1. Evolution

2. What is evolution? Evolution is defined as “descent with modification”
a.k.a. “Change over time”
“A CHANGE IN GENE FREQUENCY OVER LONG PERIODS OF TIME”
Over a large number of years, evolution produces tremendous diversity in forms of life.
Leaves on trees change color and fall over several weeks.
Mountain ranges erode over millions of years.

3. Isn’t Evolution ‘just’ a theory?
Scientific theories are explanation that are based on lines of evidence, enable valid predictions, and have been tested in many ways.
In contrast, there is also a popular definition of theory – a “guess” or “hunch”
These conflicting definitions cause some confusion when it comes to evolution…

4. Who is Charles Darwin? An English scientist
Considered the “father of modern evolutionary theory”
Studies animal and plant life as a ship’s naturalist. From these findings he was able to develop his theory of evolution

5. The Galapagos Islands He traveled the island on the H.M.S Beagle
Darwin studied & compared the anatomy of many species of:
Reptiles
Insects
Birds**
Flowering plants
All of which were unique to the island, but similar to species found around the world

6. Darwin notices… Competition for space & food
Need to escape from predators
Need to find enough prey
Ability to find AND secure shelter
SURVIVAL OF THE FITTEST…

7. MICHAEL PHELPS
ARNOLD SCHWARZENEGGER

8. What is Natural Selection?
natural selection  organisms that are BEST suited for their environment are more likely to SURVIVE, REPRODUCE, and pass on those beneficial traits to their offspring
Natural selection is one
of the basic mechanisms
of evolution, along with
mutation, migration,
and genetic drift.

9. To find out how Natural Selection works, imagine a population of beetles:
1. There is variation in traits.
For example, some beetles are green and some are brown
2. There is differential reproduction.
Since the environment can’t support unlimited population growth, not all individuals get to reproduce to their full potential. In this example, green beetles tend to get eaten by birds and survive to reproduce less often than brown beetles do.

10. To find out how Natural Selection works, imagine a population of beetles (continued…)
3. There is heredity.
The surviving brown beetles have brown baby beetles because this trait has a genetic basis.
4. End result:
The more advantageous trait, brown coloration, which allows the beetle to have more offspring, becomes more common in the population. If this process continues, eventually, all individuals in the population will be brown.

11. Natural Selection Overview
In nature, there is a tendency towards the overproduction of offspring
In any population of organisms, individuals will exhibit slight variations
Individuals with variations that are favorable for a particular environment are more likely to survive and pass those variations on to the next generation than are individuals with less-favorable variations
Gradually, offspring of survivors will make up a larger proportion of the population and eventually a population may look entirely different

12. What is fitness?
Biologists use the word fitness to describe how good a particular genotype is at leaving offspring in the next generation relative to how good other genotypes are at it.
Fitness is a relative thing. A genotype’s fitness depends on the environment in which the organism lives.
The brown beetles have a greater fitness relative to the green beetles.

13. Fitness Strategies in NatureB C
(A), Caring for your offspring
(B) producing thousands of young
(C) sporting fancy feathers that attract females
These strategies increase fitness because they help the parents get more of their offspring into the next generation.

14. Jean Baptiste Lamarck
Believed that organisms altered their bodies in response to an environmental change -> ACQUIRED TRAITS
Believed in “SPONTANEOUS GENERATION”:
By the selective use and disuse of organs, organisms acquired or lost certain traits during their lifetime
These traits could be passed on to their offspring. (wrong!)
Over time this could cause a change in the species. (wrong!)

15. Mechanisms of Evolution
Mutation
A mutation could cause parents with genes for bright green coloration to have offspring with a gene for brown coloration.
That would make the genes for brown beetles more frequent in the population.
Migration
Some individuals from a population of brown beetles might have joined a population of green beetles.
That would make the genes for brown beetles more frequent in the green beetle population.

16. Mechanisms of Evolution
Genetic Drift
Imagine that in one generation, two brown beetles happened to have four offspring survive to reproduce.
Several green beetles were killed when someone stepped on them and had no offspring.
The next generation would have a few more brown beetles than the previous generation—but just by chance.
These chance changes from generation to generation are known as genetic drift.
Natural Selection
Imagine that green beetles are easier for birds to spot (and hence, eat).
Brown beetles are a little more likely to survive to produce offspring.
They pass their genes for brown coloration on to their offspring.
So in the next generation, brown beetles are more common than in the previous generation.
HHMI VIDEO – NATURAL SELECTION

17. Evolution Mechanisms Understood
Mutation…
Migration…
Genetic Drift…
Natural Selection…
All of these mechanisms can cause changes in the frequencies of genes in populations, and so all of them are mechanisms of evolutionary change.
However, natural selection and genetic drift cannot operate unless there is genetic variation—that is, unless some individuals are genetically different from others.
If the population of beetles were 100% green, selection and drift would not have any effect because their genetic make-up could not change.

