# Chapter 34

## Subphylum Vertebrata

- Vertebrates
- Chordates with a backbone

Chordate features as well as:

1. Vertebral column 
    - Series of cartilaginous or bony elements
2. Cranium
3. Endoskeleton or cartilage or bone
4. Hox genes (lots of them)
5. Neural crest

[![Screenshot-from-2019-01-29-11-59-40.png](https://bookstack.aronwk.com/uploads/images/gallery/2019-01-Jan/scaled-840-0/WnHIpkqEgDgAE0Qr-Screenshot-from-2019-01-29-11-59-40.png)](https://bookstack.aronwk.com/uploads/images/gallery/2019-01-Jan/WnHIpkqEgDgAE0Qr-Screenshot-from-2019-01-29-11-59-40.png)

[![Screenshot-from-2019-01-29-12-07-52.png](https://bookstack.aronwk.com/uploads/images/gallery/2019-01-Jan/scaled-840-0/HnAoBE4j1MFZmLVK-Screenshot-from-2019-01-29-12-07-52.png)](https://bookstack.aronwk.com/uploads/images/gallery/2019-01-Jan/HnAoBE4j1MFZmLVK-Screenshot-from-2019-01-29-12-07-52.png)

### Cyclostomes

- Jawless Fishes

#### Class Myxini

- Hagfishes
- lack jaws, eyes, fins vertebrae
- skeleton comprised of notochord and cartilaginous skull
- covered in slime

#### Class Cephalospidomorphi

- Lampreys
- Has notochord, and cartilaginous vertebral column
- lacks jaws and appendages (fins)
- Oldest fossil records 510 mybp

### Class Chondrichthyes

- Cartilaginous fishes
- Sharks, skates, rays
- Cartilaginous skeleton and notochord as adults
- jawed fishes
- paired appendages (fins)
- < 900 species

### Class Osteichthyes

- Bony fishes
- Most diverse vertebrate group with < 26,000 species
- Bony skeleton (most do have this)
- Jawed
- paired appendages (fins)

## Tertapod: Gnathastomes

- Four limbs with jawed mouth
- Transition to land involved adaptions for locomotion, reproduction, desiccation (drying out) prevention, and gas exchange
- Sturdy lobe-finned fishes became animals with four limbs
- Vertebral column strengthened, ship and shoulder bones braced against backbone
- relatively simple changes in gene expression, especially Hox genes

### Class Amphibia

- >4000 species
- Amphibios 
    - greek - "living double life"
    - split their life between aquatic and terrestrial stages
- Successfully invaded land but reproduce in water
- Lunges are and adaption to semi-terrestrial lifestyle
- Three chambered heart 
    - Fishes only have a two chambered heart
- External Fertilization
- Larval stages are aquatic 
    - Undergo metamorphosis
- Not completely separated from water

[![Screenshot-from-2019-01-29-12-33-08.png](https://bookstack.aronwk.com/uploads/images/gallery/2019-01-Jan/scaled-840-0/SlypUH0QiIkh947E-Screenshot-from-2019-01-29-12-33-08.png)](https://bookstack.aronwk.com/uploads/images/gallery/2019-01-Jan/SlypUH0QiIkh947E-Screenshot-from-2019-01-29-12-33-08.png)

#### Order Anura

- Frogs and toads
- Nearly 90% of amphibians
- Carnivorous adults 
    - Herbivorous tadpoles

#### Order Apoda

- Caecilians
- Nearly blind tropical burrowers
- Secondarily legless

#### Order Urodela

- Salamanders
- Often have colorful skin patterns
- Most have four limbs

[![Screenshot-from-2019-01-29-12-33-21.png](https://bookstack.aronwk.com/uploads/images/gallery/2019-01-Jan/scaled-840-0/nX9GLgeq5Sx2Mdqq-Screenshot-from-2019-01-29-12-33-21.png)](https://bookstack.aronwk.com/uploads/images/gallery/2019-01-Jan/nX9GLgeq5Sx2Mdqq-Screenshot-from-2019-01-29-12-33-21.png)

## Amniotes

- Tetrapods with a desiccation resistant egg
- Critical innovation 
    - Development of a shelled egg
- Amniotic egg 
    - Broke the tie to water
    - Three internal membranes
- Shell is permeable to Oxygen and CO2 
    - Birds 
        - Hard and Calcareous
    - Reptiles 
        - Soft and Leathery
    - Most Mammals 
        - Embryo embeds in uterine wall
        - Only three species lay eggs 
            - These eggs are soft and leathery

[![Screenshot-from-2019-01-29-12-33-34.png](https://bookstack.aronwk.com/uploads/images/gallery/2019-01-Jan/scaled-840-0/flHkihcFr9Y2C9EF-Screenshot-from-2019-01-29-12-33-34.png)](https://bookstack.aronwk.com/uploads/images/gallery/2019-01-Jan/flHkihcFr9Y2C9EF-Screenshot-from-2019-01-29-12-33-34.png)

#### Other Key Innovations of the Amniotes

- Desiccation resistant skin 
    - contains keratin
- Thoracic breathing 
    - Negative pressure sucks air in
- Water conserving Kidneys 
    - Concentrate waste prior to elimination
- Internal fertilization

