1. The Formation of Earth Earth’s Age
Scientists think that Earth formed more than 4 billion years ago by the accumulation of dust and debris moving through space.
Radiometric Dating
The ages of rocks and other materials can be determined by measuring the amount of radioactive decay that has occurred in radioactive isotopes found in samples of those materials.
An isotope’s half-life is the time that one-half of a sample of the isotope takes to decay.

2. Radioactive Decay
Example: Potassium-40’s half-life is 1.3 billion years
After 1.3 billion years, it has been reduced by half
After another 1.3 billion years (now a total of 2.6 billion), it is reduced again by half, so 1/4 of the original amount remains
After another 1.3 billion years (now a total of 3.9 billion), it is reduced again by half, so 1/8 of the original amount remains

3. The First Cells
The first cells that formed on Earth were probably anaerobic, heterotrophic prokaryotes.
Chemosynthesis
The first autotrophic cells probably used chemosynthesis to make food.
Chemosynthesis produces energy through the use of inorganic substances, such as sulfur (instead of sunlight)

4. The First Eukaryotes
Eukaryotic cells may have evolved from large prokaryotic cells that engulfed smaller prokaryotic cells. This is known as the theory of endosymbiosis.
The engulfed prokaryotic cells may have become the ancestors of organelles such as mitochondria and chloroplasts.

5. Change in a species over time
“Nothing in biology makes sense except in the light of evolution”
~Theodosius Dobzhansky ( )

6. In science, theories are statements or models that have been tested and confirmed many times
Can be used to make predictions
Can be changed as new evidence is found

7. Why do so many different animals have the same structures, the arm bones in a human are the same bones as a flipper in a whale?
Why is the sequence of DNA very similar in some groups of organisms but not in others?
Why do the embryos of animals look very similar at an early stage?

9. Charles Darwin developed the THEORY OF EVOLUTION BY NATURAL SELECTION, which explained how organisms changed over time  (ADAPTED)

10. Lamarck's Theory of Acquired Characteristics
Thought that you would gain or lose features if you overused or didn't use them, and that these changes would be passed to offspring
 PROVEN TO BE WRONG!

11. Darwin was a naturalist (what we today call biologists)
He traveled the world and made observations and sketches of many species
His most famous travels were aboard the H.M.S. Beagle where he traveled to the Galapagos Islands

12. Darwin published this work to explain the variety of species that exist on the planet
He proposed the “Theory of Evolution by Natural Selection”

13. Darwin noted that there existed many finches on the islands, but while they had similarities, each was adapted to eating a particular type of island food
He concluded that the finches all came from one ancestral species and evolved into many new species
Cactus finch, photo courtesy of zrim, flickr creative commons

14. Darwin’s Ideas Descent with Modification Natural Selection
Darwin wrote On the Origin of Species, in which he argued that:
Descent with modification occurs, in that species descended from common ancestors, and that natural selection is the mechanism for evolution.
Natural Selection
Organisms in a population adapt to their environment as the proportion of individuals with genes for favorable traits increases.
Those individuals that pass on more genes are considered to have greater fitness.

15. Natural Selection

16. 1. Variation exists among individuals in a species. 2
1. Variation exists among individuals in a species. 2. Individuals will compete for resources (food, mates, and space) 3. Competition would lead to the death of some individuals while others would survive 4. Individuals that had advantageous variations are more likely to survive and reproduce.
This process came to be known as Natural Selection The favorable variations are called Adaptations

17. Say in a species of blob, there exists blobs of all shapes and sizes (variation)
Blobs eat the little purple organisms that live underground and on the surface.

18. During a particularly hot year, food became less abundant (competition), & blobs that had the ability to dig into the soil to get food had a better chance of survival.
Many blobs died that year…….

19. The ones that survived mated and passed their genes to the next generation. (Reproduction)

20. The next generation had move blobs with the pointed noses
The next generation had move blobs with the pointed noses. That is NATURAL SELECTION.
Variation
Competition
Survival
Reproduction

21. Comparing body structures
Evidence of evolution can be found by comparing several kinds of data, including the fossil record, anatomical record, comparative embryology, and molecular record.
Evolutionary theories are supported when several kinds of evidence support similar conclusions.
1.) Fossil record
Shows change over time
2.) Anatomical record
Comparing body structures
Homologous, analogous, and vestigial structures
3.) Comparative Embryology
Shows similar patterns of embryonic development in different species
4.) Molecular record
Comparing protein & DNA sequences

22. Evidence of Evolution: Fossil Record
Layers of rock contain fossils
New layers cover older ones
Creates a record over a long period of time
Fossils show a series of organisms have lived on Earth

