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What was the earth called before life?
How old is the earth estimated to be?
4.5 billion years
How were simple biological chemicals such as amino acids and DNA bases made during early earth?
using energy from lightning--with no consumers of the chemicals, they can accumulate
What can break down the chemicals, so they collect in areas with less sun?
What was probably the first self-replicating molecule?
What are the oldest organisms and how old are they?
- 3.5 to 3.9 billion years ago
What did bacteria use up?
hydrogen sulfide from volcanoes
After bacteria used up hydrogen sulfide from volcanoes, what did it use as its source of hydrogen?
What does bacteria start to produce once it develops photosynthesis?
What is proof of oxygen showing up on Earth?
seeing how old the oldest rust is (rust is oxidized iron)
How long ago did oxygen show up?
2.3 billion years ago
What did oxygen do to some organisms when it first showed up?
How long ago did eukaryotes develop?
1.7 billion years ago
What was the benefit of multicellular organisms?
their larger size made them harder to eat
How long ago did animals show up?
600 million years ago
What are advantages to land life?
- for plants, much stronger sunlight
- higher amounts of nutrients in soil than in water
- no predators (yet)
What are the problems for plants on land?
- need to acquire water--first plants were in wetlands, low to ground
- used to pollinate using water--new plants used eggs and sperm on the same plant, developed pollen, then seeds, flowers
What were the first animals on land?
arthropods (insects, spiders, scorpions, crabs)
Why is development of specialized cells important?
each cell no longer has to do everything, can spend more energy on particular functions
What are skeletons on the outside?
What were probably the ancestor for amphibians?
What were two things that lobefin fish had that helped them transition to land?
- primitive lungs
- fins for crawling
What improvements over amphibians did reptiles have?
- shelled eggs
- internal fertilization
- water resistant skin
What were some advantages for birds and mammals over reptiles?
- feathers, hair
- they could remain active at night
- birds kept feathers and eggs, mammals kept hair, developed live young method of birth
- birds likely descended from reptilian dinosaurs