There have been many theories as to why dinosaurs became extinct over 56 million years ago. One popular theory is that a huge comet crashed into the earth, throwing tonnes of ash and debris into the atmosphere and changing environmental conditions.

A large meteor striking the Earth could have sent enough dust and debris into the atmosphere that sunlight would have been almost totally blocked out. The resulting climatic change would have been enormous. Temperatures would have dropped as there was no sunlight to warm the earth. Animals would need more food to keep their body temperatures constant and many would have died when they were unable to find enough food.

The biggest effect of the global winter would have been the lack of sunlight. With the amount of dust clouding the atmosphere little energy could reach the plants so they would be unable to convert this energy into starch and sugars. Fewer plants would have been available to the first order consumers and they would not have been able to gain the energy they needed to survive.

When the first order consumers began to die the secondary consumers began would have lost their food source. The lack of animals to hunt meant that they would not have been able to find enough energy to survive.

Larger dinosaur
Small dinosaur
Plants

If you remove the plant matter from the base of this food pyramid the ecosystem becomes unbalanced. Organisms higher up on the pyramid have no source of energy and can not survive. So which animals did survive the changed environmental conditions?

• Frogs and salamanders - 100% survival
• Champosaurs - 100% survival
• Sharks, skates and rays - 90% survival
• Turtles - 85% survival
• Crocodiles and alligators - 80% survival
• Ray-finned fishes - 60% survival
• Lizards - 30% survival
• Marsupial mammals (small) - 10% survival
• Dinosaurs (non-avian) - no survivors

Bibliography

Scott, M. Young Oxford Books - Ecology. (London: Oxford)

Time Understanding Life and Science, Ecology. (Nederlands: Time-Life, 1968)

Baker, et al. Pathways into Senior Geography. (Melbourne: Nelson, 1995)

Pain, Bliss & Smith. Pathways to Geography HSC Course. (Melbourne: Macmillan, 1995)

The Book of Popular Science Encyclopaedia. (New York: Grolier, 1961)

The Software Toolworks Multimedia Encyclopaedia, Release 6. (New York: Grolier, 1996)

Snyder, et al. Biology - The Spectrum of Life. (Melbourne: Oxford University Press, 1990)

Encarta 96 Encyclopaedia. (Redmond: Microsoft, 1996)