Fossil Atmospheres – Zooniverse

By comparing some features of fossilised plants with the same features of plants living today, scientists hope to be able to learn more about the effect of changing carbon dioxide (CO₂) levels in our atmosphere and to understand what effect climate change might have on life on Earth in the long term.

This project involves citizens categorising two types of cell on images taken by electron microscopes of the underside of gingko tree leaves.

URL: www.zooniverse.org/projects/laurasoul/fossil-atmospheres/about/research

Reach: Worldwide

Nature of science focus: Online citizen science (OCS) projects can be used to develop any of the Nature of Science (NoS) substrands. Identify aspects of NoS that your students need to get better at or understand more fully and then frame your unit to be very clear about these things when you do them.

Science capability focus: Gather and interpret data, Interpret representations

Science focus: climate change, fossils, plant cell structure, atmosphere

Some suggested science concepts:

• Fossils are the preserved remains of living organisms or of traces of their activities.
• Fossils provide a record of previous life and living conditions on Earth.
• Some features of plants can only be observed with microscopes.
• The living and non-living things that make up planet Earth are closely interlinked and delicately balanced. Changes to one thing can result in changes to others.
• Some cells have specialised jobs to do (Living World level 5).

Many concepts could be learned – focusing on a few can often be more powerful. Develop your learning outcomes and success criteria from these concepts as well as the Nature of Science strand and the science capabilities.

Some examples of learning outcomes:

Students can:

• describe how fossils are formed
• explain how fossils provide a record of previous life and living conditions on Earth
• explain the purpose of stomata
• compare and contrast the stomatal index at varying CO₂ levels
• comment on the meaning of CO₂ variation in our atmosphere for our world
• critique aspects of the method used in the Fossil Atmospheres project.

About stomata

Stomata are microscopic pores found on the surfaces of plant leaves and some plant stems. The pores are surrounded by specialised cells called guard cells. When the guard cells are swollen (contain a lot of water), they enlarge into a bean shape and the pore opens. When the guard cells are flaccid (contain less water), their more oval shape means that the pores are closed.

Stomatal pores are important for plants because they enable CO₂ to enter the plant. CO₂ is used for photosynthesis. This means that stomata open during the day when there is sunlight (which is also needed for photosynthesis). The downside to open stomata is water loss: water vapour exits through the open pores. To reduce the amount of evaporation from the plant, there needs to be a balance between keeping the stomata open for CO₂ to get in and reducing the amount of water vapour being lost. Excess oxygen produced during photosynthesis also exits the plant through the stomata.

When there is more CO₂ in the atmosphere, plants tend to have fewer stomata. They are able to easily get the CO₂ they need and conserve water. Paleoclimatologists are interested in changes to the number of stomata in fossilised plants because they are very sensitive indicators of past CO₂ levels. Increased levels of atmospheric CO₂ are currently contributing to climate change.

This project would offer a useful application for knowing about cell structure at level 5 and above or as a link to the effect of changing CO₂ levels in relation to climate change.

About Fossil Atmospheres

In Fossil Atmospheres, citizen scientists classify the cells in images as either a stomata or a normal cell. What scientists are looking for is the ratio between stomata and normal cells – called the stomatal index – to give clues about the atmosphere at the time the plant was growing.

Images are taken using an electron microscope and are either of fossilised gingko leaves or current gingko leaves.

Gingko trees have survived three mass extinctions, including the one that eventually caused the dinosaurs’ demise. Although there have been many different species of ginkgo, they all belong to one genus and the leaves are recognisably similar in all the different species. This makes them an ideal plant to study because they can provide a record from 300 million years ago through to the present.

The categorising of cells is very easy. Although it is not possible to view the ratios of the images you analyse, you can view some results achieved to date.

Extensive explanation is provided to support both teachers and students. Alongside citizen scientists contributing to the analysis of images, there is a live experiment taking place in which gingko trees are being grown in chambers with a different controlled amount of CO₂ in each one.

The sensitivity of climate to CO₂ has enormous economic and societal implications because of the effect climate change will have on sea level, food production, storm strength, water availability, and many other factors. By improving our ability to quantify the effects of CO₂ on climate, you will be contributing to the basic science underlying projections of future environmental change.

Fossil Atmospheres