Life Cycles Life Cycles Observing Observing Evolutionary Trends Evolutionary Trends in the Life Cycles of in the Life Cycles of Protists, Plants and Protists, Plants and Animals Animals
Dec 24, 2015
Life CyclesLife Cycles
Observing Evolutionary Observing Evolutionary Trends in the Life Cycles of Trends in the Life Cycles of Protists, Plants and AnimalsProtists, Plants and Animals
Generalized Life CycleGeneralized Life Cycle
Haploid Phase
Meiosis
Gametes
Fertilization/Syngamy
Haploid Cells
Haploid Adult
Diploid Adult
Mitosis
Fusion of gametes
Fusion of haploid nuclei
Diploid Phase
Mitosis
Mito
sis in specialized
structuresDiploid Cell
Categories of Life CyclesCategories of Life Cycles
HaplonticHaplontic Haploid phase Haploid phase is predominantis predominant
ChlamydomonasChlamydomonasUlothrixUlothrix
DiplohaplonticDiplohaplontic Haploid and Haploid and diploid phases diploid phases are equally are equally representedrepresented
UlvaUlva
DiplonticDiplontic Diploid phase is Diploid phase is predominantpredominant
FernFernEchinodermEchinodermAscarisAscarisHumanHuman A
nim
als
Ani
mal
s
Haplontic Life CycleHaplontic Life Cycle
Haploid Phase
Diploid Phase
Mei
osis
Haplo
id C
ells
Isogametes
Fertilization/Syngamy
Diploid Cell
Haploid CellsMito
sis
in poor conditions, cells of opposite mating type can fuse
same size
Haplontic Life Cycle of Chlamydomonas
• Photosynthetic protist showing an early eukaryotic life cycle
• No mitosis in diploid phase
Resting spore withstands poor
conditions
Gametangium: cell that
produces gametes by
mitosis
Sporangium: cell that
produces spores by
mitosis
Haplontic Life Cycle of Ulothrix
Gametophyte: multicellular
haploid structure that produces
gametes
Isogametes fuse to form diploid
zygote
• Photosynthetic Protist
• No mitosis in diploid phase
• Zygote produces spores by meiosis
• Haploid gametophyte grows from spore by mitosis
• Gametophyte can produce gametes or zoospores
• Motile spores (zoospores) formed by mitosis or meiosis
Spore: haploid cell that
can grow by mitosis
Applying Your KnowledgeApplying Your Knowledge
A.A. For For UlothrixUlothrix, spores are produced by, spores are produced byB.B. Growth of a gametophyte occurs byGrowth of a gametophyte occurs byC.C. For For ChlamydomonasChlamydomonas, spores are , spores are
produced byproduced byD.D. For For UlothrixUlothrix, gametes are produced by, gametes are produced by
1.1. MitosisMitosis
2.2. MeiosisMeiosis
3.3. Both Mitosis and Meiosis Both Mitosis and Meiosis
Diplohaplontic Life CycleDiplohaplontic Life Cycle
Haploid Phase
Diploid Sporophyte
Haploid Gametophyte Mito
sis
Diploid Phase
Mitosis
Gametes
Fertilization/SyngamyM
itosi
sMeiosis
Haploid Cells
in specialized
structuresZygote
Diplohaplontic Life Cycle of Ulva• Photosynthetic
Protist• Introduction of
Mitosis in Diploid phase
• Gametophyte produces isogametes
• Isomorphic gametophyte and sporophyte
Sporophyte: multicellular
diploid structure that produces
spores by meiosis
Applying Your KnowledgeApplying Your Knowledge
A.A. Where is the sporophyte found?Where is the sporophyte found?
B.B. Zoospores are part of which phase?Zoospores are part of which phase?
C.C. Where is the gametophyte found?Where is the gametophyte found?
D.D. Where is the zygote found? Where is the zygote found?
1.1. Diploid PhaseDiploid Phase
2.2. Haploid PhaseHaploid Phase
3.3. Both Diploid and Haploid PhasesBoth Diploid and Haploid Phases
Diplontic Life Cycle in FernDiplontic Life Cycle in Fern
Haploid Phase
Diploid Phase
Mitosis
Gamet
es
Ferti
lizat
ion/
Syng
amy Meiosis
Haploid Cells
Zygote
Haploid Gametophyte Mito
sis
Diploid Sporophyte
Mito
sis
i n sp
ecial i ze d
st ructu
re s
Diplontic Life Cycle of Fern• Plant
• Smaller gametophyte
• Larger, longer-lived sporophyte with tissues and organs
• Spores producedby meiosis in sporangia on the underside of sporophyte leaves
Archegonium: organ that
produces eggs by mitosis
contain sporangia(singular: sorus)
Antheridium: organ that
produces sperm by mitosis
Antheridium: organ that
produces sperm by mitosis
Archegonium: organ that
produces eggs by mitosis
Sperm swim to archegonium and
one sperm fertilizes the egg
Applying Your KnowledgeApplying Your Knowledge
• If a fern species has 5 pairs of If a fern species has 5 pairs of homologous chromosomes, how homologous chromosomes, how many chromosomes would be found many chromosomes would be found in a(n)in a(n)– SporophyteSporophyte
– ArchegoniumArchegonium
– SporeSpore
– GametophyteGametophyte– Sporangium Sporangium (not including spores inside)(not including spores inside)
Diplontic Life Cycle in AnimalsDiplontic Life Cycle in Animals
Haploid Phase
Diploid Phase
Fert
iliza
tion
/Syn
gam
yZygote
Diploid Organism
Mito
sis
i n sex o
rga n
s
Gam
etes
Meiosis
Evolutionary TrendsEvolutionary Trends
• Reduced length of haploid phaseReduced length of haploid phase• Reduced amount of mitosis in haploid phaseReduced amount of mitosis in haploid phase• Increased amount of mitosis in diploid phaseIncreased amount of mitosis in diploid phase• Increased size of diploid adult organismIncreased size of diploid adult organism• Role of mitosis changes from reproduction in Role of mitosis changes from reproduction in
haploid phasehaploid phasegrowth in haploid growth in haploid phasephasegrowth in diploid phasegrowth in diploid phase
• Single cells Single cells Multicellular organisms Multicellular organisms• Increased tissue differentiationIncreased tissue differentiation• Longer-lived speciesLonger-lived species• Note that the role of meiosis and fertilization Note that the role of meiosis and fertilization
remains the same: to generate new remains the same: to generate new combinations by sexual reproduction combinations by sexual reproduction