What is Life

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What is Life?
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• The creature at your feet dismissed
• as a bug or a weed is a creation in and of
  itself.
• It has a name, a million year history, and a
  place in the world. Its genome adapts it to a
  special niche
• in an ecosystem. The ethical value substantiated
  
• by close examination of its biology is that life
  forms around us are too old and too complex to be
  carelessly disregarded.
• Edward O. Wilson, The Future of Life, 2002

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Properties of Life

• Organisms do not spontaneously generate
• Organisms are composed of cells
• Organisms display a distinct order
• Organisms acquire and use energy, undergo
  metabolism and produce waste
• Organisms grow and develop
• Organisms reproduce
• Organisms display both genetic continuity and
  change
• Organisms interact with their environment
• Populations evolve

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Some Properties of Life
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Core Theme Evolution

• A change in the gene pool of a population
• Often called the core theme of biology
• In any population, genetic/hereditary variations
  exist
• Members of a population reproduce and compete for
  resources
• Organisms that best survive and reproduce in
  their environment pass their genes on, while
  those organisms with disadvantageous traits will
  not
• The process of differential survival and
  reproduction is known as natural selection
• Note artificial selection is done by breeders
• The theory of evolution has stood for more than
  150 years

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Theory vs. Law

• Theories are rigorously tested statements of
  general principles, supported by the consensus of
  scientists
• They are broad, encompassing a wide variety of
  facts into a complex statement that explains the
  how of scientific phenomena
• A scientific theory stands until proven wrong
  it is never proven correct
• Examples include evolution, germ theory of
  disease, atomic theory, quantum theory, and the
  theory of relativity
• Laws are narrow in scope, and state what is
  (e.g., law of gravity, laws of thermodynamics,
  laws of motion, Mendels laws of inheritance)

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Levels of Biological Organization
1 The biosphere
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The totality of life is a membrane of organisms
wrapped around Earth so thin that it cannot be
seen edgewise from the space shuttle, yet so
internally complex that most species composing it
remain undiscovered.Edward O. Wilson, The
Future of Life, 2002
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The Diversity of Life

• All organisms are placed into categories based on
  their relative similarities
• The the 3-Domain system of classification
• Domain Archaea
• Domain Bacteria
• Domain Eukarya
• Protista (will ultimately become several
  kingdoms)
• Kingdom Plantae
• Kingdom Fungi
• Kingdom Animalia

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Exploring Lifes Three Domains
100 µm
4 µm
Bacteria are the most diverse and widespread
prokaryotes, and are now divided among multiple
kingdoms. Each of the rod-shapedstructures in
this photo is a bacterial cell.
Protists (multiple kingdoms) are unicellular
eukaryotes and their relatively simple
multicellular relatives. Pictured here is an
assortment of protists inhabiting pond water.
Scientists are currently debating how to split
the protistsinto several kingdoms that better
represent evolution and diversity.
Kingdom Plantae consists of multicellular
eukaryotes that carry out photosynthesis, the
conversion of light energy to food.
0.5 µm
Many of the prokaryotes known as archaea live in
Earths extreme environments, such as salty
lakes and boiling hot springs. Domain Archaea
includes multiple kingdoms. The photoshows a
colony composed of many cells.
Kingdom Animalia consists of multicellular
eukaryotes thatingest other organisms.
Kingdom Fungi is defined in part by
thenutritional mode of its members, suchas this
mushroom, which absorbs nutrients after
decomposing organic material.
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Domain Bacteria

• Prokaryote no nucleus
• Unicellular or colonial
• Size ranges from 1-5 mm in diameter (other living
  cells range from 10 to 100 mm)
• The most familiar types of prokaryotic organisms

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Example E. coli

• Escherichia coli
• E. coli is ubiquitous
• Some strains live in the gut of animals (like
  us!)
• It is one of the most commonly used organisms in
  research

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Domain Archaea

• These prokaryotes are diverse enough from
  bacteria to be considered a separate taxonomic
  group
• There are many significant molecular and
  biochemical differences
• These organisms are found in some of the most
  extreme environments on the planet

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Domain Archaea Examples

• Extreme Barophiles
• Hundreds of species inhabit the Challenger Deep
  of the Mariana Trench, located at a depth of
  35,750 feet
• The pressures here are 1000 times or more greater
  than at the surface
• Extreme Thermophiles
• Inhabit volcanic hydrothermal vents
• Pyrolobus fumarii prefers 210 degrees, can
  reproduce at 235 degrees, stops growing at 194
  degrees (too cold!)

