After the dino-killer asteroid, rapid evolution helped life bounce back quickly

asteroid: A rocky object in orbit around the sun. Most asteroids orbit in a region that falls between the orbits of Mars and Jupiter. Astronomers refer to this region as the asteroid belt.

atmosphere: The envelope of gases surrounding Earth, another planet or a moon.

average: (in science) A term for the arithmetic mean, which is the sum of a group of numbers that is then divided by the size of the group.

biology: The study of living things. The scientists who study them are known as biologists.

Chicxulub: The name given an asteroid (or possibly a comet) that crashed into Earth around 66 million years ago. It left a crater more than 180 kilometers (110 miles) wide near the town of Chicxulub in what is now Mexico. The collision released an immense amount of energy — equivalent to billions of atom bombs the size of those dropped on Japan during World War II. This event changed the planet’s climate and is widely believed to have triggered a mass extinction of species — including the end of the dinosaurs.

climate: The weather conditions that typically exist in one area, in general, or over a long period.

climate change: Long-term, significant change in the climate of Earth. It can happen naturally or in response to human activities, including the burning of fossil fuels and clearing of forests.

core: (in geology) Earth’s innermost layer. Or, a long, tube-like sample removed with a drill from ice, soil or rock. Cores allow scientists to examine layers of sediment, dissolved chemicals, rock and fossils to see how the environment at one location changed through hundreds to thousands of years or more.

cosmic: An adjective that refers to the cosmos — the universe and everything within it.

crater: A large, bowl-shaped cavity in the ground or on the surface of a planet or the moon. They are typically caused by an explosion or the impact of a meteorite or other celestial body. Such an impact is sometimes referred to as a cratering event.

dinosaur: A term that means terrible lizard. These reptiles emerged around 243 million years ago. All descended from egg-laying reptiles known as archosaurs. Their descendants eventually split into two lines. Many large dinosaurs died out around 66 million years ago. But some lived on. They are now the birds we see today.

diversity: (in biology) A range of different life forms or a range of traits within the population of some species.

ecosystem: A group of interacting living organisms — including microorganisms, plants and animals — and their physical environment within a particular climate. Examples include tropical reefs, rainforests, alpine meadows and polar tundra. The term can also be applied to elements that make up some artificial environment, such as a company, classroom or the internet.

epoch: (in geology) A span of time in the geologic past that was shorter than a period (which is itself, part of some era) and marked when some dramatic changes occurred.

evolution: (v. to evolve) A process by which species undergo changes over time, usually through genetic variation and natural selection. These changes usually result in a new type of organism better suited for its environment than the earlier type. The newer type is not necessarily more “advanced,” just better adapted to the particular conditions in which it developed. 

extinction: (adj. extinct) The permanent loss of a species, family or larger group of organisms.

foraminifera: Single-celled organisms (neither plants nor animals) that are abundant in ocean water. They make up the base of the marine food web.

fossil: Any preserved remains or traces of ancient life. There are many different types of fossils: The bones and other body parts of dinosaurs are called “body fossils.” Things like footprints are called “trace fossils.” Even specimens of dinosaur poop are fossils. The process of forming fossils is called fossilization.

global warming: The gradual increase in the overall temperature of Earth’s atmosphere due to the greenhouse effect. This effect is caused by increased levels of carbon dioxide, chlorofluorocarbons and other gases in the air, many of them released by human activity.

helium: An inert gas that is the lightest member of the noble gas series. Helium can become a solid at -272 degrees Celsius (-458 degrees Fahrenheit).

marine: Having to do with the ocean world or environment.

millennium: (plural: millennia) A unit of time equal to 1,000 years.

mineral: Crystal-forming substances that make up rock, such as quartz, apatite or various carbonates. Most rocks contain several different minerals mish-mashed together. A mineral usually is solid and stable at room temperatures and has a specific formula, or recipe (with atoms occurring in certain proportions) and a specific crystalline structure (meaning that its atoms are organized in regular three-dimensional patterns).

model: A simulation of a real-world event (usually using a computer) that has been developed to predict one or more likely outcomes. Or an individual that is meant to display how something would work in or look on others.

paleobiologist: A scientist who studies organisms that lived in ancient times — especially geologically ancient periods, such as the dinosaur era.

Paleocene Epoch: The term for a span of geologic time that lasted from 65 million to 54.8 million years ago.

peninsula: A parcel of land that is that is attached to the mainland but surrounded by water on three sides.

physical: (adj.) A term for things that exist in the real world, as opposed to in memories or the imagination. It can also refer to properties of materials that are due to their size and non-chemical interactions (such as when one block slams with force into another).

plankton: (sing. plankter) Small organisms that largely drift or float in the sea. Depending on the species, plankton range from microscopic sizes to organisms about the size of a flea. Some are tiny animals. Others are plant-like organisms. Although an individual plankter is very small, these organisms often form massive colonies, numbering in the billions. The largest animal in the world, the blue whale, lives on plankton.

sediment: Material (such as stones and sand) deposited by water, wind or glaciers.

shell: The normally hard, protective outer covering of something. It could cover a mollusk or crustacean (such as a mussel or crab), a bird’s egg or some other relatively soft tissue that needs protection (such as a tree nut or peanut).

soot: Also known as black carbon, it’s the sometimes oily residues of incompletely burned materials, from plastics, leaves and wood to coal, oil and other fossil fuels. Soot particles can be quite small — nanometers in diameter. If inhaled, they can end up deep within the lung.

species: A group of similar organisms capable of producing offspring that can survive and reproduce.