Biological Evolution

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Biological Evolution
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Evolutionary Bush -- thousands of earlier and
later branches.
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At any given moment (e.g. the present), all we
see is current diversityall extinct forms are
gone (99.9)
Time ?
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Four Causes of Evolution

1. Mutation fundamental origin of all genetic (DNA)
   change.

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Four Causes of Evolution

1. Mutation fundamental origin of all genetic (DNA)
   change.

Point mutation
some at base-pair level
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Four Causes of Evolution

1. Mutation fundamental origin of all genetic (DNA)
   change.

Crossing-over
others at grosser chromosome level
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Four Causes of Evolution

1. Mutation fundamental genetic shifts.
2. Genetic Drift isolated populations accumulate
   different mutations over time.

In a continuous population, genetic novelty can
spread locally.
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Four Causes of Evolution

1. Mutation fundamental genetic shifts.
2. Genetic Drift isolated populations accumulate
   different mutations over time.

Local spreading of alleles
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Four Causes of Evolution

1. Mutation fundamental genetic shifts.
2. Genetic Drift isolated populations accumulate
   different mutations over time.

Local spreading of alleles
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Four Causes of Evolution

1. Mutation fundamental genetic shifts.
2. Genetic Drift isolated populations accumulate
   different mutations over time.

Spreading process known as gene flow.
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Four Causes of Evolution
But in discontinuous populations, gene flow is
blocked.
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Four Causes of Evolution
Variations accumulate without inter-demic exchange
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Four Causes of Evolution
Of course, this works at many loci
simultaneously
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Four Causes of Evolution

1. Mutation fundamental genetic shifts.
2. Genetic Drift isolation ? accumulate mutations
   
3. Founder Effect sampling bias during
   immigration. When a new population is formed,
   its genetic composition depends largely on the
   gene frequencies within the group of first
   settlers.

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Founder Effect.--
Human example your tribe had to live near the
Bering land bridge
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Founder Effect.--
to invade settle the New World!
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Galapagos Finches
Audeskirk Audeskirk, 1993
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Four Causes of Evolution

1. Mutation fundamental genetic shifts.
2. Genetic Drift isolation ? accumulation of
   mutations
3. Founder Effect immigrant sampling bias.
4. Natural Selection differential reproduction of
   individuals in the same population based on
   genetic differences among them.

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Four Causes of Evolution

• Mutation fundamental genetic shifts.
• Genetic Drift isolation ? accumulation of
  mutations
• Founder Effect immigrant sampling bias.
• Natural Selection reproductive race
• These 4 interact synergistically

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Evidence of Evolution
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Evidence of Evolution

• Biogeography
• Geographical distribution of species

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Evidence of Evolution

• 2. Fossil Record
• Fossils and the order in which they appear in
  layers of sedimentary rock (strongest evidence)

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Fossils

• Oldest fossils are the approximately 3.465
  billion-year-old microfossils from the Apex
  Chert, Australia
• colonies of cyanobacteria (formerly called
  blue-green algae) which
• built real reefs

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Fossils

• 1600's - Danish scientist Nicholas Steno studied
  the relative positions of sedimentary rocks
• Layering is the most obvious feature of
  sedimentary rocks
• formed particle by particle and bed by bed, and
  the layers are piled one on top of the other
• any sequence of layered rocks, a given bed must
  be older than any bed on top of it
• Law of Superposition is fundamental to the
  interpretation of Earth history, because at any
  one location it indicates the relative ages of
  rock layers and the fossils in them.

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Relative and Absolute Dating

• Relative Dating
• Can determine the age of fossil with respect to
  another rock or fossil.
• You compare the depth of a fossils position,
  layers.
• Some drawbacks include limitations on accuracy.

• Absolute Dating
• Can determine the age of a fossil IN YEARS.
• You determine the age by finding the amount of
  radioactive and nonradioactive isoptope in a
  specimen.
• Some drawbacks are that it is difficult to
  perform in a lab.

