History of Life on Earth Flashcards
Approximate age of planet Earth
4.6 billion years
How many million years in 1 billion?
1000
Years ago that scientists see the first evidence of life on our planet?
3.8 billion years ago
Anaerobic
Organisms which do not need oxygen to obtain energy from food
Aerobic organisms
Organisms require oxygen for obtaining energy from food.
Increased oxygen levels in te atmosphere resulted in…
- Increased variety of living organisms
- One hypothesis is that this resulted in the Cambrian Explosion
Fate of most initial oxygen released into the oceans and atmosphere
Reacted to form oxides e.g. iron oxide (rust)
Ice ages
- Periods of drastic decreases in temperature of the earths surface and atmosphere
- Glacers form, especially over the poles
Glaciation
Large ice sheets form, especially over the poles, due to cooling temperatures
Example global changes during a shift towards an ice age
- Lower temperatures,
- Species shift ranges towards equator where it is warmer,
- Climate drier as less evaporation and more ice,
- Sea level drops affecting aquatic habitat ranges,
- Extinctions as species lose habitat
Ice age status we are currently experiencing
- We are currently in an “ice age”
- We are currently experiencing a warmer “interglacial” period with smaller ice caps.
- Human impact on the environment means we are causing unprecedented global warming effects.
Continental drift
The gradual movement of the continents across the earth’s surface through geological time.
Pangaea
- Pangaea was the single supercontinent that existed from earlier continental units
- From approximately 300 million years ago
- It began to break apart about 175 million years ago.
The two continents formed when Pangaea split up
- Gondwana
- Laurasia
Who introduced the Theory of Continental Drift?
Alfred Wegener (1912)
Example evidence for Continental Drift
- Geological similarities between varying locations around the globe
- Fossil comparisons from different continents
- The jigsaw puzzle shape of the landmasses on Earth.
The mechanism for continental drift.
Plate Tectonics
Biogeography
The study of the distribution of species and ecosystems in geographic space and through (geological) time.
Fossils
- Preserved complete organisms/ organism remains/ imprints or traces of organisms
- Usually preserved in rock
The study of plant and animal fossils
Palaeontology
Scientists who study fossils
Palaeontologists
Some uses of fossils
- Evidence of earlier life on earth
- Give indications of past environments (e.g. climates)
- Help geologists to create the geological time scale (e.g. by using known index fossils)
Marine or freshwater mollusc with a soft body in a shell of thwo parts
Bivalve
An extinct marine snail with a flat, spiral shell divided into chambers with wavy interlocking walls.
Ammonites
