Animal Kingdom

Characteristics

* Eukaryotic
* No cell wall
* Reproduce sexually (embryo undergoes state of development)
* ingest/digest food
* mobile

Differences between vertebrates and invertibrates

Invertibrates: Don’t have a backbone, generally small, make up multiple phyla

Vertibrates: have a back bone, generally large, chordates

Characteristics used to classify animals

Levels of organization, #of germ layers, symmetry, body cavities, digestive system, segmentation, mobility, reproduction, nervous system 

Levels of organization

* based on difference sin tissue and organ systems
* Tissue: a group of cells that perform similar functions

\#of germ layers

* Ectoderm: outside (nerve tissue, skin, sense organs)
* Mesoderm: middle (muscles, blood, kidneys)
* endoderm: inner (lungs, liver, kidney, heart)

classified based on whether they have 1/2/3 layers

symmetry

* Asymmetrical body plans: irregular shaped body (sponge)
* Radial symmetry: can be divided along any plane and cut into roughly equal halves
* Bilateral symmetry: can be cut along one plane and divides into 2 equal halves

body cavities

* Coelum: fluid filled body cavity that holds organs in place/developes them
* Organs are contained in body cavity
* Can be:
* coelomate: have
* Acoelomate: without
* pseudocoelomate is similar to coelom but lacks a layer of cells
* Advantages: allows for quick responses and movement and development of complex organs

digestive system

* **No digestive system** (sponges)
* **Incomplete digestive system:** only one opening, food goes in and waste comes out of the same hole
* **Complete digestive system:** digestive tube has 2 openings
* **Protostome:** mouth develops first
* **Deuterostome:** anus develops first

segmentation

* The division of the body into repetitive segments or sections
* Advantages: If one section is damaged, the rest continue to work. Mobility is also more effective

mobility,

* Most animals are mobile
* Sessile: some animals are stationary and stay in one place, but at some point in its early stages it had movement

reproduction

* Reproduce sexually
* produced by either external or internal fertilization
* External: fertilization happens outside of the body
* Internal: Gameters combine inside the body

\*some animals like aphids reproduce sexually/asexually

nervous system 

* Some have it, some don’t
* **Cephalization:**
* nervous tissue is concentrated at one part of an organism (eg. the brain)
* **Ceph:** means brain