Name: ______Period: ______
Scientific Theory of Biological Evolution Notes
History
1. Thomas Malthus (1798)
A. Human population will grow faster than the space and food supplies needed to survive – leads to poverty, famine, etc.
· Carrying Capacity: -
______
______
2. Jean-Baptiste Lamark - Inheritance of Acquired Traits (1809)
A. Hypothesis: ______
______
B. Examples:
· A lizard that didn't use it legs would eventually not have legs and its offspring wouldn't have legs
· A giraffe stretched its neck to reach higher leaves, and this stretched neck would be a trait inherited by its offspring
C. This hypothesis was not supported by scientific evidence and so was discarded.
D. Effect: Lamark was the first to recognize that organisms are well suited for their environment – a key concept for future work.
3. Charles Lyell (1833)
A. ______
______
4. Charles Darwin - On the Origin of Species by Means of Natural Selection (1859)
A. 1831 - Darwin sails on the H.M.S. Beagle to the Galapagos Islands.
· made numerous observations of how populations differed from island to island
· collected evidence to support a new hypothesis about the way life changes over time.
B. Effect on Darwin: Darwin realized this “struggle for existence” would apply more strongly to plants and animals, because they have more offspring than humans do. (Malthus)
C. Effect on Darwin: Darwin realized if the Earth could change over time, life itself might change over time in response to physical changes of the Earth and that the changes he proposed would require many, many years. (Concluded the Earth is very old.) (Lyell)
D. 1859 – published On the Origin of Species by Means of Natural Selection (1859)
E. Evidence for this hypothesis has since been described in many diverse studies and is so well supported that Darwin’s original hypothesis is now known as the Scientific Theory of Biological Evolution
These studies include:
· the fossil record
· population genetics
· animal behavior
· DNA fingerprinting
· antibiotic resistance in bacteria
How does Natural Selection Drive Evolution?
1. Different organisms within a species have differences in morphology and physiology
a. Morphology – ______
b. Physiology – ______
2. These differences change the ability of an organism to survive and reproduce.
a. When an inherited characteristic increases an organism’s chance of survival and its ability to reproduce, that characteristic is called an adaptation.
b. Example: Monarch butterfly – bright colors warn predators that it is poisonous to eat
3. Those individuals who are better able to survive and reproduce (higher fitness for their environment) pass on their morphological and physiological differences to their offspring.
4. Over time the population is changed based on selective pressures of the environment.
a. selective pressure is any factor that makes is hard for some organisms to continue surviving, and rewards any advantage that some organisms may have been born with.
i. some selective pressures: climate changes, food supply change, predators, sexual selection
ii. Example: Lions are fast and powerful because their prey is so swift and elusive. (Because any slow and weak lions would not be able to survive long enough to reproduce). The reason antelopes are so swift and elusive is because lions are so fast and powerful. (Because any slow antelopes, and any that lack the instinct to run in a zig-zag pattern, would not survive long enough to reproduce.)
Looking for Proof of Similar Ancestry
1. Embryology
a. Embryology – ______
______
2. Body structure
a. Homologous body structures – ______
______
______
b. Analogous structures – ______
______
c. Vestigial Structures – ______
______
Example: ______Example: ______
3. Genetic data
a. Comparative studies of DNA sequences of organisms shows how similar DNA is between some species, and different from other species
b. This can confirm what was previously thought, or it can cause scientists to rethink relations between organisms.
4. Fossil Record
a. Shows that species that once existed are now extinct.
b. Shows transitional forms – fossils or organisms that show intermediate states between an ancestral form and that of its descendants.
c. Within the fossil record you can see different rates of change.
i. gradualism - ______(subtle)
ii. punctuated equilibrium - ______(dramatic)
iii. stasis - ______
d. Relative Dating – layering of fossils: older fossils are found below more recent ones. Living organisms resemble fossils although differences may be evident.
e. Radioactive dating – Using carbon dating on rocks and fossils to determine a more accurate time frame in which the organism lived.
5. Geologic Time Scale – How long has that been going on???
a. The fossil record has been used to help determine the Earth’s age. Evidence has been collected and scientists have organized the data, creating the Geologic Time Scale.
b. The Earth is estimated to be 4.6 billion years old.
c. The Geologic Time Scale marks different time frames of importance.
6. Biogeography - Geographic distribution of Living Organisms
a. Geographic location of fossils – fossils show where extinct organisms used to thrive. Plate tectonics shows where distributions of fossils meet like pieces of a puzzle.
b. Each island in the Galapagos had similar organisms but the organisms were different enough to be different species. Could they have changed over time from a common ancestor from the mainland?
i. ______
ii. ______
c. Organisms that are unrelated in the same types of habitats elsewhere in the world had the same selective pressures acting on them, and therefore, developed the similar characteristics.
Summary of Darwin’s Theory:
1. Individual organisms of a population differ and much of this variation is heritable.
2. Organisms produce more offspring than can possibly survive and those that do not survive do not reproduce.
3. Each unique organism has different advantages and disadvantages in the struggle for existence. Individuals best suited to their environment survive and reproduce most successfully. These organisms pass their heritable traits to their offspring. This process causes species to change over time in response to selective pressures.
4. Species alive today are descended from ancestral species that lived in the distant past. This process by which diverse species evolved from common ancestors unites all organisms on Earth into a single tree of life.
What is a Scientific Theory?
· ______
· ______
· ______
· ______
· ______
Hypothesis - ______
______
Truth or Misconception?
a. Hypotheses are more important than theories.
b. Theories are used to make predictions.
c. A scientific law has been proven and a theory has not.
d. Theories include observations.
e. A theory never changes.
f. Theories are incomplete, temporary ideas.
g. Theories have been tested many times.
h. Theories can include personal beliefs or opinions.
i. Theories are "hunches" scientists have.
j. Theories are explanations strongly supported by evidence.