1. Linnaean Taxonomy ( )

2. Lamarckian Evolution
Jean-Baptiste Lamarck ( ) was a naturalist who believed that traits acquired by an organism after birth were passed along to offspring.

3. Example: a giraffe stretches its neck reaching for high leaves and passes the trait for stretched out neck to offspring
Theory largely abandoned, although recently the study of epigenetics has rekindled interest

4. Darwinian Evolution
Charles Darwin ( ) was a naturalist who believed that traits were inherited through the process of natural selection
During his 5 year voyage on the HMS Beagle, he made extensively detailed observations of plants, animals, and geological formations
He theorized that organisms evolved to fill specific niches

5. Darwin’s Finches Beak Evolution 1. Cracking nuts 2. Small, soft seeds
3. Insects
4. Insects

6. DNA Changes Drive Evolution
DNA is the instruction manual of a cell
Central Dogma: DNA → RNA → Protein
Changes in DNA can produce changes in protein
Changes in protein can affect the function of a cell
Changes in DNA can be good, bad, or neutral
Good = new function provides selective advantage
Bad = loss of function (cancer)
Neutral = no change to amino acids or change does not affect protein function

7. DNA Changes Accumulate
On average, in humans DNA mutates at a rate of about bases per generation
Occasionally, larger segments of DNA mutate, giving rise to completely new genes

8. To Summarize… Evolution is the result of changes to DNA over time
To be passed from one generation to the next, DNA mutations must occur in the gametes which are inherited by offspring
Inherited DNA mutations that provide a survival advantage in a given environment tend to be preserved in a population
What type of cell division produces gametes? What are the male and female gametes?

9. DNA Changes Everything
We can compare the DNA from different species to determine genetic similarity
Species with similar DNA are more closely related than species with dissimilar DNA
If DNA mutates at a constant rate, it can be used to determine the time it has taken two species to diverge (constant rate of mutation)

11. Punctuated Equilibrium
There are gaps in the fossil record which have led to the concept of “punctuated equilibrium”
The idea is that there are evolutionary “jumps” that seem to come out of nowhere

12. Viruses Facilitate Evolution
Punctuated equilibrium may be partially explained by:
An incomplete fossil record
The transfer of genetic material (DNA) between species by retroviruses
Retroviruses contain RNA, which they insert into a host cell. The host cell reverse transcribes the retrovirus RNA to DNA, and the new DNA is inserted into the host’s DNA

13. Retroviruses Add DNA
Retroviruses include: HIV (human immunodeficiency virus), the Herpesvirus family, HTLV (human T cell leukemia virus)

14. Retrovirus DNA can be Inherited
If a retrovirus inserts its DNA into a meiotic host cell (egg or sperm), it can be passed along to offspring
However, the DNA may not produce an active gene product if it is inserted into a region of host DNA that lacks a promoter region
In that case, the DNA may continue to evolve as a non-conserved region (mutating more quickly than an important gene)

15. Pseudogenes

16. Pseudogenes have many sources
Inactive retroviral DNA insertion
Gene duplication
Mutations in the promoter sequence of an existing gene
Pseudogenes can be reactivated if…
Promoter sequence mutation results in re-activation
Transposons “jump” into a position to activate genes

17. Transposons (Jumping Genes)
Dr. Barbara McClintock was awarded the Nobel Prize in 1983 (Physiology or Medicine category) for her discovery that gene regulation can change based on DNA segments moving around an organism’s genome.

18. Last Universal Common Ancestor
All of this information contributes to our search to understand who we are and how we fit in to the world around us. DNA has literally re-shaped our understanding of the Tree of Life.