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Domain Archaea Radiophiles

• Can survive huge exposures to radiation
• Humans die within weeks if exposed to 1000 rads
  of radiation energy
• Damaged DNA is repaired at a rate of 2-3 bases at
  a time by human enzymes
• Deinococcus radiodurans can survive up to 3
  million rads
• Damaged DNA is repaired at a rate of 500 bases at
  a time by D. radiodurans enzymes

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Prokaryote vs. Eukaryote

• A great divide exists between the prokaryotes
  and eukaryotes
• There are tremendously significant differences in
  structure, behavior, genetics, organization and
  metabolism between the prokaryotes and eukaryotes
  
• These differences are far more dramatic than any
  between the eukaryotic kingdoms (including those
  between plants and animals)

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Eukaryotic Prokaryotic Cells
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Endosymbiosis

• Symbiosis is an ecological relationship in which
  two organisms live in direct contact (examples
  are parasitism, mutualism and commensalism)
• Endosymbiosis is an ecological relationship in
  which one organism literally resides inside the
  other
• Examples of endosymbiosis include bacteria in our
  gut that aid in the synthesis of vitamins B K
  as well as food digestion
• Another example are the bacteria living in the
  guts of cows and termites that aid in the
  degradation of cellulose

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Endosymbiotic Theory

• Specifically refers to the engulfing of a small
  prokaryote by a larger one
• Theory suggests that after the prokaryote was
  engulfed, it was incorporated into the host
  providing the host cells energy needs in
  exchange for being allowed to keep its own DNA
  and not being digested
• Consider the advantage such an organism would
  have over cells without such an arrangement
• Proposed by Lynn Margulis

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Evidence Mitochondria

• This organelle resembles bacteria
• They are responsible for the primary energy
  transformations inside the cell
• Mitochondria are found in all eukaryotic cells
• They grow and divide at their own pace
• They have their own DNA
• Unlike the DNA found in the nucleus, the
  mitochondrial DNA has no contribution from the
  father, it originates solely from the mother

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Evidence Chloroplasts

• These organelles also resemble bacteria
• They are responsible for the energy acquisition
  in plants and some protists
• Organisms with plastids (e.g., chloroplast) do
  not have to eat to receive energy, they harness
  sunlight energy directly
• Like mitochondria, these organelles have their
  own DNA

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Evidence Porphyridium

• The DNA in the plastids of this red seaweed is
  closer in sequence to that of a bacterium than it
  is to the DNA in the nucleus of that seaweed

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The Protists

• Eukaryote - true nucleus
• Examples include Amoeba, Paramecium, algae
  (including kelp), and mildew
• This category continues to be modified

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Kingdom Fungi

• Eukaryote
• Heterotrophic by absorption, important decomposer
  in ecosystems, responsible for food spoiling
• Basic body unit is the hypha
• Non-motile
• Forms nutritionally important symbiotic
  relationships with green algae (lichen) and roots
  (mycorrhizae)

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The Largest Organism on Earth

• Fungus Amarillium, located in Eastern Oregon
• 2200 acres in size

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Kingdom Plantae

• Eukaryote
• Autotrophic
• Multicellular
• Most complex cells of any organism, contain
  plastids for photosynthesis
• Cell wall made of cellulose

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Kingdom Animalia

• Eukaryote
• Heterotrophic by ingestion
• Herbivores generally have longer digestive tracts
  than carnivores, reflecting the longer time
  needed to digest vegetation
• Multicellular

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Phylum Chordata

• Notochord (this structure is manifested as the
  discs separating each vertebra in humans)
• Dorsal hollow nerve cord (this is the spinal cord
  in humans)
• Pharyngeal gill slits (in humans, present in
  embryological stages only)
• Post anal tail (in humans, embryological stages
  only)

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Subphylum Vertebrata Classes

• Agnatha (lampreys (jawless fish))
• Placodermi (extinct class of fish)
• Chondrichthyes (sharks, skates, rays)
• Osteichthyes (bony fish, e.g., salmon)
• Amphibia (frogs) 4200 known species
• Reptilia (snakes)
• Aves (birds) 9000
• Mammalia (people, puppies, ponies) 4000

