1. Principles of Life Science Rainier Jr/Sr High School Mr. Taylor
Plants: Part 1
Principles of Life Science
Rainier Jr/Sr High School
Mr. Taylor

2. Plants
Plants are thought to have evolved from ancient photosynthetic green algae that formed a plant group called charophyceans.
These plants had to overcome some challenges to start growing on land;
1. Prevention of dehydration
Cuticle: a waxy, thick, waterproof layer that retains water
Stomata: openings in the cuticle with special guard cells that let air in while controlling loss of water.

3. Plants
These plants had to overcome some challenges to start growing on land;
2. Transporting water and other nutrients throughout plant
Some plants just use diffusion; this limits their size!
Other plants have developed a vascular system (a system of tubes running up and down the plant) that moves nutrients and water up into the plant from the soil and moves starches (food) into the roots for storage.

4. Plants
These plants had to overcome some challenges to start growing on land;
3. Support for plant parts
Cell walls of cellulose strengthened by variable amounts of lignin make strong, sturdy supports.
(Cellulose + lignin = wood)

5. Plants
These plants had to overcome some challenges to start growing on land;
4. Reproduction
Some use standing water or dew droplets
Some have developed pollen grains, flowers, and seeds.
Seeds contain the embryo of a plant and provide:
Protection: seed coat
Nourishment: stored food-endosperm
Plant dispersal: wind, animal, water
Delayed growth: germinate only with favorable conditions.

6. Alternation of Generations
Plants switch between spore-producing (diploid) sporophytes and gamete-producing (haploid) gametophytes.
In nonvascular plants (like moss) the gametophyte is the “plant” you see.
In vascular plants (like trees, flowers) the sporophyte is the “plant” you see.

7. Vascular Tissues There are two types of vascular tissue:
Xylem: hollow, hard-walled cells that transport water.
Phloem: hollow, soft-walled cells that transport food and other organic materials

8. Plant Types: Non-vascular
Non-vascular plants lack true roots, stems, or leaves due to not having xylem or phloem
Small plants: must use diffusion to move food & water.
The large gametophyte is anchored by rhizoids (root-like structures) for support and produces small sporophytes
Sperm need water to swim to ova: must live in damp environments.

9. Plant Types: Non-vascular
Moss: phylum Bryophyta
What we see as “leaves” is the gametophyte
The long stalk of the sporophyte supports a spore capsule.
Liverworts: phylum Hepatophyta
The gametophyte is sometimes liver-lobed shaped
Similar to mosses with shorter stalk for sporophyte.

10. Plant Types: Non-vascular
Hornworts: phylum Anthocerophyta
Gametophyte is flat and green
Sporophyte is green and horn-like

11. Plant Types: Vascular
Vascular tissues allow the formation of true leaves, stems, and roots.

12. Plant Types: Seedless Vascular
Contain xylem and phloem
The sporophyte is the largest structure
Allows for wind dispersal of spores
The gametophyte grows on or in the ground
Sperm need water to swim to ovum … need damp conditions to reproduce
Spores have thick wall to keep them from drying out
Four major groups

13. Plant Types: Seedless Vascular
Ferns: phylum Pterophyta
Are common and familiar in our area
Have roots and leaves, no stems
Mature leaves are called fronds, immature leaves are called fiddleheads.
Spores form in sporangia on the underside of fronds.

14. Plant Types: Seedless Vascular
Club Moss: phylum Lycophyta
Have roots, leaves, and stems
Spores form in sporangia on specialized leaves that sometimes form a cone.

15. Plant Types: Seedless Vascular
Horsetails: phylum Sphenophyta
Have roots, stems, and leaves
Vertical stems are hollow and jointed with whorls of leaves at the joints
Spores grow in cones on the tops of the stems.

16. Plant Types: Seedless Vascular
Whisk ferns: phylum Psilotophyta
Have highly branched stems and no leaves or roots.

17. Plant Types: Seed-producing Vascular
There are two major groupings of seed-producing vascular plants:
Gymnosperms
Angiosperms

18. Gymnosperms
Seeds are NOT surrounded by a fruit; most are borne on cones
Small gametophytes usually form in these cones.
Large sporophyte often forms a tree
Wind-pollinated; do not need water for fertilization.
Four major groups; we will study only 3.

19. Gymnosperms Conifers: phylum Coniferophyta Cycads: phylum Cycadophyta
Cone-bearing with leaves that are needles or flattened scales (minimizes water loss).
Examples: pines, firs, cedars, spruce, hemlock
Cycads: phylum Cycadophyta
Short stems and palm-like leaves
Male and female cones on separate plants

20. Gymnosperms Ginkgo: phylum Ginkgophyta Only one living species
Fan-shaped leaves
Male and female trees do NOT produce cones

21. Angiosperms Flowering plants
Flowers have adaptations that increase the likelihood of fertilization of the ovum.
Fruits are structures within which the seeds develop. Their major function is to aid seed dispersal.
Endosperm is a supply of stored food for the developing embryo; this increases embryo survival.
There are two major groups of angiosperms (monocots and dicots … next slide)

22. Angiosperms Monocots: Dicots: One seed leaf (cotyledon)
Vascular tissue bundles are randomly arranged in stems.
Flower parts occur in 3’s or multiples of 3.
Veins in leaves are parallel, leaves are usually long & thin
Roots are diffuse.
Dicots:
Two seed leaves (cotyledons)
Vascular tissue bundles are arranged in rings in stems
Flower parts occur in 4’s and 5’s (or multiples of 4 or 5)
Veins in leaves are branched or networked.
Roots: often a single taproot (deep)

23. Angiosperms
Both monocots and dicots are further classified by their life cycles:
Annuals: complete their life cycles in one growing season.
Biennials: complete their life cycles in two growing seasons producing a “storage” plant the first year and flowers and seeds the second year.
Perennials: flowering plants that live for more than two years typically producing flowers and seeds every year.