1. Natural Selection 5.2

2. Mechanism for Evolution
Provided a framework for understanding Earth’s diversity of organisms and their relationships to one another and their environment.
Darwin & Wallace suggested a mechanism for evolution: Natural Selection
Natural Selection begins with overproduction and the presence of natural variation in the population

3. Mechanism for Variation
Mutation in DNA
Meiosis
Sexual Reproduction

4. Mechanism for Variation
Mutation
Mutations can be bad (disease) or they can give an advantage (faster growth or incredible healing powers )

5. Mechanism for Variation
Meiosis & Sexual Reproduction
Meiosis enables the production of haploid cells to make gametes
Sperm and egg cells
At the end meiosis, 4 cells are produced that are genetically different from each other and only 50% of the parent cell’s genome.
An individual that reproduces sexually can produce huge numbers of possible combinations of half the genetic material it possesses

6. Mechanism for Variation
Meiosis & Sexual Reproduction
Variety in the population allows some individuals to be better adapted to whatever change in the environment is harmful to others.

7. Double Lottery
The two ways that genes are mixed during sexual reproduction can be thought of as a double lottery:
Lotto 1 – Meiosis
Lotto 2 – Fertilization

8. Adaptation
Adaptations are characteristics that make an individual suited to its environment and way of life
An organism that has characteristics that are well adapted for its environment is said to be fit
The characteristics it possesses fit well into its environment

9. Adaptation
Natural Selection tends to eliminate from a population individuals that show low fitness whereas the fitness individuals in a population have a higher likelihood of surviving.
Difficulties in feeding for example make it difficult to survive making it less likely to reproduce.

10. Adaptation – Too Many Offspring
Species tend to produce more offspring than the environment can support
This is done to maximize the chances of some offspring surviving even if survival rate is less than 1%

11. Adaption & Survival Evolution is not based on chance
Individuals that are better adapted tend to survive and produce more offspring while the less well adapted tend to die or produce fewer offspring.

12. The steps of evolution by natural selection:
Adaption & Survival
The steps of evolution by natural selection:
Overproduction of offspring and in those offspring natural variation as a result of genetic differences
Body size, morphology, pigmentation, visual acuity, resistance to disease
Useful variations allow some to survive
Harmful variations make it difficult to survive

13. Adaption & Survival The steps of evolution by natural selection:
Individuals with genetic characteristics that are poorly adapted for their environment tend to be less successful at accessing resources and have less chance of surviving to maturity
Individuals with genetic characteristics that are well adapted for their environment tend to be more successful at accessing resources and have a better chance at surviving to maturity.
These individuals have better fitness

14. Adaption & Survival The steps of evolution by natural selection:
Surviving to adulthood successful organisms have a better chance to reproduce and passing on their genetic characteristics to the next generation.
Over many generations the accumulation of changes in the heritable characteristics of a population results in evolution
Plower Eggs
Plower Chicks

15. Adaption & Survival
Memorize: Darwin's steps of how Natural Selection leads to evolution:
Overproduction of offspring
Variation within the population as a result of meiosis, sexual reproduction, and mutations
Struggle for survival because there are not enough resources for all members of the population
Differential survival , those best fit to survive better
Individuals that are better adapted tend to survive and produce more offspring, while less adapted tend to die and produce less offspring, each generation contains more offspring better adapted to survive.
Reproduction those who can survive can pass their genes to the next generation
The frequency of characteristics that make individuals better adapted increases & frequency of other charteristics decrease.

16. Passing on Successful Characteristics
Individuals showing high fitness has a better chance to survive
Thus having the possibility of passing out their genetic material
Natural Selection increases the frequency of characteristics that make individuals better adapted and decreases the frequency of other characteristics leading to changes within the species.

17. Heritability and Evolution
Although some characteristics can be inherited from your parents acquired characteristics cannot.
Arms of a tennis player increases in size over time it cannot be passed down
Yes being athletic is a trait that can be passed down

18. Adaptation on Daphne Major
Galapagos Islands

19. Beaks of Finches on Daphne Major
From 1975 to 1995 mean beak size has changed due to weather conditions
During drought conditions mean beak size would increase in size
During wet conditions mean beak size would decrease.

21. Pesticides
Poisons used to kill insects that are pest in crops and in homes
At first pesticides are very effective
Later they are less effective
Why: If an insects survives First attack (no pesticide
is 100% effective)
Survivors replicate – offspring inherit gene for
pesticide resistance
Not immune; immunity occurs over a lifetime resistance

22. Antibiotic Resistance in Bacteria
Evolution of Antibiotic Resistance in Bacteria
Antibiotics – Medicines that kill or slow the growth
of bacteria
Widespread use has caused the evolution of antibiotic – resistant populations of the very bacteria that antibiotic is trying to kill
Antibiotic resistance evolves by Natural Selection
Some bacteria always survive
Multiply quickly
So Do Not Take Antibiotics Unless Necessary And Take Them All

23. Antibiotic Resistance in Bacteria
Since bacteria reproduce asexually they do not change often
Two sources of possible change in genetic make – up
Mutations
Plasmid Transfer

24. Health Science and Evolution
Plasmid transfer involves one bacterium donating genetic information to another bacterium

