Unit 5, 6, and 7

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Unit 5, 6, and 7
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Difference Between Meiosis and Mitosis!

• You need to understand the difference between
  mitosis and meiosis. Theyre similar, but
• Mitosis makes more body or SOMATIC cells.
• Meiosis Makes more sex cells or gametes.
• Meiosis a form of cell division that halves the
  number of chromosomes when forming specialized
  reproductive cells, such as gametes or spores.
• There are two stages of meiosis, Meiosis I and
  Meiosis II
• In animals, meiosis produces haploid gametes or
  sex cells, sperm and eggs

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Formation of Haploid Cells

• Before the process of meiosis, like mitosis, the
  DNA replicates.
• This makes a cell with how many chromosomes?
• There are 8 stages in Meisois, and they should
  sound familiar

• MEIOSIS I
• Prophase I
• Metaphase I
• Anaphase I
• Telophase I and cytokinesis
• MEIOSIS II
• Prophase II
• Metaphase II
• Anaphase II
• Telophase II and cytokinesis

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Meiosis I
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Meiosis II
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Crossing-Over and Random Fertilization

• DNA exchange during crossing over in Prophase I
  adds even more recombination to the independent
  assortment of chromosomes, making even MORE
  genetic combinations!
• Crossing-Over a type of genetic recombination
  that occurs when portions of a chromatid on one
  homologous chromosome are broken and exchanged
  with the corresponding chromatid, increasing
  genetic diversity.

• Meiosis, gamete-joining, and crossing-over are
  essential to evolution because these processes
  generate genetic variation very quickly.
• The pace of evolution is sped of by genetic
  recombination!

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Sexual and Asexual Reproduction

• Some organisms have two parents, other only have
  one.
• Reproduction can be sexual or asexual.
• Sexual Reproduction two parents form
  reproductive cells that have one-half the number
  (haploid) of chromosomes which combine to make a
  diploid individual.
• Asexual Reproduction a single parent passes
  copies of all its genes to each of its
  offspringno fusion of haploid cells such as
  gametes.
• Clone an organism that is genetically identical
  to its parent.

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Hypotheses for Heredity

• Prior to Mendels work, people thought offspring
  were a blend of their parents.
• Mendels work did not support the blending
  hypothesis.
• Mendel concluded that each pea had two separate
  heritable factors for each characterone from
  each parent.
• When sperm and eggs (gametes) form, each receives
  only one of the organisms two factors for each
  character.
• When the gametes fuse, each offspring has two
  factors for each character.

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Mendels Hypotheses

• For each inherited character, an individual has
  two copies of the geneone from each parent.
• There are alternative versions of genesa pea
  plant can have a purple version or a white
  version.
• Allele the different versions of a gene

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Mendels Hypotheses

• 3. When two different alleles occur togetherone
  of them may be completely expressed, while the
  other may have no observable effect on the
  organisms appearance.
• Dominant the expressed form of the character
• Recessive the trait not expressed when the
  dominant form is present.

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Mendels Hypotheses

• 4. When gametes are formed, the alleles for each
  gene in an individual separate independently of
  one another. Thus, gametes carry only one allele
  for each inherited character. When gametes unite
  during fertilization, each gamete contributes one
  allele.

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Mendels Findings in Modern Terms

• Dominant Traits Capital letter
• Recessive Traits lower case letter
• Pea Plants
• PurpleDominant P (capital P)
• WhiteRecessive p (lowercase p)
• Homozygous if the two alleles of a particular
  gene are the same in an individual
• Heterozygous if the two alleles of a particular
  gene are different in an individual

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Mendels Findings in Modern Terms

• Genotype the set of alleles that an individual
  has for a character.
• The genes they actually have.
• Phenotype the physical appearance of a
  character.
• How they look.

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The Laws of Heredity

• The Law of Segregation the two alleles for a
  character segregate (separate) when gametes are
  formed.
• This is the behavior of chromosomes during
  meiosis.
• The Law of Independent Assortment The alleles of
  different genes separate independently of one
  another during gamete formation.
• The inheritance of one character does not
  influence the inheritance of another, as long as
  theyre on separate chromosomes!

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Punnett Squares

• Punnett Square A diagram that predicts the
  outcome of a genetic cross by considering all
  possible combinations of gametes in the cross.

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Inheritance

• Dominant If the gene is autosomal dominant,
  every individual with the condition will have a
  parent with the condition.
• Recessive If the condition is recessive, an
  individual with the condition can have one, two,
  or neither parent exhibit the condition.
• Heterozygous/Homozygous If individuals with
  autosomal traits are homozygous dominiant or
  heterozygous, their phenotype will show the
  dominant allele. If individuals are homozygous
  recessive, they will show the recessive allele.

