2: What is a Plant? Flashcards
Algae and Evolutionary Trees
Algae = paraphyletic photosynthetic group (includes Euglenozoa, Dinoflagellates, Phaeophyta, etc.)
Cyanobacteria often grouped as “blue-green algae” but are bacteria
What is Photosynthesis?
Converts light to energy for metabolism
In plants: CO₂ + H₂O → C₆H₁₂O₆ + O₂
Involves chloroplasts:
thylakoid (light reactions) and stroma (Calvin cycle)
Origin of Photosynthesis
First evolved in cyanobacteria
Transferred to eukaryotes via endosymbiosis
All plants have chlorophyll a & b
Six Key Plant Evolution Events
- Photosynthesis
- Photosynthetic eukaryotes
- Transition to land/air
- Vascular tissue
- Seeds
- Flowers
Transition to Land – Nutrients & Desiccation
Nutrients from soil: evolved symbiosis with arbuscular mycorrhizae
Desiccation: evolved waxy cuticle → later, stomates for gas exchange
Sexual Life Cycle Types
Haploid dominant (most algae): zygote undergoes meiosis
Diploid dominant (animals, some algae): only haploid cells are gametes
Alternation of generations (some algae): both haploid & diploid multicellular stages
Isomorphic vs. Heteromorphic Life Cycles
Isomorphic: gametophyte and sporophyte look similar
Heteromorphic: look different
Originated in aquatic environments
Embryophytes – Zygotes on Land
Embryo = early growth after fertilization
Fertilization within female gametophyte
Embryo nourished/protected → critical land adaptation
Emerged ~450 MYA
Vascular Tissue (types)
Xylem: water up from roots
Phloem: water + solutes up/down
Enabled large size and terrestrial success
Early vascular plants: Lycophytes, Monilophytes (ferns)
Seeds and Flowers (what are they ?)
Seed = embryo + nutrient reserve + seed coat
Flowers = reproductive structure of angiosperms
What does the ovary contain?
Ovary contains to attract pollinators
- seed;
- petals/sepals
Zizania palustris (Manoomin) significance
Monocot, family Poaceae (grasses)
Traditional food for Indigenous peoples (Anishinaabeg)
Freshwater habitats; sensitive to pollutants
Morphology: separate male/female inflorescences; sharp trichomes
Economic Externalities & Wild Rice
Externalities = costs/benefits to non-participants
Adam Smith: “Invisible hand” – individual gain may benefit society
Fertilizer runoff = negative externality for wild rice harvesters
Most are negative (e.g., pollution)
Cuticle is?
a waxy outer layer.
Conserves water but also
inhibits diffusion of O2 and
CO2 during photosynthesis
Major groups of vascular plants (without seeds)
Moniophytes: ferns and allies
Lycophytes: mosses
