Plant Sciences Test 2 Modules 3 & 4

Stages of Plant Evolution

Charophycean Green Algae

Protists-
Plant ancestors

Bryophyte-like plants (moss) evolved after algae, what primary characteristics did they present?

Retained: chlorophyll, chloroplasts,
Alternation of Generations,
cellulose cell membranes,
photosynthesis
NEW! Cutin on leaves
NEW! Multicellular
gametangia

(Rhizoids for anchorage instead of true roots, and a non-vascular system that limited them to small size and moist environments)

Seedless Vascular Plants (Ferns, Horsetails, and other seedless
tracheophytes) evolved after bryophyte-like plants, what primary characteristics did they present?

• Vascular tissue improves sporophyte
efficiency (xylem carries water, phloem carries the
products of photosynthesis)
(Devonian Period)

Major evolutionary events in
land plant evolution – Seed
Plants

• 1) evolution of seeds- A seed is a structure that encloses and protects a developing embryo

• 2) evolution of pollination – transfer of male gametophyte to the female gametophyte without water

Seed plants evolved to do what, and how?

Gametophyte much reduced and dependent

on sporophyte

• Seed consists of sporophyte embryo

packaged along with a food supply within a

protective coat

• Adapted for terrestrial existence

• Pollination replaces swimming as the

mechanism for delivering sperm to the egg

Gymnosperms

• Naked seeds
  • Lack the enclosed chambers (ovaries) in which
  angiosperm ovules and seeds develop
  * Rather, gymnosperm ovules and seeds develop on the
  surfaces of specialized leaves called sporophylls
  • Wind pollination
  * Water not needed for pollination
  • All are woody plants (no herbaceous species)
  • Date from 350 mybp

Ginkgophyta

• Only one species

• Tree with fan-shaped leaves

• Ovules develop into yellow, cherry-like

seeds

• Gymnosperms

Cycadophyta

• Stem unbranched with terminal palm-like
leaves
• Cone-like sporophylls

• are gymnosperms that reproduce using cones and are often mistaken for palms due to their appearance.

Coniferophyta

• Sporophylls modified into cones
• Wind-pollinated
• Xylem with tracheids but no vessels

Evolution of flower & fruit

• First fossils: late Jurassic period of Mesozoic era
• Diversified during Cenozoic era
• Coevolution with pollinators

Major evolutionary events in
land plant evolution -
Angiosperms

• 1) Evolution of flowers – many co-evolve
with animal pollinators
• 2) Evolution of fruits – mechanism to
enhance seed dispersal or seed germination
success

Anthophyta - flowering
plants

Reproductive organs within a flower
• Gametophytes greatly reduced
• Ovules embedded within sporophyte tissue
(ovary)
• Seeds within a fruit
• Appeared in early Cretaceous
• Most pollination by insects and birds

Monocots - parallel venation

in leaves and four or three floral parts. They have one cotyledon, fibrous root systems, and vascular bundles scattered in the stem.

Dicots – reticulate (net)
veination

pattern in leaves and usually possess floral parts in multiples of four or five. They have two cotyledons, taproot systems, and vascular bundles arranged in a ring in the stem.

Dicot and Monocot
Seedlings

are the two main groups of flowering plants, distinguished by their number of cotyledons. Monocots have one cotyledon, while dicots have two, leading to differences in leaf venation, root system, and floral structure.

cotyledon

seed leaf within the embryo of a seed, helping supply the nutrition an embryo needs to germinate and become established