilateral symmetry
3. Body cavities
6. Skeleton and Jointed Appendages
7. Complex Nervous and Sensory System
characteristic of more complex animals. longitudinal cut will produce equal halves. usually have complex nervous tissue at the anterior end. extensive set of muscles. more active and mobile. cephalization. increased metabolic rate. allowed foro specialization of body parts.
body plan where any cut through central axis results in 2 equal halves. pie-like. usually sessile (little mobility), sit and wait predators. able to monitor environment in all directions. low metabolic rates.
nervous tissue and sense organs are concentrated in the anterior.
radial cnadarian. sessile. captures prey with nematocysts on tentacles.
bilateral flatworm. simplest animal that posesses a true organ system (two or more tissues and specialized function). have simple nervous system, excretory and digestive systems. Tripoblastic
benefits of bilateral movement
seeking mates, locating food, escaping enemies.
animals whose embryos have three tissue layers (ectoderm, endoderm and mesoderm.) mesoderm gives rise to major body muscles. forms complex sense organs on the head.
primitive animals (like Hydra) come from embryos with two tissue layers. ectoderm and endoderm.
Internal Body Cavities
major organ systems suspended in fluid filled internal body cavities. allow organs to function without pressures from muscle contractions. fluid acts as circulatory system.
3 Types of Tripoblastic, Bilaterally Symmetric Animals
Acoleomates, Pseudocoelomates and Eucoelomates
no body cavity besides digestive system. ex- flatworm
a body cavity develops between the mesoderm and endoderm. Ex- nematodes (roundworms)
body cavity develops from an opening of tissues within the mesoderm- called eucoelom. digestive and reproductive systems form within coelom. tube within a tube body plan.
parasitic roundworm of swine and humans. contains a pseudocoelom.
earthworm. coelom separates the body wall from the digestive tract.
serial succession that occurs in a segmented body.
Advantages of serially homologous segments
1. duplication of function can allow animal to survive damage to a segment
2. independent movement allows for flexibility. more effective locomotion
3. different segments can modify to perform special functions.
Segmentation in Arthropods
crayfish's body is segmented. each segment has modified to perform different tasks, maintain the same design.
Segmentation in Chordates
Lancelets: muscle segmentation. Humans: abdomen muscles.
segments are fused into functional units.
advantages of tagmosis
several segments working in a coordinated manner have greater effect than working independently.
Tagmosis in Arthropods
segments of crayfish fuse to form cephalothorax. extensive tagmosis. posterior segment forms the abdomen.
tagmosis in chordates
segmentation hard to see externally in chordates. head of perch becomes integrated for feeding, respiration. many chordates based off of segmental plan.
occured in arthropod and chordate lineages. facilitates movement and feeding. elevate the body above substrate. increase leverage. requires rigid skeleton.
Jointed Skeletons and Appendages in Arthropods
crayfish have hard exoskeltons that give protection and structural support.
Nervous and Sensory Systems
highly mobile animals need to develop sensory systems to take in the quickly changing world and a brain to process information.