EPS SCI 15 Lecture Notes - Lecture 8: Woody Plant, Pikaia, Cycad
29 Apr 2018
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Lec 8: ???
April 26
THE BIG QUESTION: How does novelty arise?
● if there is a selective advantage to having a longer neck → giraffes will eventually
develop longer necks over time (through natural selection)
● How does novelty arise? (ex. dinosaurs with feathers, fish with legs)
○ Pikaia
CASE STUDY: MOVING TO LIFE ON LAND
● Brief Timeline of Transitions to Land → middle to late Paleozoic
○ fungi = ~400 million years ago (Mya)
○ plants = ~420 Mya
○ invertebrates (esp. arthropods) = ~410 Mya
○ vertebrates = ~370 Mya
● Difficulties of moving to land
○ 1) weight bearing
○ 2) heat protection
○ 3) use of water - need to keep & conserve water (in comparison to living
in water)
○ 4) filtering waste products
○ 5) respiratory system - can no longer passively diffuse oxygen from the water
● Why move to land?
○ less competition
(esp. for “founders”)
■ plants = competition for sunlight
■ animals = competition for habitat space
○ more resources
■ oxygen is much more plentiful in air
■ plants = sunlight isn’t diffused in air, like it is in water (more direct
sunlight)
○ escape predation
● Cycad (early plant) Adaptations to Land
○ Traits:
■ Permian (maybe Carboniferous)
■ waxy leaves
■ seeds
■ woody (ligneous) trunk
○ these traits evolved in a stepwise manner
■ first to colonize land
■ mosses
- small & first to invade land
● some protection against desiccation (cuticle)
● need water to reproduce
■ ferns
- strong cuticle & support
Document Summary
If there is a selective advantage to having a longer neck giraffes will eventually develop longer necks over time (through natural selection) How does novelty arise? (ex. dinosaurs with feathers, fish with legs) Brief timeline of transitions to land middle to late paleozoic. Fungi = ~400 million years ago (mya) 3) use of water - need to keep & conserve water (in comparison to living in water) 5) respiratory system - can no longer passively diffuse oxygen from the water. Oxygen is much more plentiful in air. Plants = sunlight isn"t diffused in air, like it is in water (more direct sunlight) These traits evolved in a stepwise manner. Mosses - small & first to invade land. Can transport nutrients & water & support themselves. Seed plants - independent of water for reproduction. Crustaceans (ex. crabs, lobsters, shrimp) = tealliocaris (devonian)
