1. TEK: Analyze and evaluate how natural selection produces change in populations, not individuals.[7C]

2. LEARNING TARGET: By the end of class today… I can analyze and evaluate how natural selection produces change in populations, not individuals…

3. The Mechanisms of Evolution!!!!!

4. First Lets Find this out
-What is a “Mechanism”(in terms of biology)?
-2 minutes to search and discuss with a partner and answer in your notes

5. Mechanisms:
Interacting parts or processes that contribute to produce one or more effect
In other words…. Many factors working together to cause a result.

6. Evolution Changes in a population over time.
Mechanisms of evolution (8)
Mutations
Gene flow
Genetic drift
Natural Selection (survival of the “fittest”)
Artificial Selection
Recombination
Non-Random Mating
Isolation

7. Section 15.1 Summary – pages 393-403
Natural Selection
Natural selection is the idea that organisms with favorable/beneficial traits survive, reproduce, and pass those traits to the next generation.
ENVIRONMENTALLY CONTROLLED
Organisms without these variations/traits are less likely to survive and reproduce.
Section 15.1 Summary – pages

8. Section 15.1 Summary – pages 393-403
Darwin and Natural Selection
One of the things Darwin observed is that in nature, the traits of individuals vary in populations.
Then these variations are passed to offspring.
Darwin hypothesized that there was a force in nature that picked traits which are better for survival in a species.
Section 15.1 Summary – pages

9. Section 15.1 Summary – pages 393-403
Darwin and Natural Selection
He also observed that individuals struggle to compete in changing environmental conditions.
What do individuals compete for?
RESOURCES
Only some individuals survive the competition and live to produce offspring.
Section 15.1 Summary – pages

10. There are different forms of selection seen in nature
So we are going to make a tree map

11. Section 15.2 Summary– pages 404-413
NATURAL SELECTION
There are three different types of natural selection: stabilizing, directional, and disruptive.
Stabilizing selection is a natural selection that favors average individuals in a population.
Evolution will not occur
Middle sized Siberian Huskies are selected for
Section 15.2 Summary– pages

12. Section 15.2 Summary– pages 404-413
NATURAL SELECTION
Directional selection occurs when natural selection favors one of the extreme variations of a trait.
This type of selection can lead to rapid evolution of a population.
Section 15.2 Summary– pages

13. Section 15.2 Summary– pages 404-413
NATURAL SELECTION
In disruptive selection, individuals with either extreme of a trait’s variation are selected for.
This results in eventually having no intermediate form of a trait, and leading to two separate species.
Section 15.2 Summary– pages

14. Natural Selection on Polygenic Traits
Shifts to
middle range
2 extremes
1 extreme

15. Now you may grab your white board
On your whiteboard, we are going to practice identifying different types of selections in different scenarios on your worksheet.
Lets practice first.

16. Peppered Moths
We all know the peppered moth story from yesterday. There are black moths, white moths, and peppered moths living in the same population creating a very stable environment. Peppered moths thrived until the industrial revolution changed the environmental conditions in which they lived in(trees are now black). Name the selection that is taking place and make a graph showing the original population and the population after the I.R.

17. Work Time Work together In groups of 3.
Answer all 3 selection scenarios and draw the graph on your whiteboards
1 scenario for 1 board
Do not write your answers on your paper until we discuss as a class.

18. Natural Selection Mutations Gene Flow Genetic Drift
Recombination
Gene Flow
Genetic Drift
What does this mean?
Artificial Selection
Non-Random Mating
Isolation

19. 17 Minutes with a Partner On the inside of the flap:
Describe how this “mechanism” contributes to the overall theme of evolution
Give me one example
** your assignment from Tuesday is a great resource
**notes from moodle (mechanisms of evolution) is a great resource

20. Journal Q #3
In some species of deer, implantation of embryos after breeding is delayed. The deer breed in July or August, but do not give birth until the following May or Jun. During the winter, the embryo rests in a state of dormancy. Why would this “delayed implantation” be an advantageous adaptation for the deer?

21. Mechanism of Evolution: Mutations
Original Population

22. Mechanism of Evolution: Mutations
After Mutation

23. Mechanism of Evolution: Mutations
Many Generations Later
Make sure students compare the original population to the population many generations later. This will help them see how the population changed as a result of the mutation.

