Introduction to Plants

What is a Plant?

Multicellular Eukaryotic Photosynthetic Has cell walls

containing cellulose

Lacks mobility

What did they evolve from?

Green Algae

Similarities contain

chlorophyll have cell walls

made of cellulose

store energy as starch

Original Habitat

The simplest plants live surrounded by water because water satisfies many of their needs: prevents cells from drying out gives structural support provides nutrients helps with spore dispersal and meeting of

sex cells

With time, plants adapted to live on land

Adaptations for Land

Adaptation Definition Advantage(s)

1. Cuticle waxy coating on the outer surface of plant cells

prevents the cell from drying out & acts as a barrier to pathogens

2. Stomata openings in the outer layer of leaves and some stems that allows the exchange of gases

enables exchange of gases for photosynthesis

Adaptations for Land

Adaptation Definition Advantage(s)

3. Vascular Tissues

transport tissues that move nutrients and water throughout the plant

faster transport than with osmosis or diffusion & provide structure and support for the plant

4. Reproductive Strategies

adaptations that allow sperm to meet egg without water (e.g. spores that have waterproof coverings, seeds)

enable plants to reproduce without being surrounded by water

Plant Life Cycle

The lives of plants consist of two alternating stages, or generations: a gametophyte generation and a sporophyte generation.

The stage that produces gametes (sperm and eggs) is the gametophyte generation. It is haploid.

The stage that produces spores is the sporophyte generation. It is diploid.

Plant Life Cycle

One generation is dominant over the other. This means that it is larger and lasts longer.

In most plants, the diploid sporophyte generation is dominant. In mosses, the gametophyte dominates.

How are Plants Classified?

No phyla, rather plants are organized into 12 divisions.

Non-Vascular Plants

Include mosses, liverworts, & hornworts

1. Do not have true roots, stems and leaves - absorb water through cell walls; water moves via osmosis.

2. No vascular tissue - no xylem and phloem to transport water and nutrients

Non-Vascular Plants

3. Small size- no support from vascular tissues

4. Depend on water for reproduction- water is needed for the sperm to swim to the egg

Vascular Plants

1. Have true roots, stems and leaves

2. Contain vascular tissue- xylem transports water - phloem transports food and nutrients- run continuously through the roots, stems and the leaves

Vascular Plants

3. Larger size- vascular tissues provide support against gravity

4. Cuticle- reduces water evaporation from leaves and some stems

Seedless Plants

Most plants have vascular tissue but may or may not produce seeds.

Ferns, horsetails, and club mosses are seedless vascular plants that reproduce by spores.

Gymnosperms

Plants that reproduce by seeds are divided into 2 groups: gymnosperms and angiosperms.

Gymnosperms have "naked" seeds usually protected by cones. They include the evergreens.

Angiosperms

Angiosperms are flowering plants whose seeds are produced and protected within fruit.

Further divided into monocots and dicots.