Transcript Life Builds from the Bottom Up

Chapter 02
Life Builds from the Bottom Up
• Every individual is a colony of smaller
individuals
• Our ancestors were similar to bacteria
that evolved from self-replicating
molecules
• Bacteria invented all of life’s essential
chemical systems
Cooperating Communities of Cells
• The taste buds on
our tongues are
small communities
of cells
From Bottom Up to Top Down
• As multicellular creatures evolved, they
created new environments for already
existing simpler creatures
• Bacterial and viral parasites evolved
after their hosts; it is likely many
parasites have become simpler than
their ancestors were
Viruses
• Viruses cannot exist without using
another organism’s molecular
machinery to travel and reproduce
Sponge
• Cells function as a
cooperating group of
individuals
• Different types of cells
cooperate to maintain
constant water
flow,trap food, maintain
shape, and transport
nutrients and waste
Life Assembles Itself Into Chains
• Chains: simple
units linked
together in long
flexible strands
• Sequence of
links in a chain
molecule
conveys
information
Chain Molecules
• Information chains:
store and transmit
information
(example – genes)
• DNA and RNA are
made of four
different
nucleotides
Chain Molecules
• Working chains:
carry out business
of living (example
– proteins)
• Proteins are made
of twenty different
amino acids
Information Chain to Working
Chain
• Genes carry
information
that becomes
proteins
Protein Folding
• Shapes that
proteins take
depend on the
interactions
among the
amino acids
that make up
the protein
chain
Reading Information
• Living creatures have the ability to
read environmental information
• Proteins imbedded in cells are
activated and altered by tiny
differences in their surroundings
Life Needs an Inside and an
Outside
• Life’s molecules must be kept close
together so that they can meet
frequently and react readily
• Cell membrane maintains an inner
environment that is different from the
outside
Cell Membrane
• Consists of double layer of fat molecules
• Water-liking heads of fat molecules face
outside, fat-liking tails face inward
• Second row of fat molecules aligns tail to tail
with outer layer, heads facing inward
• Several pumps imbedded in membrane move
materials in and waste out
Cell Membrane
Protein Pump
Membranes
• Outer cell membrane: plasma
membrane
• Nucleus surrounded by membrane
enclosing DNA
• Mitochondria are surrounded by
membranes
• Mitochondria and chloroplasts use inner
membranes for electron conduction
Membranes
Membrane Functions
• Keep things out of cells that aren’t
wanted
• Bring things into cells that are needed
and keep them there until used
• Conduct waste material out of cells
Plasma Membrane
• Some
molecules can
pass across the
lipid bilayer;
others cannot
Gaia Hypothesis
Earth as Organism
• Atmosphere, oceans, soils, living
organisms comprise a biosphere
• Terrestrial vegetation acts as protective
membrane for the land
• Atmosphere acts as membrane for the
earth
Inward Similarity – Outward
Diversity
• All living creatures are based on a small
number of underlying patterns and rules
• Simple rules, used in different contexts,
produce great variety
Homology
Different Proportions – Same
Pattern
• Differences in shape are a matter of
proportion
• The fundamental pattern is the same
Different
Proportions –
Same Pattern
Patterns of Multiplication
• Dividing and
adhering
cells can
occupy
space in four
basic ways
Organization with Information
• Genes contain information on how and
when to make proteins
• Proteins work collectively to perform
life’s functions
Enzymes
• Proteins that act as chemical reaction
facilitators (catalysts)
• Perform straightforward chemical tasks
at incredible speeds without being
changed in the process
Enzymes
• Teams of
enzymes work
in a
coordinated
fashion to
maintain life
Enzymes
Example: Glycolysis
• Ten enzymes convert six-carbon glucose into threecarbon pyruvate
• Two ATP (energy molecules) are produce from one
glucose
Combining Information
• Nature creates new combinations by
exchanging information
• Large number of combinations can
result from a small number of variables
Genetic Information
• Each of us has two sets of genes – one
from our mother and one from our father
• Many matched pairs of genes are not
exactly alike
• Differences in our genes account for our
uniqueness
Recombining Genetic Information
• In making sperm and eggs, our genetic
information chains are brought together
lined up, recombined and separated so
that each sperm and egg gets half
• In mating, we combine the recombined
chain with one from the mate
Recombining
Information
Making Eggs
and Sperm
Combining Genetic Information
• With each alteration in information,
creatures become better or worse
suited to their environment
• Better suited individuals survive to
reproduce and pass on their genetic
information
Selective Breeding
• Genes are purposefully recombined to
control the characteristics of an organism
By selecting only chickens with elaborate head
plumage to breed with one another, breeders can
quickly vary the appearance of these chickens
Genetic Engineering
• Genes from one organism are inserted
into another, turning that organism into
a factory for making specific proteins
Cloning a Human Gene in a Bacterium
Cloning a Human Gene in a Bacterium
Accidents Ensure Novelty
• Cellular mechanisms make errors in
copying genes
• Altered gene sequence changes the
information being transmitted and can
show up in the offspring as a defect
• Once in a while, the alteration is an
improvement that makes the offspring
better adapted for survival
Improving Mutation
• Wrinkled skin increases surface area and
cools the elephant more efficiently,
allowing the elephant to grow larger
• Albinism, a defect in pigmentation, allows
polar bears to blend into their
surroundings
Mutations – Good or Bad?
