The history of earth and life
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The History of Earth and Life. Fossils & Ancient Life . The study of ancient life using fossil records Paleontologist- A scientist who studies fossils to infer what past life and life forms were like. Fossil Record- Collection of fossils used as information about past life.

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The History of Earth and Life

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The history of earth and life

The History of Earth and Life

Fossils ancient life

Fossils & Ancient Life

  • The study of ancient life using fossil records

    • Paleontologist-A scientist who studies fossils to infer what past life and life forms were like.

    • Fossil Record-Collection of fossils used as information about past life.

      • Provides evidence about the history of life on Earth.

      • Shows how different groups of organisms changed over time.

      • 99% of all species that have ever lived on earth have become extinct.

How fossils form

How Fossils Form

  • The Steps to fossil formation

    • Water carries small rock particles to the bottom of lakes and seas.

    • Dead organisms at the bottom of lakes and seas are buried by the layers of sediment which forms new rock.

    • The weight of the new rock compresses on the lower layers of the new rock and minerals replace all or part of the dead organisms body

    • The preserved remains may later become exposed due to a variety of factors.

  • Most fossils form in sedimentary rock.

Interpreting fossil evidence

Interpreting Fossil Evidence

  • Relative Dating: The age of a fossil is estimated by comparing the fossil to other fossils.

    • Index Fossils- Those fossils used for comparison purposes in relative dating. These fossils are distinctive fossils from specific time periods.

    • This type of fossil dating provides no information about absolute age of the fossil

  • Radioactive Dating: The age of the fossil is calculated based on the amount of remaining radioactive isotopes it contains.

    • Half-life- the length of time it takes for half of the radioactive atoms in a sample to decay.

    • Radioactive dating uses half-lives to determine the age of the fossil.

Geologic time scale

Geologic Time Scale

  • Scale used to represent evolutionary time.

  • Major changes on fossil records of plants and animals are used to mark where one segment ends and another begins.

  • The basic divisions of the scale are

    • Eras & Periods

Formation of earth

Formation of Earth

  • Earth was created approximately 4.6 billion years ago.

    • Clouds and dust condensed into a sphere.

    • Gravity pulled this cosmic debris (matter) together to form a planet.

    • Collisions with other objects ( some as large as planets) produced enough heat to melt the globe.

    • After the earth melted its elements rearranged themselves according to density.

Formation of earth cont

Formation of Earth Cont…

  • 4 Billion years ago Earth cooled.

    • Volcanic eruptions and meteor showers brought the materials to earth to create solid rock.

  • 3.8 Billion years ago the Earth’s surface cooled off enough for water to remain in liquid form.

    • Oceans form.

  • Earths original atmosphere lacked oxygen to support life.

The first organic molecules

The First Organic Molecules

  • Stanley Miller and Harold Urey conducted laboratory simulations of early earth to explain how early organic molecules emerged from simpler compounds.

    • Energy from an lightning strike may have provided the electrical spark needed to combine atoms of the atmosphere and form molecules necessary for life on Earth to exist.

    • Earth can now produce organic molecules like carbohydrates, proteins, lipids and amino acids.

The puzzle of life s origin

The Puzzle of Life’s Origin

  • Formation of Microspheres

    • Under certain conditions large macromolecules can form tiny bubbles called proteinoid microspheres, which can exhibit the properties of cells.

    • Some scientists believe these microspheres took on more and more of the cells characteristics and eventually became what we know of as cells.

  • Evolution of RNA and DNA

    • Neither DNA or RNA can exist without each other.

    • So which can first??????

      • Scientists think RNA existed first and gave way to DNA

      • However, many questions still exist about the evolution of DNA and RNA.

Free oxygen

Free Oxygen

  • Microfossils- fossils of microscope organisms found in rock 3.5 million years ago.

  • These organisms were single celled prokaryotic organisms known as anaerobes(organisms that lived without oxygen).

    • Anaerobes today exist in airless environments.

  • Photosynthetic bacteria evolved and began to put oxygen into the atmosphere.

    • Gives way to aerobes (organisms that need oxygen).

    • Many anaerobes died because oxygen was toxic to them.

    • Ozone layer now forms.

Origin of eukaryotic cells

Origin of Eukaryotic Cells

  • Prokaryotic cells (those cells that don’t have a nucleus) gave way to Eukaryotic cells (those cells that do have a nucleus).

  • Endosymbiotic Theory- Eukaryotic cells formed from a symbiosis among several different prokaryotic organisms.

  • Sometime after eukaryotic cells emerged they began to reproduce sexually which allowed evolution to speed up.

Evolution of multi cellular life

Evolution of Multi-cellular Life

  • Eras:

    • Cenozoic

    • Mesozoic

    • Paleozoic

    • Precambrian

  • Periods:

    • Quaternary

    • Tertiary

    • Cretaceous

    • Jurassic

    • Triassic

    • Permian

    • Carboniferous

    • Devonian

    • Silurian

    • Ordovician

    • Cambrian

    • Vendian

Patterns of evolution

Patterns of Evolution

  • Macroevolution: The large scale evolutionary patterns and processes that occur over long periods of time.

  • Extinction: The elimination of the existence of a species.

    • Natural selection has caused 99% of all species to go extinct.

    • Mass extinction- the extinction of an entire ecosystem.

      • Serious large event that causes the mass extinction.

      • Dinosaurs wiped out this way.

      • Clears the way for the evolution of modern species like mammal and birds.

Patterns of evolution cont

Patterns of Evolution Cont….

  • Adaptive Radiation: Process by which a single species or group of species evolves into several different forms that live in different ways.

    • Leads to rapid growth in diversity

  • Convergent Evolution: Process by which unrelated organisms independently evolve similarities when adapting to similar environments.

Patterns of evolution cont1

Patterns of Evolution Cont….

  • Co-evolution: The process by which two species evolve in response to change in each other over time.

    • EX: Plants and the insects that pollinate them.

  • Punctuated Equilibrium: Describes pattern of long stable periods interrupted by brief periods of more rapid change.

  • Gradualism: Slow, steady, gradual change.

Developmental genes and body plans

Developmental Genes and Body Plans

  • Small changes in the activity of control genes that can many other genes and cause larger changes in adult animals.

  • Changes caused by changes in activation genes.

    • EX: Many pairs of wings on ancient insects but only a single pair of wings on modern insects.

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