Lecture 17: Evolution and Developemtn in Plants

Question 1

plant evolution: types

Answer 1

Charophyceans Bryophytes Pteridophytes Gymnosperms Angiosperms

Question 2

Development of a male gametophyte (within pollen grain)

Answer 2

MEIOSIS:
-Micro-sporocyte 
- divide to form microspores (4) 
-each 4 microspores survive 
MITOSIS: 
-Generative cell (will form 2 sperm) 
-Male gametophyte (within pollen grain)

Question 3

Development of a female gametophyte (embryo sac)

Answer 3

MEIOSIS:
-Ovule: Sporangium, megasporocyte, integuments
-divide = 4 megaspores only one survives
MITOSIS:
-female gametophyte forms = Antipodal cells (3), Polar nuclei (2), Egg (1), Synergids (2). Integuments + ovule

Question 4

Alternation of generations: higher + lower plants

Answer 4

-Higher plants contain a dominant sporophyte form and a minor gametophyte form
-Lower plants contain
a dominant gametophyte form and a minor sporophyte form

Question 5

Bryophyte examples:

Answer 5

moss, liverworts

Question 6

Bryophyte life cycle:

Answer 6

GAMETOPHYTE DOMINANT

• spores (n)
• Gametophyte (n) release sperm / egg
• Zygote forms (2n)
• Sporophyte formed (2n) + gametophyte

Question 7

Pteridophytes =

Answer 7

ferns

Question 8

Pteridophyte life cycle:

Answer 8

• fertilisation = zygote
• mitosis = new sporophyte + gametophyte
• mature sporophyte
• sporangium
• meiosis releases spore
• young gametophyte release archegonium (egg) + antheridium (sperm) -REPEAT

Question 9

Gametophyte within the pollen generates

Answer 9

the sperm nuclei (gametes)

Question 10

Gametophyte within the ovule generates the

Answer 10

egg (gamete)

Question 11

As plants colonised the land, a reduction in the gametophyte generation reduced

Answer 11

dependancy on water

Question 12

Can we understand the evolution of developmentally controlled structures at a molecular level?

Answer 12

EvoDevo studies

Question 13

Stomata present on the earliest vascular plants (400 Ma), yet function unknown. What approach is used to provide clues to how they may have evolved and operated?

Answer 13

• Evo-devo approach is the only means of providing clues to how they may have evolved and operated.
• It allows the analysis of conserved sequence and function of genes involved in a developmental process

Question 14

how can we identify genes expressed in the sporophyte at the time of stomata development

Answer 14

-use microarrays
▪ Microarray chip represents all known Physcomitrella genes (ca. 36,000).
▪ Each chip contains >20K probes for mRNAs.
▪ RNA samples stick to probes and fluorescence detected.
▪ Dot-matrix-like image is scanned for quantitative intensity values.