Fossils in each layer usually of those organisms that lived at the time the layer was formed. Fossils in lower layers represent species that lived earlier than those found in the upper layers. Relative position only tells which are older and which younger.
Evolution of the Horse Over time (higher layers of sediment) horse fossils became larger Separate toes became a single-toed hoof Teeth became adapted to grinding grasses
Radiometric Dating Some elements, such as uranium, undergo radioactive decay to produce other elements. Scientists have observed that radioactive elements (isotopes) decay at a constant rate over time
Radiometric Dating The amount of radioactive elements remaining in a rock can help scientists determine how much time has elapsed since the rock was formed and cooled. Common isotopes used for long-term dating (old rocks) include uranium as it decays to lead, and potassium as it decays to argon. The carbon-14 isotope can be used for dating of more recent fossils and artifacts
Radiocarbon Dating Carbon-14 is a radioactive isotope found in all living organisms. It decays at a known rate. Carbon-12 does not decay. By comparing the ratio of C-12 to C-14 scientists believe they can determine the age of a fossil
A timescale Based on radiometric data, scientists have proposed a timeline for the history of the earth. Composed of four primary eras Archeozoic (oldest) [aka Precambrian period] Paleozoic Mesozoic Cenozoic (most recent)
Contemporary Changes Evidences we can observe within our lifetime Pesticide resistance in insects
Contemporary Changes Evidences we can observe within our lifetime Antibiotic resistant bacteria
Indirect evidences Scientists cite these indirect evidences as evidence of common ancestry Homologous structures Embryonic development patterns Biochemical evidence Vestigial organs They at least demonstrate a common pattern of development
Parts of the body with similar structure (homologous) BatWhaleCatHuman
Similar patterns of embryonic development (homologous) BirdReptileSwineHuman Yes, you had a tail as an embryo!
Homologous Development – actual photos of embryos BirdReptileRabbitHuman
Biochemical similarities – DNA and Proteins The ability to analyze individual biological molecules (DNA and proteins) has provided evidence for biochemical similarities
Charles Darwin and Natural Selection (1859) Naturalist on the HMS Beagle
Charles Darwin and Natural Selection (1859) Exploration of South America (3 ½ years) Visited the Galapagos Islands
Darwins theory of Natural Selection 1.Living things increase in number geometrically (overproduction) 2.There is no net increase in the number of individuals over a long period of time Spider eggs: Many more produced than will survive
Darwins theory of Natural Selection 3.A struggle for existence since not all individuals can survive 4.No two individuals exactly alike (variation)
Darwins theory of Natural Selection 5.In the struggle for existence, those variations which are better adapted to their environment leave behind them proportionately more offspring than those less adapted Survival of the Fittest
A Modern Perspective 1.Mutation – a sudden change in the genetic material (a source of variation) Example: The DNA of one bacteria changes (becomes mutated), allowing it to become resistant to an antibiotic. It survives long enough to reproduce. Each succeeding generation has the mutated copy and is resistant to the antibiotic.
A Modern Perspective 2.Recombination of genes within a population (sexual reproduction) Provides new combinations for natural selection to try. Shows how the percentage of a gene in a population can change.
A Modern Perspective 3.Isolation – separation of a population from others of the same kind (species) Prevents recombination of genes Species become different overtime Example: A species of primrose existed together where the Promontory Range (Northern Utah) now exists. When the range lifted up, it isolated two groups. Both became different as they adapted to the different environments on either side of the range. They have become so different they can no longer reproduce.
A Modern Perspective 4.Natural Selection – certain traits give an adaptive advantage to organisms and they leave behind more offspring They survive long enough to reproduce and pass on their genetic information INDIVIDUALS DO NOT EVOLVE... POPULATIONS EVOLVE OVER TIME
Species A group of individuals that LOOK similar and are capable of producing FERTILE offspring in the natural environment.
Population All of the members of the same SPECIES that live in particular AREA at the same TIME.
Variation in a population Bell Curve - The distribution of traits (Average is the middle.) Mode - The number that occurs most often (High pt.) Range - The lowest number to the highest number
Gene pool The collection of GENES for all of the traits in a POPULATION
Hardy-Weinberg Principle Genetic Equilibrium – no CHANGE in the gene pool
Conditions that must exist for genetic equilibrium 1. No MUTATION 2. No MIGRATION 3. Large POPULATION 4. Random MATING 5. No NATURAL SELECTION
Natural Selection Three types of selection 1. Stabilizing Selection 2. Directional Selection 3. Disruptive Selection
Stabilizing Selection Individuals with the AVERAGE form have the ADVANTAGE Example – lizards that are small are not fast enough to avoid predators; lizards that are large cannot hide easily from predators; those of average size are both fast enough to get away from predators and small enough to hide – giving them the selective advantage.
Directional Selection Individuals with one of the EXTREME forms have the ADVANTAGE Example – Peppermoth in Great Britain during the industrial revolution – melanistic (dark colored) moths had the selective advantage after trees where covered in coal soot. After air quality improved, the selection advantage returned to the lighter colored moths.
Directional Selection Peppermoth – find two moths per picture
As the ants dig deeper, anteaters with longer tongues have the adaptive advantage – survive to reproduce.
Disruptive Selection Individuals with either of the EXTREME forms have the ADVANTAGE Example: a shellfish living in shallow ocean water is preyed upon by a bird. Originally those with the neutral color (sand colored) had the advantage because they were camouflaged in the sand. As the birds fed on the shellfish and left their feces behind in the water, the ocean floor became white in color. Those shellfish that were sand colored are now easily found while the lighter colored shellfish are able to blend in, as are the darker colored shellfish if they are found on the darker rocks.
Natural Selection an organisms ability to SURVIVE and pass on its GENETIC information to its offspring.
Selective Breeding Also known as Artificial Selection Human control over organisms passing on their genetic information. Human determination of those crops and livestock allowed to reproduce Based on desired traits
Selective Breeding In what ways is selective breeding similar to natural selection? In what ways is it different?
Archeozoic Era Oldest known rocks and fossils Animals without backbones Jelly-fish, worms, sponges Bacteria and blue-green algae
Paleozoic Era Estimated from 248-550 million years ago Animals: Fish, amphibians, and insects Plants: Algae and simple plants; first conifers
Mesozoic Era Estimated from 65-248 million years ago Age of the Dinosaurs Animals: Reptiles and birds Plants: Conifers and first flowering plants
Cenozoic Era Estimated from present to 65 million years ago Age of the Mammals Animals: Mammals and birds Plants: Flowering plants