evolutionary history of plants

Land plants evolved from green algae

Morphological evidence:

1. Rosette-shaped cellulose synthesizing complexes

2. Peroxisome enzymes

3. Structure of flagellated sperm

4. Formation of a phragmoplast

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.

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.


Coleochaete exhibits many characteristics that would

make a transition from an aquatic to a terrestrial habitat

possible.


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.


Coleochaete

Why is Coleochaete evolutionarily important?

May be an intermediate

form in the evolution of

sporic meiosis from

zygotic meiosis.


Coleochaete


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.


Coleochaete


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).


• unfiltered sunlight

• more CO2

• soil rich in nutrients and minerals

• few herbivores and pathogens (at first)


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.

evolutionary history of plants

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