25. Antibiotic Resistance in Bacteria
Examples of antibiotic – resistant bacterial diseases:
Syphilis - develops in stages, and symptoms vary with each stage. The first stage involves a painless sore on the genitals, rectum, or mouth. After the initial sore heals, the second stage is characterized by a rash. Then, there are no symptoms until the final stage which may occur years later. This final stage can result in damage to the brain, nerves, eyes, or heart.
Tuberculosis - The bacteria that cause TB are spread when an infected person coughs or sneezes. Most people infected with the bacteria that cause tuberculosis don't have symptoms. When symptoms do occur, they usually include cough (sometimes blood-tinged), weight loss, night sweats, and fever.
MRSA

26. Evidence for Evolution 5.1
In 1858; Darwin and Alfred Wallace another Naturalist released, nearly identical theories independently.
Evolution is the process of cumulative change in the heritable characteristics of a population

27. Evidence for Evolution
Heritable means that the changes must be passed on genetically from one generation to the next.
Evolution does not happen overnight
Cumulative stresses the fact that one change is usually not enough to have a major impact on a species
Population means that changes do not affect an individual

28. Evidence for Evolution
Speciation the rise of a new species
Occurs if enough changes occur in the population
Evolution requires that allele frequencies change with time in populations
Remember different species are marked by the inability to interbreed

29. Evidence for Evolution
Fossils
The petrified remains or traces of animals and plants
The fossil record is the accumulation of evidence from these remains and traces, such as footprints and skeletons

30. Scientist who study fossils
Paleontologist
Scientist who study fossils
Have discovered fossils of many ancestral life forms that link past and present
Evidence that paleontologist discovered that support evolution:
The life that existed more than 500 million years ago was vastly different in appearance from life today
Fish fossils have been found to be 500 million years old or less (less than 15% of the 3,5 billion year existence of life on our planet)
Top predators today are mammals; none existed at the time of the dinosaurs
Apart from a few: sharks, cockroaches, and ferns the majority of living organisms have no similar form in the fossil record.

31. The chronological collection of life’s remains in the rock layers
Aging Fossils
The chronological collection of life’s remains in the rock layers
Older rocks lower in the crust

32. Aging Fossils
The age of a rock can be determined by carefully examining differences in the ratios of isotopes
For example the more carbon 14 a bone or a shell has the younger it is
C is radioactive, it loses its radioactivity slowly
As it loses its radioactivity it changes to nitrogen 14 (a stable daughter of C)
This is called decay
The speed at which this occurs is called half-life
Half-life is the time it takes for half of the parent isotope to decay into a stable daughter isotope 14

33. Half - Life The half-life of C is 5730 years
Looking at the ratio of radioactive C to stable N it is possible to determine the age of a fossil
There are other radioactive isotopes with much longer half-lives
Potassium 40 ( K)
Comes from crystallized magma
After magma hardens no more K can be added
Can be used to date items from 100,000 to 4.6 billion years ago 14 14 40 40

34. Half - Life

35. Artificial Selection
The selective breeding of domesticated plants and animals to produce offspring with genetic traits that humans value
Evidence to support evolution
Plant Breeder: might seek to improve grain production, disease resistance, or protein content
Animal Breeder: seek growth rate or temperament
Selective breeding of domesticated animals shows that artificial selection can cause evolution

36. Artificial Selection
Darwin noticed that Artificially Selected species could produce a great deal of change in a short time
He compared this through Natural Selection but reasoned it would take 1000’s of years
Artificial Selection – Humans Choose
Natural Selection – Benefits organisms in their
particular environment

37. Homologous Structures
Can provide clues to evolutionary history
Homologous Structures – similar structures in
seemly dissimilar
species
Pentadactyl Limbs = penta means 5; dactyl refers to fingers
Vertebrates share an ancestor that had pentadactyl limbs
Function is different to adapt to different functions

38. Homologous Structures
Darwin explained that homologous structures were evidence of a common ancestor
More evidence “proving” evolution?
Species Divergence – populations of a species can gradually diverge into separate species by evolution
Speciation due to divergence can be gradual or rapid

39. Adaptive Radiation
Occurs when many similar but distinct species evolve relatively rapidly from a single species.
Many different groups have evolved from the common ancestor but because they adopted different types of locomotion the limbs developed in widely different ways
By natural selection and a barrier a new species can evolve.

40. Adaptive Radiation
FYI Lemurs can only be found (in the wild) in Madagascar and the Comoro Islands.
Reproductive isolation of a population can be temporal, behavioral, or geographic
Temporal - an evolutionary mechanism that keeps individuals of different species from interbreeding, even if they live in the same environment.
Different Mating seasons
Behavioral – different courtship behaviors
Geographic – an actual barrier, like a mountain

41. Gene Pool (10.3)
Consist of all genes and their different alleles, present in an interbreeding population

42. Gene Pool
Can be thought of as a reservoir of genes from which a population can get various traits
A large gene pool exists in a population that shows substantial variety of traits
Small gene pool exists in a population that show little variation
Found in populations where inbreeding is prevalent
Inbreeding is the practice of closely related organisms mating

43. Continuous Variation
Continuous variation across the geographical range of a related populations matches the concept of gradual divergence.
It is possible to see that within a species that has a wide geographical distribution there can be measurable differences in DNA
Selective Pressure – populations that are best adapted to their areas

44. Transient Polymorphism
Different versions of a species
Polymorphism means different shapes
Can be the result of mutation
Peppered moth
Melanistic – dark varieties of a typically light colored insect