General Biology

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General Biology Unit Four Objective One
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Charles Darwin
Theory of Natural Selection descent with
modification
Influenced by his voyage on the Beagle, James
Hutton, Charles Lyell, Thomas Malthus and others
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HMS Beagle Voyage
Darwin noticed gradual changes in the same
species as he moved from north to south and up in
elevation, leading to the hypotheses of
gradualism and adaptive traits
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James Hutton
Hutton, a geologist, proposed the theory of
gradualism
Darwin took the ideas of Hutton and thought if
the earth can gradually change over long periods
of time, why not organisms?
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Charles Lyell
Lyell, a geologist, stated the concept of
uniformitarianism
Darwin took the ideas of Lyell and thought if the
earth can gradually change over long periods of
time, why not organisms?
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Thomas Malthus
Malthus was an economist that stated if a
population outgrew its resources, it would
restrain the population
Darwin applied this to organisms
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Erasmus Darwin
Darwin was Darwins grandfather who formulated
one of the first theories of evolution
Darwin wrote of life evolving from common
ancestors, but did not present a mechanism
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Jean-Baptiste Lamarck
Lamarck published his theory of evolution the
year Darwin was born
Larmarcks mechanism of evolution was acquired
characteristics
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Alfred Wallace
Wallace was a contemporary of Darwins and
developed the same theory of natural selection
Wallaces letters to Darwin prompted Darwin to
write and publish the theory first
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Darwins Four Postulates of Natural Selection
1. Each generation will produce more offspring
than can possibly survive
2. Inherited variations occur due to random
mutations. These can be harmful, helpful or
neutral
3. Because of limited resources, not all
offspring survive. Those with the most
advantageous variations will survive.
4. The adaptive traits are perpetuated in the
following generations non-adaptive are
eliminated
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Sources of Evidences for Natural Selection
Comparative morphology
Comparative biochemistry
Comparative cytology
Biogeography
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Sources of Evidences for Natural Selection
Comparative morphology
- examines the physical features of extinct and
extant organisms
- uses homologous and vestigial structures to
determine phylogeny
- vestigial structures are those that are
retained, but not longer used
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Homologous structures
Can
Divergent evolution
lead to
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Analogous structures
Convergent evolution
indicate
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Mutual adaptations
lead to
Parallel evolution
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Sources of Evidences for Natural Selection
Comparative biochemistry
- examines the sequences of amino acids and
nucleotides
- quantifies the similarities among extant
organisms
- usually cannot be used on extinct organisms
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Sources of Evidences for Natural Selection
Comparative cytology
- examines the numbers and sizes of chromosomes
in extant organisms
- compares how cells and tissues develop
- usually cannot be used on extinct organisms
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Sources of Evidences for Natural Selection
Biogeography
- examines the geographic distribution of
organisms
- implies that we find modern species where they
are because their ancestors lived there
- analyzed in the context of extinct and extant
organisms
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Three Traits of Populations
Morphological traits
Physiological traits
Behavioral traits
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Microevolution Macroevolution
Microevolution is the modification of a
population (gene pool) by small changes in allele
frequencies
These changes are brought about by mutation,
natural selection, gene flow and genetic drift
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Microevolution Macroevolution
Macroevolution is the appearance and extinction
of a species
Macroevolution is many times the result of
accumulating microevolutionary changes
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Microevolution Macroevolution
Macroevolution tends to span enormous time
frames, whereas microevolution happens rapidly
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Hardy-Weinberg Equilibrium
An unlikely situation which mathematically
describes what happens if evolution does not occur
Produces a baseline for comparison
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Hardy-Weinberg Equilibrium
Hardy-Weinberg conditions large population
mating is random no migration,
mutation or natural selection
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Hardy-Weinberg Equilibrium
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Hardy-Weinberg Equilibrium
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Natural Selection
A gene pool is all the genes found in an entire
population
In theory, this is a pool of genetic resources
shared by all members and passed on to the next
generation
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Natural Selection
Remember, each gene is present in two or more
forms called alleles
These different forms can create a tremendous
amount of variation
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Natural Selection
Allele frequency is the abundance of each kind of
allele in a population
Due to the size of a gene pool, the frequency
does not change rapidly, usually taking many
generations
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Natural Selection
Genetic equilibrium is a theoretical reference
point in which the allele frequency of a given
gene remains stable from one generation to the
next
If this stability continues, the population is
not evolving in respect to that gene
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Natural Selection
Crossing over, independent assortment,
fertilization, change in chromosome number or
structure will lead to new combinations of genes
BUT NOT NEW GENES!
