What is a plant?

What is a plant?

What is a plant?• An organism that is Photosynthetic,• eukaryotic,• multicellular with a cell wall made of

cellulose, • contains chloroplasts,• and lacks the power of locomotion.

Plant cells

Ancestor of algae & plants. •Formed by a Union between a Protozoan-like host and A cyanobacterium (a Bacteria that uses photosynthesis forEnergy). •It moved into the cell & became thechloroplast of the first algae.

History• 1st plants emerged from

ocean 3.4 billion years ago• Algae dominated the ocean

of the Precambrian times• Somewhere between 400 –

500 million years ago algae made the transition onto land

• Origin: green filamentous algae (Spriogyra)

1st land plants• Struggle to:–Maintain water in cells on land– Exchange gases– Support self outside of water– Reproduce on land– Anchor selves on land

First Plants Caused Ice Ages, New Research Reveals

• the invasion of the land by plants -- a pivotal time in the history of the planet -- brought about huge climate changes.

• removed carbon dioxide from the atmosphere, forming new carbonate rocks in the ocean. This cooled global temperatures by around five degrees Celsius.

• Our discovery emphasises that plants have a central regulatory role in the control of climate: they did yesterday, they do today and they certainly will in the future."

• ScienceDaily (Feb. 1, 2012)

• Vascular plants appeared 350 million years ago

• Forests followed 50 million years later

• Swamp forests of Carboniferous period formed the fossil fuel deposits that power us today

Seed plants came nextCone-bearing plants came firstFollowed by flowering plants (140 mya)Today 96% of all plants are flowering

Bryophytes• Hornworts, liverworts, mosses– Non-vascular– One cell thick – absorbs water by

osmosis– No roots, stems, or leaves– Reproduce by spores & alternation of

generation. Gametophyte generation dominant.– Needs water for reproduction

Bryophytes 1st land plant

One cell thick – each cell absorbs water from environmentNo roots, stems, or leaves – lives in moist environmentGametophyte dominant generation – needs water for sexual reproduction

Plants move away from water:

• vascular tissue for transport,

• lacks protective seed.– Vascular tissue forms xylem to transport water phloem to transport sugar

Pterophyta – ferns & horsetails

Ferns

Seed Plants• Conifers – seeds in cones– Gymnosperms

• Flowers – seeds in flowers– Angiosperms

Pine, Eastern WhitePine, LoblollyPine, LongleafPine, PitchPine, PondPine, ShortleafPine, SlashPine, SprucePine, Table Mountain Pine, Virginia

Eastern Red Cedar

Flowering plants