Darwins Finches

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Darwins Finches
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• Darwins Theory of Natural Selection
• 3 inferences based on 5 basic observations
• Too many individuals for limited resources
• Those with better traits survive and reproduce
• Their traits dominate in population and cause it
  to evolve

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Darwin did not know how traits were passed from
parent to offspring
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What do we need to know about to understand the
inheritance of genetic traits?
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Cell division

• Some definitions
• Mitosis ( cytokinesis)
• Meiosis ( cytokinesis)
• Life cycles

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Definitions

• Gamete haploid sex cells that fuse to form a
  zygote
• Syngamy(fertilization) that process of sexual
  fusion
• Zygote first diploid cell following
  fertilization

• Diploid 2n double set of chromosomes
• Haploid 1n single set of chromosomes
• Cytokinesis division of the cytoplasm

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Mitosis Cytokinesis

• Well organized and orchestrated
• Duplication division
• Starts with 1 cell
• Results in 2 cells identical to starting cell

• Happens in ALL eukaryotic cells, except
• Cells that have stopped dividing
• Cells that undergo meiosis (next topic)

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Cell Cycle
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Result of mitosis of one chromosome

• Chromosome just after previous division
• Same chromosome just prior to the next division
• Two new daughter chromomsomes after the next
  division

Fig 12.3
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mitosis animation
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Meiosis of one homologous chromosome pair

• Homologous pair after prior (mitosis)
• Homologous pair before meiosis
• Separation of pairs
• Separation of chromatids

Figure 13.6
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Meiosis Cytokinesis

• Well organized and orchestrated
• Reduction division
• Starts with 1 diploid cell
• Results in 4 haploid cells (each cell has half
  the number of chromosomes)
• Only happens to form sex cells of eukaryotes
• Gametes (unite as zygotes)
• Haploid spores (grow into haploid adults)

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Meiosis Cytokinesis
Meiosis Animation
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Independant assortment increases genetic
variability
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Crossing over increases genetic variability.
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Random fertilization leads to genetic
variability The random assortment of a womans
23 chromosomes leads to 8 million possible
combinations. The random assortment of a mans
23 chromosomes leads to 8 million different
possible combinations.
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Life cycles

• Diagrams of a generation in the life of an
  organism
• A good way to remember some of the biological
  details of organisms
• Human life cycle typical for animals but there
  are many others

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Human life cycle
Figure 13.4
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Other possible life cycles
Figure 13.5