Data Source:
Berner RA (2003) The long-term carbon cycle, fossil fuels and atmospheric composition. Nature, 426, 323-326
The changes in atmospheric O2 concentrations over the past ~550Ma (the Phanerozoic eon) are closely linked to biological evolution. For example the large rise in O2 prior to 300Ma is believed to be caused by the evolution of large vascular land plants. The plants caused increased burial of organic matter because of the introduction of lignin (and hence increased O2 production from respiring bacteria that break down organic debris in the soils). Similarly, increasing O2 concentrations through the Carboniferous and Permian caused gigantism in several arthrodpod groups, and body size increased across primitive reptile-like animals and their descendants. Dropping O2 or relatively low O2 concentrations also had evolutionary consequences. Several extinctions appear to coincide with declining O2 concentrations. This can be shown using the 'Mass Extinctions' data on the timeplot tool.
Using the 'O2' data and 'Carbon Burial' data in the timeplot tool, it is possible to see that oxygen increase in the Carboniferous correlates with carbon burial. You might like to consider this in the context of soil bacteria respiration, as well as plant productivity since the ability to synthesise lignin is apparently highly dependent on levels of atmospheric O2. This is also reflected in the 'C:S' (Carbon:Pyrite) data over the Phanerozoic.
Large fluctuations in relative CO2 and O2 concentrations are likely to have been important imposing selective pressure on plant physiology since O2 is a competitive inhibitor to Rubisco. This can be investigated this further using the 'Photosynthesis', 'Physiological Developments' and 'Leaf Evolution' data in the timeplot tool.
Relevant lecture references:
Data Source:
Berner RA and Kothavala Z (2001) American Journal of Science. 301, 182-204
(ppmv = parts per million by volume)
The long term global carbon budget shows that 100x the carbon content of the biosphere is turned over every million years in the long term carbon cycle. Geochemical activity restores CO2 to the atmosphere, whilst plants bury carbon and accelerate weathering.
By maintaining the balance between carbon burial and carbon degassing, plants are likely to have prevented runaway green house or ice house conditions through the Phanerozoic. This hypothesis can be investigated further using the 'Leaf Evolution' data, and the links to papers written by Beerling DJ (2005) and Beerling DJ and Berner RA (2004).
Relevant lecture references:
Data Source:
Veizer J et al. (2004)
This graph shows the long-term evolution of oxygen isotope ratios during the Phanerozoic eon as measured in fossils, reported by Veizer et al. (1999), and updated online in 2004 (see data source for link). Such ratios reflect both the local temperature at the site of deposition and global changes associated with the extent of permanent continental glaciation. As such, relative changes in oxygen isotope ratios can be interpreted as rough changes in climate.
It is estimated that each part per thousand change in δ18O represents roughly a 1.5-2°C change in tropical sea surface temperatures (Veizer et al. (2000)). On geologic time scales, the largest shift in oxygen isotope ratios is due to the slow radiogenic evolution of the mantle. This can be investigated using the 'Tectonic Activity' data provided in this timeplot tool. Note that large decreases in temperature coincide with major periods of glaciation. This can be shown using the 'Ice Ages' data in the Timeplot tool.
Data Source:
van Andel TH (1994) New Views on an Old Planet: A History of Global Change 2nd Edition. Cambridge University Press, Cambridge, UK
Ice ages are important in plant evolution for several reasons. Primarily, they are often associated with periods of low concentrations of atmospheric CO2. This can be investigated using the 'CO2' data in the Timeplot tool. Ice ages were also very dry periods since water was locked up in large polar glaciers. This reduction in water availability, as well as low atmospheric CO2 concentrations was a significant strain on plant photosynthesis since both conditions promote photorespiration. In the most recent Ice Age, the dry, low CO2 ppmv conditions are thought to have driven the evolution of C4 photosynthesis. This can be investigated using the 'Photosynthesis' data in the Timeplot tool. Note that Ice Ages are correlated with tectonic activity, such as the Tibetan orogeny that is believed to have driven the most recent ice age. This can be investigated further using the 'Tectonic Activity' data in the Timeplot tool.
