1. Chapter 28: Plant Evolution and Classification
Section one: Overview of plants

2. Adapting to Land
Nothing could live on land until 475 million years ago.
The Ozone layer developed, which offered protection from UV rays
3 adaptations allowed plants to survive on land:
Preventing water loss
Ability to reproduce without water
Ability to absorb and transport nutrients

3. Preventing Water Loss
Plants had to go from having total exposure to water to the constant threat of evaporation.
Cuticle – a waxy covering on a plants surface that prevents water loss
See any problems with this?

4. Preventing Water Loss
They needed protection from evaporation that didn’t cut off their supply of CO2
Stomata – Small openings in the surface which allow the exchange of CO2 and Oxygen.
Cuticle
Stomata

5. Reproducing by Spores and Seeds
Plants had to develop reproductive structures that didn’t dry out.
Spores -
Seeds -
Haploid reproductive cells surrounded by a hard outer wall – allowed for wide dispersal of plants
An embryo surrounded by a protective coat. Some contained the tissue endosperm which nourished the developing plant.

6. Absorbing and Transporting Materials
Some plants have Vascular Tissue – transports water and dissolved substances from one part of a plant to another. It also helps support the plant. It’s made up of two parts
When plants lived in water, they could absorb the materials around them
Plants needed a way to get the nutrients from the ground up into their entire structure.
Xylem – Carries water and inorganic nutrients FROM the roots TO the stems and leaves
Phloem – Carries organic compounds (carbohydrates) and some inorganic compounds to wherever the plant needs them.

7. Classifying Plants
There are 12 phyla of plants (used to be called divisions)
First they are separated based on if they are Vascular or Non-Vascular
Non-Vascular plants: No true vascular tissue, roots, stems or leaves
Vascular plants: Have vascular tissue, roots, stems and leaves

8. Vascular Plants
These can be further separated: Seedless vs. Seed plants
Seed plants can be even further divided: Gymnosperms and Angiosperms
Gymnosperms: Seeds are not enclosed into a fruit
Angiosperms: (Flowering plants) Produce seeds that are enclosed into a fruit

10. Alternation of Generations
Plants have a life cycle with two phases:
Sporophyte or diploid cycle:
Spores produced
Gametophyte or haploid cycle:
Gametes (Egg and sperm) produced
The plants will alternate between both cycles

11. Alternation of Generations
In Non-Vascular plants the gametophyte is the dominant stage. (Like in the video)
In Vascular plants, the sporophyte is the dominant stage. (example: Oak Tree)

12. In seed plants the gametophyte is usually is a very small parasite of the sporophyte. Example: gametophytes of flowering plants are microscopic parts of their flowers that aren’t photosynthetic.
In seedless vascular plants the gametophyte is usually a separate small organism, that is really different from the sporophyte