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Natural Selection
Changes in gene frequencies occur through
mutations and gene flow
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Natural Selection
Mutations are changes in DNA sequence that can
produce new alleles
Mutations can be lethal, neutral or beneficial
Beneficial mutations are very rare, but can
increase fitness
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Natural Selection
Population members with the best adaptations
(beneficial genes) are the ones that survive to
reproduce
Over many generations the survivor genes can
alter the allele frequencies
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Natural Selection
Gene flow is the movement of genes into and out
of a population (gene pool)
Immigration new genes entering the pool
Emigration current genes leaving the pool
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Natural Selection
Genetic drift is the random change in allele
frequency brought about by chance alone
The larger the population, the less chance of
drift
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Natural Selection
Genetic drift can be caused by
inbreeding
bottleneck effect
founders effect
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Natural Selection
Inbreeding the constant mixing of genes among
closely related individuals
Inbreeding produces the effect of concentrating
alleles found only in the closely related group
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Natural Selection
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Natural Selection
Founders effect occurs when a small group breaks
away from the original population
The genes carried by these individuals may cause
a change in the allele frequency found in the
original population
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Natural Selection
Founders effect
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Natural Selection
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Mechanisms of Selection
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Stabilizing Selection
Intermediate forms of a trait are favored
Extreme forms of a trait are eliminated
Tends to counteract the effects of mutations,
gene flow genetic drift to preserve the most
common phenotype
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Directional Selection
Forms of a trait shift toward one extreme due to
environmental changes
Adaptive mutations can also cause this shift
Tends to reduce or eliminate the original most
common phenotype
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Disruptive Selection
Extreme forms of a trait are favored
Intermediate forms of a trait are eliminated
Tends to shift to the extreme forms due to
extremes in the environment
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Biological Species Definition
A group of populations in which genes are
exchanged through reproductively isolated mating,
producing viable offspring
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Speciation Patterns
Allopatric Speciation
Sympatric Speciation
Parapatric Speciation
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Allopatric Speciation
This type of speciation occurs due to the
development of a physical barrier
The physical barrier splits the population,
preventing gene flow
Due to possible differences in the genetic
variations of the new groups, speciation may occur
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Sympatric Speciation
This type of speciation occurs within the home
range of the population
A very slight ecological separation may influence
sexual selection, leading to speciation
This speciation can also occur in plants through
polyploidy
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Parapatric Speciation
This type of speciation occurs when two
neighboring populations become distinct species
Interbreeding may occur in a hybrid zone between
the two populations
These adjacent populations may evolve into two
distinct species while maintaining contact along
a border
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Reproductive Barriers
Prezygotic reproductive isolation - six forms
Postzygotic reproductive isolation - two forms
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Reproductive Barriers
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Evolutionary Patterns
Gradualism a pattern of slow, steady changes
over a long period of time
This the pattern proposed by Darwin in his theory
of natural selection
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Evolutionary Patterns
Punctuated equalibrium a pattern of long
periods of time with no change, interrupted by
short periods of dramatic change
This pattern was proposed by Stephen J. Gould and
Niles Eldridge
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Evolutionary Patterns
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Evolutionary Patterns
Gradualism
Punctuated Equilibrium
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Geological Time Scale
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Geological Time Scale
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Domains
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Eukarya
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Archaea
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Eubacteria
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The Six Kingdom Classification System
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Eubacteria
Prokaryotic
Unicellular (single celled)
All have cell walls
Autotrophic (producer) or heterotrophic
(consumer)
Asexual reproduction (binary fission) and
conjugation (gene mixing)
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Archaebacteria
Prokaryotic
Unicellular (single celled)
All have cell walls
Heterotrophs and chemotrophs
Have some eukaryotic like genes and live in
extreme conditions
Asexual reproduction (binary fission) and
conjugation (gene mixing)
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Protista
Eukaryotic
Unicellular (single celled)
Many have cell walls
Autotrophic (producer) or heterotrophic
(consumer)
Asexual reproduction (binary fission) and
conjugation (gene mixing)
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Fungi
Eukaryotic
Multicellular (most)
All have cell walls
Heterotrophic (consumer)
Sessile
Asexual sexual reproduction
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Plantae
Eukaryotic
Multicellular
All have cell walls
Autotrophic (producer)
Sessile
Asexual sexual reproduction
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Animalia
Eukaryotic
Multicellular
None have cell walls
Heterotrophic (consumer)
Capable of movement
Asexual sexual reproduction
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Carolus Linnaeus
The Father of Modern Taxonomy
Hierarchical system of taxa
Latinized names
Binomial nomenclature
The scientific name
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Domain
Eukarya
Kingdom
Animalia
Phylum