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Autosomal or Sex-Linked

• Autosomal gene occurs on an autosome.
• If a trait is autosomal, it will appear in both
  sexes equally.
• Sex-Linked gene occurs on an X or Y chromosome.
• A female with a recessive trait will only show it
  if it occurs on both of her X chromosomes.
• Thus, males are more likely to exhibit sex-linked
  recessive traits.

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Complex Control of Characters

• Patterns of heredity are complex. Most of the
  time, characters display more complex patterns of
  heredity than the simple dominant-recessive
  patterns discussed so far.
• Characters can be influenced by several genes.
• It isnt always as easy as Punnett squares make
  it seem!
• Polygenic inheritance when several genes
  influence a character.
• Determining the effect of any one of these genes
  can be difficult. Due to crossing-over and
  independent assortment, many different
  combinations appear in offspring.
• Familiar examples of polygenic traits include eye
  color, hair color, skin color, height, and weight.

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Intermediate Characters

• In Mendels pea-plants, one allele was dominant
  over another. Sometimes, however, there is an
  intermediate between the two parents.
• Incomplete Dominance an individual that displays
  a phenotype that is intermediate between two
  parents.
• In snapdragons (on right), the flowers in a cross
  between red and white parents appear pink because
  neither the red or white allele is completely
  dominant over the other allele.

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Genes with 3 or more Alleles

• Multiple Alleles Genes with three or more
  alleles.
• Example ABO Blood Groups are determined by three
  alleles
• IA, IB, i
• IA and IB are both dominant over I
• Combinations of these three alleles makes four
  blood groups.

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Codominance

• Codominance Both traits are displayed at the
  same times.
• Example AB Blood GroupA and B are both dominant
  traits, and if someone has both alleles they have
  an AB blood type.

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Decoding the Information in DNA

• Gene A segment of DNA in a chromosome that codes
  for a particular protein.
• Traits such as eye color are determined by
  proteins built according to instructions coded in
  genes in the DNA.
• Proteins are not built directly from DNA. RNA is
  also involved.
• RNARibonucleic Acid
• Three Differences between DNA and RNA
• RNA is singled stranded rather than double
  stranded.
• RNA has ribose sugar rather than deoxyribose
  sugar.
• RNA has Uracil (U) rather than Thymine (T) bases.
  U pairs with A.

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Decoding the Information in DNA

• A genes instructions for making a protein are
  coded in the sequence of nucleotides in the gene.
  The instructions for making a protein are
  transferred from a gene to RNA in a process
  called transcription.
• Transcription Making RNA using one strand of DNA
  as a template.
• Translation in ribosomes, when mRNA (messenger
  RNA) molecules are used to specify the sequence
  of amino acids in polypeptide chains (precursors
  of proteins)

Gene Expression The manifestation of the
genetic material of an organism in the form of
specific traits.
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Transcription Making RNA
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The Genetic Code Three-Nucleotide Words

• Different types of RNA are made during
  transcription, depending on the gene being
  expressed.
• When a cell needs a particular protein, mRNA
  (messenger RNA) is made.
• Messenger RNA (mRNA) a form of RNA that carries
  the instructions for making a protein from a gene
  and delivers it to the site of translation.
• The information from mRNA is translated from the
  language of RNA (nucleotides) to the language of
  proteins (amino acids).
• The RNA instructions are written as a series of
  three-nucleotide sequences on the mRNA called
  codons.
• Each codon along the mRNA strand corresponds to
  an amino acid or signifies a start of stop signal
  for translation.

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RNAs Roles in Translation

• Transfer RNA (tRNA) molecules and ribosomes help
  in the synthesis of proteins.
• Transfer RNA (tRNA) single strands of RNA that
  can carry a specific amino acid on one end, folds
  into a compact shape and has an anticodon.
• Anticodon a three-nucelotide sequenceo n a tRNA
  that is complementary to an mRNA codon.
• Ribosomal RNA (rRNA) RNA molecules that are part
  of the structure of ribosomes.

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Protein Synthesis in Prokaryotes

• Operator piece of gene that controls RNA
  polymerases access to the genes.
• An operon is a group of genes that code for
  enzymes involved in the same functionthis is the
  lac operon.
• Repressor is a protein that binds to an operator
  and physically blocks RNA polymerase from binding
  and strops transcription.

