Algae and the Move to Land

Question 1

Algae

Answer 1

• All photosynthetic eukaryotes except land plants

- Roughly 50% of the primary productivity on Earth

Question 2

Archaeplastida

Answer 2

• Red Algae: monophyletic group
• Green Algae: Polyphyletic
  > Chlorophytes
  > Charophytes
• Land Plants (some secondarily aquatic): monophyletic

Question 3

What defines Algae?

Answer 3

• aquatic
• eukaryote
• uni or multicellular
• photosynthetic
• lacks differentiation into shoots and roots

Question 4

Evidence that land plants evolved from green algae

Answer 4

• Charophytes are the closest relatives to plants

- They are the only algae that share distinctive traits with land plants

Question 5

Charophytes shared features with plants

Answer 5

1. Rings of Cellulose-synthesizing proteins
2. Structure of flagellated sperm
3. Phragmoplast formation: microtubules organize production of cell plate in dividing cell

Question 6

Challenges of Living on Land

Answer 6

• Gravity
• Desiccation (removal of moisture)
• Dispersal
• CO2 abundant but waxy surface inhibit absorption
• Light abundant but competition
• Resources separated (light and CO2 in air, nutrients and H2O in ground

Question 7

Solutions to the Challenges of Living on Land

Answer 7

• Gravity: lignin for support/structure
• Desiccation: waxy surfaces, cells to protect gametes and spores
• Dispersal: adaption for gamets and spores
• CO2 abundant but waxy surfaces impeded absorption: pores for gas exchange
• Light Abundant but competition: height and vascular tissues moves resources around
  Resources separated: roots and shoots acquire resources

Question 8

Derived traits of Land Plants

Answer 8

• Alteration of generations: dominated by gametophyte in nonvascular plants
• Multicellular dependant embryos: multicellular diploid zygote retained and nourished by female gametophyte
• Apical Meristems: tissue found in the buds of growing tips of roots in plants that trigger the growth of new cells Walled spores produced in sporangia

Question 9

Multicellular Gametangia

Answer 9

• Antheridia: sperm

- Archegonia: egg surrounded by protective cells; fertilization takes place within archegonium

Question 10

Origin of Nonvascular Plants- Derived traits

Answer 10

Derived traits:

- roots and shoots: apical growth through continued division of specialized cells