Plants – Characteristics and Plants – Characteristics and FunctionFunction

Evolution of PlantsEvolution of Plants

• Scientists believe that terrestrial plants evolved from green algae as both show the following similarities:

• Use starch as their primary food reserve

• Have cellulose in their cell walls

• Use chlorophyll a and b for photosynthesis

Evolution of PlantsEvolution of Plants

• In order to adapt to the drier, terrestrial environment, plants developed specialized structures to avoid water loss (bark), obtain nutrients (roots, stems, leaves) and reproduce/grow (spores, seeds, flowers)

Evolution of PlantsEvolution of Plants

• The first plants were non-vascular, like moss, that depended on osmosis and diffusion to get water and nutrients.

• Vascular plants evolved which had specialized cells used for the transport of water (Xylem) and nutrients (Phloem), called vascular tissue.

Plant TissuePlant Tissue• Like animals, plants are made up of four types of tissue:

1. Meristematic tissue is where cell growth occurs.

2. Dermal tissue is the outermost cell layer of the plant. It is used for protection and to prevent water loss.

Plant TissuePlant Tissue3. Ground tissue is the inner cell layers of the plant that

is not vascular tissue. This is where nutrients are stored and where the plant does photosynthesis.

4. Vascular tissue are the cells involved in transporting water and nutrients through the plant.

Main types of vascular plantsMain types of vascular plants

• Gymnosperms: mainly coniferous trees, seeds appear on cones, make up the majority of Canadian forests, termed ‘softwood’ by lumber companies and provide most of the money earned by Canada’s forestry industry.

Main Types of Vascular PlantsMain Types of Vascular Plants

• Angiosperms: many more species than gymnosperms, live in a wider variety of habitats, use flowers to reproduce and encase the seed in a ‘fruit’, divided into monocots and dicots.

Monocots and DicotsMonocots and Dicots

Criterion Monocots Dicots

Seed Leaves 1 2

Veins in Leaves

Parallel Netlike

Vascular Bundles in

Stems

Scattered Arranged in a ring

Flower Parts Petals are multiples of 3

Petals are multiples of 4 or

5

MonocotsMonocots

• Only about 10% have a woody stem (bamboo and palm trees).

• Most have a herbaceous stem which is soft and fleshy (grass, tulips, etc…)

• Rice, corn, wheat, onions, carrots, …

DicotsDicots

• Deciduous trees are dicots.• Termed ‘hardwood’ and make up a good portion of the lumber

industry in Canada.• Other dicots: beans, potatoes, most wildflowers and salad

ingredients (tomatoes, lettuce, cabbage, radishes…)