Changes through time “Survival of the Fittest”
Fossil Record • Fossils are remains or traces of organisms that lived in the past.
Fossil Record • Fossils are usually found in sedimentary rock. • Organisms are buried soon after death and the hard parts become fossilized.
Fossil Record • Fossils indicate a great deal about the actual structure of the organisms and their environment.
Types of fossils • Petrified Bones
Types of fossils • Imprints
Types of fossils • Molds/Casts
Types of fossils • Fossils preserved in tar, amber, or ice
Relative Age of Fossils • Layering of fossils: • Older fossils are found in the lower levels of sediment
Relative Age of Fossils • Layering of fossils: • Newer fossils deposited on top of older fossils and sediment • Sometimes flipped by earthquakes, etc.
Relative Age of Fossils • 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)
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
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) Human Cat Whale Bat
Similar patterns of embryonic development (homologous) Human Swine Reptile Bird Yes, you had a tail as an embryo!
Homologous Development – actual photos of embryos Reptile Bird Rabbit Human
Biochemical similarities – DNA and Proteins • The ability to analyze individual biological molecules (DNA and proteins) has provided evidence for biochemical similarities
Jean Baptiste Larmarck • French naturalist and evolutionary theorist • 1744-1829 • Proposed the inheritance of acquired characteristics • Based on an “inner need” to change
Larmarck’s theory • His theory was disproved
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
Darwin’s theory of Natural Selection • Living things increase in number geometrically (overproduction) • There is no net increase in the number of individuals over a long period of time Spider eggs: Many more produced than will survive
Darwin’s theory of Natural Selection • A “struggle for existence” since not all individuals can survive • No two individuals exactly alike (variation)
Darwin’s theory of Natural Selection • 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 • 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 • 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 • 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 • 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
Sexual Selection • Preferential choice of a MATEbased on the presence of a specific trait
Speciation • The formation of new SPECIES
Isolation • Separation of a formerly successful BREEDING population
Geographic Isolation • Separated PHYSICALLY from each other