Data Source:
Niklas KJ (1997) The evolutionary biology of plants. The University of Chicago Press, Ltd., London
When considering the evolution and radiation of Pteridophytes, Gymnosperms and Angiosperms, you may like to consider the 'Tectonic Activity' data, and the 'CO2' data in the timeplot tool.
This is a list of most of the plant species mentioned in the Part IA lectures. It allows you to contextualise the species, and to see how they fit in with important chronological events. If you click on a species name, you will able to find links to Wikipedia, taxonomy and phylogeny information.
At the broadest scale, the overall pattern of plant evolution appears to be concentrated in distinct intervals in geological time rather than evenly spread throughout. This is reflected by the clustering of species shown in the timeplot, as well as the distribution of 'Physiological Developments'.
Similarly, increases in morphological complexity and total plant species diversity have occurred during relatively short intervals of geological time, interspersed by longer periods of relative stasis (in terms of major evolutionary innovations) and plateaus in species diversity. This is illustrated in the diagrams below.
The peaks of plant originations seen in the plant fossil record, do not appear to match those seen in the animal record, which tend to follow mass extinction events. Furthermore the peaks of plant extinction do not coincide with at least four of the 'big five' mass extinction events. You might like to consider this further using the 'Mass Extinction' data on the timeplot tool.
Five mass extinction events have been recognised in the marine faunal record over the pasat 600 million years. These are often referred to as the 'big five'. Although the pattern and timing of mass extinciton events in Earth history are most sharply defined by family-level diversity loss in the marine fossil record, similar trends are also observed among terrestrial aunas for at least thee of 'the big five'. The trends in plant extinctions, and the overall diversity changes, on the other hand, are more ambiguous. There are no major peaks of extinction in the plant fossil record comparable to those of the faunal mass extinction events.
It has been suggested that the lack of mass extinction in the plant fossil record as opposed to the faunal record is due, in part, to the greater ability of plants to withstand major ecological trauma. You might like to consider the following additional arguments:
The life cycle of an organism enables mulitcellularity. Multicellularity has evolved several times (see image below right), so that different organisms (such as plants and animals) have different strategies for achieving multicellularity (i.e. they have different life cycles).
The strategy used by plants involves two phases: a haploid and a diploid stage. All terrestrial plants show show this strategy, but vary in the length of life spent in the haploid and diploid states, and also in the independence or interdependence of the two phases. The cycle between haploid and diploid phases is is called the 'Alternation of Generations'. During their evolution, terrestrial plants have gradually changed from haploid (gametophyte) dominance to diploid (sporophyte) dominance. More primitive plants have a more dominant haploid phase, whereas plants that evolved much later (such as the angiosperms) have a dominant diploid phase. This influences the genetic structure of different plant groups and thus the environments they can colonise.
Find out more:
Multicellularity Carroll SB (2001) Chance and necessity: the evolution of morphological complexity and diversity. Nature, 409, 1102-1109
Sporic Life Cycles University of the Western Cape, Botany Department
The evidence from the plant fossil record suggests that the period between the late Ordovician and early Silurian was a time of major innovation. The terrestrialisation process included the evolution of a reproductive system that was not primarily dependent on water (see 'Developments in Life Cycle' in the timeplot tool) and various physiological mechanisms to enable plant growth outside of an aquatic medium. Click on the chart to find out more information and view further links.
Summary of Part IA lecture:
Relevant Part II references:
Several authors have hypothesised that the origin of angiosperms, and the tempo and pattern of their subsequent radiation, was mediated by changes in the browsing behaviour of large herbivorous dinosaurs (tetrapods).
A paper by Barrett and Willis ( Barrett PM and Willis KJ (2001) Did dinosaurs invent flowers? Biol. Rev. Camb. Philos. Soc. 76,3, 411-447) reviews the evidence for dinosaur/angiosperm interactions during the Cretaceous Period.