Sickle Cell Disease:
• Result of mutation in hemoglobin gene
• Causes inflammation and tissue
destruction, but provides some
protection against malaria
• Sickle cell disease is common in
equatorial Africa where malaria is
endemic
Mutations
Mutations are generally caused by:
• Mistakes made by DNA duplicating
machinery when cells divide
• X-rays or UV and cosmic radiation
impinging on DNA
• Certain toxic chemicals interacting with
DNA
Life Occurs in Water
• Life began in water
• Our cells are 70% water
• Most of the essential molecules of life
dissolve and transport easily in water
Water
• Polar molecule
• Forms weak
bonds with itself
and with many
other types of
molecules
Water
• Expands when it freezes, making ice
less dense than liquid water
• Ice provides an insulating layer that
prevents further freezing of lakes, rivers,
and oceans
Water Organizes and Orients
Molecules
• Water molecules attract and repel charged molecules
and therefore orient them
Water Organizes and Orients Molecules
Phospholipids in Cell Membrane
• Hydrophilic
(water-liking)
charged ends
orient towards
water molecules
• Hydrophobic
(water-shunning)
fatty tails stay
away from water
Life Runs on Sugar
Sugars:
• Energy-packed
chains of three to
seven carbon atoms
with hydrogen and
oxygen
• Glucose: six carbon
atoms; life’s central
sugar
=
Photosynthesis Preview
• Plants, marine
algae, and
certain
bacteria
convert CO2
and hydrogen
from water
into sugar
using energy
from sunlight
Respiration Preview
• Plants, algae, bacteria, and animals
transform energy from sugar’s bonds
into ATP, which powers all of life’s work
• Carbon and oxygen are discarded as
CO2
• Hydrogen is linked to oxygen from the
air and is discarded as H2O
Sugar
• Starting material for assembly of amino
acids and nucleotides
Life Works in Cycles
• Each protein performs a
simple task in assemblyline fashion
• Initial protein keeps
track of overall output;
as products pile up or
become scarce, it
adjusts speed of overall
operation
Life Works in Cycles
Self-Correcting
Maneuvers:
• A feedback loop is
maintained between the
owl’s eyes, brain, wing
and tail muscles and
the mouse’s
movements
Circular Flow of Materials
• Intake and output are balanced in the
living world
• One organism’s waste is another’s food
or building material
• End product of one process becomes
the starting point of another
Fever Feedback
Breathing
Feedback
Circular Flow of Materials
Photosynthesis and Respiration
• O2, byproduct of
photosynthesis, is
essential for
respiration
• CO2 waste from
respiration is
taken up by plants
for photosynthesis
Carbon Cycling
Life Maintains Itself by Turnover
• Organisms routinely take apart
molecules and reassemble them
• Turnover provides flexibility
• Change in environment often calls for
new proteins which can be made from
disassembled old ones
Cell Turnover
• Cells that turn
over in days or
weeks – liver,
intestine, skin
Cell Turnover
• Cells that rarely
turn over –
neurons
Life Maintains Itself by Turnover
• Turnover requires a
constant supply of
raw materials and
energy
• The bottom layer of
these skin cells is fed
by tiny blood vessels,
providing a constant
supply of raw
materials
Life Maintains Itself by Turnover
• In the digestive tract,
starches and fats are
broken down into
smaller molecules,
which diffuse through
the finger-like cells of
the intestinal mucosa
into the bloodstream
Optimize Rather than Maximize
• Life operates elaborate signaling and
management systems to maintain
optimum levels
• Maximizing any single value tends to
reduce flexibility in the overall system,
so that it may not be able to adapt to
adverse environmental change
Optimize Rather than Maximize
• In times of crisis, the most specialized
(maximized) organisms tend to become
extinct; the most adaptable (least
specialized) survive
• Following a mass extinction, adaptive
radiation (evolution of many different
species from a few ancestors) occurs
on a large scale
Optimal Surface-Volume
Relationships
Life is Opportunistic
• Life makes do with whatever is available
in its surroundings
• Life flourishes even in the world’s
harshest places
• The genetic code and the protein
structure of all living things permit great
flexibility
Competition and Cooperation
Strategies for fitting in:
• Every creature acts in its own interest
• The living world works through
cooperation
Competition and Cooperation
• Creatures are self-interested, but not
self-destructive
• Self-defeating strategies get weeded
out by evolution
Competition and Cooperation
Predator/Prey Relationship:
• Usually predators can take only the
smallest, weakest, or most unhealthy of
their prey species, leaving the better
adapted members to survive and
reproduce
From Predation to Cooperation
• Ancestors of
chloroplasts and
mitochondria originally
acted as small
predators, invading
larger bacteria
• They exploited, but did
not destroy their host
Interconnected and Interdependent
Co-evolution:
• Any successful change of strategy by
one organism will create a ripple of
adjustments in the community
Interconnected and Interdependent
• As moths develop better ways to hear
(and avoid) predator bats, bats must
develop better ways to hunt moths