Evolution, Biodiversity, and Community Processes

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Evolution, Biodiversity, and Community Processes

• La Cañada High School
• Dr. E

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What types of Life exist on the Earth?
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Types of Organisms

• Prokaryotic Kingdom single-celled organisms
  containing no internal structures surrounded by
  membranes (therefore there is no nucleus)
• Monera bacteria and cyanobacteria

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Endosymbiotic Theory
Chloroplast
Plants and plantlike protists
Aerobic bacteria
Ancient Prokaryotes
Photosynthetic bacteria
Nuclear envelope evolving
Mitochondrion
Primitive Photosynthetic Eukaryote
Animals, fungi, and non-plantlike protists
Ancient Anaerobic Prokaryote
Primitive Aerobic Eukaryote
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Types of Organisms

• Eukaryotic Kingdoms all organisms consisting of
  cells which contain membrane-bound nuclei
• Protista - mostly one-celled organisms have
  characteristics of all three other Eukaryote
  Kingdoms
• Fungi - organisms which decompose stuff
• Plantae - organisms which use photosynthesis to
  make their own food
• Annuals complete life cycle in one season
• Perennials live for more than one season
• Animalia - organisms which must get organic
  compounds from food they eat - most are able to
  move
• Invertebrates no backbone
• Vertebrates Fish, Amphibians, Reptiles, Birds
  and Mammals

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Naming Species
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Naming of Species

• The system of naming species was first developed
  by Swedish botanist and physician, Carolus
  Linnaeus in the mid- 1700s
• Taxonomy, which seeks to describe, name and
  classify organisms
• begins with assigning all species a two-part
  Latin name called a binomial
• first word of the binomial is the genus name of
  the species,
• second word is the specific epithet for the
  species. 
• scientific name for the blue crab  is Callinectes
  sapidus
• Callinectes, the genus name, is the collective
  term which includes many species of crabs closely
  related to the blue crab
• sapidus, describes exactly which of the
  Callinectes species is being identified

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Definition of Species

• Morphological Species Concept (MSC)
• traced back to the philosophies of Plato and
  Aristotle, and which continued to be used until
  the first half of the twentieth century
• defines species purely by their phenotypic traits
  rather than their genetic complement or potential
  interbreeding
• number of species classified was large because
  each group of individuals that exhibited a slight
  phenotypic difference were considered a different
  species

http//www.falcons.co.uk/mefrg/Falco/13/Species.ht
m
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Definition of Species

• Biological Species Concept (BSC)
• a species is a group of interbreeding
  populations that are genetically isolated from
  other groups by reproductive isolating mechanisms
  such as hybrid sterility or mate acceptability
• Phylogenetic Species Concept (PSC
• Each population of sexually reproducing organisms
  that possesses at least one diagnostic character
  present in all population members but absent from
  all closest relatives is considered a species
• each geographically distinct form is classified
  as a species

http//www.falcons.co.uk/mefrg/Falco/13/Species.ht
m
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How did Life Originate?OrChemical Evolution
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EVOLUTIONisGradual Change
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Origin of Life

• 600 BC Anaximander
• life began in water.
• early forms were simple.
• simple forms begat more complex forms over time
• Aristotle (350 BC)
• decaying material could be transformed by the
  Spontaneous Action of Nature' into living
  animals
• ArchBishop Usher (early 1600s) and his scholars
• provided exact dates for all the various
  occurrences in the new Bible being translated for
  King James
• proved to the King that the world was created
  on Tuesday, October 8, 4004 BC at 930 in the
  morning

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Chemical Evolution

• Oparin Hypothesis (early 1930s)
• 1) Formation of the planet with gases in the
  atmosphere that could serve as the raw materials
  for life.
• most widely accepted astronomical theory for the
  origin of the earth and the rest of the solar
  system is that the solar system formed about 4.7
  billion years ago from a diffuse dust cloud
• central portion probably condensed to form the
  sun and areas in the outer parts of the cloud
  condensed to form the planets
• beginning of the universe according to the "Big
  Bang" theory occurred about 15 billion years ago

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Chemical Evolution

• Oparin Hypothesis
• 2) Random synthesis of simple organic molecules
  (such as amino acids that make up proteins) from
  the gases in the surrounding atmosphere.
• 3) Formation of larger, more complex molecules
  (Macromolecules) from the simple organic
  molecules, e.g., the formation of simple
  proteins.
• 4) Formation of coacervates - unique droplets
  containing the macromolecules , i.e., a
  coacervates consists of chemicals suspended
  within a liquid surrounded by a membrane, e.g. a
  droplet consisting of chemicals in water
  surrounded by an oil layer membrane.