According to the authors, it is likely that other animal groups (insects, some mammals) had a greater impact on angiosperm diversity during the Cretaceous than herbivorous dinosaurs. Elevated levels of atmospheric CO2 might also have played a critical role in the initial stages of the angiosperm radiation. You may like to consider this using the available 'CO2' and 'Insect' data on this time plot tool.
Data Source:
Carroll SB (2001)Chance and necessity: the evolution of morphological complexity and diversity. Nature, 409, 1102-1109
This shows the first appearances of some of the major groups of animals and plants. It highlights how late the Angiosperms arise in the geological record.
The Angiosperms first appear in the fossil record in the Early Cretaceous period, about 130 million years ago, and then radiate very quickly over the next 40 million years to give the huge diversity we see today. Darwin described the speed of Angiosperm radiation as 'an abominable mystery'.
Using the 'Tetrapod', 'Insect', and 'CO2' data, you can begin to assess why Angiosperms appeared so late and what might have caused their rapid radiation.
Data Source:
Berner RA (2003) The long-term carbon cycle, fossil fuels and atmospheric composition. Nature, 426, 323-326
Carbon burial is calculated using variable isotope fractionation during photosynthesis (see Beerling DJ (2005)). The broad maximum centred about 300 Ma illustrates the importance of lignin evolution in the late Ordovician (see 'Physiological Developments' in the Timeplot tool). Lignin is a relatively non biodegradable organic matter, which, when buried in sediments, gave rise to increased global burial of organic carbon. This was particularly prominent as plants grew larger in the Carboniferous and Permian, giving rise to the great coal swamps.
Note that carbon burial correlates positively with O2 reflecting the extent of soil bacteria respiration, and correlates negatively with atmospheric CO2 concentrations. However, atmospheric CO2 concentrations never reach zero, illustrating a negative feedback regulation that prevents the 'runaway' of CO2 decline. This can be investigated further using the 'Leaf Evolution' data in the Timeplot tool. See Beerling DJ and Berner RA (2004) and the diagram (right), for more information.
<Data Source:
Veizer J et al. (1999) 87Sr / 86SRr, δ13C and δ18O evolution of Phanerozoic seawater. Chemical Geology, 161, 59-88
The data presented here includes an 87Sr/86Sr curve and six major 'pulses' of tectonic activity over the Phanerozoic.
The 87Sr/86Sr curve reflects the relative contributions of strontium to the ocean from continental weathering and from hydrothermal activity along mid-oceanic ridges. Most of the Phanerozoic is characterized by a general decrease in 87Sr / 86Sr due to increasing activity along mid-ocean spreading ridges. The late Cenozoic marine sediments experienced a dramatic increase in 87Sr due to climate cooling (see 'Ice Ages' and 'Paleo Temperature' data) and increased rates of continental weathering by glaciation.
The six major 'pulses' of Tectonic activity (from Willis and McElwain (2000) are provided to show correlations with periods of significant innovation or radiation in plant evolution. This can be investigated further using the 'Major Groups', 'Physiological Developments' and 'Photosynthesis' data in the Timeplot tool. For example, note the correlation between the Tibetan orogeny in the late Paleogene, the current ice age, the decline in CO2 and the evolution and diversification of C4 photosynthesis.
Date Source:
Goodfellow W (2007) Mineral Deposits of Canada. Geological Survey of Canada
Data Source:
Berner RA (2003) The long term carbon cycle, fossil fuels and atmospheric composition. Nature, 426, 323-326
Ratios of the burial rates of organic carbon and pyrite (sulphur) (C:S) illustrate net oxic or anoxic aquatic conditions, and describe the nature of the environment at the time of deposition.
C:S data is shown here since it provides a good illustration of how proxies can be used to recreate paleo-environments. Other important proxies include stomatal ratios and Carbon, Strontium and Oxygen isotopes (see 'Stomata', 'Tectonic Activity' and 'Paleotemperature' data in the Timeplot tool).
