Transcript One - Dr Debra Anderson

WHAT IS LIFE?
Chapter 1
All living things exhibit five
characteristics in combination.
A. Characteristics of Life
1. Organization
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chemical (atom -> molecule ->
macromolecule)
organelle
cell
tissue
organ
organ system
multicellular organism
Biological organization beyond
individual organisms
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Population: two or more members of
the same species living in the same place
at the same time
• Community: Populations of different
species in a particular area
• Ecosystem: The living and nonliving
components of an area
• Biosphere: the parts of the planet
that can sustain life and the organisms
that live there
Each level of biological organization
exhibits emergent properties.
Ex. Capillaries transport
blood (property not
exhibited by individual
endothelial cells).
2. Energy Use & Metabolism
Metabolism - biochemical reactions
that acquire & use energy.
Why do organisms need energy?
• to combat entropy (the tendency
towards disorder)
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to build new structures
to repair/break down old structures
to reproduce
How do organisms obtain energy?
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By extracting energy from the
environment
• Producers: get energy from non-
living sources
• Consumers: get nutrients made by
other organisms
• Decomposers: get nutrients from
dead organisms
3. Maintenance of Homeostasis
• Homeostasis - the ability of an
organism to maintain its internal
environment despite conditions in
the external environment.
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Failure to maintain homeostasis can have
drastic consequences including death
Ex. Human body temperature is ~98.6ºF
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if body temperature rises, you sweat.
if body temperature lowers, you shiver.
4. Reproduction, Growth &
Development
Asexual reproduction - involves a
single parent; progeny are
genetically identical to the parent.
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Often used in unicellular organisms
Sexual reproduction - involves 2
parents; progeny are genetically
diverse.
Is it essential for an individual to
reproduce?
Not necessarily . . .
• The population needs to be
maintained
Organisms that successfully reproduce
over several generations compose a
species
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5. Irritability & Adaptation
Irritability - immediate response to a
stimulus.
Adaptation - an inherited
behavior or characteristic
that enables an organism
to survive & reproduce.
Over time, adaptations are modified by
natural selection.
Natural Selection - the enhanced
survival & reproductive success of
individuals whose inherited traits
better adapt them to a particular
environment.
Evolution
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Genetic change within a population
Natural selection is one of the driving
forces
• Mutations in DNA provide genetic
variation upon which natural selection
acts
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An ongoing process
B. Biodiversity
Life on earth is diverse, yet similar.
Taxonomists place organisms into groups
based upon evolutionary relationships.
Broadest, most inclusive group (taxon) is
the domain.
Domain  Kingdom  Phylum or Division
 Class  Order  Family  Genus 
Species
Genus & species refer to the organism’s
binomial (name).
The Three Domains:
• Bacteria - unicellular prokaryotes
• Archaea - unicellular prokaryotes
• Eukarya - eukaryotes
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Kingdom Protista
Kingdom Plantae
Kingdom Fungi
Kingdom Animalia
Human classification scheme:
Domain
Kingdom
Phylum
Class
Order
Family
Genus & species
Eukarya
Animalia
Chordata
Mammalia
Primates
Hominidae
Homo sapiens
C. The Study of Life
Scientists study life by using the
scientific method.
What is difference between
hypothesis, theory & law?
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Hypothesis - “an educated guess”; a
tentative explanation of phenomena
which is experimentally tested.
Theory - a widely accepted explanation
of natural phenomena; has stood up to
thorough & continual testing.
Law - a statement of what always
occurs under certain conditions.
Validity can be influenced by:
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Sample size
The appropriate use of controls
• A control group is treated like
the experimental group except
for the one variable being tested
• Placebos are a form of control
Use of double blind studies
THE EVOLUTION OF
EVOLUTIONARY THOUGHT
Chapter 15
Biological evolution - genetic change
in a population over time.
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Macroevolution - large scale
evolutionary changes [speciation,
extinction] that occur over relatively
long periods of time.
• Microevolution - changes in individual
allele frequencies within a population
that occur over relatively short
periods of time.
Often, accumulating microevolutionary
changes lead to macroevolutionary
changes.
