Unit 10 (Chapters 14-15)

 Scientists have observed that species do change over time.  Over time, scientists believe that characteristics change so much that new species form.  Evolution is the slow, gradual change in a population of organisms over time.

 English naturalist who sailed on the HMS Beagle in  Made observations that led to his “theory of evolution”.  Collected thousands of plant/animal specimens.  The most famous site he visited were the Galapagos Islands.  Wrote On the Origin of the Species

Darwin returned 5 years later in 1836

 Most well known stop on Darwin’s voyage.  Small group of volcanic islands 1000 km West of South America  Different climates on each island.  Island species vary from mainland species & from island-to-island species

 Darwin noticed that the animals/plants on the Galapagos Islands were very similar to those in nearby Ecuador.  Specifically, the finches on each of the islands were different than the finches in Ecuador.  Each finch had a different shape beak depending on the type of food it ate.

 Occurs whenever a physical barrier divides a population which results in individuals no longer being able to mate.  Can lead to the formation of a new species. (speciation) ◦ This could explain the Galapagos finches. ◦ A natural disaster could have drove the finches from Ecuador and forced them over time to evolve into the unique species of finches we find on each of the islands today.

 Darwin knew that organisms could be bred in order to produce desirable traits in the offspring.  This is called artificial selection.  Also called “selective breeding”  For example: if a dog breeder wants a litter of chocolate labs, his best bet will be to breed two chocolate labs.  Darwin began to think that this could occur naturally in the environment.

 Darwin proposed in his book that evolution happens through a process called natural selection.  Natural selection states that organisms that are best adapted to their environment will survive and reproduce more successfully than other organisms without the adaptations. AS A RESULT, they will pass their adaptations on to their offspring.  DRIVING FORCE BEHIND THEORY OF EVOLUTION!

1.The Struggle for Existence  Competition for food, mates, living space, water, etc.  Some organisms will die due to this. 2.Survival of the Fittest  The strongest will be able to survive and reproduce and pass on their traits to their offspring.

 Fitness ◦ Ability of an Individual To Survive & Reproduce  Adaptation ◦ Inherited Characteristic That Increases an Organisms Chance for Survival copyright cmassengale16

 Adaptations Can Be: ◦ Physical  Speed, claws, quills, thorns, mimicry, camouflage ◦ Behavioral  Herds, packs, migration, hibernation, etc.

 Fitness is central to the process of evolution.  Individuals With Low “Fitness”: ◦ Die quicker ◦ Produce fewer offspring copyright cmassengale18

Key concept: ◦ Over time, natural selection results in changes in the inherited characteristics of a population. These changes increase a species’ fitness in its environment

 Cannot Be Seen Directly  It Can Only Be Observed As Changes In A Population Over Many Successive Generations ◦ Radiation ◦ Fossil Record

 Key Concept: Species today look different from their ancestors  Each Living Species Has ◦ Descended ◦ With Changes ◦ From Other Species ◦ Over Time

 Implies ◦ All living organisms are related  A Common Descent ◦ All species, living & extinct, were derived from common ancestors

 “Evidence” in favor of evolution can be found in the sediment (layers of rock and soil that has hardened over time).  Older layers are found beneath newer layers.  We find fossils in this sediment. ◦ A footprint left in clay ◦ A fly trapped in amber ◦ Dinosaur bones ◦ Wooly mammoth  Using fossils, scientists have made a “timeline” of life called the fossil record.

Evidence for Evolution – The Fossil Record

Structural features with a common evolutionary origin. Have the same function and/or arrangement. Used as evidence that these organisms may have evolved from a common ancestor.

 Body parts of organisms that have no common evolutionary origin (arrangement) but have similar functions. ◦ Do not have a similar appearance but have similar jobs.

 A body structure in a present-day organism that no longer serves its original purpose.  A structure becomes vestigial when the species no longers needs it for its orignal function.  Examples: Whales have hip bones, but can’t walk. Blind mole rats have eyes, but don’t use them for vision. Blind mole rats

 Human appendix is thought to be a vestigial structure.  It serves no purpose in humans.  Darwin believed it is basically the remnants of a portion of the large intestine that our supposed primate ancestors used to digest leaves.

Evidence for Evolution - Comparative Embryology  Many organisms have similar appearances in the womb.  This leads biologists to believe they evolved from a common ancestor.

Similarities in DNA Sequence  Many organisms share similar DNA sequences.  The order of their base pairs is often similar, in other words.