24. Gene Flow
Genes move with individuals when they move (emigrate or immigrate) into and out of a population…and it changes the gene pool

25. Genetic Drift
Genetic Drift – the random fluctuation due to chance occurrences alone
It is more significant in smaller populations
It increases the chance of any given allele becoming more or less prevalent when the number of individuals is small
Founder Effect

26. Non-Random Mating Blue = BB or Bb Red = bb x Original Population
Students may need to think about Punnett squares probability of offspring. It maybe helpful to do a cross between two heterozygotes and also two red individuals. This will show students that not only are red individuals all red offspring but blue individuals are also producing red offspring as well. Because of this and non-random mating, the frequency of red alleles will increase many generations later. x

27. Many Generations Later
Non-Random Mating
Many Generations Later

28. Recombination & Genetic Shuffling
As we learned in the genetics unit, recombination leads to genetic material being shuffled.
This shuffling, along with sexual reproduction, leads to variation within populations. This variation leads to selection, which ultimately leads to evolution.
Locate an appropriate website or websites with real world examples of recombination and genetic shuffling. Possible websites to consider are the Berkeley Evolution website and the Learn Genetics Utah website. These online libraries have many resources which you may find appropriate for your students and district. Embed examples onto this slide.

29. What is the difference between artificial and natural selection?
Section 1 Check

30. Section 15.1 Summary – pages 393-403
Breeding organisms with specific traits in order to produce offspring with ideal traits is called artificial selection.
(Intentional breeding for certain traits)
A Goldendoodle
(Golden retriever/ Poodle)
Section 15.1 Summary – pages

31. Reproductive Isolation
Two way reproductive isolation occur:
Prezygotic mechanisms
Postzygotic mechanisms

32. Lets Discuss Isolations

33. Darwin and Natural Selection
Charles Darwin ( )
He was an English scientist and it took him years to develop his theory of natural selection.
He began in 1831 at age 22 when he took a job as a naturalist on the English ship HMS Beagle, which sailed around the world on a five-year scientific journey.

34. Section 15.1 Summary – pages 393-403
ADAPTATIONS
Recall that an adaptation is any variation that aids an organism’s chances of survival in its environment.
Examples are:
Thorns on plants
Special colorings for an organism
Enhanced night vision
Section 15.1 Summary – pages

35. Section 15.1 Summary – pages 393-403
ADAPTATIONS
Some other structural adaptations are subtle.
Mimicry is a structural adaptation that enables one species to resemble another species.
In one form of mimicry, a harmless species has adaptations that result in a physical resemblance to a harmful species.
Section 15.1 Summary – pages

36. Section 15.1 Summary – pages 393-403
ADAPTATIONS
Another subtle adaptation is camouflage, an adaptation that enables species to blend with their surroundings.
Because well-camouflaged organisms are not easily found by predators, they survive to reproduce.
Section 15.1 Summary – pages

37. Darwin’s 5 points Population has variations.
Some variations are favorable.
More offspring are produced than survive
Those that survive have favorable traits.
A population will change over time.

38. Section 15.2 Summary– pages 404-413
SPECIATION
The evolution of new species, a process called speciation.
This occurs when members of similar populations change so much from each other that they no longer interbreed to produce fertile offspring.
Section 15.2 Summary– pages

39. Section 15.2 Summary– pages 404-413
SPECIATION
In nature, physical barriers can break large populations into smaller ones.
Geographic isolation occurs whenever a physical barrier divides a population and over time they change and become two different species.
Reproductive isolation…
Section 15.2 Summary– pages

40. Section 15.2 Summary– pages 404-413
SPECIATION without a physical barrier
Some speciation occurs while the organisms still exist in the same area…
Reproductive Isolation
Behavioral, Temporal, Mechanical
Section 15.2 Summary– pages

41. Speciation Northern Arctic Fox Spreads northward and
Adapted to heat
through lightweight
fur and long ears,
legs, and nose, which
give off more heat.
Adapted to cold
through heavier
fur, short ears,
short legs, short
nose. White fur
matches snow
for camouflage.
Gray Fox
Arctic Fox
Different environmental
conditions lead to different
selective pressures and evolution
into two different species.
Spreads
northward
and
southward
separates
Southern
population
Northern
Early fox

42. Section 15.2 Summary– pages 404-413
Types of Change
Divergent evolution is when species that are similar and closely related become increasingly different from each other. THEY DIVERGE
This is also called Adaptive Radiation….because it has to do with ADAPTING to different environments and RADIATING out into different species.
Section 15.2 Summary– pages

43. Section 15.2 Summary– pages 404-413
Types of Change
When distantly-related organisms evolve to become more similar, it is called convergent evolution.
Convergent evolution occurs when unrelated species occupy similar environments in different parts of the world.
Also: Co-Evolution & Parallel Evolution
Section 15.2 Summary– pages

44. Rate of Speciation Current debate:
Does speciation happen gradually or rapidly? Or both?
Gradualism
Punctuated equilibrium

45. Gradualism Gradual change over long spans of time
assume that big changes occur as the accumulation of many small ones develop over time.

46. Punctuated Equilibrium
Rate of speciation is not constant
rapid bursts of change
long periods of no change
species undergo rapid change when they 1st bud from parent population
Time