22: Transition to Land

Opportunities of moving from water to land (back then)

More light above water (especially more than deep water)

High CO2 access

Less competition (at first)

New habitats to engineer, new niches

Challenges of moving form water to land (back then)

Drying out in air

No buoyant support

Patchy nutrients

Motile sperm can’t move around

Green plants

all green algae and land plants together

What are the closest living relatives of land plants?

Freshwater green algae in the charophyte lineage

What are embryophytes?

Land plants

How did land plants solve the issue for each challenge?

Cuticle + spores (reduces water loss, protects dispersal stages)

Gametangia + embryo (protects gametes and young sporophytes)

Mycorrhizae (expands nutrient and water access)

Vascular tissue (transport water and provide support)

How was symbiosis a part of terrestrialization of land plants?

Early soils were nutrient-poor, so fungal hyphae traded inorganic nutrients for plants’ organic carbon

Mitosis

Duplicate parent cell to two copies of the original chromosome set (identical daughter cells)

Meiosis

Produces haploid daughter cells (4)

Plants, fungi, and animal life cycles

Animal: diploid multicellular organism, haploid gametes for fertilization

Plants: diploid sporophyte, haploid gametophyte

Fungi: haploid uni/multicellular organism, diploid zygote that does meiosis into spores that mitosis into organism

Bryophytes

moss, liverworts, hornworts

What is the dominant/independent stage of the bryophyte?

Gametophyte

The sporophyte is an ugly long-ass bulb on the top that feeds from gametophyte and just spread spores into the air

Is water necessary for moss?

Yes, for sperm movement for fertilization

It also has no vascular tissue, so each cell has to touch water on the outside to get water

How is fern different from bryophytes?

They have vascular tissue, which gives it structure

Which -phyte is dominant/independent?

sporophyte and gametophyte are both independent, neither are dominant

Do ferns need water?

Yes, they can survive out of water, but still dependent on it for fertilization (sperm swimming from antheridium to egg in archegonium)

What is the visible large plant in ferns?

The diploid sporophyte

Where does meiosis occur in bryophytes and ferns?

Sporangium (spore, angium = case)

How did terrestrialization change the biosphere?

photosynthesis turns CO2 into plant biomass, decreasing atmospheric CO2, so the Earth started to cool down

the roots, mycorriyzae, and decomposition started to build soil

plants also created habitat structures for animals, fungi, and microbes

Cuticle

protective water-repellant waxy layer covering plants

secreted by epidermal cells