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Chapter 1
WHAT IS LIFE?
All living things exhibit five characteristics in combination.
A. Characteristics of Life1. Organization
• chemical (atom -> molecule -> macromolecule)
• organelle• cell• tissue• organ• organ system• multicellular organism
Biological organization beyond individual organisms• 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 & MetabolismMetabolism - biochemical reactions
that acquire & use energy.Why do organisms need energy?• to combat entropy (the tendency
towards disorder)• to build new structures• to repair/break down old
structures• to reproduce
How do organisms obtain energy?
• 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.
• Failure to maintain homeostasis can have drastic consequences including death
Ex. Human body temperature is ~98.6ºF• if body temperature rises, you sweat.• if body temperature lowers, you shiver.
4. Reproduction, Growth & DevelopmentAsexual reproduction - involves a
single parent; progeny are genetically identical to the parent.
• 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
maintainedOrganisms that successfully
reproduce over several generations compose a species
5. Irritability & AdaptationIrritability - 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• Genetic change within a
population• Natural selection is one of the
driving forces• Mutations in DNA provide genetic
variation upon which natural selection acts
• An ongoing process
B. BiodiversityLife 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
• Kingdom Protista• Kingdom Plantae• Kingdom Fungi• Kingdom Animalia
Human classification scheme:Domain EukaryaKingdom AnimaliaPhylum ChordataClass MammaliaOrder Primates Family HominidaeGenus & species Homo sapiens
C. The Study of LifeScientists study life by using the
scientific method.
What is difference between hypothesis, theory & law?
• 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:• 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
Chapter 15
THE EVOLUTION OF EVOLUTIONARY THOUGHT
Biological evolution - genetic change in a population over time.
• 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 Views1. Aristotle (384-322 B.C.) & others
• 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.
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.
• 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 (1831-1836) 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 & MalthusDarwin 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.
• 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.• 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 - EpidemiologyBiological evolution is a continual
and ongoing process.
1. Emerging Infectious Diseases• resurgence of some diseases
(measles, cholera, diphtheria & tuberculosis)
• appearance of “new” diseases (toxic shock syndrome, Legionnaires’ disease, AIDS & Ebola)
2. Rise of Antibiotic ResistanceResistant 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.
• This is a case of artificial selection
Today, some laboratory strains of Staphylococcus are resistant to ALL known antibiotics.
Chapter 16
THE FORCES OF EVOLUTIONARY CHANGE -
MICROEVOLUTION
Evolution occurs at the population level as allele frequencies change.
A. Hardy-Weinberg EquilibriumA 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:• mating population is large• mating is entirely random• there is NO migration, mutation,
or natural selection
Hardy-Weinberg Equationp2 + 2pq + q2 = 1
p2 = frequency of homozygous dominant individuals
2pq = frequency of heterozygotesq2 = frequency of homozygous
recessive individualsp = frequency of dominant alleleq = 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 = 0.6p + 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 0.32pq = 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.
0.49Calculate the frequency of homozygous
recessive individuals. 0.09If there are 1000 individuals in this
population, how many are:• heterozygous? 420• homozygous dominant? 490• homozygous recessive? 90
H-W equilibrium provides a background against which microevolution can be detected.• 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 MatingNonrandom 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. MigrationIndividuals migrate between
populations.• Immigrating individuals introduce
new alleles and migrating individuals remove alleles.• Gene flow is the movement of alleles
between populationsEx. New York City’s waves of immigration
3. Genetic DriftA 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.
• 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.
• 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. MutationA change in the DNA - introduces
‘new’ alleles into the population.
Mutations can be beneficial, “silent”, or harmful.
5. Natural SelectionThe 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.
• Disruptive SelectionEnvironment selects
against intermediate phenotype, allowing both extremes to become more prevalent.
• Stabilizing SelectionEnvironment selects
against two extreme phenotypes, allowing the intermediates to become more prevalent.
Balanced PolymorphismA 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.
Chapter 44
COMMUNITIES AND ECOSYSTEMS
EcosystemAll 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 FlowEnergy flows in one direction
through an ecosystem.Route of energy flow is determined by an
ecosystem’s trophic structure.
photo- or chemoautotrophs
animals that eat producers
animals that eat herbivores
animals that eat carnivores
Food web - several species function at more than one trophic level.
The Antarcticweb of life
Food web – severalspecies function at morethan 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:
algae store 1,500 kcal
aquatic herbivores store 150 kcalsmelt fish store 15 kcalhumans store 1.5 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.
• pyramid of biomass - shows total weight of organisms at each trophic level.