15-3 Darwin Presents His Case

Slide 2 of 25 Publication of On the Origin of Species  15.3 NOTES #1  Outline the events leading to Darwin’s theory.  DARWIN RETURNS TO ENGLAND FROM THE GALAPAGOS IN  DARWIN CONTEMPLATES HIS IDEAS AND WRITES HIS MANUSCRIPT.  IN 1858 DARWIN RECIEVES AN ESSAY FROM ALFRED RUSSEL WALLACE ABOUT HIS THOUGHTS ON EVOLUTION.  IN 1859 DARWIN PUBLISHES “ON THE ORIGIN OF SPECIES”

Inherited Variation and Artificial Selection  Natural variation  Nature provides differences among individuals of a species  Today, we know that heritable variation in organisms is caused by variations in genes  Darwin said this variation mattered

Slide 4 of 25 Inherited Variation and Artificial Selection  Artificial Selection  Nature provided the variation, and humans selected those variations that they found useful

Slide 5 of 25 Inherited Variation and Artificial Selection  15.3 NOTES #2  Describe how natural variation is used in artificial selection.  NATURE PROVIDES VARIATION.  HUMANS SELECT THE VARIATION THEY FIND USEFUL.

Evolution by Natural Selection  Fitness  Darwin said this is the ability of an individual to survive and reproduce in its specific environment  Adaptation  Any inherited characteristic that increases an organism’s chance of survival

Slide 7 of 25 Evolution by Natural Selection  What is survival of the fittest?  Can you see the organisms in these photos?

Slide 8 of 25 Evolution by Natural Selection  Survival of the fittest = Natural selection  The hunting lioness is hard to see!  Individuals that are better suited to their environment survive and reproduce most successfully  Over time, natural selection results in changes in the inherited characteristics of a population. These changes increase a species’ fitness in its environment.

Slide 9 of 25 Evolution by Natural Selection  15.3 NOTES #3  Explain how natural selection is related to a species’ fitness.  INDIVIDUALS WITH CHARACTERISTICS/TRAITS WHICH ARE BEST SUITED FOR THEIR ENVIRONMENT WILL SURVIVE AND REPRODUCE.  THIS IS “SURVIVAL OF THE FITTEST”  THESE INDIVIDUALS ARE NATURALLY SELECTED FOR.

Evidence of Evolution  Fossils are fun!  Darwin argued that living things have been evolving on Earth for millions of years.  Evidence for this process could be found in the fossil record, the geographical distribution of living species, homologous structures or living organisms, and similarities in early development.

Slide 11 of 25 Evidence of Evolution  Homologous structures  Structures that have different mature forms but develop from the same embryonic tissues

Slide 12 of 25 Evidence of Evolution  15.3 NOTES #4  Identify evidence Darwin used to present his case for evolution.  THE FOSSIL RECORD ALLOWED DARWIN TO SEE A HISTORY OF LIFE ON EARTH.  GEOGRAPHIC DISTRIBUTION OF SIMILAR SPECIES THAT SHARE A COMMON ANCESTOR.  STRUCTURES DEVELOP FROM THE SAME EMBRYONIC TISSUE, OR HOMOLOGOUS STRUCTURES.  SIMILAR EMBRYONIC CELLS DEVELOP IN THE SAME ORDER IN RELATED SPECIES.

Slide 13 of 25 Evidence of Evolution  15.3 NOTES #5  State Darwin’s theory of natural selection.  Individuals differ, hence variation is heritable.  More offspring are born than can survive.  Competition occurs among organisms.