18. Natural Selection & Adaptation
Any trait that aids the chances of survival and reproduction of an organism
Can be explained by applying Darwin’s theory of natural selection
We will focus on two types of adaptations:
Structural
Changes in the structure of body parts
Physiological
Changes in an organism’s metabolic processes

19. Structural Adaptations
Can be used as defense mechanisms
Mimicry
A structural adaptation that provides protection for an organism by copying the appearance of another, more threatening, species
Camouflage
A structural adaptation that enables an organism to blend in with its surroundings
Non-poisonous king snakes mimic poisonous coral snakes.
Katydids have camouflage to look like leaves.

20. Physiological Adaptations
A metabolic change in an organism making it better suited to cope with environmental changes
Anti-biotic Resistance:
Individual bacteria in a population show variation
Some bacteria possess a gene that makes them resistant to some antibiotic
When the population is exposed to the antibiotic, some individuals die, but resistant bacteria survive
Resistant bacteria survive and reproduce
In time, the entire population is resistant to a certain antibiotic

21. “Why does Evolution matter NOW. ” Video Questions http://www. pbs
Why is the Russian prison system considered to be "ground zero" in the fight against TB?
What is responsible for the evolution of TB strains that are resistant to multiple drugs?
How does the misuse of antibiotics affect the evolution of disease-causing bacteria? Use the theory of natural selection to explain the growing resistance to antibiotics.
Why should we care about a resistant strain of TB in Russia?

22. Evidence for Evolution
Fossils can show evolutionary changes over time
Found in sedimentary rocks
Age of fossil determined by carbon dating
With all of the pain, time, and money that are put into dealing with wisdom teeth, humans have become just a little more than tired of these remnants from their large jawed ancestors. But regardless of how much they are despised, the wisdom teeth remain, and force their way into mouths regardless of the pain inflicted. There are two possible reasons why the wisdom teeth have become vestigial. The first is that the human jaw has become smaller than its ancestors’ and the wisdom teeth are trying to grow into a jaw that is much too small. The second reason may have to do with dental hygiene. A few thousand years ago, it might be common for an 18 year old man to have lost several, probably most, of his teeth, and the incoming wisdom teeth would prove useful. Now that humans brush their teeth twice a day, it’s possible to keep one’s teeth for a lifetime. The drawback is that the wisdom teeth still want to come in, and when they do, they usually need to be extracted to prevent any serious pain.

23. more Evidence for evolution
Anatomical structure indicates evolutionary relationship:
-ANALOGOUS STRUCTURES:
- Same function, but no common descent.
-HOMOLOGOUS STRUCTURES:
Different function, common descent.
Genetic and embryological comparisons
reveal hidden relationships

24. Evidence for Evolution
Vestigial Organs or Structures:
-indicate evolutionary pathways
Seemingly functionless parts such as:
appendix, wisdom teeth.
Embryology
Similarities in early embryos
suggest evolution from a common
ancestor
Biochemistry
The sequences of RNA or DNA can be compared between organisms.
The closer in sequence a gene is, the more closely related the organisms are to each other.
HHMI BIOLOGY OF SKIN COLOR VIDEO

25. Natural Selection 3 Models
Stabilizing selection operates to eliminate extreme expressions of a trait when the average expression leads to higher fitness
Directional selection makes an organism more fit.
Disruptive selection is a process that splits a population into two groups.

27. Mechanisms of Evolution Populations
Hardy-Weinberg principle states that when allelic frequencies remain constant, a population is in genetic equilibrium and evolution doesn’t occur. (Rare)
First Generation:
2 grey, 1 red
Second Generation:
2 grey, 1 red
Genotypic ratio
Stayed the same

28. Speciation
Evolutionary process where new species arise and similar species cannot interbreed. Commonly due to Geographic Isolation.

29. Rate of speciation
Evolution proceeds in small, gradual steps according to a theory called gradualism
Punctuated equilibrium explains rapid spurts of genetic change causing species to diverge quickly.

31. Patterns in Evolution

32. Patterns in Evolution Divergent evolution (aka-adaptive radiation)
Convergent
Coevolution

33. Divergent evolution (adaptive radiation)
When one species gives rise to many in response to the creation of a new habitat or another ecological opportunity by geographical isolation.
(HOMOLOGOUS STRUCTURES)

34. Convergent evolution Unrelated organisms appear alike
Due to having a similar environment or having the same selective pressures
Do NOT share a common ancestor (share ANALOGOUS STRUCTURES)

35. Traits favorable to environment
Evolution
CONVERGENT
DIVERGENT
(adaptive radiation)
Nat. sel. favors…
Traits favorable to environment
Type of habitat
Similar
Different
Reflected in…
Analogous traits
Homologous and Vestigial traits
Result 
Unrelated species appear alike
Related species may appear unalike

36. Coevolution (2 evolve together)
One species adapts in response to another’s adaptation
If a species of flower adapts larger petals. The pollinator species, who relies on the flower for food, must also adapt a longer beak in order to reach the nectar.

38. Natural Selection Brain Pop
Guess the Embryo
Lucy Video