Changes in Living Things Over Time

1. Changes in Living ThingsOver Time

2. Changes Over Time • In order for a species to survive, in an ever changing environment, they must change as well – evolution. • As scientists study organisms from the past and compare them to organisms that currently live on the planet, they have discovered many evidences that organisms have gradually changed over time. • If a species does not change (adapt) it will ultimately die and the species will become extinct.

3. Evidence of Evolution • Evidence that supports the theory of evolution : • Fossil Evidence • Radioactive Dating • Law of Superposition • Anatomical Evidence • Chemical Evidence

4. 1. Fossil Evidence • Remains of a once living thing. • Bone, print, shelter, pollen, seeds • Not the complete organism but only the hard parts.

5. 2. Radioactive Dating • Measures the age of a fossil through radioactive elements. • Decay rate of radioactive element = half life. • Half life = amount of time for half the element to decay. C14 half lives 1 half life = 5730 yrs 2 half lives = 11460 yrs 3 half lives = 17190 yrs 4 half lives = 22920 yrs 5 half lives = 28650 yrs www.ipj.gov.pl/

6. 3. Law of Superposition • Where an organism’s fossils can be found in the rock record. • Youngest on top • The most recent event to occur • Oldest on the bottom • The earliest event to occur www.sd41.k12.id.us/

7. 4. Anatomical Evidence • Jean-Baptiste de Lamarck (early 1800’s) • Concluded: living things had changed over time. • Homologous structures – body parts of different organisms with similar structures. • Human arm, bat wing, whale flipper and dog leg • Things did evolve thus becoming better adapted for their environment. www2.visalia.k12.ca.us/

8. Anatomical Evidence • Lamark’s downfall! • Believed that body structures change because of an inborn will to change and use. • Birds – had the desire to fly and over time thus developed wings • Giraffe neck- Started off short but with continual stretching it lengthened. • Eventually lost all credibility because of this.

9. www.bellrevolution.com/

10. 6. Chemical Evidence • DNA is the basic unit of heredity. • More similar the DNA = more closely related the organisms. • Human vs. Human = 100% • Human vs. Chimpanzee = 98% • Human vs. Mouse = 92% • Protein molecule similarities can also determine common ancestors. • Scale of protein change = molecular clock

11. Who is the common ancestor to the Trachodon and Triceratops? • Who is more closely related: • Trachodon and Stegosaurus • Apatosaurus and Triceratops • Tyrannosaurus and Coelophysis • Coelophysis and Theodont Camptosaurus Split most recently from each other

12. Natural Selection • Charles Darwin • 1831, 5yr voyage on the Beagle • Studied plants and animals • Galapagos – noticed difference between island and mainland creatures. • Perfectly adapted to survive in a particular environment. • 1858 – Published On the Origin of Species • Stated his theory of evolution – natural selection www.charlesdarwinresearch.org/

14. Natural Selection • Natural Selection – survival and reproduction of those organisms best adapted to their surroundings. • 2 ways: • Overproduction - Producing more offspring than can survive. • Competition for both food and shelter • Those best adapted will survive and reproduce – survival of the fittest! • The fittest are selected by their surroundings

15. Overpopulation Salmon eggs Tadpoles Dandelion Seeds

16. Variation • Variation - No two members of a species are exactly alike. • Polar Bears – fur thickness • Survival of temperature variation is dictated by fur. • Peppered Moths – body colors • Pollution levels change bark colors – camouflage determines survival.

17. Variation Polar Bear fur thickness Mouse color Peppered Moths color