A. Pre-Darwinian Views
1. Aristotle (384-322 B.C.) & others
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Species are fixed & unchanging.
Earth is relatively young (only a few
thousand years old).
Species could not become extinct.
2. Georges Buffon (1707-1788)
• Individuals within a species change.
• The earth is very old.
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3. James Hutton (1726-1797)
Forces that formed the earth acted
in a gradual, yet uniform, way.
[uniformitarianism]
4. Georges Cuvier (1769-1832)
• Fossils represent extinctions.
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Older, simpler
fossils appeared
in the lower
layers of rock.
[superposition]
5. Jean-Baptiste de Lamarck (1744-
1829)
• Strong advocate of evolution.
• Proposed that species evolve from
existing species as a result of
interactions with their environment.
• Mechanism for evolution – “progeny
inherit acquired characteristics
from parents”.
6. Charles Lyell (1797-1875)
• Renewed idea of uniformitarianism.
B. Charles Darwin (1809-1882)
Received degree in Theology (1831);
embarked on a 5-year voyage (18311836) as a naturalist aboard the
HMS Beagle.
Throughout his voyage, Darwin developed
his theory of evolution on basis of:
• observations during the voyage
• ideas of Hutton, Cuvier, Buffon,
Lamarck, Lyell & Malthus
Darwin published On the Origin of
Species by Means of Natural Selection
in 1859 - 22 years after his voyage!
Almost scooped by Alfred Russell
Wallace in 1858.
Darwin’s main ideas:
• Populations include individuals that
vary for inherited traits.
• More individuals are born than
survive to reproduce.
• Individuals compete with each
other for limited resources.
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Within populations, the characteristics
of some individuals make them more
able to survive a particular
environmental challenge.
The mechanism of evolution is natural
selection.
Natural selection is the differential
survival & reproduction of
organisms whose genetic traits
better adapt them to a particular
environment.
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The direction of natural selection
can change.
Natural selection does not lead to
perfection.
Sexual selection is a form of natural
selection that directly affects
traits that increase an individual’s
chance of reproducing.
Evolution by means of natural
selection explains both the unity &
diversity of life on earth.
• Shared ancestry (descent from a
common ancestor) explains
similarities among species.
• Natural selection accounts for
much of the diversity.
C. Evolution Today - Epidemiology
Biological evolution is a continual and
ongoing process.
1. Emerging Infectious Diseases
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resurgence of some diseases
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appearance of “new” diseases (toxic
(measles, cholera, diphtheria &
tuberculosis)
shock syndrome, Legionnaires’ disease,
AIDS & Ebola)
2. Rise of Antibiotic Resistance
Resistant bacteria appeared just 4
years after the medical community
started prescribing antibiotics.
Antibiotics kill susceptible bacteria,
but leave behind those that can
resist it - creating a situation where
they can flourish.
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This is a case of artificial selection
Today, some laboratory strains of
Staphylococcus are resistant to ALL
known antibiotics.
THE FORCES OF
EVOLUTIONARY CHANGE MICROEVOLUTION
Chapter 16
Evolution occurs at the population
level as allele frequencies change.
A. Hardy-Weinberg Equilibrium
A theoretical state in which allele
frequencies of a population do not
change from one generation to the
next.
H-W equilibrium is only possible if:
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mating population is large
mating is entirely random
there is NO migration, mutation, or
natural selection
Hardy-Weinberg Equation
p2 + 2pq + q2 = 1
p2 = frequency of homozygous dominant
individuals
2pq = frequency of heterozygotes
q2 = frequency of homozygous recessive
individuals
p = frequency of dominant allele
q = frequency of recessive allele
NOTE: p + q = 1
H-W example #1:
In a certain population, 36% have sickle
cell anemia. What is the frequency of
the dominant allele?
What do we know? (p2, 2pq, q2, p or q)
q2 = 36% or 0.36
What do we want to find?
p
Calculations:
q2 = q
0.36 = 0.6
q = 0.6
p+q=1
Thus, p = 1 - 0.6 or 0.4
H-W example #2:
In a certain population, the frequency of
the dominant allele is 0.7. What is the
frequency of heterozygous individuals?
What do we know? (p2, 2pq, q2, p or q)
p = 0.7
What do we want to find?