When lactose is present, the lactose binds to the
repressor and changes the shape of the repressor.
The change in shape causes the repressor to fall
off of the operator. Now the bacterial cell can
begin transcribing the genes that code for the
lactose-metabolizing enzymes.
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Controlling the Onset of Transcription

• Eukaryotic cells have more DNA than prokaryotic
  cells therefore there are more opportunities for
  regulating gene expression.
• Transcription factors help arrange RNA
  polymerase in the correct position on the
  promoter
• Enhancer can be bound by an activator away from
  the gene

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Intervening DNA in Eukaryotic Genes

• In eukaryotes, a gene is not an unbroken stretch
  of nucleotides.
• Many genes are interrupted by introns.
• Intron long segments of nucleotide that have no
  coding information.
• Exons portions of a gene that are translated.
• This adds options to evolution!
• appropriately joined

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Karyotype

• Karyotype number of Chromosomes in a cell
• 22 pairs of autosomes, 1 pair of sex chromosomes
• 44 autosomes total, 2 sex chromosomes total
• XXfemale
• XYmale
• Can be used to identify gender and chromosomal
  disorders.
• Incorrect chromosome numbers are caused by
  nondisjunction of chromosomes in meiosismeaning
  that the chromosomes do not separate correctly.

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Chromosome Disorders

• Sex Chromosome Disorders
• Klinefelters syndrome (XXY)
• Triple X Syndrome (XXX)
• Turners Syndrome (XO)
• Jacobs Syndrome (XYY)
• Autosomal Disorders
• Down Syndrome (Trisomy 21)
• Monosomy 21
• Pataus Syndrome (Trisomy 13)
• Edwards Syndrome (Trisomy 18)
• Cri du Chat (partial deletion of chromosome 5)

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The Evolution of Prokaryotes
http//www.dkimages.com/discover/Home/Plants/Fungi
-Monera-Protista/Cyanobacteria/Cyanobacteria-2.htm
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• Scientists use fossils to study evidence of early
  life on Earth.
• Fossil the preserved or mineralized remains or
  imprints of an organism that lived long ago.
• The oldest fossils are 3.5 billion year old
  prokaryotes.
• Some of the first prokaryotes were marine
  cyanobacteria.
• Cyanobacteria photosynthetic prokaryotes
• Helped release oxygen gas into oceans, and
  eventually the air.

http//www.mbari.org/staff/conn/botany/phytoplankt
on/phytoplankton_cyanobacteria.htm
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The origins of Mitochondria and Chloroplasts

• Most biologists think that mitochondria and
  chloroplasts originated as described by the
  theory of endosymbiosis.
• Theory of Endosymbiosis mitochondria are the
  descendants of symbiotic, aerobic eubacteria and
  chloroplasts are the descendants of symbiotic,
  photosynthetic eubacteria
• Bacteria entered larger cells, and began to live
  inside the cell performing either cellular
  respiration or photosynthesis.

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Other Organelles

• The folding in the plasma membrane may have been
  the forerunner of both the endoplasmic reticulum
  and nuclear envelope based on similar structure
  and biochemical analysis.
• Part of cell specialization a process where
  cells become modified to perform specific
  functions in an organism.

http//picsbox.biz/key/rough20endoplasmic20retic
ulum20function
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http//en.wikibooks.org/wiki/Structural_Biochemist
ry/Cell_Organelles/Endoplasmic_ReticulumSmooth_En
doplasmic_Reticulum_.28SER.29
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Multicellularity
A singled celled protist

• Protists were the first eukaryotes. Protists
  make up a large varied group of both
  multicellular and unicellular organisms.
• Unicellular organisms are very successful, but
  each cell must carry out all the activities of
  the organism.
• Distinct types of cells in one body can have
  specialized functions (like in your immune
  system, for example).
• Almost every organism you can see without a
  microscope is multicellular.
• Fossils of the first multicellular organisms are
  about 700 million years old.

http//bio.rutgers.edu/gb101/lab6_protists/m6a.ht
ml
Multicellular protistsbrown algae
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http//sopastrike.com/strike
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Mass Extinction and Continental Drift

• The fossil record indicates that a sudden change
  occurred at the end of the Ordovican perioda
  large percentage of organisms became extinct.
• Extinction the death of all members of a
  species.
• Mass Extinction an episode during which large
  numbers of species becomes extinct.
• Mass extinctions can allow new species to adapt
  and fill niches previously occupied by the
  now-extinct species, and thus help drive
  evolution.

• Continental drift also played an important role
  in evolution.
• Continental Drift the movement of Earth's land
  masses over Earths surface through geologic
  time. Resulted in present-day position of the
  continents.
• Helps to explain why there are a large number of
  marsupials in both Australia and South America,
  because these continents were once connected.

