A NIMALIA The final kingdom…

G ENERAL C HARACTERISTICS OF A NIMALS Multicellular Heterotrophic No cell walls Eukaryotic Most sexually reproduce

2 MAIN CATEGORIES : Invertebrates No backbone Examples: Vertebrates Backbone Examples

A NIMAL D EVELOPMENT Start off as a single cell Cell undergoes mitosis in which each division results in a doubling of number of cells A hollow ball of cells, called the blastula forms The blastula begins to fold inwards by a process called gastrulation Gastrulation results in the formation of body layers called germ layers

G ASTRULATION portal.com/academy/lesson/gastrulation-and-the- 3-germ-layers-ectoderm-endoderm- mesoderm.html

3 GERM LAYERS 1. Ectoderm: forms outer layer of body (becomes skin, nervous system, feathers, scales, hair, nails) 2. Endoderm: forms inner layer of body (stomach lining) 3. Mesoderm: forms middle layer (becomes organs of circulatory, respiratory, excretory & digestive systems) The more complex an organism is, the more highly evolved & specialized the tissues and organs systems are

B ODY C AVITIES “Simple” animals have a pouch-like gut with only one opening (food enters and wastes leave through the same opening) More complex animals have a gut with two openings (a mouth & an anus) which allows for one-way movement of food Areas of the gut may become specialized for specific activities (grinding or chewing food, or chemical digestion, absorption of nutrients and water)

B ODY C AVITIES Coelom: fluid-filled space or cavity located between gut and body wall → where all internal organs are found Allows more room for organs (lungs, heart, stomach) to grow & develop Allows more space for organs to fold/loop/coil – increases organs surface area to volume ratio

S YMMETRY ( SHAPE ) Assymetrical : no symmetry (no particular pattern) Radial Symmetry : any vertical cut made through the center of the organism will result in two identical halves

S YMMETRY Bilateral Symmetry: organism has a left and right side – only 1 vertical cut through the organism’s centre will result in 2 (relatively) identical halves Symmetry of an organism is related to its development and how much an organism moves Symmetry also provides information about complexity and evolutionary development of an organism Bilateral symmetry is found in more complex and more highly developed organisms

I NVERTEBRATES WITH R ADIAL S YMMETRY Usually sessile (sedentary) or move very little since they do not have a head (there isn’t one region which always leads) Usually dependent on environment to bring them food & to help them reproduce

I NVERTEBRATES WITH B ILATERAL S YMMETRY Are usually motile Usually show cephalization (developed head) in the anterior end Since animals usually move with anterior end first, this end usually contains eyes & sensory organs – allows organisms to detect its environment as it moves (ie. Locate food, danger, changes in the environment) Even though it may appear more advanced to have cephalization, not all organisms need to have a head in order to survive.

B ODY REGIONS Anterior = front end Posterior = back end Dorsal = upper side (backside) Ventral = lower side (belly side) Posterior Anterior Dorsal Ventral