### Class Reptilia

- >8000 living species
- turtles, crocodilians, lizards, snakes
- Can live away from water
- thicker skin and scales
- larger brain
- larger limbs with muscles
- enhanced kidneys
- Amniotic egg 
    - "indoor pond"

## Vertebrate Reproductive Modes

1. Oviparous 
    - Egg laying outside of the body
2. Ovoviviparous 
    - live baring wuth retention of eggs
    - No maternal connection
3. Viviparous 
    - live bearing with egg retained
    - Maternal connection

### Class Aves

- Birds
- Evolved form small dinosaurs
- Fossils 150mybp
- Adaptions for flight 
    - Feathers
    - Modified front limbs
    - Lightweight skeleton
    - Organ reduction
    - Lungs and air sacs 
        - more gas exchange
- Oviparous 
    - all leg layers
- Bill beak 
    - Encloses mouth and nasal cavity
    - Adapted for environment

[![Screenshot-from-2019-01-29-13-16-50.png](https://bookstack.aronwk.com/uploads/images/gallery/2019-01-Jan/scaled-840-0/zbb1SszkDwvQJVu5-Screenshot-from-2019-01-29-13-16-50.png)](https://bookstack.aronwk.com/uploads/images/gallery/2019-01-Jan/zbb1SszkDwvQJVu5-Screenshot-from-2019-01-29-13-16-50.png)

### Endothermic

- "Internal temperature"
- Body temperature is primarily controlled by trapped metabolic heat.
- Birds and mammals

### Ectothermic

- "External temperature"
- Body temperature is primarily related to external temperature
- Metabolic heat is generated but difficult to capture/maintain the heat
- Fishes, amphibious, reptiles

## Class Mammalia

- Milk producing Amniotes
- Evolved from amniote ancestors (reptiles) earlier than birds
- >6000 species
- Appeared ~ 225mybp 
    - Evolved from small mammal-like reptiles
- After dinosaur extinction, mammals flourished
- Range of sizes, body forms, and complexity unmatched

[![Screenshot-from-2019-01-29-13-17-55.png](https://bookstack.aronwk.com/uploads/images/gallery/2019-01-Jan/scaled-840-0/7WdVRMuItPyYC12W-Screenshot-from-2019-01-29-13-17-55.png)](https://bookstack.aronwk.com/uploads/images/gallery/2019-01-Jan/7WdVRMuItPyYC12W-Screenshot-from-2019-01-29-13-17-55.png)

- Fish-like mammals 
    - Marine mammals
- Bird-like mammals 
    - Bats
- Reptile-like mammals 
    - Three egg layers

#### Distinguishing Characteristics

- Mammary Glands 
    - Secrete milk
- All have hair 
    - In varying amounts
- Only vertebrate with multiple dentitions 
    - Heterodont 
        - Different types of teeth
        - incisors, canines, molars, premolars
    - Thecodont 
        - Teeth with long roots embedded in sockets of jawbone
    - Diphyodont 
        - Milk teeth that are mostly replaced by "adult" teeth later in life
- Pinna 
    - Flap of cartilage and lose connective tissue to channel and funnel sound
    - The "outer ear"
- Three middle ear ossicles (bones)
- Enlarged Skull 
    - Brain enlarged in large skull
    - Larger Cerebrum
    - Single lower Jawbone (Dentary)
- Anucleate red blood cells

[![Screenshot-from-2019-01-29-13-18-32.png](https://bookstack.aronwk.com/uploads/images/gallery/2019-01-Jan/scaled-840-0/4T0eaG8FZ1VQCGsf-Screenshot-from-2019-01-29-13-18-32.png)](https://bookstack.aronwk.com/uploads/images/gallery/2019-01-Jan/4T0eaG8FZ1VQCGsf-Screenshot-from-2019-01-29-13-18-32.png)

### Order Primates

- Primarily tree dwelling species
- grasping hands with opposable thumbs
- Large brain
- Some digits with flat nails 
    - Not claws
- Binocular vision
- Complex social behavior and well-developed parental care
- Enhanced sense of touch

[![Screenshot-from-2019-01-29-13-22-59.png](https://bookstack.aronwk.com/uploads/images/gallery/2019-01-Jan/scaled-840-0/pABbbU53BdQRpHGJ-Screenshot-from-2019-01-29-13-22-59.png)](https://bookstack.aronwk.com/uploads/images/gallery/2019-01-Jan/pABbbU53BdQRpHGJ-Screenshot-from-2019-01-29-13-22-59.png)

## Taxonomy of Humans

- **Kingdom** *Animalia*
    - **Phylum** *Chordata*
        - **Subphylum** *Vertebrata*
            - **Class** *Mammalia*
                - **Order** *Primates*
                    - **Suborder** *Anthropoidea*
                        - **Superfamily** *Hominoidae*
                            - **Family** *Hominidae*
                                - **Subfamily** *Homininae*
                                    - **Tribe** *Hominini*
                                        - **Genus** *Homo*
                                            - **Species** *Homo* s*apiens*