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The Ozone Layer

• While the sun gives us the light energy Earths
  organisms need, it also produces dangerous
  ultraviolet (UV) radiation.
• Early life lived in the sea, which protected it
  from dangerous UV radiation.
• However, land organisms needed protection.
• This protection is provided in the upper
  atmosphere by the ozone layer which blocks UV
  radiation.
• The Ozone (O3regular oxygen is O2layer formed
  about 2.5 billion years ago as cyanobacteria
  began adding oxygen to the earths atmosphere.

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Darwins Observations

• On his voyage, Darwin found evidence challenging
  the belief that species do not change.
• Darwin read Charles Lyells book Principles of
  Geology which proposed that the surface of Earth
  changed slowly over many years.
• Darwin saw things that could be explained only by
  a process of gradual change.
• In South America, he found fossils of extinct
  armadillos which were similar but not identical
  to modern armadillos in the area.
• Darwin visited the Galápagos Island and noticed
  that the species on the islands were similar to
  those from South America, but they changed since
  they arrived.
• Darwin called this Descent with modification, or
  evolution

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Evolution by Natural Selection

• Darwin called this differential rate of
  reproduction Natural Selection.
• In time, the number of individuals that carry
  inherited favorable characteristics will
  increase, and the population will change or
  evolve!
• Organisms differ from place to place because
  their habitats are different, and each species
  has reacted to its own environment.
• Adaptation An inherited trait that has become
  common in a population because the trait provides
  a selective advantage.

http//goose.ycp.edu/kkleiner/ecology/EvolEcology
images.htm
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Darwins Four Major Points

• Inherited variation exists within the genes of
  every population or species (the result of random
  mutation and translation errors).
• Or Not every organism is identical!
• In a particular environment, some individuals of
  a population or species are better suited to
  survive (as a result of variation) and have more
  offspring (natural selection).
• Or Some organisms do better and have more
  babies!
• Over time, the traits that make certain
  individuals of a populations able to survive and
  reproduce tend to spread in that population.
• Or Organisms that do better give their
  advantages to those babies they had!
• There is overwhelming evidence from fossils and
  many other sources that living species evolved
  from organisms that are extinct.

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Change Within Populations

• Darwins ideas were based on the idea that in any
  population, individuals that are best suited to
  survive will produce the most offspring. These
  traits will become common new generations.
• Scientists now know that genes are responsible
  for inherited traits. Certain forms of genes
  called alleles become more common.
• In other words natural selection causes the
  allele frequency to change.
• Mutations and sexual reproduction provide the
  variation needed for natural selection.
• Random gene mutation is essential to evolution!

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The Fossil Record

• Fossils offer the most direct evidence that
  evolution takes placefossils of animals show a
  pattern of development from ancestors to modern
  descendants.
• Fossils provide a record of Earths past
  life-forms.
• Evolution Change over time.
• Evolution can be observed in the fossil record.

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Anatomy and Development

• Comparisons of anatomy of different types of
  organisms often reveal basic similarities in body
  structures even though the function may differ
  between organisms.
• Vestigial Structure a structure in an organism
  that is reduced in size and function and that may
  have been complete and functional in the
  organisms ancestors.
• Similarities in bone structure can be seen in
  vertebrates, suggesting they have a relatively
  recent common ancestor
• Homologous Structures structures that share a
  common ancestry. Similar structure in two
  organisms can be found in the common ancestor of
  the organisms. Example human arm, monkey arm
• Analogous Structures are features of different
  species that are similar in function but not
  necessarily in structure and which do not derive
  from a common ancestral feature (compare to
  homologous structures) and which evolved in
  response to a similar environmental challenge.
  Example bird wing, insect wing
• Evolutionary history of organisms is also seen in
  the development of embryos. The stages of
  embryonic development are similar in many
  species.

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Homologous Structures
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Proteins and DNA Sequence

• Amino acid sequences of similar proteins were
  compared.
• If evolution has taken place, then species
  descended from a recent common ancestor should
  have fewer amino acid differences in proteins
  than do species that arent as closely related.
• This pattern does not hold true for all proteins.
  A certain protein may evolve more rapidly in
  some groups than others.
• Comparisons of proteins may not reflect
  evolutionary relationships supported by the
  fossil record and other evidence.
• More accurate hypotheses about evolutionary
  histories are based on large numbers of gene
  sequences.
• These evolutionary histories based on DNA
  sequences tend to be similar to those from the
  fossil record.

