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Lecture 8

BIOL 215 Lecture Notes - Lecture 8: Sickle-Cell Disease, Outcrossing, Aegilops

Biology (Sci)
Course Code
BIOL 215
Neil Price

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BIOL215 Lecture 8 Notes
Plants: a story of transition from water to land:
They evolved from Green Algae (aquatic seaweed)
Plates are multicellular eukaryotes
Possess cellulose rich cell walls
They are photoautotrophic
Alternation of generations
Unicellular green algae that had incorporated new genes through horizontal gene transfer and gained
organelles by endosymbiosis, transformed into multicellular photosynthetic organisms
Green algae and land plants share various similarities reflecting their common origins:
Green algae store their carbohydrate reserves as starch
Many species of algae have rigid, cellulose-reinforced cell walls, as do all land plants
Green algae and vascular plants use similar types of pigments in metabolic pathways, both green
chlorophyll (a and b) and yellow-orange carotenoids (alpha & beta)
An alternation of generation includes the sporophyte - diploid stage (2n) to a gametophyte - haploid
stage (n)
Sperm and egg are haploids which when they go together, become a zygote that is diploid
4 major evolutionary inventions in plants:
Silurian (430 mya): origin of plants
Early Devonian (390 mya): Vascular lineage
Late Devonian(360 mya): Seed lineage
Early Cretaceous (130 mya): Flower lineage
Some of the earliest land plants
Nonvascular because they lack vascular tissue & true roots to transport water & nutrients
Thrive in damp places, althought can withstand drought
Lack lignan to strengthen cell walls: means they have to stay close to the ground
Were important in two major transitions:
Water to land;
Haploid gametophyte-dominated life cycle to a diploid sporophyte-dominated life cycle
Three major divisions of bryophytes:
Major features of seedless vascular plants:
Possess vascular tissue
Allowed plant to live in drier habitats more effectively
Thrive in damn places, although can withstand drought
Well-developed cuticle and stomata - minimize H2O loss and regulate gas exchange
Ferns are most abundant: specialized underground stem the rhizome and an aerial frond
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