1. PART 1 B_5 Biological Evolution “How has life changed over time?”
Standard B-5
Demonstrate an understanding of biological evolution and the diversity of life.

2. B-5.1 Introduction (sec 10.1-2)
What is a theory?
What is biological evolution?
Explain the difference between microevolution and macroevolution.
List 2 other people who had ideas about evolution (what were their ideas)
View VIDEO #2: Who was Charles Darwin?

3. Summarize the Theory of Evolution
First of all a quick reminder of the term THEORY:
Well supported and tested explanation, which unifies a broad range of observations (evidence)
Biological Evolution
Cumulative genetic changes that occur in a population over time (GRADUAL change over TIME)
Changes due to gene mutations or crossing over
Explains the similarities and diversity of living things.
Microevolution: small changes affecting a single population (usually over a few generations); changes in allele frequencies
MACROevolution: dramatic changes that occur over long periods of time; includes speciation (formation of new species) and mass extinction

4. Origins of Evolutionary Thought
Erausmus Darwin (1731): English Doctor
Grandfather of Charles Darwin
Proposed ideas of common ancestry
Carolus Linnaeus (1735): Swedish Botanist
Devised a standard classification system for living things; based on similarities and evolutionary relationships
Kingdom, Phylum, Class, Order, Family, Genus, Species
Scientific Names: Homo sapein (Genus species)
Georges Buffon (1749): French Naturalist
Proposed that species shared ancestors instead of arising separately
Rejected that the Earth was only 6000yrs old

5. Origins of Evolutionary Thought
James Hutton (1785) – Proposes that Earth is shaped by geological forces that happen over extremely long periods of time (estimates Earth to be millions of years old)
Thomas Malthus (1798) – Predicts that the human population will grow faster than the space and food needed to sustain it.
Charles Lyell (1833) – Explained that processes occurring now have shaped Earth’s geological features over long periods of time.

6. Origins of Evolutionary Thought
Jean-Baptiste LAMARCK (1809) read pg376
Proposed that organisms over long periods of time due to the environment (evolve towards perfection and complexity)
Inheritance of Acquired Characteristics (thru use or disuse)
Use and disuse of organs cause organism to change; organism change because they need to change; Ex: Bird doesn’t fly loses wings
Alfred Russel WALLACE (1858)
1848 made an expedition to the Amazon River and then Malay Islands (made similar observations as Darwin)
Wallace shared his findings with Darwin and Darwin presented Wallace’s essay to the Linnaean Society
Charles DARWIN (1859)
Sets sail on HMS Beagle ( ), the voyage provides evidence that leads to the foundation of his theory of evolution
(1859)On the Origin of Species by Means of Natural Selection (evolution by natural selection)

8. Darwin’s Observations (do not copy)
Collected Fossil Evidence….
Fossils he collected RESEMBLED organisms that were currently living.
Was there a relationship between fossils and similar modern animals?
Found fossils shells of marine organisms high in Andes Mountains
Galapagos Islands west of South America
The Island had different climates
Tortoises on 3 different islands were different on each Island to suit their climate

9. B-5.1-4 How Does Evolution Work? (sec 10.3,11.1)
Explain evolution by natural selection.
Summarize the four factors of natural selection.
Factors that affect genetic variation.
Explain microevolution in terms of allele frequency.
View VIDEO #4: How does Evolution really work?

10. Darwin’s Proposed Theory: Evolution by Natural Selection
Organisms best fit for the environment reproduce and pass on their traits; aka… “survival of the fittest”
Variation… individual organisms differ w/in species; alleles variations cause phenotypic variations
Overproduction… Organisms produce more offspring than can survive; competition for limited resources; Struggle for Existence.
Adaptation… inherited trait (allele) that INCREASES fitness (ability to survive)
Descent with Modification… as the environment changes individuals with beneficial traits survive reproduce – resulting in new populations with different traits (phenotypes)

