the theory of evolution
DESCRIPTION
The Theory of Evolution. Darwin’s Ideas. Natural Selection A process in which some individuals have genetically-based traits that improve survival or reproduction Thus , they have more offspring surviving to reproductive age than other individuals. . Darwin’s Ideas. Common Ancestry - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/1.jpg)
TheTheory of Evolution
![Page 2: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/2.jpg)
Darwin’s Ideas
1. Natural Selection– A process in which some individuals have
genetically-based traits that improve survival or reproduction
– Thus, they have more offspring surviving to reproductive age than other individuals.
![Page 3: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/3.jpg)
Darwin’s Ideas
2. Common Ancestry– All life forms share a
common ancestor– We are all in the same “tree of life”
![Page 4: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/4.jpg)
The Definition of Evolution
Evolution is….• Descent with Modification
– Small-scale evolution: Changes in gene frequency in a population from one generation to the next. (microevolution)
– Large-scale evolution: The descent of different species from a common ancestor over many generations. (macroevolution)
![Page 5: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/5.jpg)
Which of these represents descent with modification?
Big Beetles go through a drought and have limited food
Next generation is physically smaller due to lack of food
90% of the beetles have the gene for green color
30% of the beetles have the gene for green color
In this example, what exactly is being modified?
or
Phenotypic traits of a population are modified over time.
This is measurable as changes in “allele frequencies”
![Page 6: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/6.jpg)
A change in allele frequencies in a population is evidence of
microevolution
Let’s further study how allele frequencies can change in an
activity called “Breeding Bunnies”
![Page 7: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/7.jpg)
Basic requirements of Micro-evolution
1. There is variation in traits.(diversity)
2. There is differential reproduction.Due to selective forces in the environment, not all individuals get to reproduce to their full potential.
3.There is heredity.
![Page 8: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/8.jpg)
How do populations introduce variation or diversity?
1. Mutation• A change in a DNA sequence
– usually because of errors in replication or repair.
• Mutation is the ultimate source of genetic variation.
![Page 9: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/9.jpg)
2. Migration (Gene Flow) • Individuals from one group move into
another group.– Brings in new genes or changes frequency
of genes in the population.
How do populations introduce variation or diversity?
![Page 10: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/10.jpg)
How do populations introduce variation or diversity?
3. Genetic DriftIn each generation, some individuals may, just by chance, leave behind a few more descendents (and genes, of course!) than other individuals.
But does genetic drift always increase diversity?
Let’s consider the
following game of
chance to find out
![Page 11: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/11.jpg)
Genetic Drift: A game of chance• Imagine a game in which you have a bag holding 100
marbles– 50 of which are brown and 50 green.
• You are allowed to draw 10 marbles out of the bag. • Now imagine that the bag is restocked with 100
marbles– with the same proportion of brown and green marbles as you
have just drawn out. • The game might play out like this:
How does the diversity of the 4th generation compare to that of the
starting population?The variation has __________ in response to selective pressures
decreased
![Page 12: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/12.jpg)
What effect does genetic drift have on smaller populations?
1. Genetic drift acts faster and has more drastic results in smaller populations. This effect is particularly important in rare and endangered species.
![Page 13: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/13.jpg)
Examples of Genetic Drift
1. Population Bottleneck– An event in which a population’s
size is greatly reduced
Initial Diverse Population
Event that causes the population to be reduced in size
Final population
Northern Elephant Seal
Cheetah
![Page 14: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/14.jpg)
Examples of Genetic Drift
2. Founder Effect– Changes in gene
frequencies that usually accompany starting a new population from a small number of individuals.
![Page 15: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/15.jpg)
Driftworm Activity
• Turn your intNB to the driftworm activity, and get out: – Five colored pencils
• Color in Generation 0 of your driftworms
![Page 16: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/16.jpg)
Driftworm Activity
• Each of these worms reproduces asexually
• The population size is constant• The generations do not overlap • These are haploid organisms
![Page 17: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/17.jpg)
Driftworm Activity1. Roll the die.2. This number represents which worm
survives (by chance)and can be colored in for the next generation.
3. Do this four more times.
![Page 18: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/18.jpg)
Driftworm Activity4. Repeat this in as many generations as
possible• That is, until there is only one phenotype
“fixed” in the population.
![Page 19: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/19.jpg)
What factors prevent an allele from becoming “fixed” in a population?
1. Mutation2. Migration (Immigration and Emigration)
this is sometimes called “gene flow”3. Meiosis and Sexual Reproduction4. A large population (to avoid the effects of
genetic drift)
![Page 20: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/20.jpg)
Genetic variation (diversity) is
required for what micro-evolutionary
process?
![Page 21: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/21.jpg)
Natural Selection
• A process in which some individuals have genetically-based traits that improve survival or reproduction
• They have more offspring surviving to reproductive age than other individuals.