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Types of Radioactive Isotopes

• Carbon 14
• Use for more recent fossils (60,000 yrs old)
• Can be used with high accuracy
• Half life of 5,730 years
• Decays into Nitrogen

• Potassium 40
• Used for older fossils
• Half life of 1.3 billion years
• Decays into Calcium
• Less common element

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Half-life for a given radioisotope is the time
for half the radioactive nuclei in any sample to
undergo radioactive decay
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Half-life for a given radioisotope is the time
for half the radioactive nuclei in any sample to
undergo radioactive decay
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Evidence of Evolution
3. Taxonomy Classification of life forms.
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Evidence of Evolution

• Homologous
• structures
• Structures that are similar because of common
  ancestry (comparative anatomy)

Turtle
Alligator
Bird
Mammals
Typical primitive fish
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Evidence of Evolution

• Comparative
• Embryology
• Study of structures that appear during embryonic
  development

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Evidence of Evolution

• 6. Molecular biology
• DNA and proteins (amino acids)

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History of Theories of Evolution
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Old Theories of Evolution

• Jean Baptiste Lamarck (early 1800s) proposed
• The inheritance of acquired characteristics
• He proposed that by using or not using its
  body parts, an individual tends to develop
  certain characteristics, which it passes on to
  its offspring.

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The Inheritance of Acquired Characteristics

• Example
• A giraffe acquired its long neck because its
  ancestor stretched higher and higher into the
  trees to reach leaves, and that the animals
  increasingly lengthened neck was passed on to its
  offspring.

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Charles Darwin

• Darwin set sail on the H.M.S. Beagle (1831-1836)
  to survey the south seas (mainly South America
  and the Galapagos Islands) to collect plants and
  animals.
• On the Galapagos Islands, Darwin observed species
  that lived no where else in the world.
• These observations led Darwin to write a book

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Giant Tortoises of the Galápagos Islands
Pinta
Tower
Marchena
Pinta IslandIntermediate shell
James
Fernandina
Santa Cruz
Isabela
Santa Fe
Hood Island Saddle-backed shell
Hood
Floreana
Isabela Island Dome-shaped shell
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http//www.galapagosislands.com
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Charles Darwin

• Wrote in 1859
• On the Origin of Species by Means of Natural
  Selection
• Two main conclusions
• Species were not created in their present form,
  but evolved from ancestral species.
• Proposed a mechanism for evolution NATURAL
  SELECTION

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Darwins Observations

1. Most species produce more offspring than can be
   supported by the environment
2. Environmental resources are limited
3. Most populations are stable in size
4. Individuals vary greatly in their
   characteristics (phenotypes)
5. Variations that survive are inherited. (genotypes)

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Natural Selection

• Individuals with favorable traits are more likely
  to leave more offspring better suited for their
  environment
• Also known as Differential Reproduction
• Example
• English peppered
• moth (Biston betularia)

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Modes of Action

• Natural selection has three modes of action
• 1. Stabilizing selection
• 2. Directional selection
• 3. Diversifying selection

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1. Stabilizing Selection

• Acts upon extremes and favors the intermediate.

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2. Directional Selection

• Favors variants of one extreme.

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3. Disruptive Selection

• Favors variants of opposite extremes.

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Evidence for Natural Selection
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Artificial Selection

• The selective breeding of domesticated plants and
  animals by man.
• Question Whats the ancestor of the domesticated
  dog?

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Biodiversity
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Biodiversity

• Biodiversity
• increases with speciation
• decreases with extinction
• Give-and-take between speciation and extinction ?
  changes in biodiversity
• Extinction creates evolutionary opportunities for
  adaptive radiation of surviving species

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Interpretations of Speciation

• Two theories
• 1. Gradualist Model (Neo-Darwinian)
• Slow changes in species overtime
• 2. Punctuated Equilibrium
• Evolution occurs in spurts of relatively rapid
  change

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Adaptive Radiation

• Emergence of numerous species from a common
  ancestor introduced to new and diverse
  environments.
• Example
• Hawaiian Honeycreepers

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Convergent Evolution

• Species from different evolutionary branches may
  come to resemble one another if they live in very
  similar environments.
• Example
• 1. Ostrich (Africa) and Emu (Australia).
• 2. Sidewinder (Mojave Desert) and
• Horned Viper (Middle East Desert)

