Evolution by Evolution by Natural Selection Change over time

What is evolution by natural selection? Adaptations will spread throughout a population (species) if:  It helps an organism GET FOOD  It helps an organism AVOID PREDATION  If helps an organism ATTRACT A MATE Adaptations will spread throughout a population (species) if:  It helps an organism GET FOOD  It helps an organism AVOID PREDATION  If helps an organism ATTRACT A MATE

How does NATURAL SELECTION WORK?  VARIATIONS (don’t help survival, just provide differences among organisms) exist in a population  Ex: Eye color: does it help you…  GET FOOD?  AVOID PREDATION?  ATTRACT A MATE?  VARIATIONS (don’t help survival, just provide differences among organisms) exist in a population  Ex: Eye color: does it help you…  GET FOOD?  AVOID PREDATION?  ATTRACT A MATE?

How does NATURAL SELECTION WORK?  Adaptations: These traits do help you survive  Examples: A peacock’s bright colors, red cardinals, a rattle snake’s rattle, a turtle’s shell……what else?  Adaptations: These traits do help you survive  Examples: A peacock’s bright colors, red cardinals, a rattle snake’s rattle, a turtle’s shell……what else?

NATURAL SELECTION IS A THEORY What is a theory?  A theory is a well supported testable explanation of phenomena that have occurred in the natural world  Some common theories include:  Gravity  Heliocentric theory (earth revolves around the Sun)  A theory is a well supported testable explanation of phenomena that have occurred in the natural world  Some common theories include:  Gravity  Heliocentric theory (earth revolves around the Sun)

Galapagos Islands, Ecuador

Darwin’s Observations  Was fascinated at how WELL ADAPTED the animals were to the island  Noticed that many of the animals he saw on the island closely resembled the animals on the main land but were a BIT DIFFERENT!  Was fascinated at how WELL ADAPTED the animals were to the island  Noticed that many of the animals he saw on the island closely resembled the animals on the main land but were a BIT DIFFERENT!

Darwin’s Finches

Natural Selection  The struggle for existence  The struggle for existence = survival of the fittest  Fitness = ability to survive and reproduce; the result of adaptations  Members of the same species compete for food, living space, and mates  Those that are faster or better camouflaged, etc are more likely to survive…sometimes leading to new traits!  The struggle for existence  The struggle for existence = survival of the fittest  Fitness = ability to survive and reproduce; the result of adaptations  Members of the same species compete for food, living space, and mates  Those that are faster or better camouflaged, etc are more likely to survive…sometimes leading to new traits!

Darwin’s Theory of Natural Selection 1.Overproduction:  more offspring are produced than can survive to maturity 2.Genetic variation:  No 2 organisms are exactly alike (so when competition exists, some may win!). 3.Struggle to survive:  Organism BEST ADAPTED to the new environmental pressures will survive to REPRODUCE (and pass on adaptation to offspring) 4.Differential reproduction:  In time….. (millions of years)….. the traits in a population will change (and may form new species). 1.Overproduction:  more offspring are produced than can survive to maturity 2.Genetic variation:  No 2 organisms are exactly alike (so when competition exists, some may win!). 3.Struggle to survive:  Organism BEST ADAPTED to the new environmental pressures will survive to REPRODUCE (and pass on adaptation to offspring) 4.Differential reproduction:  In time….. (millions of years)….. the traits in a population will change (and may form new species).

Evidence: The Fossil Record  Fossils are the remains of once living organisms  Many different species were present on this planet in the past  Fossils are the remains of once living organisms  Many different species were present on this planet in the past

a)Ancient sea scorpion Jaekelopterus rhenaniae b)Trilobite Isotelus rex c)Dragonfly Meganeura monyi d)Millipede Arthropleura armata e)Reconstruction of a fossil claw from the ancient sea scorpion (390 mya) Comparative sizes of a human male with aquatic creatures that existed between 460 and 255 mya:

 Superposition  If no major disturbance has occurred, a layer of rock at one place was formed after the layer below it  Provides relative age of fossil  Observe life forms change over time Evidence: The Fossil Record

Homologous = similar anatomical structures in different species  Ex: Forearms of a human, cat, whale, and bat are similar in structure.  Indicates that these organisms shared a common ancestor. Homologous = similar anatomical structures in different species  Ex: Forearms of a human, cat, whale, and bat are similar in structure.  Indicates that these organisms shared a common ancestor. Evidence: Homologous Structures

 Analogous = anatomical structures that serve a similar purpose, but are different in structure.  Ex: The wings of a bat and a bird are not similar in structure but are both meant for flying.  Species with analogous structures do NOT share a common ancestor.  Just adapted to a similar environment (convergent evolution).  Analogous = anatomical structures that serve a similar purpose, but are different in structure.  Ex: The wings of a bat and a bird are not similar in structure but are both meant for flying.  Species with analogous structures do NOT share a common ancestor.  Just adapted to a similar environment (convergent evolution). Evidence: Analogous Structures

 Vestigial = Organs that are no longer useful to the organism  Humans: coccyx, wisdom teeth, eye fold  Eyes on the naked mole rat  Were present and used in the past and have since become useless.  Not considered vestigial anymore: appendix  Vestigial = Organs that are no longer useful to the organism  Humans: coccyx, wisdom teeth, eye fold  Eyes on the naked mole rat  Were present and used in the past and have since become useless.  Not considered vestigial anymore: appendix Evidence: Vestigial Organs

 Vertebrates all have similar structures in the early developmental stages  Ex: Gill slits  Shows the similarities of the different vertebrates; suggests common ancestor  Vertebrates all have similar structures in the early developmental stages  Ex: Gill slits  Shows the similarities of the different vertebrates; suggests common ancestor Evidence: Embryology

 By comparing the DNA, RNA, & Proteins of organisms scientists can quantify how alike or different two organisms are.  There is a high level of similarity among all organisms.  Can you believe it??? All life on this planet is over 90% the same when viewed at the DNA level  By comparing the DNA, RNA, & Proteins of organisms scientists can quantify how alike or different two organisms are.  There is a high level of similarity among all organisms.  Can you believe it??? All life on this planet is over 90% the same when viewed at the DNA level Evidence: Biochemical Evidence