Evolution Notes

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Evolution Notes

• Unit 6

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The History of Life
Chapter 14
14.1 Fossil Evidence of Change
Land Environments

• Earth formed about 4.6 billion years ago.
• Pangaea the supercontinent believed to have
  existed 300 million years ago where all of the
  continents today were one large land mass.

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The History of Life
Chapter 14
14.1 Fossil Evidence of Change
Clues in Rocks

• A fossil is any preserved evidence of an organism.

• Why are there gaps in the fossil record?
• Most organisms decompose before they have a
  chance to become fossilized.

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The History of Life
Chapter 14
14.1 Fossil Evidence of Change
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The History of Life
Chapter 14
14.1 Fossil Evidence of Change
Fossil Formation

• Nearly all fossils are formed in sedimentary rock.

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The History of Life
Chapter 14
14.1 Fossil Evidence of Change
Dating fossils

• Relative dating is a method used to determine the
  age of rocks by comparing them with those in
  other layers.

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The History of Life
Chapter 14
14.1 Fossil Evidence of Change
Radiometric Dating

• Uses the decay of radioactive isotopes to measure
  the age of a rock

• Half-life amount of time required for half of a
  radioactive isotope to decay.

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The History of Life
Chapter 14
14.1 Fossil Evidence of Change
The Geologic Time Scale

• The geological time scale is a model that
  expresses the major geological and biological
  events in Earths history.

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Terminology to know!

• Hypothesis? An Ifthen statement or proposal of
  an outcome of an experiment.
• (Ex. If I study, then I will pass the test.)
• Theory? A hypothesis that has withstood extensive
  testing by a variety of methods, and in which a
  higher degree of certainty may be placed (Ex.
  Theory of Evolution)
• Law? Considered universal and invariable facts of
  the physical world
• (Ex. Law of Gravity)

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The History of Life
Chapter 14
14.2 The Origin of Life
Cellular Evolution

• Scientists hypothesize that the first cells were
  prokaryotes.

• These would compare to our modern day bacteria

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The History of Life
Chapter 14
14.2 The Origin of Life
The Endosymbiotic Theory

• Eukaryotic cells arose from communities formed by
  prokaryotic cells.

• This theory explains the origin of chloroplasts
  and mitochondria.

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The History of Life
Chapter 14
14.2 The Origin of Life
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The History of Life
Chapter 14
The History of Life Self Check!

• How would you explain to someone the way fossils
  demonstrate evidence of evolution?
• Describe how relative dating is used to identify
  similarly aged rocks in different locations.
• Mitochondria and chloroplasts containing their
  own circular DNA is evidence that supports what
  theory?

Fossils are the main evidence of evolution
because they show ancestors of modern species.
They show that ancient species share similarities
with species now on Earth.
How deep the rock layer is where the fossils were
found.
Endosymbiot Theory
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Evolution
Chapter 15
15.1 Darwins Theory of Natural Selection
Darwin on the HMS Beagle

• His job was to collect biological and geological
  specimens during the ships travel.

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What can explain the large extent of biological
diversity on earth?

• Evolution change over time
• How life has changed over time

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Evolution
Chapter 15
15.1 Darwins Theory of Natural Selection
The Galápagos Islands

• Darwin began to collect mockingbirds, finches,
  other animals on the 4 islands.

• He noticed that the different islands seemed to
  have their own, slightly different varieties of
  animals.

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The Galapagos Islands

• West of South America
• Group of islands each with different climates
• Tortoises varied from island to island in neck
  length and shell shape
• Finches varied in beak shape
• Characteristics of plants and animals varied from
  island to island

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Evolution
Chapter 15
15.1 Darwins Theory of Natural Selection
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Evolution
Chapter 15
15.1 Darwins Theory of Natural Selection
Darwin Continued His Studies

• Darwin inferred that if humans could change
  species by artificial selection, then perhaps the
  same process could work in nature.

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Evolution
Chapter 15
15.1 Darwins Theory of Natural Selection
Natural Selection

• Individuals in a population show variations.

• Variations can be inherited.

• Organisms have more offspring than can survive
  with available resources.

• Variations that increase reproductive success
  will have a greater chance of being passed on.

• Survival of the Fittest

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Evolution
Chapter 15
15.1 Darwins Theory of Natural Selection
The Origin of Species

• Darwin published On the Origin of Species by
  Means of Natural Selection in 1859.

• It is a means of explaining how evolution works.

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Lamarcks Theory

• Pre-Darwin scientist
• Inheritance of acquired traits
• Organs used a lot could grow and change shape
• Organs not used would shrivel and disappear
• Theory was incorrect but significant because he
  was the first scientist to recognize that
  organisms had changed over time

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Evolution
Chapter 15
15.2 Evidence of Evolution
Support for Evolution

• The fossil record

• Provide a record of species that lived long ago.

• Show that ancient species share similarities with
  species that now live.

Armadillo
Glyptodont
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Evolution
Chapter 15
15.2 Evidence of Evolution
Support for Evolution

• Geographic Distribution

• The distribution of plants and animals that
  Darwin saw first suggested evolution to Darwin.
• Biogeography The study of the distribution of
  plants and animals on Earth.

Rabbit
Mara
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Evolution
Chapter 15
15.2 Evidence of Evolution

• Derived traits are newly evolved features, such
  as feathers, that do not appear in the fossils of
  common ancestors.

• Ancestral traits are more primitive features,
  such as teeth and tails, that do appear in
  ancestral forms.

