1. 1/31/12
Objective: Understand that the characteristics of organisms change over time
Warm-Up: Give one example of how life on earth has changed since the formation of Earth

2. Vertebrates over Time

3. Background We know that the Earth is 4.6 billion years old!
We also know that there has been life on Earth for about 3.5 billion years
The life that was around 3.5 billion years ago looked very different than the life on Earth today
Humans were not around 3.5 billion years ago
Humans are vertebrates, a group of animals that includes other mammals, fish, amphibians, reptiles, and birds

4. More about Vertebrates
Most of the animals you are most familiar with are vertebrates
Vertebrate means that the animal has a spinal chord protected by a backbone
Some animals are invertebrates, which means that they do not have a backbone
There are some characteristics that all vertebrates share, but there are some important differences
The earliest characteristics, or traits, of vertebrates began to appear in animals about 530 million years ago

5. Common Traits Vertebrae (spinal bones)
Spinal cord (part of the nervous system)
Gills in embryos (an embryo is a developing organism)
Every vertebrate embryo has gills!
Including human embryos

6. Vertebrae

7. Spinal Cord

8. Embryonic Gill Slits

9. Special Traits: Fish
Fish are vertebrates, so they have vertebrae, a spinal cord, and embryonic gills
They also have some unique traits:
Fins
Gills (in adults)
Scales

10. Special Traits: Amphibians
Unlike fish, amphibians have four limbs and lungs
Smooth, moist skin
Jaw has 3 bones
All teeth are the same type

11. Special Traits: Pre-Mammals
Also have four limbs and lungs
Eggs with special membranes
Different kinds of teeth

12. Special Traits: Mammals
Also have four limbs and lungs
Jaw with only 1 bone
Different kinds of teeth
Fur
Eggs with special membranes

13. Special Traits: Reptiles
Four limbs & Lungs
Scaly skin
Eggs with special membranes
Jaw with 3 bones

14. Special Traits: Birds Four limbs & Lungs Feathers Hollow bones
Eggs with special membranes