Fossils and Dating Methods

Fossils

• Remains of organisms preserved in Earth.
• Two methods of dating: relative and absolute.

Relative Dating

• Compares fossils based on their position in the Earth.
• Deeper fossils are generally older.

Absolute Dating

• Determines the actual age of a fossil.
• Uses radioactive elements found in rocks and fossils.
• Measures the amounts of uranium and lead.
• More lead indicates an older fossil.

Fossil Record

• Information about fossils found in a specific area.

Early Life Forms

• Unicellular organisms existed 3.8 billion years ago.
• Early atmosphere had a low oxygen content.
• Multicellular organisms emerged around 1.2 billion years ago.
• They had specialized cells and included tiny seaweeds.

Geological Changes

• 250 million years ago: No mountains, shallow water.
• 70 million years ago: Flat shallow seas.
• 53 million years ago: Tropical rainforests replaced shallow seas.
• 37 million years ago: Volcanic eruption covered land with hot ash.
• 16,000 years ago: Environment similar to today.

Transition to Land

• 500 million years ago: Multicellular organisms transitioned from water to land.

Mass Extinctions

• Periods of widespread species extinction in a short time.
• Permian Extinction (250 million years ago): 90% of ocean species extinct.
• Many land-dwelling animals disappeared.
• Cretaceous Extinction (65 million years ago): Dinosaurs became extinct.
• Linked to the Chicxulub crater.

New Species Development

• Extinctions can lead to the development of new species.

Evolution

• The process of species change over time.
• Driven by changes in genetic material passed to offspring.

Jean Baptiste de Lamarck

• French scientist who proposed the first model of evolution.
• Idea that organisms acquire new traits during their lifetime and pass them to offspring.
• Lacked evidence to support his theory.

Charles Darwin

• British naturalist who spent 5 years on the Beagle.
• Observed animals in different locations had unique traits for survival.
• Published the basis for modern evolution theory.

Artificial Selection

• Process used by breeders to develop specific traits in organisms.

Natural Selection

• Members of a species best suited to their environment survive and reproduce at higher rates.
• Based on overproduction, variation, adaptations, and selection.

Overproduction

• Organisms produce more offspring than the environment can support.
• Only a few survive.

Variation

• Naturally occurring differences within a species.
• Genetic material changes can create new variations.

Adaptation

• Inherited traits that provide an advantage in the environment.
• Caused by mutations.

Selection

• Organisms with beneficial adaptations are more likely to survive & reproduce.
• This drives the evolution of a species through natural selection.

Speciation

• Evolution of new species from existing species.
• Occurs when the environment changes significantly.

Isolation

• Separating populations can contribute to speciation.

Theory

• A widely accepted explanation based on scientific evidence.

Fossil Evidence for Evolution

• Shows similarities between past and present species.
• Demonstrates how species evolve and adapt to different environments.
• Supports the idea of a common ancestor.

Biological Evidence for Evolution

• Similarities in the structure and development of organisms.
• Vestigial organs provide evidence of evolutionary adaptation.

Vestigial Organs

• Reduced and unused structures that were functional in ancestors.

Similarities in Structure

• Suggests organisms share a common ancestor.
• Natural selection causes variations in structure.

Similarities in Development

• Some animals appear similar in early life stages and become more distinct as they grow.
• Embryonic development reveals shared ancestry.

DNA

• Contains genetic information for growth and maintenance.
• Consists of four bases: A, T, C, and G.
• Genes are segments of DNA responsible for specific traits.

The Clock Gene

• Related to the function of waking and sleeping.
• Identified in many mammals.

DNA Similarities

• Closely related species have more similar DNA sequences.

Explore the fascinating world of fossils and the methods used to date them. This quiz covers relative and absolute dating techniques, the fossil record, and the evolution of early life forms over billions of years. Test your knowledge on geological changes and the history preserved in Earth’s layers.