1. Natural selection and mechanisms of evolution pt 1

2. Going public 7 years have passed since the Beagles voyage
1844: Darwin gave his wife a 213 page manuscript outlining his theory
Worried of public feedback, he didn’t go public
By 1858 he had written 250,000 words!!
250, 000!!
That same year he received a letter from a certain Alfred Russell Wallace, naturalist in Malaysia
He had arrived at the same conclusions, independently of Darwin==uh oh
Darwin 20 years vs. Wallace 2 days

3. Still going public
Darwin submitted his paper along with Wallace’s at the next Linnaean Society meeting, July 1, 1858
A year and a half later, Darwin
condensed his 250, 000 word behemoth into On the Origin of the Species.

4. Natural Selection
Darwin’s words: “…can we doubt that individuals having any advantage, however slight, over others, would have the best chance of surviving and procreating their kind? On the other hand, we may feel sure that any variation in the least degree injurious would be rigidly destroyed. This preservation of favourable traits and the rejection of injurious variations I call Natural Selection.”

5. Evolution by natural selection
Observation 1
Individuals within a species vary in many ways
Observation 2
Some of this variability can be inherited
Observation 3
Every generation produces far more offspring than can survive and pass
on their variations.
Observation 4
Populations of species tend to remain stable in size
Inference 1
Members of the same species compete with each other for survival
Inference 2
Individuals with more favourable variations are more likely to survive
and pass them on. Survival is not random.
Inference 3
As these individuals contribute proportionately more offspring to
succeeding generations, the favourable variations will become more
common. (This is natural selection.)

6. Opposition
The publication of his book did not come without critical opposition
Recall, evolution requires time==many people didn’t believe in the view that earth was many millions of years old
Fossil record wasn’t as extensive during their time==many gaps
Looking back at whales, today scientist have found 50-million year old whale fossils with fully functioning hips and hind limbs.
They also have found 38-million year old ancestral whales that have tiny, non-functional hind limbs.

7. Environmental change
Before the industrial revolution most trees in England were covered with a light coloured lichen
This lichen provided good camouflage for light coloured peppered moths
With the onset of the industrial revolution in the early 1800’s most plant life became covered in black soot
By the late 1800’s most of the lichen was dead and everything became black==started to see a new black variety of the moth
By 1920, almost all of the peppered moths were black
Any guesses why?

8. Biggest "flaw"
Darwin and Wallace’s theory failed to provide and explain where new variations came from
The answer to this lie in the work of
Mendel and his experiment testing
inheritance within the pea plant
Today new variation is attributed largely to genetic mutation and recombination
Advances in genetics have provided further evidence for evolution and solved most of the evolutionary puzzle

9. Genetic Variation Geneticists study changes in the
inheritable traits of organisms.
Inheritable traits are represented
by genes: these are portions of
DNA (nucleic acid) that code for
polypeptides (i.e. proteins and traits)
Genes are located at specific points (loci) of the chromosomes
Most eukaryotic organisms are diploid==2 sets of chromosomes; one from each parent

10. GV continued Genes can come in multiple forms called alleles
An organism whose alleles are the same for a given trait is said by homozygous
Conversely, if that organism has different alleles for that trait then they are heterozygous

11. More GV
All individuals of a species possess the same genome: which is the complete set of chromosomes, genes and DNA, for that organism
However each individual will have a different genotype, which is the set of all alleles possessed by the individual
The phenotype, is the physical manifestation of the individual’s traits, based on the interaction between genes and the environment
And these phenotypes are acted on by natural selection

12. Genomes With the advances in genomic
technology such as DNA sequencing,
scientists have the power to map
genomes, analyzing and comparing
genetic code
Results?
Amount of DNA varies from species to species
The larger the genome the greater potential for genetic diversity==more mutation
Many eukaryotic organisms such as humans have non-coding sequences in their DNA==introns
The greater the number of alleles for a gene the greater the genetic diversity

13. Amount of DNA Species Common name DNA kilobases Estimated
number of genes
Mycoplasma genetalium
bacterium
580
470
Saccharomyces cerevisiae
yeast
1200
6500
Drosophila melanogaster
fruit fly
13 000
Xenopus laevis
toad
unknown
Macaca nigra
macaque
Homo sapiens
human
42 000
Necturus maculosus
mud puppy
Amphiuma means
newt
Trillium species
trillium
Amoeba dubia
amoeba

14. Populations
A population consists of all members of the same species living in the same region
The amount of genetic diversity goes through the roof through sexual reproduction
For example: an organism with 10, 000 genes is only heterozygous at 10% of the loci. This means that the organism could produce 2^1000 = × 10301
This is more than the total number of atoms in the universe! (if you were curious this number is around 10^81)
Needless to say, unless dealing with twins or clones, no two offspring will ever ever have the same genotype
Note: this number is purely based on probability alone and doesn’t take mutation or crossing over into account

15. References
Pgs Review Q’s: Pg 516 #1, 6, 9 Pg 518 #3 Pg 528 #3, 4, 7, 8 Pg 546 #1, 3