Diversity of life week 5 >:(

Land plants were derived from? 

Zygnematales, a group of aquatic green algae

Liverworts, mosses, hornworts

bryophytes

Lycophytes, ferns, gymnosperms, angiosperms

Vascular plants

Colonisation of land

land plants 400mya from algae living in shallow water. Plants first moved into freshwater where the charophyte algae learned to accomodate low salinity so they can eventually adapt to terrestrial environments with freshwater rain.

How plants support their body plant

Vascular tissues to account for a lack of a water column. These also allowed nutrient and water transport. 

Advantage of land colonisation

CO2, sunlight, no competitiors, no herbivores (at first)

Land plant characteristics

cellulose cell wall, store carbohydrates as starch, chlorophyll a and b ← from green algae. Also: cuticle impervious to water to prevent drying. Stomata for gas exchange which is otherwise limited by the cuticle, sporopollenin surrounding spores to prevent drying, 

Bryophyte groups

liverworts, mosses, hornworts. Monophyletic despite previous conflicting phylogenies. Mosses and liverworts are sister to each other in a clade sister to hornworts.

bryophyte morphology

small with limited support due to lack of vascular tissue. Can occur in millions to carpet ecosystems. Vegitative phase with

Vegitative phase

haploid cells - green arial tissue grown from haploid spore, subterranial rhizoidal filaments called rhizoids. Haploid tissue makes gametes via mitosis which swims through water film to female haploid to make a zygote - grows into arial section of plant (capsule) where meiosis occurs.

generations

gametophyte generation, sporophyte generation.

Hornworts

small (under 5cm) limited to humid temperate areas. cannot grow on rocks or tree trunks, annuals dying at the end of the year.

Liverworts

grow in moist conditions. rocks, forest floors, tree trunks. gametophyte generation feeds sporophyte generation. Capsule contains spores produced by meiosis that disperse to form new gametophytes.

Asexual reproduction liverworts

gemmae in gemmae cups are splattered by rain allowing plant growth

mosses

more structured. can grow high supported by cushions of thousands of small plants. Abundant in areas of high moisture e.g. wet woodland.