23. Evidence of Evolution: Fossil Record
Transitional Species
Fossils of transitional species show evidence of descent with modification
Transitional Species: Considered “intermediate species” between an ancestor and its descendants
Show slight structural changes as a particular species evolved, indicating that change is taking place over time

24. Evidence of Evolution: Fossil Record
The Earth is old
Life is old
Life on Earth has changed

25. Evidence of Evolution: Anatomical Record
Animals with different structures on the surface
But when you look under the skin…
It tells an evolutionary story of common ancestors

26. Evidence of Evolution: Anatomical Record
The same bones under the skin
But…limbs perform different functions, despite being built from the same bones
Examples: Forelimbs of humans, cats, whales, & bats
Same structure on the inside
Same development in embryo
Different functions
on the outside
Evidence of common ancestor
Homologous structures have a COMMON evolutionary origin.

27. Evidence of Evolution: Anatomical Record
Divergent Evolution
In divergent evolution, related populations become less similar as they respond to different environments.
Started with a common ancestor, so homologous structures are apparent
But over time, each structure has evolved a different function

28. Evidence of Evolution: Anatomical Record
But don’t be fooled by these…
Analogous structures are similar in function but have different evolutionary origins.

29. Evidence of Evolution: Anatomical Record
Analogous Structures
Dolphins: Aquatic mammal
Fish: Aquatic vertebrate
Both adapted to life in the sea
NOT closely related

30. Evidence of Evolution: Anatomical Record
Flight evolved 3 separate times —
evolving similar solutions to similar “problems”
Convergent Evolution
In convergent evolution, organisms that are not closely related resemble each other because they have responded to similar environments.

31. Evidence of Evolution: Anatomical Record
Vestigial Structures
A species with a vestigial structure probably shares ancestry with a species that has a functional form of the structure.
Examples:
Human tailbone
Hind leg bones on whale fossils
Why would whales have pelvis & leg bones if they were always sea creatures?
Because they used to walk on land!

32. Evidence of Evolution: Anatomical Record
Comparing Convergent and Divergent Evolution

33. Evidence of Evolution: Comparative Embryology
Development of embryos tells an evolutionary story
Similar structures during development
Indicates a common ancestor
All vertebrate embryos have a “gill pouch” at one stage of development

34. Evidence of Evolution: Comparative Embryology
Human fetus at 8 weeks

35. Evidence of Evolution: Molecular Record
When comparing the DNA of one species to another, more similarities are found in species that are more closely related.
Similarity in the subunit sequences of biological molecules such as RNA, DNA, and proteins indicates a common evolutionary history. 10 20 30 40 50 60 70 80 90
100
110
120
Lamprey
Frog
Bird
Dog
Macaque
Human 32 8 45 67
125
Compare common genes
Compare common proteins
Number of amino acids different from human hemoglobin

36. Building “Family Trees” (Cladograms)
Closely related species are branches on the tree — Coming from a common ancestor
Common ancestor to all these organisms on the tree

37. Interpreting “Family Trees” (Cladograms)
Derived characters can be used to construct a cladogram, a diagram that shows the evolutionary relationships among a group of organisms.
Common ancestor to all
Organisms after a “derived character” all have that character in common, although their ancestor does not

38. Interpreting “Family Trees” (Cladograms)
Organisms with a greater number of shared derived characters are more closely related
Example: Primates and rodents & rabbits all have a vertebrate, bony skeleton, four limbs, an amniotic egg, and hair (5 shared characteristics)…so they are more closely related to each other than to amphibians, which only have a vertebrate, bony skeleton, and four limbs (3 shared characteristics)

39. Interpreting “Family Trees” (Cladograms)
You Try:
1.) Which characteristics does a horse share in common with a dog?
2.) Which characteristics does a horse share in common with a lizard?
3.) Is a horse more closely related to a dog or a lizard?
4.) Which characteristic do all organisms on this cladogram share?

40. Artificial Selection
How do we know natural selection can change a population?
We can recreate a similar process
“Evolution by human selection”
The great variety of dog breeds is an example of artificial selection
The environment (nature) is not selecting for traits in these organisms; humans are
Humans are the ones breeding the dogs for traits that we think are desirable

41. Coevolution
Coevolution: When two or more species influence each other’s adaptations and evolution
1.) The increasing occurrence of antibiotic resistance among bacteria is an example of coevolution in progress.
Humans create antibiotics to fight bacteria, who in turn evolve to be resistant to the antibiotics
2.) Plants and insects (such as flowers and their pollinators) are another good example
Insects rely on the pollen for food
Plants rely on the insects to spread the pollen to allow for fertilization and reproduction