How to Grow a Planet

Plants transformed the earth from a barren rock to our home by transforming light into food. This transformation allowed plants to colonize the whole planet and allowed other forms of life to evolve.

3 Billion years ago: The earth had very li"le oxygen and was covered in toxic gasses and didn’t really have an atmosphere. Therefore, the harsh UV radiation from the sun prevented life on land (it was 100x stronger than it is now).

The early oxygen that they created can be seen deep in the ground in iron ore. The red stripes are rust, iron oxide, and Iain extracts the oxygen and breathes it in: 2.5 billion years old. !is is considered “the great oxidation event” and it allowed for life on earth.

Eden project experiment - Iain is placed in an airtight chamber with 300 plants to see if they can produce enough oxygen for him to stay alive. The oxygen in the chamber is partially removed: they bring it from about 21% in our air to about 12%. Once in the chamber, the low oxygen starts to affect his cognitive functioning, if he remained in 12% oxygen, he would be unconscious in 24 hours. Fortunately, the plants (once they turn the lights on) are able to recover the oxygen levels to normal in under 48 hours, and as Iain leaves the chamber a$er 48 hours, the levels are still going up. Iain stresses the dependance we have on plants.

Photosynthesis review is shown about light reactions: Plants split water and release the oxygen, and use the hydrogens and electrons to make sugar. !ey collect sun light in their chloroplasts, using chlorophyll, to get the power to do this.

Once the plants were able to make oxygen, the oxygen went into the air and created ozone (O3) and this created a protective layer that #ltered the harmful radiation from the sun. !is allowed plants to move onto the land eventually. Here is where Iain shows the primitive plant with no leaves or roots that is fossilized in the stone wall in scotland. It was able to live along the water’s edge.

Evolution of roots: allowed plants to smash up the rocky earth and create soil. !is takes a long time (1000 years to make 2 cm of soil), but small pressures exerted over time allowed the plants to colonize further inland, since their roots could #nd water (they were not con#ned to the water’s edge). All of this created a more hospitable earth for animals, and small animals from the water were able to move onto the land as well. !e horseshoe crab is a very evolutionarily conserved organism (meaning it hasn’t changed much in millions of years), and it has book gills, which allow it to breathe oxygen from the sea and from the air, so they come onto shore to mate. !is is similar to prehistoric animals and their move from sea to land.

Calvin cycle review: Plants make sugar from the water, carbon dioxide, and sunlight, which they store in roots and use for growth. It can get moved to the roots within 15 minutes (radio-tagged carbon glowing plant).

Plants thrived on land and used up the CO2, levels plummeted by 90% and they started to struggle. !ey needed a way to breathe in more CO2 so they evolved leaves, which increased surface area.

Evolution of leaves: rich in stomata (open/close to let in gasses), allowed plants to avoid starvation and take in more CO2 and light. Tropical forests evolved (fossilized tree trunks), and with that, oxygen levels soared to double what they are today. !is allowed animals, particularly insects, to grow to be VERY big! Dinosaurs had a huge impact on the plant kingdom: 2/3 of 700 dinosaur species were vegetarian, including sauropods. Sauropods were 4 stories tall and ate 1,500 kg of vegetation a day and they roamed in herds of about 30. !is took a huge chunk out of plant life, and again they evolved, this time: defense. Plants evolved protection from herbivores such as barbs, spikes, and chemical warfare in the form of toxins and poisons, far more powerful than chiles. !ey also are able to communicate, using gas molecules. !ese molecules, given off when a plant is harmed, signal to other plants to release fast acting chemicals to ward off herbivores.

Eventually, plants evolved the ability to make wood (cellulose) and grow big and tall, taller than the huge dinosaurs and over take them. !e giant conifers like the sequoia trees covered the whole earth, including the poles, since the earth was warm and there was no ice. !ey can be 90m tall (more than 300 feet), and enabled plants to stay alive even with the dinosaurs.