Lecture 6: Land plant evolution: tempo and mode

Question 1

Important features of land plants:

Answer 1

• they are relatively simple organisms
• plants are essentially sedentary, however reproductive propagules are dispersed - often huge distances
• During times of stress plants can react and later regenerate
• Dispersed reproductive propagules can persist for long periods of time
• can readily hydrdrise
• polyploidy is rife in plant kingdom
• asexual reproduction is common
• mosaic evolution is common
• population size dynamics are not a problem

Question 2

-they are relatively simple organisms

Answer 2

only 40 or so cell types occur throughout the entire plant kingdom, and all plants have very basic needs

Question 3

Plants are essentially sedentary. However, reproductive propagules are dispersed—often huge distances

Answer 3

(i.e. they can cross oceans and mountain ranges).

Question 4

During times of stress plants can react and later regenerate.

Answer 4

They can lose leaves or even whole branch systems. They can die back and regenerate from underground stems or rhizomes.

Question 5

Dispersed reproductive propagules can persist for long periods of time

Answer 5

i.e. they can see out bad times

Question 6

Mosaic evolution is common among plants

Answer 6

(during times of environmental stress plants can adapt by a single organ evolving, say leaves, while essentially maintaining their genetic makeup).

Question 7

Population size dynamics are not a problem

Answer 7

(very small populations may persist).

Question 8

a hybridisation followed by a polyploidy event instantaneously ..

Answer 8

gives rise to a new species

Question 9

autopolyploidy is when

Answer 9

abnormal mitosis or meiosis results in an increase in number of copies of chromosomes

Question 10

Allopolyploidy is when

Answer 10

hybridization occurs and offspring contain sets of chromosomes from both parents

Question 11

Living fossils:

Answer 11

• Bryophytes
• Lycopsids
• Ferns
• Sphenopsids
• Gymnosperms-cycads
• Gymnosperms-ginkgos
• Gymnosperms-conifers
• Gymnosperms-gnetales

Question 12

Bryophytes:

Answer 12

Liverworts unchanged since at least the Middle Devonian (390 Ma) and possibly the Ordovician (450 Ma)

Question 13

Lycopsids:

Answer 13

Lyco