Question

Which are the remains of species that existed on Earth for relatively short periods of time, were abundant, and were widespread geographically? A. trace fossils C. carbon films B. index fossils D. body fossils

Short answer

B. index fossils

Step-by-step solution

Understanding the Question

The question asks us to identify the type of fossil that represents species which existed for a short time, were abundant, and had a widespread geographic distribution.

Analyzing the Options

We have four options: trace fossils, carbon films, index fossils, and body fossils. We need to determine which option describes the type of fossils that meet the criteria provided in the question.

Defining Trace Fossils

Trace fossils are geological records of biological activity but not the remains of the organism's body parts. They include footprints, burrows, and fecal matter.

Understanding Carbon Films

Carbon films are thin layers of carbon residue left by decaying organisms. They usually show only the silhouette of an organism but do not indicate the organism's abundance or geographic spread.

Examining Index Fossils

Index fossils are remains of species that were widespread geographically, abundant, and only existed for short, well-defined time periods. These characteristics make them ideal for identifying and correlating geological layers.

Interpreting Body Fossils

Body fossils are actual remains of organisms, such as bones and shells. They do not necessarily represent species that were widely distributed, abundant, or existed briefly.

Choosing the Correct Answer

Based on the criteria given and the characteristics of each option, index fossils (Choice B) are the best fit since they meet all the specified criteria.

Key concepts

Trace Fossils

Trace fossils, also known as ichnofossils, provide fascinating insights into the behavior of ancient organisms. These are not the actual remains of the creature itself. Instead, they capture the activities and movements of organisms as they interacted with their environment. Common examples of trace fossils include footprints left in soft sediment, burrows dug into the ground, and even fecal deposits known as coprolites.
Trace fossils can reveal a lot about the past environment, such as the kind of animals that lived there, their behaviors, and in some cases, their social structures. For example, a series of footprints can suggest a group of animals traveling together, possibly indicating migration or herd behaviors.

• They help us understand the interaction between organisms and their habitats.
• Often indicate behavioral patterns like feeding, locomotion, or dwelling.
• Importance lies in their ability to transcend species, as many different types of organisms could leave similar traces.

Carbon Films

Carbon films are an intriguing type of fossil that preserve a thin layer of carbon residue from the decay of an organism. This type of fossilization commonly occurs for soft-bodied organisms that lack hard parts like bones or shells, which usually don't fossilize well. Over time, as the organism decays, it leaves behind a thin layer of carbon residue, creating a delicate imprint or silhouette of the original organism.
They are particularly useful for studying ancient plants and insects. Despite their fragile nature, carbon films can offer detailed information about the organism's structure and shape. This process often results in fossils that are beautiful to look at, capturing even minute details of ancient life.

• Often preserve soft parts of organisms not usually fossilized, like feathers or leaves.
• Do not indicate an organism's abundance or geographical reach.
• Provide significant insights into ancient life forms' anatomical structures.

Body Fossils

Body fossils are the actual preserved parts of ancient organisms, such as bones, teeth, and shells. These types of fossils provide direct evidence of the organism's existence and can offer extensive information about its physical characteristics. Unlike trace fossils, body fossils reflect the solid remains of creatures and not their behaviors.
Body fossils can range from tiny microorganisms to massive dinosaurs, each holding a piece of history within them. The hard parts of organisms, like bones or shells, have a higher likelihood of being preserved over the softer tissues. In paleontology, these fossils help reconstruct entire skeletons and give us a glimpse of what life forms inhabited the Earth long ago.

• Enable scientists to understand the organism's anatomy in detail.
• Used to identify different species and understand evolutionary relationships.
• Help track changes in biodiversity and environmental conditions over time.