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2. Prokaryotic Conjugation
Nucleoid - genome (pilus-forming genotype)
Plasmid - small circular DNA
Nucleoid - genome
(not a pilus-forming
genotype)
Pilus x x
Conjugation
Parasexual process
Involving partial recombination (just a plasmid)
Cells separate
Only one participant leaves changed
Compare Fig Pg. 256

3. Prokaryotic Pornography?
What is going on in this micrograph?
Which of these is the pilus-forming individual?
Is there evidence that the genes for pilus formation have been moved to the recipient?

4. Biology: What is Life? life study of Properties of Life
Cellular Structure: the unit of life, one or many
Metabolism: photosynthesis, respiration, fermentation, digestion, gas exchange, secretion, excretion, circulation--processing materials and energy
Growth: cell enlargement, cell number
Movement: intracellular, movement, locomotion
Reproduction: avoid extinction at death
Behavior: short term response to stimuli
Evolution: long term adaptation

5. Syngamy is always a two step process:
Plasmogamy - union of gamete cytoplasms (makes a dikaryotic…heterokaryotic cell)
Karyogamy - union of the two gamete nuclei (makes a diploid cell)
In many species, plasmogamy and karyogamy are separated by moments in time and so are often omitted from books.
Among fungi, these two steps may be separated by much longer intervals, including centuries!
The details of syngamy and meiosis help distinguish the three major groups of fungi.

6. Evolution of Gametes for Syngamy:
Isogametes - Anisogametes - Oogametes + –

7. Unicellular Life Cycle
Your book uses “fertilization” as a synonym for syngamy. That word is confusing and inaccurate…to refer to the union of gametes. Syngamy is clear and precise!
No multicellular body: ever!
SYNGAMY 1N 2N
gametes
zygote
spores
sporocyte
MEIOSIS
Syngamy and Meiosis are Compensating Processes
But have very different Evolutionary Origins
Syngamy evolved from Conjugation

8. Domain Eukarya Kingdom Plantae Phylum Chlorophyta
Green Algae
Domain Eukarya
Kingdom Plantae
Phylum Chlorophyta

9. Chlamydomonas flagella contractile vacuole eyespot cellulosic wall
contractile vacuole
mitochondria
chloroplast
eyespot
cellulosic wall
nucleus
cell membrane
cytosol
starch
pyrenoid

10. Chlamydomonas cells of opposite mating type join in syngamy to form a zygote which develops a thick wall as a hypnospore.
Upon return to better conditions, the zygote undergoes meiosis and releases flagellated cells of both mating types.

11. Unicellular Life Cycle
No multicellular body: ever!
SYNGAMY 1N 2N
gametes
zygote
spores
sporocyte
MEIOSIS

12. Multicellular Life Cycles
Compare Figs , Pg. 641
No multicellular haploid: diplontic
No multicellular diploid: haplontic
SYNGAMY 1N 2N
gametes
zygote
mitosis
germination
gametangia
mitosis
differentiation
differentiation
Gametophyte
Sporophyte
differentiation
differentiation
mitosis
sporangium
mitosis
germination
spores
sporocyte
MEIOSIS
When both haploid and diploid multicellular bodies are formed the life cycle is diplohaplontic

13. Life Cycle Classifications
Has a Multicellular
Unicellular
Haplontic
Diplontic
Diplohaplontic
Haploid No
Yes
Diploid
Example
Chlamy-domonas

14. Ulva lactuca thallus
A thallus is a plant-like multicellular body lacking any vascular tissue (xylem or phloem).

15. Some species of Ulva are anisogamous.
Ulva life cycle
There are three isomorphic thalli:
syngamy
isogametes
zygote
Some species of Ulva are anisogamous. + –
settles on substrate 1N 2N + –
Gametophytes
Sporophyte
settle on substrate
holdfast + –
Since they are motile, they are also called zoospores.
meiosis
sporocyte
The life cycle is: √
The meiospores made by the sporophyte are of two mating types.
diplohaplontic
diplontic
haplontic

16. Life Cycle Classifications
Has a Multicellular
Unicellular
Haplontic
Diplontic
Diplohaplontic
Haploid No
Yes
Diploid
Example
Chlamy-domonas
Ulva

17. Codium

18. √ Codium Life Cycle The life cycle is: diplohaplontic diplontic
syngamy √
zygote 1N 2N
Sporophytes
2 sexes
anisogametes
holdfast
sporangium
meiosis
sporocytes
zoospores

19. Life Cycle Classifications
Has a Multicellular
Unicellular
Haplontic
Diplontic
Diplohaplontic
Haploid No
Yes
Diploid
Example
Chlamy-domonas
Ulva
Codium

20. Oedogonium thallus

21. Oogonium

22. Oedogonium
This is either the meiospore or the sperm in SEM. They are morphologically similar.
When both oogonium and antheridium appear on the same filament the alga is homothallic.

23. Oedogonium Life Cycle
Since antheridia and oogonia are on the same filaments, this species is homothallic.
syngamy
sperm
zygote (hypnospore)
(in oogonium)
empty antheridia 1N 2N
egg
(in oogonium)
chemotaxis
The zygote divides meiotically to release 4 zoospores.
Zoospores settle down with a holdfast and grow into a filament.
meiosis
This life cycle is haplontic.

24. Life Cycle Classifications
Has a Multicellular
Unicellular
Haplontic
Diplontic
Diplohaplontic
Haploid No
Yes
Diploid
Example
Chlamy-domonas
Codium
Ulva
Oedo-gonium
Life Cycle Evolution:
Sequence unclear: elaborations vs reductions?
Multiple pathways in different groups?