Evolution of Autotrophy & Land Plants

Photosynthesis reaction

6CO2 + 12H2O → C6H12O6 + 6O2 + 6H2O

Ecological & evolutionary impacts

Ecological: energy base of ecosystems, atmospheric composition, nutrient cycles
Evolutionary: oxygen led to aerobic respiration, led to evolution of multicellular organisms, evolution of plants to compete for light

Cyanobacteria

2.5BYA, first photosynthetic bacteria, introduced oxygen

photosynthesis in eukaryotes

1.5BYA, cyanobacteria → chloroplasts; proteobacteria → mitochondria

timeline/changes in earth’s atmosphere

O2 increased with first photosynthetic bacteria, first eukaryotes, first multicellular eukaryotes, slowed with invasion of land via land plants before increasing again, slowed with flowering plants

aerobic respiration/multicelluarity

allows for faster production of ATP/needs more ATP but also produces more

embryophytes

land plants

cuticles

waxy layer on surface; protection from UV radiation, prevents water loss

pores

facilitates gas exchange, open all the time

stomata

regulated uptake of CO2 and loss of H2O (gas exchange)

sporopollenin

outer layer of spore; protection from UV radiation + desiccation

Apical meristems

continuously dividing cells that enable growth at shoots and roots; good since nutrients are both underground or in air

benefits of aquatic environment

surrounded by water/nutrients, protection from UV radiation, structural support, mobility facilitated

challenges of terrestrial environment

desiccation, nutrients in ground, UV radiation exposure, no structural support, mobility not facilitated

Alternation of generations definition

succession of multicellular haploid and multicellular diploid phases

gametangia

Structure that protects gametes and young embryos from desiccation

gametophyte

multicellular, haploid (n) organism that produces gametes (n)

sporophyte

multicellular, diploid (2n) organism that produces spores (n)

alternation of generations stages

Tracheophytes

Specialized conducting tissues present in Vascular plants

Xylem

tracheids, vessels, dead cells, structural support

Phloem

sieve cells/companion cells, alive cells

True leaves/roots

possesses vascular tissues that conduct water and nutrients

spermatophytes

seed plants

seeds

germinates when conditions are met, protects embryo + provides nutrients until germination, dispersion via ecological interactions

pollen

male gametophyte of plants, removes dependence on water for fertilization, dispersed via ecological interactions, gymnosperms (naked seeds) and angiosperms (seeds within fruits)

notes about wood

xylem tissue resulting from secondary growth from a lateral meristem; structural support/conducting tissue

gametophyte dominant life cycle

sporophyte dominant life cycle