Transcript GENERALITIES of the PLANT KINGDOM

GENERALITIES of the PLANT KINGDOM
• Multicellular eukaryotes that are photosynthetic and
autotrophic
• Most are terrestrial (some have returned to water)
• Plants are immobile  evolved to cope with stress:
– water loss, consumers, mechanical damage, temperature
extremes, pathogens, odd soils, etc.
• Terrestrial plants evolved from aquatic green algae
Features Shared In Common
with Green Algae
• Pigments: Chlorophyll a & b; carotenoids
• Food Reserve: Starch
• Cell Walls: Cellulose
• Cell Division: Cell Plate
• Body Structure: Multicellular
• Life Cycle: Heteromorphic Alternation of Generation
• Sexual Reproduction: Oogamy
Bryophytes
Pteridophytes
Division Chlorophyta (green algae) Order Charales
features: multicellular, chlorophyll a, b, and carotenoids,
starch storage, cellulose walls
In Aquatic Habitat
• All Cells Surrounded or Close to Water
• Dissolved Minerals
• Dissolved CO2 and O2
• Water Supports Weight of the Plant
• Unicellular Reproductive Structures
• Motile Gametes
• All Cells Photosynthetic
Evolutionary steps for the colonization of land:
• How to disperse gametes in drier environment
• How to protect embryos from drying out
• How to take up water and nutrients from below ground
• How to take up CO2 from the air
• How to transport water and nutrients long distances
Adaptations to Land Correlated with Development of
Structures to Circumvent Water Requirements:
• Epidermis: cuticle (cutin), stomates
• Vascular Tissue: Xylem (water conduction), Phloem
(carbohydrate conduction)
• Roots
• Lignin - found in all vascular plants, reinforces cell walls
• Multicellular gametangia: Antheridium (sperm),
Archegonium (egg)
• Embryo Develops Within the Archegonium
Pangaea (meaning
"all lands" in Greek)
Silurian land plants (425 - 408 MYA)
Devonian land plants (408 - 362 MYA)
Carboniferous land plants (362 - 290 MYA)
Permian land plants (290 - 245 MYA)
The warm zone spread in the northern hemisphere, where extensive dry deserts
appeared. The rocks formed at that time were stained red by iron oxides, the
result of intense heating by the sun of a surface devoid of vegetation cover. The
old types of plants and animals died out.
Triassic land plants (245 - 208 MYA)
Jurassic land plants (245 - 208 MYA)
Sporophyte (2n)
Ca. 0.5 cm long
Gametophyte (1n)
Bryophytes
Mosses, liverworts and
hornworts
Reproduce by spores
Reproduction dependent
on water
No true vascular system,
no hard tissues, therefore
they remain small
Vascular Plants (all the rest = ferns,
gymnosperms & angiosperms)
Have true roots, leaves, & vascular tissues
Produce hard or lignified tissues
xylem
phloem
Seedless Vascular
Plants: Ferns & allies
Have vascular tissue & true roots
Reproduction depends on water
Reproduce w/ spores
Evolution of seed plants: Gymnosperms & Angiosperms
-Reproduction independent of water
- Sperm enclosed in pollen; dispersed by wind, animals, etc
- Eggs enclosed in protective ovule – matures into a seed
-Seeds are highly protected embryos
- embryo protected (cones, fruits, etc)
- often specialized dispersal (animal, water, wind)
- Woody tissues common
Gymnosperms‘Naked seed’
Old lineage; 700 species today
Adaptive radiation during Earth’s
dry periods
New invention
- true seeds! protects embryo
Conifers are largest group
- make male & female cones
eudicots
Angiosperms
Most recently derived group
- 300,000 - 450,000 species
- Two main groups:
1. eudicots
2. monocots
New Innovations:
-Flowers
-Fruit
monocots
Angiosperms
monocots
eudicots
Almost all angiosperms
fall naturally into two
groups (clades),
monocots (one
cotyledon, or seed leaf)
and dicots (two
cotyledons).
A few dicots (early
lineages) do not form a
clade, but the huge
majority that do are called
true dicots, or eudicots.