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Coevolution

• Evolutionary change, in which one species act as
  a selective force on a second species, inducing
  adaptations that in turn act as selective force
  on the first species.
• Example
• 1. Acacia ants and Acacia trees
• Yucca Plants and Yucca moths
• Lichen

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Extinction

• Extinction of a species occurs when it ceases to
  exist may follow environmental change - if the
  species does not evolve
• Evolution and extinction are affected by
• large scale movements of continents
• gradual climate changes due to continental drift
  or orbit changes
• rapid climate changes due to catastrophic events

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Extinction

• Background extinction - species disappear at a
  low rate as local conditions change
• Mass extinction - catastrophic, wide-spread
  events --gt abrupt increase in extinction rate
• Five mass extinctions in past 500 million years
• Adaptive radiation - new species evolve during
  recovery period following mass extinction

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Mass Extinctions
http//www.geog.ouc.bc.ca/physgeog/contents/9h.htm
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Date of the Extinction Event Percent Species Lost Species Affected
65 mya (million years ago) 85 Dinosaurs, plants (except ferns and seed bearing plants), marine vertebrates and invertebrates. Most mammals, birds, turtles, crocodiles, lizards, snakes, and amphibians were unaffected.
213 mya 44 Marine vertebrates and invertebrates
248 mya 75-95 Marine vertebrates and invertebrates
380 mya 70 Marine invertebrates
450 mya 50 Marine invertebrates
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Community Relationships
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Niche

• a species functional role in its ecosystem
  includes anything affecting species survival and
  reproduction
• Range of tolerance for various physical and
  chemical conditions
• Types of resources used
• Interactions with living and nonliving components
  of ecosystems
• Role played in flow of energy and matter cycling

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• Niche is
• the species occupation and its
• Habitat
• location of species
• (its address)

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Niche

• Fundamental niche set of conditions under which
  a species might exist in the absence of
  interactions with other species

Realized niche more restricted set of conditions
under which the species actually exists due to
interactions with other species
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Species Interaction
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Competition

• any interaction between two or more species for a
  resource that causes a decrease in the population
  growth or distribution of one of the species
• Resource competition
• Preemptive competition
• Exploitation competition
• Interference competition

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Competition
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Competition
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Predation prey adaptations

• Avoid detection
• camouflage, mimics,
• diurnal/nocturnal
• Avoid capture
• flee
• resist
• escape
• Disrupt handling (prevent being eaten)
• struggle?
• protection, toxins

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Rewards of Mutualism

• Food energy and nutrients
• Protection
• from other species (competition, predation)
• from the physical environment (shelter)
• Gamete or zygote dispersal (the most common of
  all)
• Pollination and fruit dispersal (between plants
  and animals).

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Pollination (hummingbird/bee and flowering plants)

• animals visit flowers to collect nectar and
  incidentally carry pollen from one flower to
  another
• animals get food and the plant get a pollination
  service

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Yucca moth and yucca

• Yuccas only pollinator is the yucca moth. Hence
  entirely dependent on it for dispersal.
• Yucca moth caterpillars only food is yucca
  seeds.
• Yucca moth lives in yucca and receives shelter
  from plant.

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Lichen (Fungi-algae)

• Symbiotic relationship of algae and
  fungaeresults in very different growth formas
  with and without symbiont.
• What are the benefits to the fungus?

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Seed Disperser

• Many birds and mammals consume fruits and
  incidentally disperse the seeds contained in
  those fruits
• Animals get food and the plant gets seed
  dispersal (often with fertilizer)

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Ant-tended plants

• Ants live inside swollen Acacia thorns or hollow
  stems, e.g. Cecropia trees.
• Patrol for caterpillars or leaf predators and
  storm out to repel intrudersincluding you!

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Commensalists

• Benefit from the host at almost no cost to the
  host
• Eyelash mite and humans
• Us and starlings or house sparrows
• Sharks and remora

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Parasites

• Parasites draw resources from host without
  killing the host (at least in the short term).

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Bibliography

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