Evolution

What is evolution?  Evolution is the process of biological change by which species of organisms change over time.  Evolution is a central theme in all fields of biology today.

Evolution is when organisms change over time. So, modern organisms descended from ancient ones.

Evolution is a Theory – Just like Gravity! Evolution is a well supported explanation of phenomena that have occurred in the natural worldEvolution is a well supported explanation of phenomena that have occurred in the natural world A theory in science is a well tested hypothesis, not just a guessA theory in science is a well tested hypothesis, not just a guess

Evolutionary Scientists  Charles Bonnet mid-1700s  First to use term evolution  Studied fossils  James Hutton  1795 Theory of Geological change  Jean-Baptiste Lamarck 1809  Charles Lyell  Geographical features can be built up or torn down  Charles Darwin  Thomas Malthus  Russell Wallace  Gave Darwin the drive to publish his findings

Malthus Malthus  Reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone

Jean-Baptiste Lamarck  He proposed the idea of inheritance of acquired characteristics:  changes in an environment caused an organism’s behavior to change  this would lead to greater use or disuse of a structure or organ.  the structure would become larger or smaller and would then be passed down to offspring  For example: giraffes’ long necks  Idea was WRONG!!

Charles Darwin  Natural selection was the theory he proposed to explain evolution.  He attempted to provide reasons for the biological diversity on Earth.  Developed his theory from personal observations and research of other scientists.

Charles Darwin ( ) Sailed around the world on the British ship H.M.S. Beagle. Charles Darwin ( ) Sailed around the world on the British ship H.M.S. Beagle.

What did Darwin’s Travels reveal?  The diversity of living species was far greater than anyone had previously known!!  These observations led him to develop the theory of evolution!!

What did Darwin do?  He observed the land and its inhabitants.  Finches and Tortoises  He noticed the physical differences among island species.  Species on one island looked different from those on another island.  Island species looked different from those found on the mainland. This is known as variation.  He noticed that the physical differences among the species were appropriate for their environment and diet.

Finches  Finches that live in the area with hard shelled nuts had stronger beaks.  Finches with delicate beaks were found where insects and fruits were available.

Galapagos Tortoises  Darwin observed the saddle-back and the domed tortoises.  Saddle back tortoises have long necks and legs and live in areas with necks and legs and live in areas with tall plants. tall plants.  Domed tortoises have shorter necks and legs and live in wet necks and legs and live in wet areas rich in mosses and shorter areas rich in mosses and shorter plants. plants.

Darwin finally published his ideas in  Other naturalists were developing the same theory that Darwin did.  Even though he was afraid of the Church’s reaction to his book he wanted to get credit for his work.

Natural Selection  The traits that help an organism survive in a particular environment are “selected” in natural selection

Natural Selection Mechanism by which individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals.Mechanism by which individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals. –Survival of the fittest.

Natural Selection Characteristics are passed down to offspring only if they are beneficial to individual.Characteristics are passed down to offspring only if they are beneficial to individual. –More successful individuals are “naturally selected” to live longer and to produce more offspring that share the beneficial characteristics. Natural selection acts only on existing traits.Natural selection acts only on existing traits.

Natural Selection  Four main principles: 1.Variation of physical traits. 2.Competition for limited natural resources. 3.Organisms produce more offspring than can survive.  Predation, diseases 4.Individuals with beneficial traits will survive and reproduce.  Beneficial traits are passed to offspring.

Artificial Selection  nature provides variation, humans select variations that are useful.  Example - a farmer breeds only his best livestock

Descent with Modification  Each living species has descended with changes from other species over time

Evidence of Evolution 1.Fossil Record 2.Homologous Body structures 3.Similarities in Embryology 4.Biochemical Evidence

Evidence of Evolution: The Fossil Record  Fossil record provides evidence that living things have evolved  Fossils show the history of life on earth and how different groups of organisms have changed over time

Relative vs. Absolute Dating

Relative Dating  Can determine a fossil’s relative age  Performed by estimating fossil age compared with that of other fossils  Drawbacks – provides no info about age in years

Absolute Dating  Can determine the absolute age in numbers  Is performed by radioactive dating – based on the amount of remaining radioactive isotopes remain  Drawbacks - part of the fossil is destroyed during the test

–A half-life is the amount of time it takes for half of the isotope to decay. Radiometric dating uses decay of unstable isotopes. –Isotopes are atoms of an element that differ in their number of neutrons.

Primate Fossils AustralopithecusHomo erectusHomo sapien

Primate Bone Structure

Evidence of Evolution: Homologous Body Structures  Structures that have different mature forms but develop from the same embryonic tissues Ex: Wing of bat, human arm, leg of turtle Turtle Alligator Bird

Evidence of Evolution: Homologous Structures  Features that are similar in structure but appear in different organisms and have different functions.  Strong evidence for common ancestor.  Ex: forelimbs of humans, bats and moles. Human hand Bat wingMole foot

Analogous Structures  Structures that perform a similar function. Not evidence of common ancestry.Not evidence of common ancestry.

Vestigial Structures  Remnants of organs or structures that had a function in an early ancestor.  Ex: Ostrich wings, used for balance but not flight  Ex: Humans’ appendix

Evidence of Evolution: Similarities in Embryology In their early stages of development, chickens, turtles and rats look similar, providing evidence that they shared a common ancestry.

Embryological Development

Evidence of Evolution: Biochemical Similarities  Scientists study nucleotide sequences in DNA and proteins in different organisms to determine ancestry.  If the organisms are closely related they will have similar sequences of nucleotides in their DNA and arrangement of amino acids in proteins.

Evidence of Evolution: Biochemical Similarities OrganismAmino Acid Differences OrganismAmino Acid Differences Human beta chain 0Mouse27 Gorilla1Kangaroo38 Rhesus monkey8Chicken45 Dog15Frog67 Cow25Soy bean124 The more similar the

Adaptation  Darwin’ observations led him to realize that species must somehow be able to adapt to their surroundings.  Adaptations allow species to better survive in their surroundings.  Adaptations can lead to genetic change in a population over time.

Variation  Speciation  Individuals with beneficial trait are well suited for the environment  They reproduce and pass the beneficial trait to their offspring  Individuals without the beneficial trait are less likely to survive and reproduce  Their traits are not passed.  Beneficial traits are passed while other traits disappear  These changes can eventually cause speciation

Rates of Evolution  Two main views:  Gradualism  Evolution occurs slowly and constantly over a long period of time  Darwin  Punctuated Equilibrium  Evolution occurs in spurts  Period of rapid speciation then long period of little to no change  Caused by random mutations or sudden changes in environment  Cambrian explosion