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Palaeo-speak: Eight concepts that will impress a palaeontologist... providing you know what they mean!

#1 Palaeontologist -- a scientist who studies fossil animals (fauna) and plants (flora).

Palaeontology research provides information on animal and plant evolution, as well as on ancient environments, and in so doing provides insight into contemporary issues such as climate change and rates of extinction.

• There are many sub-specialties, such as palynology or the study of the history and development of pollen. There are only about a dozen part- and/or full-time dinosaur palaeontologists in Canada.
• The term palaeontologist is often confused or conflated with archaeologist. While both groups of scientists dig, they are digging for very different evidence. Archaeologists are concerned with human remains and cultural products of the relatively recent past (the last 25, 000 years or so).

#2 Fossil -- the remains of a once living organism.

While most people think of remains preserved in or as rock, a fossil is any remains. There are many types of fossils, including:

• trace fossils, in which only an impression of the organism is left (e.g., dinosaur footprint in rock);
• coprolites (animal dung);
• fossils preserved in amber (remember the dinosaur-stinging mosquito from the film Jurassic Park); and
• mummified or frozen specimens (such as ice-age Mammoth remains).

#3 Geologic time -- The Gregorian calendar that we use for day-to-day scheduling isn't of much use to palaeontologists. For these scientists, the Earth itself is a timepiece. The passage of time is measured in two ways:

• absolute time is determined using one form or another of radioactive dating and gives a precise age; and
• relative dating is based on using fossils and sediments to place rock sequences, and thus events, in order.

The geologic time periods -- for example the Mesozoic and Cretaceous -- have their origins in relative dating, based on the distinctive fossils found in each geologic time period.

#4 Dinosaur -- a broad term that refers primarily to a diverse group of terrestrial reptiles that lived mainly during the Mesozoic. Its literal translation is "terrible lizard".

Dinosaurs are distinct from the flying (e.g., pterosaurs) and swimming reptiles (e.g., mosasaurs) of the same period. The historic dinosaur period covers 170 million years, from about 235 million to 65 million years ago. Over this enormous time period, many species of dinosaurs evolved, and became extinct. The consensus among palaeontologists -- particularly based on fossil finds of the past decade -- is that modern birds evolved from one sub-group of dinosaurs. Thus we live in a period of enormous dinosaur diversity!

#5 Evolution -- change, with continuity, over successive generations of organisms.

The phenomenon is demonstrated by the fossil record. Evolutionary changes over geologic time are significant enough for scientists to recognize distinct eras, (e.g., the Cambrian, or Jurassic). Evolution is not synonymous with "development", which refers to changes that take place in a single organism over the course of its lifetime.

#6 Mass extinction -- a period in geologic time when over 50% of all the life forms on Earth died out.

There have been five mass extinctions in the Earth's history. The most famous of these is known as the Cretaceous/Tertiary boundary extinction, or colloquially as the dinosaur extinction event. Some key points to note:

• Mass extinctions are thought to be caused by a variety of factors, all of which result in rapid, major environmental changes to which populations of animals cannot adapt. The environmental factors include climate change, changing sea levels, volcanism and cosmic events such as asteroid impacts or changes in the Earth's orbit.
• The rate of species loss documented by palaeontologists for the mass extinctions has led some ecologists to state that we are now in the midst of a human-induced "sixth mass extinction".

#7 Radioactive dating -- the most precise method for dating rocks and organic material.

While the indicators used for dating may vary, the general principle is based on measuring the relative percentages of parent and daughter isotopes (variants of a particular atom) of a radioactive atom.

For organic material, the process is known as radio-carbon dating (or carbon dating) because of its use of radioactive carbon, also known as carbon-14 (14C).

• Carbon is used because it is the backbone of all organic material.
• Because carbon-14's half-life (the time it takes for half of the sample to decay into its stable daughter form) is about 5568 years, this technique is only applicable to samples that are less than 70,000 years old.
• Older samples have too little carbon-14 to provide an accurate measurement.

For rocks, minerals and lithified fossils, the radioactive isotopes measured include potassium/argon and uranium/lead. These isotopes have much longer half-lives. For example, potassium 40/argon 40 has a half-life of 1.5 billion years.

#8 Species -- a group of organisms that closely resemble one another physically; from the Latin speculare, meaning, to look.

In a dynamic sense, the term refers to a population of similar individuals who can interbreed; that is, can successfully share genetic material. For example, all human beings are a single species. There are thousands of species of dinosaurs.

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