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Lecture 16

LIFE 121 Lecture Notes - Lecture 16: Lichen, Meiosis, Chitin

Life Sciences
Course Code
LIFE 121
Roberto Cortinas

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Invasion of Land Plants & Fungi
Conquest of Land
o New Opportunities
Unfiltered sunlight
More CO2
Few herbivores and pathogens
o New Challenges
Lack of water
Preadaptatio’s of Charophtes
o Adaptations that enabled move to land
Shallow freshwater ponds
Durable polymer that prevents charophyte zygotes from
drying out
Innovation of Land Plants
o Alternation of generations
Multicellular haploid and diploid organisms
Not present in charophytes though present in some algae
o Multicellular, dependent embryos
Retained within gametophytes
o Walled spores in sporangia
Found in sporophyte (2n)
multicellular organs that produce spores
Sporopollenin present in spores
Protects against harsh conditions
o Apical meristems
Regions of cell division at tips of roots and shoots
Divide otiuousl durig plat’s life
Irease plat’s eposure to resoures
o Waxy cuticle
Covering of wax and other polymers
o Functions
resists drying out
Protects against bacterial infections
Early Lan Plants
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o Fossil evidence indicated that plants were on land at least 470 million
years ago
o Fossilized spores and tissues have been extracted from 450-million year
old rocks
o Large plant structures appeared in the fossil record 425 may
o by 400 may, a diverse assemblage of plants on land
o Unique traits
Specialized tissues for water transport
Branched sporophytes
o Lacked true roots and leaves
How did early plants absorb soil nutrients?
o protists
o Amoeba-like
o Small (~50 um)
o Pilose pseudopods
o Spherical or flattened body
o Soil,freshwater habitats
o Most consume algae or cyanobacteria
o Most closely related to fungi
o Large group of organisms
100k described (probably 1.5 million app.)
Found worldwide
Diverse habitats
Marine, freshwater, terrestrial
o Importance
Ecosystem function and health
Food industry
Fungal Characteristics
o Reproduce sexually and asexually
o No chloroplasts
o Cell walls and vacuoles
o Chitin in cell wall
Besides fungi, only arthropods have chitin
o All groups, except the chytrids, have lost posterior flagellum
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