LESSON 2: Plant origins Flashcards
What type of life was present on Earth 541 mya?
Nothing (no birds, animals, nor plants).
What happened in preceding eons that radically changed Earth’s atmosphere?
Cells that produced oxygen as a by-product of photosynthesis evolved.
In the preceding eons, what happened to the oxygen produced by some cells?
Solar radiation converted it into a dense ozone layer that acted as a shield for lethal doses of ultraviolet radiation.
How did the ozone layer affect the early organisms living below water’s surface!?
With more protection against ultraviolet radiation, they were able to populate the land.
What do we call a rapid evolution and divergence of varied species?
Radiation
What brought on a dramatic radiation of varied plant species?
Ecological opportunities (ozone layer + cells) and the quantity of ressources available such as nutrients, light and space.
What are the 4 challenges ancestral green algae had to overcome in order to give rise to land plants?
1) Avoiding desiccation
2) Physically supporting the plant body in air
3) Obtaining nutrients from soil
4) Reproducing sexually in environments where water would not be available for dispersal of eggs and sperm
What are the ancestors of modern plants? Where did they lived?
Charophytes. They lived near water’s edge or in a moist terrestrial environment 480 mya.
What is a synapomorphy in phylogenetics?
A shared derived trait that comes from a common most recent ancestor.
What is an homoplasy in phylogenetics?
A shared trait that is due to convergent evolution, not to a comment ancestor.
What 3 synapomorphies do land plants and green algae share?
1) Cellulose cell walls
2) Store energy captured during photosynthesis as starch
3) Their light absorbing pigments include both chlorophyll a and b
What are the 4 majors steps of plant evolution?
1) Move to land
2) Vascular tissue
3) Seeds
4) Flowers
What group represents the movement to land evolution?
Bryophytes
What group represents the apparition of vascular tissue evolution?
Seedless vascular plants
What group represents the evolution of seeds?
Gymnosperms
What group represents the evolution of flowers?
Angiosperms
