1' Explain why organisms only reproduce their own kind, and why offspring more closely resemble thei

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1. Explain why organisms only reproduce their own
kind, and why offspring more closely resemble
their parents than unrelated individuals of the
same species.

• It is a consequence of heredity, which results
  from the transmission of genes from parents to
  offspring
• Because they share similar genes, offspring more
  closely resemble their parents or close relatives
  than others ?

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2. Explain what makes heredity possible.

• DNA is precisely replicated producing copies of
  genes that can be passed along from parents to
  offspring
• Sperm and ova carrying each parents genes are
  combined in the nucleus of the fertilized egg ?

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3. Distinguish between asexual and sexual
reproduction.

• Asexual
• Single parent ? passes on all of its genes
• Offspring are genetically identical to parent
• Results in a clone
• Genetic differences may occur as a result of
  mutation (change in DNA)

• Sexual
• 2 parents ? each parent passes on ½ of its genes
• Offspring have a unique combination of genes
  inherited from both parents
• Results in greater genetic variation offspring
  vary genetically from their siblings parents ?

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4. Diagram the human life cycle and indicate
where in the human body that mitosis and meiosis
occur which cells are the result of meiosis and
mitosis and which cells are haploid.

• Mitosis ? somatic cells, diploid (46
  chromosomes) growth
• Meiosis ? gametes, haploid (23 chromosomes)
  sperm cells and ova ?

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5. Distinguish among the life cycle patterns of
animals, fungi, and plants.

• Animals
• Gametes are the only haploid (n) cells
• Meiosis halves the cells (2n ? n n)
• Fertilization makes the 2n organism ?

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• Fungi
• Only diploid (2n) stage is the zygote
• Resulting haploid (n) cells divide by mitosis to
  make the n organism
• Gametes produced by mitosis ?

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Life cycles

• Plants
• Alternate generations
• 2n stage sporophyte (makes spores by meiosis)
• Haploid spores divide mitotically to produce a
  multicellular haploid gametophyte (haploid
  gametes produced by mitosis)
• Fertilization produces a diploid zygote
  sporophyte ?

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6. List the phases of meiosis I and meiosis II
and describe the events characteristic of each
phase.

• Meiosis I ? cell division that segregates the two
  chromosomes of each homologous pair and reduces
  the chromosome number by one-half includes four
  phases
• 1. Prophase I
• 2. Metaphase I
• 3. Anaphase I
• 4. Telophase I and Cytokinesis ?

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Meiosis I

• Prophase I ? long and complex 90 of time for
  meiosis
• - synapsis occurs (homologous chromosomes come
  together to form a tetrad four chromatids)
• - crossing over occurs
• Metaphase I ? tetrads align at metaphase plate
• Anaphase I ? homologues separate and are moved
  toward the poles by the spindle apparatus
• Telophase I cytokinesis ? the spindle apparatus
  continues to separate homologous chromosome pairs
  until the chromosomes reach the poles ?

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Meiosis II

• Meiosis II ? this division separates sister
  chromatids of each chromosome includes four
  phases
• 1. Prophase II
• 2. Metaphase II
• 3. Anaphase II
• 4. Telophase II and Cytokinesis ?

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Meiosis II

• Prophase II ? spindle apparatus forms and
  chromosomes move toward the metaphase II plate
• Metaphase II ? chromosomes align singly on the
  metaphase plate
• Anaphase II ? centromeres of sister chromatids
  separate, sister chromatids of each pair move
  towards opposite poles of the cell
• Telophase II and cytokinesis ? nuclei form at
  opposite poles of the cell
• - cytokinesis occurs producing four haploid
  daughter cells ?

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7. Describe the process of synapsis during
prophase I, and explain how genetic recombination
occurs.

• Synapsis ? homologous chromosomes come together
  as pairs
• Crossing over can happen where the nonsister
  chromatids are linked ?

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8. Describe key differences between mitosis and
meiosis explain how the end result of meiosis
differs from that of mitosis.

• Meiosis
• 1. Is a reduction division
• 2. Creates genetic variation
• 3. Is 2 successive nuclear divisions
• - produces gametes in animals
• Mitosis
• - crossing over doesnt occur
• - occurs in somatic cells (body cells)
• - copies the cells ?

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9. Explain how independent assortment, crossing
over, and random fertilization contribute to
genetic variation in sexually reproducing
organisms.

• Independent assortment orientation of the
  chromosome pairs is random at the poles (meiosis
  I)
• - each homologous pair orients independently of
  the others at metaphase I
• Crossing over exchange of genetic material
  between homologues (prophase I)
• - occurs when homologous portions of 2 nonsister
  chromatids trade places
• Random fertilization an egg is representative
  of 1 in 8 million possible chromosome
  combinations (same with sperm)
• - resulting zygote can have 1 in 64 trillion
  possible diploid combinations (not including
  crossovers) ?

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10. Explain why inheritable variation was crucial
to Darwins theory of evolution.

• It is the basis for natural selection
• - variations selected that increase reproductive
  success
• - adaptation (the accumulation of heritable
  variations) ?

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11. List the sources of genetic variation.

• Sexual reproduction ? independent assortment,
  crossing over, random gamete fusion
• Mutation ? random and rare structural changes
  made during DNA replication in a gene that could
  result from mistakes ?