12.1

Question 1

What catastrophic event is associated with the emergence of land plants?

Answer 1

The Late Ordovician Mass Extinction (LOME)

Question 2

How much of the marine species was affected by the Late Ordovician Mass Extinction?

Answer 2

85%

Question 3

What clade do green algae and modern land plants belong to?

Answer 3

Viridiplantae

Question 4

Why are green algae studied alongside embryophytes?

Answer 4

• They form a monophyletic group
• Evolution from green algae coincided with land plants inhabiting terrestrial environments

Question 5

What significant evolutionary event occurred in 1999 regarding green algae?

Answer 5

Confirmation that a green alga is the ‘mother’ of all plants

Question 6

What is a characteristic feature shared by all members of Viridiplantae?

Answer 6

Cellulosic cell wall

Question 7

What is cellulose and its role in plant cells?

Answer 7

A rigid material that forms a supportive meshwork acting as a cellular exoskeleton

Question 8

What does the Serial Theory of Endosymbiosis suggest about chloroplasts?

Answer 8

Chloroplasts arose from prochlorophytes, a type of cyanobacteria

Question 9

What are the main features that differentiate green algae chloroplasts from red algae and glaucophytes?

Answer 9

• Lacks phycobilin
• No bacterial wall
• Contains chlorophylls a and b and carotenoid accessory pigments

Question 10

What is the function of thylakoids in chloroplasts?

Answer 10

Increase surface area for photosynthetic pigments

Question 11

What processes occur inside chloroplasts?

Answer 11

Photosynthesis producing ATP and NADP

Question 12

What is starch and its significance in plants?

Answer 12

A polysaccharide that serves as a temporary storage unit for energy

Question 13

What phenomenon is linked to the evolution of multicellularity in land plants?

Answer 13

Transition from microscopic unicellular green algae to macroscopic multicellular forms

Question 14

What reproductive strategy is notable in the evolution of green algae?

Answer 14

Oogamy

Question 15

What do plasmodesmata facilitate in plant cells?

Answer 15

Cytoplasmic continuity between cells and transport of growth-mediating compounds

Question 16

What does molecular phylogenetics suggest about the ancestor of embryophytes?

Answer 16

An extinct Charophyceae resembling extant members

Question 17

What adaptations have charophyte algae developed for survival?

Answer 17

• Cell division via phragmoplast
• Growth via apical cells
• Mechanisms to survive drying of aquatic habitats

Question 18

What environmental changes prompted early plants to colonize land?

Answer 18

• Depletion of aquatic mineral resources
• Availability of carbon dioxide and sunlight

Question 19

What is xyloglucan and its role in plant cell walls?

Answer 19

A major component linking microfibrils and aiding wall rigidity

Question 20

What is the significance of dormant, drought-resistant spores in plant evolution?

Answer 20

Enhances lineage survivability

Question 21

What are some tough polymers found in plants that resist decay?

Answer 21

• Lignin
• Sporopollenin
• Cutin

Question 22

What is the earliest record of cryptospores, and when does it date back to?

Answer 22

Middle Ordovician

Question 23

What method is used to estimate the early emergence of land plants?

Answer 23

Molecular clock method

Question 24

What is the earliest record of cryptospores?

Answer 24

The earliest cryptospora record dates back to the middle Ordovician

More cryptospores were traced to the late Ordovician.

Question 25

What method supplements sparse fossil data to establish the evolutionary timescale of early land plants?

Answer 25

The molecular clock method ## Footnote It estimates the early emergence of land plants between middle Cambrian and early Ordovician.

Question 26

What are bryophytes characterized as?

Answer 26

Non-vascular plants ## Footnote They lack deep rooting systems.

Question 27

What significant global change did the first land plants initiate during the late Ordovician?

Answer 27

Global climate change ## Footnote This was due to their enhancement of chemical weathering.

Question 28

What phenomenon occurred as a result of increased silicate weathering introduced by early land plants?

Answer 28

Carbon burial leading to Earth's cooling ## Footnote This culminated in the Late Ordovician Mass Extinction (LOME).

Question 29

What event is referred to as the Late Ordovician Mass Extinction (LOME)?

Answer 29

An abrupt global glaciation event ## Footnote It was triggered by the cooling due to carbon burial.

Question 30

What is the significance of the green alga Volvox in the study of multicellularity?

Answer 30

It is considered a model organism for multicellularity ## Footnote Certain species, like V. carteri, have a well-established genome that illuminates molecular genetic origins.

Question 31

What two distinct types of cells are found in a vegetative Volvox colony?

Answer 31

Somatic cells and gonidia ## Footnote Gonidia give rise to daughter colonies inside the mother colony.

Question 32

What major evolutionary transition occurred around 480-440 MYA?

Answer 32

The first land plants with innovative strategies to colonize land ## Footnote This transition was aided by bacteria through serial endosymbiosis.

Question 33

What adaptation allowed green algae to dominate the waters?

Answer 33

A compact cell wall ## Footnote It protected the alga from environmental stress.

Question 34

What is a key consequence of the first plants emerging from water onto dry land?

Answer 34

They caused extinction to other inhabitants of the planet ## Footnote This highlights the impact of bryophytes as the first land plants.

Question 35

True or False: The first land plants were vascular plants.

Answer 35

False ## Footnote The first land plants, bryophytes, are non-vascular.