Lecture 9: Plants Cool the Planet Flashcards
What are the three eras in the Phanerozoic Eon?
Palaeozoic, Mesozoic, Cenozoic
What are the 6 periods within the Palaeozoic era in chronological order?
Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian
What are the three periods within the Mesozoic era in chronological order?
Triassic, Jurassic, Cretaceous
What are the two periods within the Cenozoic era in chronological order?
Tertiary, Quaternary
Which era in the Phanerozoic eon is the biggest?
Palaeozoic
Give 6 characteristics of the earth before the presence of plants?
Less oxygen 15X more CO2 7 degrees warmer Anoxic Ocean Arthropod tracks Freshwater algae (ancestors of land plants)
What was the process that led to the creation of eukaryotic algae?
Around 2.5Ga cyanobacteria were consumed by eukaryote cells to become photosynthesising algae
What do the eukaryotic algae start to do in the Proterozoic eon?
Make multi-cellular sea weeds and freshwater algae
What are bryophytes?
Earliest forms of land plants reliant upon moist habitats which are also not able to maintain their water pressure so were therefore quite floppy
What is the significance of bryophytes?
They are the earliest forms of land plants even though they are still reliant upon very moist environments
When were the earliest land plants discovered?
Ordovician period
Because it is difficult to find fossils of the earliest land plants, how are they analysed?
Through the spores that they produced which are hard and therefore well preserved in the ground
When and what are the first fragments of actual land plant discovered?
460Ma Bryophyte remains
What are bryophytes?
Part of a plant that are responsible for releasing spores
What are trilete spores and when were they found?
~445Ma. These are type of pollen spore which are resistant against dry conditions suggesting that they had evolved from initially being heavily reliant upon moist environments
When were the first vascular plants uncovered?
~425Ma in the Silurian period.
What are important characteristics of the first vascular plants?
They can maintain their internal water pressure which allows them to keep shape. No leaves or roots means the photosynthetic pigment would be in stem and branches
How efficient was the photosynthesis process carried out by the first vascular plants? and why?
Not very - because the photosynthesis pigment is in the stem probably
What discovery was made toward the end of the Silurian period?
Fossils of bigger plants such as clubmosses which had interesting leaf structures and roots that would have been more efficient when carrying out photosynthesis compared to the first vascular plants
When were the first clubmosses discovered in the late Silurian?
~420Ma
What are protaxites fossils?
Not sure exactly - probably giant fungi due to variance of carbon isotope composition
When were the first protaxite fossils discovered?
420-370Ma
What phenomenon was thought to be responsible for preserving a whole ecosystem in good condition during the early Devonian period and what date exactly?
A volcanic phenomenon ~410Ma
What did the ecosystem that was preserved by the volcanic eruption in the early Devonian consist of?
Plants, fungi and insects. Interactions between these different forms of life were evident
What were three interactions between the components of the early Devonian ecosystem?
Plant-mycorrihizal fungi symbiosis (plant combines with fungi to provide carbohydrates in return for nutrients and minerals)
Nutrient recycling by fungi and animals that feeds the plants
Fungi infecting plants promoting evolution
Is the early Devonian preserved ecosystem important?
Yes
What were the first tree types and when were they dated to?
Wattieza around 385ma (Mid Devonian)
Where were the first Wattieza discovered and how was the picture completed?
First discovered in New York as stumps that were matched up with branches found elswhere
How tall were Wattieza thought to be and why?
~8m high so they could spread spores
What were the second tree types and when were they dated to?
Archaeopteris trees dated to ~~375Ma (late Devonian)
What was important about archaeopteris trees?
They had characteristics of trees that are more present on earth today
How tall and wide were archaeopteris trees?
~10m high and 1.5 trunk diameter
What was an indication of the success these early tree types were enjoying? what did this mean for weathering rates?
Forests were discovered around the same time (late Devonian) - means a lot of organic carbon buried increasing weathering
What are most continental rocks made of?
Silicates
How do plants combine with rainwater to begin the weathering process? (Carbon dioxide balance)
They dissolve rocks with fungi which combined with the carbon in the rain (which acts as acid rain) weathers the rocks. the rainwater then runs off the surface of the earth
What happens to the ions released by the weathering process and some of the carbon that was in the rainwater? (Carbon dioxide balance)
It gets washed to the oceans - here it can be released to the atmosphere or they can form new carbonate rocks or organisms shells where they then over time sink to form new rocks or get buried in the sea floor which prevents them from interacting with the atmosphere. Locking it up.
What does the locking up of carbon in carbonates or organism shells mean for the temperature of the planet?
It prevents a GHG forming which means the temperature falls
Why do plants and fungi want to weather rocks?
To get nutrients and minerals
How do plants and fungi actually weather rocks?
They make acids that dissolve solid rock
How is plants and fungi’s weathering process assisted? and how does it happen?
Organic matter in soill from decomposed plants and organisms later becomes organic carbon which is consumed later by living plants and fungi which convert it in to CO2. This is then all trapped in the soil which reacts with rainwater to increase the concentration of carbonic acid that helps weathering.
What are two non-chemical weathering processes?
recycling of water that physically weathers as well as bioturbation of plant roots
What can happen to some of the phosphorus molecules released by weathering?
They can find their way out of plant cycle in to new production cycles to increase production of oxygen
How does the weathering out of ions contribute to the climate?
They cool the planet to the degree which plants are happy with
What events are thought to have coincided with CO2 reductions?
Glacial periods
What event happened between the transition between the Ordivician and Silurian periods?
A major glaciation
What was the result of the glass moss experiment?
mosses were found to accelerate the weathering of rocks by a factor of 2 to 5 or even 9 depending on the rock type
What degree of reduction in carbon dioxide levels is thought to be enough to trigger a glaciation period?
Halving
