The Fossil Record

Fossil Record• Provides evidence about the history of life on Earth.• Shows how different groups of organisms have

changed over time.

• A natural cast forms when flowing water removes all of the original tissue, leaving an impression.

• A mold is an empty space in the rock in the shape of the organism

• Trace fossils record the activity of an organism.

• Amber-preserved fossils are organisms that become trapped in tree resin that hardens after the tree is buried.

Petrification occurs when an exact stone copy of an organism is made where dissolved minerals replace organic matter.

An imprint is a fossil that is formed before the sediments harden. A typical imprint is a dinosaur footprint that is left before the ground hardens or reforms.

• Specific conditions are needed for fossilization.• Only a tiny percentage of living things became

fossils.• Paleontologists are scientists that study fossils.

• Relative dating estimates the time during which an organism lived.

– It compares the placementof fossils in layers of rock.

– Scientists infer the order inwhich species existed.

• Radiometric dating uses decay of unstable isotopes and gives an accurate way to estimate the age of fossils.

neutrons protrons

– A half-life is the amount of time it takes for half of the isotope to decay.

– Carbon dating is used to determine the age of a once-living organism.

The Origin of Life

Beginning of Life…• Earth formed 4.6 billion years ago• 3.9 billions years ago, Earth began cooling• Around 3.5 billion years ago, the first

organisms appeared.

Earth’s Early Atmosphere

• Contained hydrogen cyanide (HCN), carbon dioxide (CO2), carbon monoxide (CO), nitrogen (N), hydrogen sulfide (H2S) and water.

• Which important element is missing? Why do you think it’s missing?

How did life form?

• Hypothesis 1: Life came from other living things (Biogenesis)

• Hypothesis 2: Life was produced from nonliving matter (Spontaneous Generation)

Spontaneous GenerationFranciso Redi designed experiment to test the idea of spontaneous generation.Two jars: One with rotting meat and no lid One with rotting meat and a cloth coveringDeveloped maggots and flies No maggots or flies

Perhaps, it was something in the air…

Louis Pasteur filled an S-shaped flask with nutrient broth and boiled it.

The design of the flask allowed air to get to broth, but not microorganisms.

After ONE year, no microorganisms entered the broth.

Miller-Urey experiment proposes how organic compounds could have formed from simpler compounds.

electrodes

heat source amino acids

water

“atmosphere”

“ocean”

The oldest known fossils are a group of marine cyanobacteria.

– prokaryotic cells

– added oxygen toatmosphere

– deposited minerals

Eukaryotic cells may have evolved through endosymbiosis.

• Endosymbiosis is a relationship in which one organism lives within the body of another.

• Mitochondria and chloroplasts may have developed through endosymbiosis.

The evolution of sexual reproduction led to increased diversity.

• Genetic variation is an advantage of sexual reproduction.• Sexual reproduction may have led to the evolution of

multicellular life.

Evolution did a number on this guy!

• Evolution is change over time– Explains how descendants differ from ancestors.

• A species is a group of organisms that can reproduce and have fertile offspring.

Fertile

Infertile

Father of Evolution – Charles Darwin• There are four main principles to the theory of

natural selection.– Adaptation– Overproduction– Variation– Descent with modification

• Natural selection - process where individuals with inherited beneficial adaptations produce more offspring than others.- Survival of the Fittest!!

• Adaptations are traits that increase an organism’s chance to survive.

-Malaria and Sickle Cell Anemia

• Variation is a difference in a physical trait.– Galápagos finches with different beaks suited for different seeds– Blood type in humans – A, B, AB and O– Mutation is a change in the DNA sequence

Artificial selection is the selection of specific traits for breeding.

Does artificial selection increase or decrease variation??

Examples of artificial breeding: Horses (racing), Dogs (purebreds), and Cows (milk)

• Overproduction occurs when more offspring of a species are produced than can possibly survive.

Thomas MalthusTheorized human population would run out of living space and food if population continued to grow.

Factors prevent populations from growing out of control: war, famine and disease.

Darwin realized that applied even more to plants and animals.

• Descent with modification is the principle that each living species has descended, with changes, from other species over time.

• Heritability is the ability of a trait to be passed down.

Lamarck’s Inheritance of Acquired Traits

Use or disuse of organs could determine the size or even elimination of organs

Evidence from Comparing AnatomyHomologous structures – similar evolution (during development), different functions

Analogous structures – evolved separately, similar functions

Wings of a pterosaur, bat and birdDifferent functions, similar bone structure

Evidence from Comparing Anatomy

Vestigial organ – organ that serves no useful function in an organism

MacroevolutionLarge-scale evolutionary patterns and processes over long periods of time.

Different Types of Evolution – Divergent and Adaptive Radiation

Divergent - Two or more related species becoming more and more different.Adaptive radiation – species that evolve into several different forms living in different ways.

Different Types of Evolution - Convergent

Convergent – organisms independently evolve similarities when adapting to similar environments.

Wings of a pterosaur, bat and birdHuman hand

Bat wing

Mole foot

Fly wing

• Coevolution can occur in competitive relationships, sometimes called evolutionary.

Different Types of Evolution - Coevolution

Opposite to Evolution – ExtinctionSpecies that has died out.More than 99% of all species are now extinct.

Types of Adaptations – Camouflage (Crypsis)

Adaptation that allows an organism to blend in with its surrounding environment.

Types of Adaptation - MimicryCopying the appearance or behavior of another organism to avoid predators.