Chordata
Class
Mammalia
Order
Carnivora
Family
Felidae
Genus
Panthera
leo
Species
Panthera leo
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Viruses
Viruses are non-living structures that are
obligatory parasites of living cells
Viruses are cell specific, causing a variety of
diseases in almost all organisms
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Viruses
Viruses are considered non-living because of the
following not made of cells no
organelles cannot metabolize they
replicate, not reproduce
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Viruses
All viruses are comprised of a nucleic acid
encapsulated by protein
The nucleic acid can be DNA or RNA and may be
single or double stranded
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Viruses
The proteins form a coat around the nucleic acid
called a capsid
Some viruses will also have an envelope made of
the cell membrane stolen from a host cell
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Viruses
Viruses are very small and come in a variety of
shapes liver cell 20µm RBC 8µm
E. coli 2µm typical virus .02µm
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Viruses
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Viral Replication Cycles
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Viral Replication Cycles
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Viral Replication Cycles
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Retroviruses
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Viral Infections
Treatment for viral infections is to let it run
its course while treating the symptoms
Preventative treatment is by way of vaccines
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Prokaryotic Cells
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Prokaryotic Cells
Coccus
Bacillus
Spirillus
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Bacterial Metabolism
Bacterial metabolism exhibits a number of
different strategies photosynthesizers
heterotrophic consumers aerobic anaerobic
respiration
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Bacterial Reproduction
Bacteria increase in numbers using a form of
asexual reproduction called binary fission
Bacteria produce genetic diversity through a
process called conjugation
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Ecological Impact of Bacteria
Bacteria have three major ecological impacts
decomposers (vast majority) nitrogen fixers
pathogens
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Ecological Impact of Bacteria
Most bacteria are decomposers, breaking down dead
organisms, lost or shed organismal parts
organic wastes
Bacterial decomposers break down organic
compounds into their elemental states
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Ecological Impact of Bacteria
Decomposition is vital to all mineral cycles in
that nutrients and minerals are returned to the
soil for use by other organisms
As a result of their decomposing activities
bacteria act as a natural maid, cleaning up
after everyone else
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Ecological Impact of Bacteria
Nitrogen makes up 78 of the atmosphere in the
form of N2
In this form nitrogen is unusable to organisms
due to its triple bonding
A large complex of bacteria fix nitrogen by
converting into a form that can be used by
organisms
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Ecological Impact of Bacteria
Nitrogen fixing bacteria live in the soil and in
nodules on the roots of certain types of plants
(legumes)
The bacterial complex carries out a series of
reactions that break the bonds of N2, converting
it to nitrates and nitrites
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Ecological Impact of Bacteria
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Ecological Impact of Bacteria
Some bacteria negatively impact their environment
by being pathogenic parasites
Bacterial pathogens cause disease by secreting
toxins that can poison or destroy cells
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Ecological Impact of Bacteria
Bacterial pathogens impact fungi, plants and
animals
Human diseases caused by bacteria are numerous
typhoid, pneumonia, cholera, tetenus,
tuberculosis, diptheria, plague, botulism,
gonorrhea, syphilis, etc.
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Ecological Impact of Bacteria
Treatment for bacterial infections can be
preventative using vaccines
Post bacterial infection treatment uses
antibiotics
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Protista
Large phylum of a variety of different eukaryotic
organisms
Most are unicellular, but a few are multicellular
Cells show distinct intracellular specialization
(division of labor)
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Protista
There are a variety of structures used for
locomotion flagella
cilia

pseudopods
Some groups have no structure for locomotion
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Protista
Protists can be grouped into three informal
categories plant-like
(algae)
animal-like (protozoans)
fungus-like (slime
molds)
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Protista
Algae occur in many forms and are named according
to their color (green, golden, red brown)
Most are unicellular, but brown, red and some
green algae are multicellular
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Protista
As they are plant-like, algae are autotrophs,
producing their own food by way of photosynthesis
Algae are all aquatic and are found in marine and
fresh waters
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Protista
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Protista
Protozoans are animal-like protists and therefore
heterotrophs
All protozoans are unicellular
Most protozoans will have one of the three types
of locomotive structures, but some have none
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Protista
Some are free living, while others are parasites
Protozoans have world wide distribution,
including terrestrial and aquatic environments as
well as being found inside organisms
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Protista
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Protista
Slime molds are fungus-like protists and
therefore heterotrophs
Like fungi, slime molds are saprophytic,
digesting their food outside their cells
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Protista
Slime molds occur as unicellular individuals and
in large masses of individuals
Slime molds are found in terrestrial environments
feeding on organic detritus and other
microorganisms
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Protista
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Protista
Protists increase in number using binary fission
(asexual reproduction)
Protists gain genetic diversity by way of
conjugation
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Protista
Protists have three major ecological impacts
photosynthesizers
plankton
pathogens