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Chemical Evolution

• Oparin Hypothesis
• 5) Development of some type of chemical
  organizers that function to give these droplets
  the ability to take in molecules, discharge other
  molecules, and control and maintain a
  characteristic chemical pattern. These chemical
  organizers would probably be similar to nucleic
  acids (that make up chromosomes).
• 6) Development of controlled reproduction to
  insure that resultant daughter cells have the
  same chemical capabilities. The droplets could
  now be considered to be primitive cells.
• 7) Beginnings of evolutionary developments so
  that a group of cells could adapt to changes in
  the environment over time.

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Miller-Urey Experiment

• conducted in 1953 by Stanley Miller with Harold
  Urey
• the first experiment to about the evolution of
  prebiotic chemicals and the origin of life on
  Earth
• mixture of methane, ammonia, hydrogen, and water
  vapor introduced into a 5-liter flask (simulate
  the Earth's primitive, reducing atmosphere)
• energized by an electrical discharge apparatus to
  represent ultraviolet radiation from the Sun
• products were allowed to condense and collect in
  a lower flask which modeled a body of water on
  the Earth's surface

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Miller-Urey Experiment

• heat supplied to this flask recycled the water
  vapor just as water evaporates from lakes and
  seas, before moving into the atmosphere and
  condensing again as rain
• after a day of continuous operation
• a thin layer of hydrocarbons on the surface of
  the water
• after about a week of operation
• a dark brown scum had collected in the lower
  flask and was found to contain several types of
  amino acids, including glycine and alanine,
  together with sugars, tars, and various other
  unidentified organic chemicals

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The Just-Right Planet

• Read Core Case Study on page 82!

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Evolution of First Life

• Formation of the earliest precursors of life
• must have self-organized
• acquired the capabilities needed to survive and
  reproduce
• Biomolecules of life became enclosed within a
  lipid membrane
• forming rudimentary assemblages that resembled
  cells or protocells
• Essential protocellular functions
• acquisition of energy from the environment
• use of energy to synthesize molecules
  metabolism
• information transfer to succeeding generations
  genetics

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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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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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Biological Evolution
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(ORGANIC) EVOLUTION change in gene frequencies
within populations from generation to generation.
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(ORGANIC) EVOLUTION ? gene frequencies
over timeno concepts of planning or
progress apply. No goals!
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Early Evolutionists Anthropocentric view
Scala Natura (ladder of life).
A linear rise from primitive to advanced.
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Early Evolutionists Anthropocentric view
Scala Natura (ladder of life).
Needless to say, we are the most advanced in
this schemeafter all, its our ladder!!
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Evolutionary Bush
One life-form splits into two and those branches
split (independently) to make more.
Time ?
?? Phenotypic distance
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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 evolutionary change

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

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Four causes of evolutionary change

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

Point mutation
some at base-pair level
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Four causes of evolutionary change

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

Crossing-over
others at grosser chromosome level
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Four causes of evolutionary change

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 evolutionary change

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 evolutionary change

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 evolutionary change

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 evolutionary change
But in discontinuous populations, gene flow is
blocked.
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Four causes of evolutionary change
Variations accumulate without inter-demic exchange
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Four causes of evolutionary change
Of course, this works at many loci simultaneously
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Four causes of evolutionary change

• Mutation fundamental genetic shifts.
• Genetic Drift isolation ? accumulate mutations
  
• 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 evolutionary change

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 evolutionary change

• 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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1. Biogeography

• Geographical distribution of species

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2. Fossil Record

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

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3. Taxonomy
Classification of life forms.
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4. Homologous Structures
Structures that are similar because of common
ancestry (comparative anatomy)
Turtle
Alligator
Bird
Mammals
Typical primitive fish
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5. Comparative Embryology

• Study of structures that appear during embryonic
  development

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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. Variation is heritable (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. Diversifying Selection

• Favors variants of opposite extremes

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Speciation

• Evolution of new species

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Reproductive Barriers

• Any mechanism that impedes two species from
  producing fertile and/or viable hybrid offspring.
• Two barriers
• 1. Pre-zygotic barriers
• 2. Post-zygotic barriers

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1. Pre-zygotic Barriers

• a. Temporal isolation
• Breeding occurs at different times for
  different species
• b. Habitat isolation
• Species breed in different habitats
• c. Behavioral isolation
• Little or no sexual attraction between species

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1. Pre-zygotic Barriers

• d. Mechanical isolation
• Structural differences prevent gamete exchange
• e. Gametic isolation
• Gametes die before uniting with gametes of other
  species, or gametes fail to unite

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2. Post-zygotic Barriers

• a. Hybrid inviability
• Hybrid zygotes fail to develop or fail to reach
  sexual maturity
• b. Hybrid sterility
• Hybrid fails to produce functional gametes
• c. Hybrid breakdown
• Offspring of hybrids are weak or infertile

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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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Population Genetics

• The science of genetic change in population
  Hardy-Weinberg

Population
A localized group of individuals belonging to the
same species
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Species

• A group of populations whose individuals have the
  potential to interbreed and produce viable
  offspring

Gene Pool
The total collection of genes in a population at
any one time
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