5.5 : History of life

• Biologie
• Middelbare school
• vwo
• Leerjaar 3

BS 5 - History of life

Fossils

1. Created when remains of organisms do not decay
   
2. Deposited layers of clay or sand cover the remains
   
3. Bacteria unable to do their work - the process of decay is stopped
   
4. Other layers of sand/clay cover the remains and over time mineralize
   

Geological timescale

• Geological time scale: Division of the     Earth's history into geological eras.
• Life on Earth evolved in these eras.
• Each era is divided into periods. 
• Periods can be divided into time slots
• Numbers indicate time in millions of years ago.
  
• You can see how many million years ago a period started and ended.

Animals on land

1. First land plants = 500 mya
   
2. Fish appeared around the same time
   
3. First land animals = 450 mya
   
4. Arthropods (centipedes in particular)
   
5. Followed by amphibians and reptiles
   
6. Reptiles were quite successful = dinosaurs  251 mya
7. First mammals and birds appeared alongside dino
   
8. Dinos wiped out 65 mya
   
9. Meteor collision with earth - Created black cloud of dust that hung over the earth’s surface for years
10. Darkened the sky = temp dropped = climate change
11. Hominids appeared 3 mya
    
12. Homo sapiens appeared 150,000 years ago

Rudimentary organs