Data Source:
Berner RA (2003) The long term carbon cycle, fossil fuels and atmospheric composition. Nature, 426, 323-326
Badger MR et al. (1998) The diversity and co-evolution of Rubisco, plastids, pyrenoids and chloroplasts based CCMs in algae. Can J Bot 76, 1052-1071
Beerling DJ (2005) Leaf Evolution: gases, genes, geochemistry. Annals of Botany, 96, 345-352
Beerling DJ and Berner RA (2005) Feedbacks and the co-evolution of plants and atmospheric CO2. PNAS, 102, 1302-1305
Raven JA (1995) The early evolution of land plants: Aquatic ancestors and atmospheric interactions. Bot J Scotl, 47, 151-175
Edwards D (1998) Climate signals in palaeozoicland plants. Proc Roy Soc B, 353, 141-157
Beerling DJ and Woodward FI (1996) Influence of carboniferous palaeoatmospheres on plant function. TREE, 11, 20-23
Beerling DJ, Osborne CP and Chaloner WG (2001) Evolution of leaf form in land plants linked to atmospheric CO2 decline in the late Palaeozoic era Nature 410, 353-354
Data Source:
McElwain JC et al. (1998) Do fossil plants signal palaeoatmospheric CO2 concentration in the geological past? Phil. Trans. B, 353, 1365, 83-96
This data illustrates estimates of palaeoatmospheric CO2 for the Phanerozoic calibrated from the stomatal ratios of fossil plants (Aglaophyton major, and Sawdonia ornata). Paleo stomatal ratios are a good illustration of how proxies can be used to recreate paleo-environments, and verify other proxies. Other important proxies include C:S ratios and Carbon, Strontium and Oxygen isotopes (see 'Stomata', 'Tectonic Activity' and 'Paleotemperature' data in the Timeplot tool).
Data Source:
Spreitzer RJ, Salvucci ME (2002) RUBISCO: Structure, regulatory interactions and possibilities for a better enzyme. ARPB, 53, 229-475
KenrickP and Crane PR (1997) The origin and early evolution of plants on land. Nature, 389, 33-39 (rbcLphylogeny)
Nisbet EG and Sleep NH (2001) The habitat and nature of early life. Nature, 409, 1083-1091
Long SP (1991) Modification of the response of photosynthetic productivity to rising temperature by atmospheric CO2. Plant Cell Environment, 14, 729-739
Tcherkez G, Farqhuar GD and Andrews TJ (2006) Despite slow catalysis and confused specificity, all Rubiscos may be nearly perfectly optimised. PNAS, 103, 7246-7251
Badger MR et al. (1998) The diversity and co-evolution of Rubisco, plastids, pyrenoids and chloroplast based CCMs in algae. Can J Bot, 76, 1052-1071
Data Source:
Willis & McElwain (2000) The Evolution of Land Plants. Oxford University Press, Oxford.
Plate boundary reorganisations involving collisions, rifting and changing patterns of intraplate stress have occurred throughout Earth history and each 'pulse' of activity will have influences almost all aspects of the global environment. Climate change associated with plate boundary reorganisations results from alterations to the major patterns of ocean current and atmospheric circulation. Geological evidence indicate that tectonic activity might have been epidosic with relatively short periods of activity separated by long periods of inactivity. Five periods of increased tectonic activity have been recognised in the geological record, and when compared to changes in the plant fossil record, some interesting patterns start to emerge. This is illustrated using the 'Major Groups' data and the 'Physiological Developments' data in the timeplot tool.
Edwards D, Kerp H, Hass H (1998) Stomata in early land plants: an anatomical and ecophysiological approach. J Exp Bot, 49, 255-278
Franks PJ and Farquar GD (2007) The mechanical diversity of stomata and its significance in gas-exchange control. Plant Physiology, 143, 78-87