11. Factors that affect genetic variation
Sexual reproduction increase genetic variation in a population.
SEXUAL: offspring have alleles from 2 parents
Meiosis creates egg and sperm with new combination of traits due to crossing over
ASEXUAL: mostly genetically identical offspring
Involves 1 parent producing identical daughter cells thru Mitosis (binary fission)
Mutations can occur and are passed on to offspring (cells)
Sources of Genetic Variation:
Mutations – random changes in DNA; if occurs in sex cells then can be passed on to offspring; creates new allele
If it increases survival it is called an ADAPTATION
Recombination (gene shuffling) – occurs thru crossing-over

12. Explain microevolution in terms of allele frequency
Vocabulary reminder:
Species = group of organisms that can reproduce to create fertile offspring.
Population = organisms of the same species living in the same area (thus are able to mate & share gene pool)
Gene pool = all alleles in population (genetic make-up of population)
Allele frequency = % of dominant of alleles compared with recessive alleles
If a genetic change (mutation) occurs in one individual it then becomes part of the gene pool & can spread thru the population
Also changing the allele frequencies in the gene pool
If mutation increases fitness, then the new allele increase in frequency
MICROEVOLUTION: If one trait (phenotype) increases an organisms fitness, then organisms with that trait may reproduce more AND
Cause Changes in the population allele frequency (gene pool)
Changes in the gene pool over time = microevolution

13. EXAMPLE: Gene Pool
How would the gene pool be affected if these mice lived in an environment where the brown fur mice were more camouflaged?
Brown allele freq = 120 brown / 200 total = .6 (60%)
Black allele freq = 80 black / 200 total = .4 (40%)
120 Brown
Allele
80 Black
Allele

14. B-5.4 Other Mechanisms of Evolution (sec 11.3 & 11.4)
Review Natural Selection (primary cause)
Summarize and provide examples of other factors that lead to evolution within a population.
Explain the Hardy-Weinberg Principle and genetic equilibrium.
View Video #6 – Why does evolution matter now?

15. Factors that Lead to Evolution
GENE FLOW: Migration
Movement of genes in (immigration) or out (emigration) of population
GENETIC DRIFT: Small Population caused by chance
Causes a SMALL population with a loss of genetic diversity
Bottleneck Effect – destructive event that leaves only a few survivors
Founder Effect – small # of individuals colonize a new area
MUTATIONS: New Alleles
Random change in DNA sequence = new alleles (variations)
SEXUAL SELECTION: Choosing a Mate
Females only produce eggs at certain time, which makes them choosy when selecting a mate
Certain traits increase mating success and over time become more pronounced
Competition between males or a display of traits
(REVIEW) NATURAL SELECTION: Survival of the Fittest
Individuals more fit in an environment survive and pass on traits (alleles)

16. GENETIC DRIFT -bottleneck effect:
Sudden reductions in population size can also alter the resulting gene pools. Any environmental condition in which many individuals are killed and only a small number survive, creates a bottleneck effect.
In this case a few peccaries with the genotype bb survive a catastrope. These individuals become the founders (originators) of a new peccary population.
As they reproduce, the new gene pool is very different from that of the original population.
GENETIC
DRIFT

17. GENE FLOW
VIDEO:

18. Hardy-Weinberg & Genetic Equilibrium
Hardy-Weinberg Principle Allele Frequencies will remain the same ONLY if ALL of the following…
Random Mating (no sexual selection)
Very Large Population (no genetic drift)
No emigration or immigration (no gene flow)
No Mutations (no new alleles added)
No natural selection ( no phenotype has advantage)
Genetic Equilibrium (constant Allele frequencies) = NO Evolution

19. Hardy-Weinberg Equation
Purpose: Use the equation to predict genotype frequencies.
Values predicted by equation are those that would be present if population was in genetic EQUILIBRIUM.
Predicted values (frequencies) are compared to actual frequencies… if the genetic data does not match the population is NOT in equilibrium: it is EVOLVING
EQUATION: p2 + 2pq + q2 = 1
p = frequency of dominant allele (T)
q = frequency of recessive allele
p2 = frequency of homozygous dominant organism (TT)
2pq = frequency of heterozygous organism (Tt)
q2 = frequency of homozygous recessive organism (tt)