![Page 22: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/22.jpg)
Natural Selection
It is often called “survival of the _________.”“Fit” often refers to a phenotype’s success in reproducing.But… is this term accurate? Is it always the biggest, fastest, strongest?Let’s read a cartoon about natural selection to find out…
fittest
![Page 23: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/23.jpg)
Types of Selection
• Artificial Selection: – People choose plants and animals with
desirable traits to reproduce.– Nature does NOT select.
![Page 24: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/24.jpg)
Types of Selection
• Directional Selection: – One allele is favored over another, and the
population shifts in one direction
![Page 25: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/25.jpg)
Types of Selection
• Stabilizing Selection: – Genetic Diversity decreases as a population
stabilizes on a particular genetic trait.–Extreme traits are
selected against.
![Page 26: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/26.jpg)
Types of Selection
• Disruptive Selection: – Selection that favors the extremes of the
distribution
![Page 27: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/27.jpg)
Overview of the types of selection
![Page 28: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/28.jpg)
Which of type of selection is/can be caused by the following…
1. Human birth weight Answer: Stabilizing Selection
2. The finches Darwin observed on the Galapagos Islands
Answer: Disruptive Selection3. Lighter moths being selected by
predators after the trees became covered with soot (post Industrial Revolution)
Answer: Directional Selection
![Page 29: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/29.jpg)
Natural Selection: Adaptations
• Adaptations: Come in many forms and help the organism survive. It could be:– Behavioral: Behaviors that an organism does
to survive– Functional: An adaptation in which one
aspect of the organism has increased function in an environment
– Structural: Physical features on an organism that enable it to survive.
![Page 30: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/30.jpg)
Q: The following are examples of what type of adaptation?
1. Katydids blending in with their surroundings.
Structural2. A bird’s mating call
Behavioral3. A protein working at human body
temperature and denaturing at higher temperatures.
Functional
![Page 31: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/31.jpg)
Q: The following are examples of what type of adaptation?
1. Echolocation in bats searching for food Behavioral
2. A bird’s beak Structural
3. The non-poisonous milk snake has a banding pattern similar, but not the same as a poisonous coral snake.
Structural: This is mimicry!
![Page 32: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/32.jpg)
What about odd features that don’t seem to serve any selective
function?
Vestigial Structures– An inherited feature that is now functionless
and usually less elaborate than in the ancestor.
– Formed when a species experiences a different set of selective pressures than its ancestors, and selection to maintain the elaboration and function of the feature ends.
![Page 33: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/33.jpg)
Misconceptions about Natural Selection
• It is not “Survival of the Fittest” - really it is “Survival of the ‘fit enough’”– Recessive alleles for disease can stay
unnoticed in a population• Organism does not choose• Perfection is not obtained
![Page 34: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/34.jpg)
![Page 35: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/35.jpg)
Coevolution
• A process in which two or more different species reciprocally effect each other’s evolution. – species A evolves, which causes species B to
evolve, which causes species A to evolve, which causes species B to evolve, etc.
– For ex. Co-Evolution of Computer – virus
B
![Page 36: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/36.jpg)
Types of Coevolution
1. Predator/prey and parasite/host 2. Competitive species 3. Mutualistic species
• Like plants and pollinators
![Page 37: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/37.jpg)
Macroevolution(Speciation)
• Form of large-scale evolution• Descent of different species from a
common ancestor
What evidence is there for
macroevolution?
![Page 38: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/38.jpg)
1. Fossil Record
![Page 39: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/39.jpg)
2. Geographic Distribution of Living Species
![Page 40: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/40.jpg)
3. Homologous Body Structures
![Page 41: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/41.jpg)
4. Vestigial Organs
![Page 42: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/42.jpg)
5. Similarities in Early Development
![Page 43: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/43.jpg)
Mechanism of MacroevolutionFor macroevolution to occur, two populations must be reproductively isolated (or separated) from one another
The separated population experience different selective pressures
Over time, they evolve in separate directions, into different species that cannot interbreed
Brown blends in with tree trunks
Green blends in with grass
![Page 44: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/44.jpg)
What is a species?
Two populations that can mate and produce fertile offspring.
Ex. donkeys and horses are considered different species because they produce mules, that are not fertile.
But… all breeds of dogs are the same species“mutts” are still fertile
![Page 45: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/45.jpg)
Does speciation occur gradually or suddenly?
Gradualism:
- Phenotypic changes due to evolution accumulate slowly over time
- Speciation occurs gradually
Punctuated Equilibrium:
- Species stay relatively unchanged over time
- Speciation is driven by major events that drastically change the environment, forcing rapid evolution
- Evolution occurs in rapid bursts, as supported by gaps in the fossil record.
![Page 46: The Theory of Evolution](https://reader036.vdocument.in/reader036/viewer/2022081422/56816731550346895ddbda00/html5/thumbnails/46.jpg)
• Speciation occurs both gradually and punctually
• There is evidence to support both ideologies
Does speciation occur gradually or suddenly?