Land plants evolved from green algae, specifically from a group of green algae called charophyceans that share many characteristics with modern land plants. Coleochaete, a type of green alga, is probably the closest living relative to the extinct algal ancestor of land plants and provides insights into what the transition from aquatic to terrestrial environments may have looked like. Coleochaete exhibits traits like a compact thallus that would help it survive out of water and may represent an intermediate form in the evolution of plant spores and meiosis.

1. Land plants evolved from green algae
The closest living relative of land plants today is a group of
green algae known as charophyceans. Charophyceans
share many characteristics with modern land plants,
suggesting that Charophyceans are the sister group to all
land plants.
Morphological evidence:
1. Rosette-shaped cellulose synthesizing complexes
2. Peroxisome enzymes
3. Structure of flagellated sperm
4. Formation of a phragmoplast

2. Land plants evolved from green algae
Coleochaete is probably the closest living relative to the
extinct algal ancestor of land plants. It provides a
snapshot of what the true ancestor to land plants might
have looked like. It also demonstrates how the transition
to land might have happened.

3. Land plants evolved from green algae
Coleochaete exhibits many characteristics that would
make a transition from an aquatic to a terrestrial habitat
possible.

4. Land plants evolved from green algae
Choleochaete
More advanced disk-shaped ones are able to live in
splash zones, often in the presence of air.
The more
compact thallus
on the right is
better equipped
to survive on
land.

5. Land plants evolved from green algae
Coleochaete
Why is Coleochaete evolutionarily important?
May be an intermediate
form in the evolution of
sporic meiosis from
zygotic meiosis.

6. Land plants evolved from green algae
Coleochaete
Why is Coleochaete evolutionarily important?
Haploid cells produce
lignin-like compunds
with antimicrobial
properties; zygote is
protected.
Ingrowths (found only
on cells adjacent to
zygote) help increase
surface area for
metabolite transfer.

7. Land plants evolved from green algae
Coleochaete
Why is Coleochaete evolutionarily important?
What if a “pampered” zygote delayed meiosis and began
dividing mitotically while still attached to the haploid
plant??
It would be a small sporophyte dependent on the
haploid plant (which is now the gametophyte).

8. Land plants evolved from green algae
It is no wonder that plants were successful on land;
terrestrial life offered many benefits that the newly adapting
organisms could not receive in their previous watery
environment.
• unfiltered sunlight
• more CO2
• soil rich in nutrients and minerals
• few herbivores and pathogens (at first)