Transcript ENVI 30 Environmental Issues

I.
Evidence for Evolutionary Theory
C.
Biogeography
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D.
Geographic distribution reflects ancestral
relationships
Ex: Nearly all living marsupials restricted to
Australia and nearby islands
Ex: Oldest horse fossils in North America
Fossil Record
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Appearance, location, time of extinct species
Some evolutionary intermediates
Fig. 22.16
Fig. 22.20
I.
Evidence for Evolutionary Theory
D.
Fossil Record
1.
Biases
a.
b.
c.
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Not all organisms fossilized equally (jellyfish vs. fish)
Fossil-bearing rocks typically form from fine sediments
(species away from fine sediments preserved less
frequently)
Tropical rain forest species decompose rapidly before
fossilizing
Fossil record biased toward organisms with hard parts
living in aquatic or arid terrestrial environments
II.
Chromosomes
Fig. 12.4
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Composed of DNA
+ Proteins
When cell not
dividing, DNA in
chromatin (long,
thin strands – 2 m
per human cell)
Chromosomes
condense during
cell division
Humans: 23 pairs
with 30-70,000
genes
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Other species:
2 (roundworm) 1000+ (fern)
chromosomes
Fig. 12.5
III.
Cell Cycle
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Growth  Stop or Divide
One cycle = generation time
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A.
Fig. 12.6
Typically 8-20 hrs
Some cells never/rarely divide at maturity (nerve, muscle,
erythrocytes)
M Phase (Mitotic Phase)
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1.
2.
B.
Cell division
Shortest part of cell cycle (~10%)
Mitosis – Division of nucleus (karyokinesis)
Cytokinesis – Division of cell
Interphase
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1.
2.
3.
Growth and replication of chromosomes
G1 (Gap) Phase – Growth phase (longest, most variable)
S Phase – DNA synthesis (chromosome replication)
G2 (Gap) Phase – Growth phase (synthesis of proteins,
other molecules)
Fig. 12.6
IV. Mitosis
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Unique to eukaryotes
Reliable: ~1 error per 100,000 cell divisions
Continuous process divided into five stages
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1)
2)
3)
4)
5)
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G2 of Interphase
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
Cytokinesis
Fig. 12.7
Fig. 12.7
IV. Mitosis
A.
Mitotic Spindle
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Composed of microtubules (polymers of tubulin)
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Microtubules are polar:
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growing (+) end
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non-growing (–) end
Moves centrosomes to opposite poles of cell
Tugs chromosomes through cytoplasm
Orients chromosomes along metaphase plate
Elongates cell during anaphase
Separates sister chromatids; pulls them to
opposite poles of cell
How do the MTs do all this?
Anaphase
Fig. 12.8
Fig. 12.9
IV. Mitosis
B.
Cytokinesis
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Cell division following telophase
Different in animal cells (no cell walls) vs.
plant cells (cell walls)
(Actin)
Fig. 12.10
Mitosis in Plant Cells
Fig. 12.11
IV. Mitosis
C.
Binary Fission
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Occurs in bacteria
Does not involve mitosis
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No mitotic spindle
Single circular chromosome
Fig. 12.12
IV. Mitosis
D.
Evolution of Mitosis
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Presumably, binary fission arose before mitosis
Some proteins involved in binary fission are
related to eukaryotic proteins (tubulin, actin)
Fig.
12.13