Changes through time
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Transcript of Changes through time
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Changes through time
“Survival of the Fittest”
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Evidence that life has changed and is now changing
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Fossil Record Fossils are remains or traces of
organisms that lived in the past.
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Fossil Record Fossils are usually found in
sedimentary rock. Organisms are buried soon after
death and the hard parts become fossilized.
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Fossil Record Fossils indicate a great deal about
the actual structure of the organisms and their environment.
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Types of fossils
Petrified Bones
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Types of fossils
Imprints
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Types of fossils
Molds/Casts
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Types of fossils
Fossils preserved in tar, amber, or ice
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Relative Age of Fossils
Layering of fossils:Older fossils are found in the lower levels of sediment
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Relative Age of Fossils Layering of fossils:
Newer fossils deposited on top of older fossils and sediment
Sometimes flipped by earthquakes, etc.
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Relative Age of Fossils
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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.
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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
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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
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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
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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
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Radiocarbon Dating
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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)
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Contemporary Changes Evidences we can observe within our
lifetime Pesticide resistance in insects
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Contemporary Changes Evidences we can observe within our
lifetime Antibiotic resistant bacteria
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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
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Parts of the body with similar structure (homologous)
BatWhaleCatHuman
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Similar patterns of embryonic development (homologous)
BirdReptileSwineHumanYes, you had a tail as an embryo!
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Homologous Development – actual photos of embryos
BirdReptile Rabbit Human
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Biochemical similarities – DNA and Proteins The ability to analyze individual
biological molecules (DNA and proteins) has provided evidence for biochemical similarities
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Methods of Change
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Jean Baptiste Larmarck French naturalist and
evolutionary theorist 1744-1829 Proposed the
inheritance of acquired characteristics
Based on an “inner need” to change
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Larmarck’s theory
His theory was disproved
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Charles Darwin and Natural Selection (1859)
Naturalist on the HMS Beagle
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Charles Darwin and Natural Selection (1859)
Exploration of South America (3 ½ years)
Visited the Galapagos Islands
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Darwin’s 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
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Darwin’s theory of Natural Selection
3. A “struggle for existence” since not all individuals can survive
4. No two individuals exactly alike (variation)
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Darwin’s 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”
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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.
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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.
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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.
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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
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Species
A group of individuals that LOOK similar and are capable of producing FERTILE offspring in the natural environment.
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Population
All of the members of the same SPECIES that live in particular AREA at the same TIME.
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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
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Sexual Selection
Preferential choice of a MATE based on the presence of a specific trait
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Speciation
The formation of new SPECIES
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Isolation
Separation of a formerly successful BREEDING population
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Geographic Isolation
Separated PHYSICALLY from each other
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Reproductive Isolation
Can no longer produce FERTILE offspring
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Extinction
When an entire SPECIES dies off.
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Gene pool
The collection of GENES for all of the traits in a POPULATION
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Hardy-Weinberg Principle
Genetic Equilibrium – no CHANGE in the gene pool
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Conditions that must exist for genetic equilibrium
1. No MUTATION 2. No MIGRATION3. Large POPULATION 4. Random MATING 5. No NATURAL SELECTION
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Natural Selection
Three types of selection1. Stabilizing Selection2. Directional Selection3. Disruptive Selection
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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.
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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.
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Directional Selection Peppermoth – find two moths per
picture
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As the ants dig deeper, anteaters with longer tongues have the adaptive advantage – survive to reproduce.
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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.
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How have crops and livestock changed over the last 50 years?
In producing better livestock or crops, what are some examples of traits for which producers select?
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Then
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Now
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Then
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Now
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Then
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Now
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Then
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Now
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Then
Removing Seeds
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Now
Seedless
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Then Dehorning
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Now Polled
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Natural Selection
an organisms’ ability to SURVIVE and pass on its GENETIC information to its offspring.
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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
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Selective Breeding
In what ways is selective breeding similar to natural selection?
In what ways is it different?
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Archeozoic Era Oldest known rocks and fossils Animals without backbones
Jelly-fish, worms, sponges Bacteria and blue-green algae
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Paleozoic Era Estimated from 248-550 million
years ago Animals: Fish, amphibians, and
insects Plants: Algae and simple plants; first
conifers
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Mesozoic Era Estimated from 65-248 million years
ago Age of the Dinosaurs Animals: Reptiles and birds Plants: Conifers and first flowering
plants
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Cenozoic Era Estimated from present to 65 million
years ago Age of the Mammals Animals: Mammals and birds Plants: Flowering plants