1. Natural Selection

2. The Origin of Species
On the Origin of Species by Means of Natural Selection or the Preservation of Favoured Races in the Struggle for Life
This is quite a title!
But it does suggest that Natural Selection must play an important role in the creation of new species

3. But what is natural selection?
Natural Selection is the way in which nature favours the reproductive success of some individuals within a population over others
In other words, some individuals are more likely to pass their genes along than others

4. How Natural Selection Works
Success can take many forms
1. Better suited to gathering resources in a population
2. Better able to avoid predators
3. Ability to adapt to a unique environment
There is no single recipe for success

5. 1. Gathering Resources Cheetahs
A faster cheetah is more likely to catch its prey than a slower cheetah
Faster cheetahs are more likely to eat regularly and stay alive
So on average, faster cheetahs are more likely to reproduce and will have more offspring than slower cheetahs

6. 1. Gathering Resources Darwin’s Finches
Variation in the size and shape of beaks
Each species has evolved to feed on unique things
Differences in diet mean that they do not compete with each other for resources

7. 1. Gathering Resources Anteaters
Ant colonies can be large tunnel complexes
Ancestors of anteaters with longer noses and tongues found it easier to eat ants directly out of the colony
They were more likely to pass their genes and anteaters now have very long noses and tongues

8. 2. Avoiding Predators Camouflage
The ability to blend in with surroundings provides an advantage in evading predators
An insect that looks more like a leaf, for example, than another is more likely to be mistaken for a leaf and more likely to be ignored by a predator
This camouflage is more likely to be passed along to future generations

9. Example of Camouflage
Common Potoo

10. 2. Avoiding Predators Cactus Found mostly in dry, arid places
Waxy coating helps keep water from evaporating
Animals living in the desert eat plants for moisture
Cacti have developed spikes to deter predators
Since cacti with spikes are less likely to be eaten, they are also more likely to breed and pass on their genes

11. 3. Adaptations to a Unique Environment
A characteristic or feature of a species that makes it well suited for survival or reproductive success in its environment

12. 3. Adaptations to a Unique Environment

13. 3. Adaptations to a Unique Environment
Fennec Fox
Fennec foxes live in the desert
Have large ears to dissipate heat
Fennec foxes with large ears are less likely to over heat in the desert and are more likely to breed

14. 3. Adaptation to a Unique Environment
Remember the cactus, with its waxy coating?
This coating prevents water evaporation in a hot, arid environment

15. 3. Adaptation to a Unique Environment
The polar bear
Among the largest bears
Has both a heavy double layer of fur and a layer of fat 4-5 inches thick, to survive extreme cold
They are very strong swimmers
Why might this be important?

16. 3. Adaptation to a Unique Environment
They are very strong swimmers
Why might this be important?
They live in oceanic areas and often live on areas of the sea frozen only during the winter months
They blend well into their surroundings, making it harder for prey to spot them

17. Predictions
The Theory of Natural Selection allowed Darwin to make predictions he could not prove at the time (theory!)
He predicted that, based on the location of great apes today, we would find fossil evidence of human ancestry in Africa (biogeography!)

18. Predictions Darwin’s orchid: flower with a very long spur
He predicted an insect must exist with a very long proboscis, in order to pollinate it
Madagascan Hawk Moth discovered in 1903

19. The Natural Selection Game
Over the next several slides, you’ll see some species that in some way demonstrate natural selection
Your job is to decide how that species has been affected by natural selection, or to decide which animal is most likely to pass it genes along

20. Giraffe

21. Roses

22. Walking Stick

23. The Cobra

24. Blue Shark

25. Venus Fly Trap

26. Octopus

27. Pangolin

28. Buckeye Butterfly

29. Angler Fish

30. Bee Orchid

31. Adaptation
A characteristic or feature of a species that makes it well suited for survival or reproductive success in its environment
Owl images

32. Adaptation
Explains why the cactus can be successful in the desert

33. Survival of the Fittest
This phrase has been used to describe Darwin’s theory
Is this misleading?

34. Types of Selection Directional Selection Stabilizing Selection
Disruptive Selection

35. Directional Selection
Selection that favours an increase or decrease in the value of a trait from the current population average

36. Directional Selection
Antibiotic Resistance in Bacteria

37. Stabilizing Selecton
Selection against individuals exhibiting traits that deviate from the current population average

38. Stabilizing Selection
Birth weight in human babies

39. Disruptive Selection
Favours two or more variations of a trait that differ from the current population average

40. Disruptive Selection
Rock Pocket Mouse

41. A Human Example
Some populations have adapted to living at extreme heights
Able to survive despite low oxygen levels

42. "The sight of a feather in a peacock's tail, whenever I gaze at it, makes me sick!” Darwin

43. Homework Questions
PG. 335 #2, 6, 11
PG. 372 #17, 32