Bio Lecture 22: Intro to Animals

Defining Characteristics of an Animal

• Eukaryotic and multicellular

• Heterotrophic: needs to consume other things for food/nutrients

• Aerobic: requires oxygen

• Motile at some point in life cycle

• Diploid body form

• Have specialized cells and tissues (nervous and muscle tissue)

Define the 2 Types of Symmetry

• Radial: 2 planes of symmetry, separating 4 identical quarters

• Bilateral: 1 plane of symmetry, separating 2 identical halves

Define the 3 Planes in Bilateral Symmetry

• Midsagittal: divides body exactly in the middle, making 2 equal left & right halves

• Frontal: divides body along vertebrae (front & back)

• Transverse: divides body perpendicular to vertebrate (top & bottom)

1. Anterior

2. Posterior

3. Dorsal

4. Ventral

5. Lateral

1. front

2. rear

3. upper side or towards back of animal

4. lower side or towards stomach of animal

5. side of body (away from midline)

1. Define Coelom

2. Define Vertebrates According to Presence of Coelom

1. fluid-filled space between the body wall and digestive track that accommodates and protects internal organs

2. Categories:

   • Acoelomates: lack a body cavity, and is filled with mesoderm where organs are fixed within mesoderm

   • Pseudocoelomates: have a “false” coelom, lined with mesoderm (muscle) on outer side of cavity where there is some fluid movement and basic organ development

   • Coelomates: have coelom that is fully lined by mesoderm (muscle) and allows for movement and provides cushioning of organs and advanced organ system development

Cephalization

when the sensory organs are concentrated towards the anterior side of the body, forming a head

1. Diploblasts

2. Triploblasts

1. animals with only 2 layers (ectoderm, nonliving layer, endoderm) including jellies, corals, sea anemones, hydras, and comb jellies (Phylum Cnidaria)

2. animals with all 3 layers (ectoderm, mesoderm, endoderm) which includes all bilaterally symmetric animals and Echinodermata

What are the 2 Main Groups of Triploblasts?

1. Protostome

   • Mouth formed first, then anus

   • nerve cord: solid and ventral

   • cleavage pattern: determinate and spiral

   • determinate cleavage: leads to a fixed developmental path for each embryonic cell

2. Deuterostome - humans!

   • Anus formed first, then mouth

   • nerve cord: hollow and dorsal

   • cleavage pattern: indeterminate and radial

   • Indeterminate cleavage: when cells developmental fate is not yet determined

Surface Area:Volume Ratio

there is a max surface area-to-volume ratio for the proper functioning of cells, and ultimately whole bodies. Because diffusion energy is lower in larger animals, there are constraints to the max size of cells and body parts (increased size = increased weight; think if an ant grew to be the size of a human, it has no bones, so it would be crushed under its own weight)