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Examples of Natural Selection

• Tuberculosis (TB) is caused by the bacterial
  species M. tuberculosis and kills more adults
  than any other infectious disease in the world.
• Two effective antibiotics because available to
  fight this bacteria.
• However, in the late 1980s, new strains of
  Tuberculosis that are resistant to the
  antibiotics appeared.
• These resistant bacteria evolved through natural
  selection.

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Gene Pools

• Natural selection utilized the diversity in a
  species gene pool.
• Gene Pool The total number of genes of every
  individual in an interbreeding population.
• Gene pools contain variations in genes, relative
  gene frequencies, and allele frequencies.
  Genetic recombination can influence the gene pool
  and variation.
• Variations A modification in structure, form, or
  function.
• Relative Frequency the average number of
  occurrences of a particular event in a large
  number of repeated trials.
• Allele Frequency the frequency of an allele
  compared to other alleles of the same gene in a
  population.
• Natural selection makes the most successful
  alleles (different copies of genes) most common
  in a population.
• In this way, natural selection changes the
  POPULATION, not the INDIVIDUALS!

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Formation of New Species

• Species formation occurs in stages.
• A species molded by natural selection has an
  improved fit to its environment.
• Divergence The accumulation of differences
  between groups.
• Divergent (split apart) Evolution The process by
  which an interbreeding population diverges
  (splits) into two or more descendant species,
  resulting in once similar or related species to
  become more and more different.
• Convergent (come together) Evolution A kind of
  evolution wherein organisms evolve parts that
  have similar structures or functions in spite of
  their evolutionary ancestors being very
  dissimilar or unrelated.
• Speciation The process by which new species
  form.

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The body structure of these organisms are
examples of convergent evolution.
http//bio1152.nicerweb.com/Locked/media/ch40/fas
t_swimmers.html
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Resources and Population Size

• As a population grows, limited resources
  eventually become depleted and population growth
  slows.
• The Logistic Model A population model in which
  exponential growth is limited by a
  density-dependent factor.
• Density-Dependent factor limited resources that
  become depleted when the population is larger.

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Growth Patterns in Real Populations

• Exponential Growth Patterns are best to describe
  faster growing organisms such as
• Many plants
• Insects
• Logistic Growth Model is best to describe slower
  growing organisms such as
• Bears
• Elephants
• Humans
• Density-Independent Factors environmental
  conditions
• Weather
• Climate

Also called a j-curve
Also called a j-curve
Also called an s-curve
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Rapidly and Slowly Growing Populations

• r-strategists grow exponentially when
  environmental conditions allow them to reproduce.
• Results in temporarily large populations.
• When environmental conditions are good, the
  population grows rapidly. When conditions are
  poor, the population size drops quickly.
• Generally r-strategists
• Have a short life span
• Reproduce early
• Many small offspring
• Offspring mature with little parental care

K-strategists organisms that grow slowly with
small population sizes and a population density
usually near the carrying capacity (K) of their
environment. Generally K-strategists Have a long
life Mature slowly Have few young Provide
extensive care for young
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Allele Frequencies

• Allele Frequency the frequency of an allele
  compared to other alleles of the same gene in a
  population.
• Biologists began to study how allele frequency
  changed in populations and wondered if dominant
  alleles (usually more common than recessive)
  would spontaneously replace recessive alleles in
  populations.
• Hardy and Weinberg demonstrated that dominant
  alleles do not automatically replace recessive
  alleles.
• They showed that the frequency of alleles in a
  population does not change.
• Also, the ratio of heterozygous individuals to
  homozygous individuals does not change unless the
  population is acted on by something that favors a
  particular allele.

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The Hardy-Weinberg Principle

• Hardy-Weinberg Principle allele frequencies in a
  population do not change unless evolutionary
  forces act on the population.
• Hardy-Weinberg Equation p22pqq21
• When no evolutionary forces are acting on a
  population, it is in
• Genetic Equilibrium A relative measure of
  reproductive success of an organism in passing
  its genes to the next generation.
• There are five principal evolutionary forces that
  can cause genotype ratios to change
• Mutation
• Gene Flow
• Nonrandom Mating
• Genetic Drift
• Natural Selection

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Five Principle Evolutionary Forces (Cause Genetic
Change in a Population)

• Mutation source of variation and makes evolution
  possible.
• Gene Flow the movement of alleles into or out of
  a population. Occurs because new individuals
  (immigrants) add alleles and Departing
  individuals (emigrants) take alleles away.
• Nonrandom Mating when individuals prefer to mate
  with others that live nearby, or are of their own
  phenotype, or based on certain traits.
• Genetic Drift the random change in allele
  frequency in a population.
• Natural Selection Causes deviations from
  Hardy-Weinberg by directly changing allele
  frequencies, since some alleles are being
  selected for.