2pq
Calculations:
p+q=1
Thus, q = 1 - 0.7 or 0.3
2pq = 2 x 0.7 x 0.3 or 0.42
From the previous example we know:
p = 0.7
q = 0.3
2pq = 0.42
Calculate the frequency of homozygous
dominant individuals.
0.49
Calculate the frequency of homozygous
recessive individuals. 0.09
If there are 1000 individuals in this
population, how many are:
• heterozygous?
420
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homozygous dominant? 490
homozygous recessive? 90
H-W equilibrium provides a background
against which microevolution can be
detected.
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If allele & genotype frequencies change
from one generation to the next, then
evolution is occurring with respect to that
particular gene.
If frequencies remain unchanged, then
evolution is not occurring.
B. Factors That Cause Microevolution
in Natural Populations
1. Nonrandom Mating
Nonrandom mating causes certain
alleles to become more common in
future generations (some individuals
leave more offspring than others).
Ex. Albinism among Arizona’s Hopi Indians
2. Migration
Individuals migrate between
populations.
• Immigrating individuals introduce
new alleles and migrating individuals
remove alleles.
Gene flow is the movement of alleles
between populations
Ex. New York City’s waves of immigration
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3. Genetic Drift
A change in the gene pool of a small
population due to chance.
Genetic drift in human populations may be
caused by the founder effect or a population
bottleneck.
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Founder effect – genetic drift due to a
few individuals leaving a large
population to found a new group.
• Unlikely that gene pool of founding
population is representative of
original population.
Ex. Ellis-van Creveld syndrome among
Pennsylvania Amish.
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Population bottleneck – genetic drift due
to high mortality in a population.
• Unlikely that gene pool of the
remaining population is representative
of original population.
Ex. Pingelapese blindness among Pingelapese
people of the eastern Caroline islands.
Decreased genetic diversity among Cheetahs.
4. Mutation
A change in the DNA - introduces
‘new’ alleles into the population.
Mutations can be beneficial, “silent”,
or harmful.
5. Natural Selection
The differential survival and
reproduction of organisms whose
genetic traits better adapt them to
a particular environment.
Considered to be the major driving
force of evolution.
Types of Natural Selection
• Directional Selection
Environment selects against
one phenotypic extreme,
allowing the other to
become more prevalent.
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Disruptive Selection
Environment selects
against intermediate
phenotype, allowing
both extremes to
become more
prevalent.
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Stabilizing Selection
Environment selects
against two extreme
phenotypes, allowing
the intermediates to
become more
prevalent.
Balanced Polymorphism
A form of stabilizing selection that
maintains deleterious recessive alleles
in a population because heterozygotes
resist an infectious disease.
• Sickle cell anemia is maintained
because heterozygotes are resistant
to malaria.
• Cystic fibrosis is maintained because
heterozygotes are resistant to
cholera & typhoid fever.
COMMUNITIES AND
ECOSYSTEMS
Chapter 44
Ecosystem
All the biotic (living) and abiotic
(nonliving) components in a defined
area.
• Ecosystems interact.
• All ecosystems require a constant
input of energy.
• Chemicals are cycled within
ecosystems.
1. Energy Flow
Energy flows in one direction through
an ecosystem.
Route of energy flow is determined by an
ecosystem’s trophic structure.
animals that eat carnivores
animals that eat herbivores
animals that eat producers
photo- or chemoautotrophs
The Antarctic
Food webweb
- several
of life
species
function at more
Food web – several
thanspecies
one trophic
level.
function
at more
than one trophic level.
Is all of the energy stored by individuals
at one trophic level available to the
next?
No - energy needs of individual, second law
of thermodynamics.
On average, ~10% (2-30%) is transferred.
Energy transfer in Cayuga Lake:
humans store 1.5 kcal
smelt fish store 15 kcal
aquatic herbivores store 150 kcal
algae store 1,500 kcal
Food chains rarely extend
beyond 4 trophic levels.
Other types of pyramids can be used to
describe ecosystems.
• pyramid of numbers - shows number of
organisms at each trophic level.
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pyramid of biomass - shows total weight
of organisms at each trophic level.