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Evolution: Change Over Time

Explore Charles Darwin's voyage on the HMS Beagle, his studies on animal and plant life, and the development of his evolutionary theory, including natural selection and adaptation. Discover how Darwin's observations and the works of influential thinkers shaped his revolutionary ideas on species change over time.

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Evolution: Change Over Time

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  1. Chapter 15 Evolution: Change Over Time

  2. Founder of modern evolutionary theory 1831 Darwin became a naturalist on the HMS Beagle Studied animal and plant life on mapping expedition to South America and South Pacific CHARLES DARWIN

  3. Darwin's Voyage

  4. Darwin studied anatomy of insects, reptiles, birds and flowering plants Galapagos Islands

  5. Galapagos Tortoises • The inhabitants...state that they can distinguish the tortoise from different islands; and that they differ not only in size, but in other characters. Captain Porter has described those from Charles and from the nearest island to it, namely Hood Island, as having their shells in front thick and turned up like a Spanish saddle, whilst the tortoises from James Island are rounder, blacker, and have a better taste when cooked.---Charles Darwin 1845

  6. Darwin was convinced that evolution occurs Species Change Over Time

  7. That there must be a struggle for existence among all individuals Organisms must struggle for Food Space Prey Darwin Concluded...

  8. Ideas that shaped Darwin's thinking • From ancient times, most people believed all living things were created by a divine being at the same time and remained unchanged. • By the time Darwin set sail, numerous discoveries, including a rich fossil record, had turned up importance evidence that caused some scientists to question these ideas.

  9. Ideas that shaped Darwin's thinking • Geologists James Hutton and Charles Lyell • After examining Earth in great detail, recognized that Earth is many millions of years old, and the processes that changed Earth in the past are the same processes that operate in the present. • Ex: volcanoes, earthquakes, erosion, continental drift, etc. The Grand Canyon, with its many layers of rock, was formed over millions of years by the Colorado River (erosion).

  10. Ideas that shaped Darwin's thinking • Jean-Baptiste Lamarck - French naturalist • Published hypothesis of Inheritance of Acquired Characteristics same year Darwin was born • Proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime. • Traits could then be passed on to offspring • Over time would lead to change in species

  11. Ideas that shaped Darwin's thinking • Thomas Malthus - English economist • Reasoned that if the human population continued to grow unchecked, eventually there would not be enough space and food for everyone • Forces such as war, famine and disease work against the growth • Darwin realized this was even more true for plants and animals because humans produce far fewer offspring

  12. Upon returning to England, Darwin began studying his specimens and filling notebooks with ideas. • Shared ideas with friends but reluctant to publish -- understood his ideas challenged scientific and religious beliefs of his day • After more than 25 years -- publishedOn the Origin of Species in 1859

  13. Charles Darwin Published:“On the Origin of Species” 1859

  14. Survival of the fittest

  15. Only some of the population survive long enough to produce offspring Survival of the Fittest

  16. Darwin’s observations led to the conclusion that individuals have different variations of traits that can be inherited Which ones survive? Darwin bred pigeons with desirable variations and he was able to produce offspring with the same features

  17. Breeder selects the particular traits Darwin wondered if there was some force in nature similar to artificial selection Artificial Selection

  18. NATURAL SELECTION Darwin's Explanation for Change...

  19. Mechanism for change in populations that occurs when organisms with favorable variations for a particular environment survive, reproduce and pass variations on to the next generation Organisms with less favorable variations are less likely to survive and pass on traits to the next generation Natural Selection

  20. Summary of Natural Selection

  21. Tendency toward Overproduction • For example: Fish lay thousands of eggs • Most of these eggs will not survive

  22. Individuals Exhibit Variations • Example: Fishes may differ slightly in color, fin and tail size and speed

  23. Individuals with favorable traits survive and pass on those genes • Ex: A fast fish with camouflaged skin will be more likely to survive and reproduce. Thus, passing along the more desirable traits to future offspring.

  24. Populations evolve, or change over time • Gradually, the offspring of the survivors make up a larger portion of the population. After many generations the population may look entirely different.

  25. Natural Selection and Adaptations

  26. Changes in structure or body parts that aide in survival Adaptation

  27. To copy the appearance of another species Mimicry

  28. Color adaptation so organism blends with its surroundings CAMOUFLAGE

  29. May take millions of years to develop or they may be rapid Ex: Slow---Sightless mole rat Fast: Antibiotic resistance Adaptations....

  30. Fossils show change over time Evidence for Evolution The Fossil Record

  31. Geographical Distribution • Geographical Distribution • Organisms live in different areas of the world, but have similar adaptations • Different ancestors, but similar environmental pressures acting against it • Descent with modification

  32. Modified structure that is seen among different groups of descendants Homologous Structures Limbs and Wings

  33. Similar in function, but different in structure Ex: Bird Wing/Butterfly Wing Analogous Structure

  34. Any body structure that is reduced in function in a living organism but may have been used in an ancestor Vestigial Structure Appendix Eyes of a sightless mole rat

  35. Fish, reptiles, birds and mammals look similar during embryological development Embryological Development

  36. Populations Evolve; Individuals Do Not

  37. Speciation, or the formation of new species, can only occur when either interbreeding or the production of fertile offspring is somehow prevented: Reproductive Isolation Geographic isolation Temporal isolation Behavioral Isolation Evolution of a Species

  38. Behavioral Isolation • Occurs when two populations are capable of interbreeding but have differences in courtship rituals or other reproductive strategies that involve behavior. • Ex. Eastern and Western Meadowlarks • Habitat overlaps, but will not mate with each other because they do not respond to each others song!

  39. Geographic Isolation • Two populations are separated by geographic barriers such as rivers, mountains, or bodies of water. • Ex. Colorado River separating the Abert squirrel and the Kaibab squirrel (about 10,000 years ago).

  40. Temporal Isolation • Two or more species reproduce at different times. • Example: Orchids. Release pollen on different days, so they cannot pollinate each other.

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