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Homo sapiens

• In 23 seconds, your entire blood volume will
  circulate through your body
• In 60 seconds, your heart will pump 5 liters of
  blood to your lungs and another 5 liters to the
  rest of your body
• In 60 seconds, you will exchange 6 liters of air
  between the atmosphere and your lungs as your
  cells consume 250 ml of O2 and produce 200 ml
  of CO2
• You have 10,000 taste buds on the surface of your
  tongue
• Your brain operates on the same amount of power
  that would light a 10 Watt light bulb
• The fastest muscles are those that cause your
  eyes to blink, contracting up to 5 times per
  second

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Homo sapiens

• Your lungs are the size of two footballs, with a
  total surface area of 750 square feet
  approximately the size of a tennis court
• There are 300 million alveoli in our lungs.
• Lungs are in a triangular shape. The right lung
  has three lobes while the left lung has two lobes
  because of the space that the heart takes up
• The body of a nerve cell in humans may be up to
  three feet long
• Nerve impulses to and from the brain travel as
  fast as nearly 290 km/hr
• The focusing muscles of the eye move about
  100,000 times a day. To give the leg muscle the
  same exercise would involve at least 80 km (50
  miles) walking a day

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Homo sapiens

• The retina inside the eye covers about 650 square
  millimeters and contains some 137 million light
  sensitive cells, 130 million rod cells for black
  and white vision, and 7 million cone cells for
  color vision
• If you go blind in one eye, you only lose about
  one fifth of your vision but all your sense of
  depth
• You can see a candle flame from 50 Km on a clear,
  dark night

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Homo sapiens

• You can hear the tick of a watch from 6 meters in
  very quiet conditions
• You can taste one gram of salt in 500 liters of
  water (.0001M)
• You can detect one drop of perfume diffused
  throughout a three-room apartment
• You can detect the wing of a bee falling on your
  cheek from a height of one centimeter!

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Homo sapiens

• You're born with 300 bones, but when you get to
  be an adult, you only have 206
• One quarter of the bones in your body are in your
  feet
• Like fingerprints, everyone's tongue print is
  different
• Every human body is naturally radioactive. It is
  so, since the body contains a little amount of
  the radioactive isotope Potassium-40 and
  Carbon-14, which is absorbed by living organisms
  from atmosphere

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Humans

• replace stomach lining every 5 days
• replace liver every 2 months
• replace 98 of the atoms in the body every year
• replace the body every 7 years
• replace skin (the largest organ) every 6 weeks
• The epidermis, the outermost layer of the skin,
  sheds itself at a rate of about a million cells
  every 40 minutes
• The average square inch of skin holds 650 sweat
  glands, 20 blood vessels, 60,000 melanocytes
  (pigment cells), and more than a thousand nerve
  endings

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More

• Humans recycle ATP at a rate of 10 million per
  second per cell
• Humans consume an average of 3 pounds of food per
  day, or 1,095 pounds per year to meet nutrient
  needs
• The human brain consumes around one-fifth of the
  food we consume
• In the second it takes to turn the page of a
  book, you will lose about 3 million red blood
  cells
• During that same second, your bone marrow will
  have produced the same number of new ones

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Biodiversity

• To date, approximately 1.8 million species have
  been discovered
• About 13,000 new species are discovered every
  year
• An estimated 4 to 40 million species may actually
  inhabit our planet
• 99 of all the species that have ever existed are
  extinct, yet we currently have the greatest
  diversity of life in geologic history
• We are in the 6th great extinction episode, with
  the current extinction rate about 27,000 species
  per year
• The cause of this massive extinction - humans
• Normal extinction rate is between 20 30 species
  per year

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The Facts of Life, For All Life .Including
Humans

• An ecosystem generates no waste (i.e., there is
  no away)
• One species waste is another species food
• Matter cycles continually through the web of life
• The energy driving these ecological cycles comes
  from the sun and flows through the ecosystem
• Diversity assures resilience
• Life from its beginning more than 3 billion years
  ago did not take over the planet by combat, but
  by partnership, cooperation and networking

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John C. Sawhill Nature Conservancy

• In the end, our society will be defined not only
  by what we create, but by what we refuse to
  destroy.