1. CHAPTER 15 NOTES

2. EVOLUTION Evolution – change over time
Evolution is a theory (a well- supported, testable explanation of phenomena that have occurred in the natural world)

3. CHARLES DARWIN
Contributed more to our understanding of evolution than anyone
Journeyed around the world on the HMS Beagle and made observations and collected evidence
Collected fossils (preserved remains of ancient organisms)
The islands that influenced Darwin the most were the Galapagos Islands (a group of islands with very different environments)

4. Other Scientists that influenced Darwin:
1. Hutton & Lyell studied geological change to show that the Earth changes over time
2. Lamarck was the first scientist to recognize that living things change over time
3. Malthus reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone (war, famine and disease help keep this growth in check)

5. Lamarck’s ideas: 1. Organisms constantly strive to improve themselves
2. Most-used body structures develop, but unused ones waste away
3. Once a structure is modified by use or disuse, the modification is inherited by the organism’s offspring (inheritance of acquired characteristics)
ALL OF THESE WERE PROVEN WRONG, but Lamarck paved the way for the work of later biologists.

7. CHARLES DARWIN
In 1859, Darwin published the results of his work in a book – On the Origin of Species – in which he proposed a theory called Natural Selection
Definitions:
Variation – differences between individual members of a population (ex. Color of fur, shape of teeth)
Adaptation – an inherited characteristic that increases an organism’s chance of survival

8. Darwin’s Theory of Natural Selection:
1. There is a variation within a population
2.  Some variations are favorable
3.  Not all young produced in each generation can survive (struggle for existence)
4.  Individuals that survive and reproduce are those with favorable variations (survival of the fittest)

9. EVIDENCE OF EVOLUTION
According to evolutionary theory, all life originated from a common ancestor.
Common descent – the theory that all species were derived from common ancestors

10. WAYS TO DETERMINE HOW RELATED ORGANISMS ARE:

11. 1. Fossils
The fossil record reveals changes in populations over time and supports the theory of evolution.
Scientists can calculate a fossil’s age by using radioactive dating or relative dating (we will discuss this later)
The fossil record is incomplete, but it still shows us relationships between species and how their structures have changed over time.
Fossils are mostly found in sedimentary rock.

12. 2. Homologous Structures
Homologous structures – structures that have different mature forms, but develop from the same tissues
Ex. Arms, wings, and flippers are all constructed from the same basic bones
Analogous structures – structures that share common function but NOT common structure
Ex. Wing of bee & bird
Vestigial structures – structures reduced in size and often unused
Ex. Leg/hip bones in pythons or appendix in humans

13. Homologous Structures
Analogous Structures
Homologous Structures
Vestigial Structures

14. 3. Embryology & Biochemistry
Embryology – compare how embryos of different species look during certain stages of development
Biochemistry – compare the chemicals that make up our body (amino acid)

16. GENETICS & EVOLUTION
Gene pool – consists of all the genes that are present in a population
Relative frequency – the number of times that an allele occurs in a gene pool
Ex. In a mouse population, the dominant allele for black fur may appear 40% and the recessive allele for brown fur may appear 60%
In genetic terms, evolution is any change in the relative frequency of alleles in a population

17. GENETIC VARIATION 2 Main Sources of Genetic Variation:
1. Mutations – change in a sequence of DNA
2. Gene shuffling that results from sexual reproduction

18. DEFINITIONS
Species – interbreeding populations of organisms that can produce fertile offspring
Speciation – formation of a new species
Reproductive Isolation – when members of two populations cannot interbreed and produce fertile offspring

19. How do organisms become isolated?
1. Behavioral isolation – when 2 populations are capable of interbreeding but have differences in courtship rituals or other reproductive strategies that involve behavior
2. Geographic isolation – when 2 populations are separated by geographic barriers such as rivers, mountains or bodies of water

20. Speciation in Darwin’s Finches
Darwin found over a dozen different species of finches on the Galapagos Islands that all evolved from a common ancestor
How?
A few finches (original species) flew or were blown to one of the Galapagos Islands
Then some birds migrated to neighboring islands and because the environments were different they adapted to their own environments and became separate species

22. DARWIN’S FINCHES Darwin’s Finches are an example of adaptive radiation
Adaptive radiation is when a single species has evolved into diverse forms that live in different ways

23. PATTERNS OF EVOLUTION
Gradualism – small genetic changes that occur slowly within a population
Punctuated Equilibrium – suggests that populations remain genetically stable for long periods of time, interrupted by brief periods of rapid genetic change (ex. Peppered moth)

24. Convergent Evolution
The process by which unrelated organisms come to resemble one another as they adapt to the same kind of environment
Example: fishes and dolphins
Structures such as dolphins fins and a fish’s tail fin, look and function in the same way, but they do NOT share a common evolutionary history. These are called analogous structures.

25. Divergent Evolution
The process where organisms within a species become very different and will no longer interbreed usually because they live in different environments
Example: Red fox and kit fox - similarities in structure indicate that they had a common ancestor, but as they adapted to different environments, the appearance of the two species diverged.

26. CoEvolution
The process by which two species evolve in response to changes in each other over time become so dependent on each other that they cannot survive or reproduce successfully without the other
Example: Flowers and insects

27. Convergent, Divergent or CoEvolution?
Divergent Evolution
CoEvolution
Convergent Evolution