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Homologous Structures

• Anatomically similar structures inherited from a
  common ancestor

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Evolution
Chapter 15
Analogous Structures
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Evolution
Chapter 15
15.2 Evidence of Evolution
Vestigial Structures

• Structures that are the reduced forms of
  functional structures in other organisms.

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Evolution
Chapter 15
15.2 Evidence of Evolution

• Comparative Morphology Analysis of the form and
  structure of multiple species.
• Ancestral Characteristics Morphological or
  biochemical feature present in various groups
  within the line of descent.
• Organisms with closely related morphological
  features have more closely related molecular
  features.

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More Terms

• Fitness ability of an individual to survive and
  reproduce in a specific environment
• Adaptation inherited characteristic that
  increases an organisms chance of survival
• Can be physical traits as well as behavioral
  traits

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Evolution
Chapter 15
15.2 Evidence of Evolution
Camouflage

• Allows organisms to become almost invisible to
  predators

Leafy sea dragon
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Evolution
Chapter 15
15.2 Evidence of Evolution
Mimicry

• One species evolves to resemble another species.

California kingsnake
Western coral snake
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Evolution
Chapter 15
15.3 Shaping Evolutionary Theory
Natural Selection

• Acts to select the individuals that are best
  adapted for survival and reproduction

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Evolution
Chapter 15
15.3 Shaping Evolutionary Theory

• Stabilizing selection operates to eliminate
  extreme expressions of a trait when the average
  expression leads to higher fitness.

• Ex. Siberian Husky

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Evolution
Chapter 15
15.3 Shaping Evolutionary Theory

• Directional selection makes an organism more fit.

• Favors the extremes

• Ex. Greyhound Dog

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Evolution
Chapter 15
15.3 Shaping Evolutionary Theory

• Disruptive selection is a process that splits a
  population into two groups.

• Ex. Black, White, Gray Rabbits

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Evolution
Chapter 15
15.3 Shaping Evolutionary Theory
Mechanisms of Evolution

• Population genetics

• Hardy-Weinberg principle states that when allelic
  frequencies remain constant, a population is in
  genetic equilibrium.

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Evolution
Chapter 15
15.3 Shaping Evolutionary Theory
Write these down know these!
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Evolution
Chapter 15
15.3 Shaping Evolutionary Theory
Genetic Drift

• A change in the allelic frequencies in a
  population that is due to chance and random mating

• In smaller populations, the effects of genetic
  drift become more pronounced, and the chance of
  losing an allele becomes greater.
• Marble Example

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Evolution
Chapter 15
15.3 Shaping Evolutionary Theory
Nonrandom Mating

• Promotes inbreeding could lead to a change in
  allelic proportions favoring individuals that are
  homozygous for particular traits

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Evolution
Chapter 15
15.3 Shaping Evolutionary Theory
Founder Effect

• The loss of genetic variation that occurs when a
  new population is established by a very small
  number of individuals from a larger population

Island 1
Island 2
Mainland
Island 3
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Evolution
15.3 Shaping Evolutionary Theory
Bottleneck

• a significant percentage of a population or
  species is killed or otherwise prevented from
  reproducing and can rebound later

• Often caused by a natural disaster

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What is a gene pool?

• Gene pool combined genetic info of all members
  of a population
• Contains two of more alleles (genes) for the same
  trait
• Allele frequency number of times an allele
  occurs in a gene pool compared to the number of
  times another allele occurs (expressed in
  percents)

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Relative Frequencies of Alleles
Section 16-1
allele for brown fur
allele for black fur
Sample Population
48 heterozygous black
Frequency of Alleles
16 homozygous black
36 homozygous brown
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Gene Flow

• Genes entering or leaving a population
• AKA. Migration
• Emigration? Genes LEAVING a population
• Immigration? INCOMING genes in a population

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What are sources for genetic variation?

• Mutations random change in the DNA, may cause
  evolution in future populations
• Genetic shuffling occurs in meiosis when
  gametes are formed

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Evolution
Chapter 15
15.3 Shaping Evolutionary Theory

• Sexual selection operates in populations where
  males and females differ significantly in
  appearance.

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Evolution
Chapter 15
15.3 Shaping Evolutionary Theory

• Prezygotic isolation prevents reproduction by
  making fertilization unlikely.

• In behavioral isolation, patterns of courtship
  may be different.
• In temporal isolation, different groups may not
  be reproductively mature at the same season, or
  month, or year.
• In ecological isolation, not in the same habitat
  where they are likely to meet.

Eastern meadowlark and Western meadowlark
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Evolution
Chapter 15
15.3 Shaping Evolutionary Theory

• Prevents offspring survival or reproduction

Liger
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Evolution
Chapter 15
15.3 Shaping Evolutionary Theory
Allopatric Speciation

• A physical barrier divides one population into
  two or more populations.

Abert squirrel
Kaibab squirrel
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Evolution
Chapter 15
15.3 Shaping Evolutionary Theory
Sympatric Speciation

• A species evolves into a new species without a
  physical barrier.

• The ancestor species and the new species live
  side by side during the speciation process.

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Evolution
Chapter 15
15.3 Shaping Evolutionary Theory
Adaptive Radiation
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Evolution
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Coevolution

• The relationship betweentwo species might be so
  close that the evolution ofone species affects
  the evolution of the other species.

• Mutualism

• Coevolutionary arms race

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Evolution
Chapter 15
15.3 Shaping Evolutionary Theory
Convergent Evolution

• Unrelated species evolve similar traits even
  though they live in different parts of the world.

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Evolution
Chapter 15
15.3 Shaping Evolutionary Theory
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.

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Evolution
Chapter 15
15.3 Shaping Evolutionary Theory