Characteristics of Plants• All are many celled• Most contain the green pigment chlorophyll• All have cell walls to provide structure• Most do not move around• All are made up of eukaryotic cells (have a membrane and nucleus)• Found in nearly every environment on earth• About 285,000 plant species have been identified and scientist believe many have not yet been found (tropical rainforests)

Origin of Plants• Earliest plants came from the sea from plant-like protists• Depended on water to sustain life• Plants eventually had to adapt to land• Cell walls made of cellulose kept plant cells from drying out.• Most land plants also have a waxy, protective layer on stems and leaves called a cuticle• The cuticle is an adaptation that enables plants to keep from drying out on land

Life on Land• Advantages of life on land:– More direct sunlight available for photosynthesis– More availability of carbon dioxide (there is more CO2 in the air than in the water)

What Plants need to Survive• Sunlight– Plants use the energy from sunlight to carry out photosynthesis– Plants have many adaptations to maximize their ability to absorb sunlight• Water– All cells require a constant supply of water– Water is used up quickly during photosynthesis because of the sun.– Plants have developed lots of adaptations to absorb water and prevent water loss.

What Plants need to Survive• Minerals– Plants absorb minerals– These nutrients are in the soil and are necessary for plant growth• Gas Exchange– Plants need oxygen for respiration as well as carbon dioxide for photosynthesis.– Plants need to exchange these two gases with the atmosphere without losing water in the process• Movement of water and nutrients throughout the plant body– Plants absorb water and minerals through their roots, but make food in their leaves.

Classification of Plants• Plants are divided into 4 major groups:– Bryophytes - Mosses• non-vascular• seedless– Ferns• vascular• seedless– Cone-Bearing Plants - Gymnosperms• Produce seeds• vascular– Flowering Plants - Angiosperms• Produce seeds• vascular

Bryophytes• Bryophytes: small plants found in damp environments like the forest floor, the edges of ponds and streams and near the ocean• Usually just a few cells thick so they can absorb water directly through their cell walls.• They are nonvascular– Vascular tissue is made up of long, tubelike cells in which water and nutrients are transported through the plant• Bryophytes do not have vascular tissue• Mosses and liverworts are in the Bryophyte Division• Bryophytes do not grow tall

Seedless Nonvascular Plants• Do not have roots, stems or leaves

• Grow form spores instead of seeds• Reproduce asexually– Can develop when a small piece of the parent breaks off • Include:– Mosses– Liverworts• Of 20,000 species of nonvascular plants, most are classified as mosses

Mosses• Rootless plant with leaf like growths in a spiral around a stalk• Held in place by root like filaments or threads, called rhizoids• Grow in damp areas range in size from 2-5 centimeters in height

Liverworts• Unlike tree leaves which have veins that conduct water, nutrients and other materials, in liverworts there is little or no conducting tissue• Tree leaves have window-like stomata which close when the leaf is threatened with drying out; liverworts have nothing like stomata, so the whole plant shrivels when dry

• Instead of bearing regular roots, liverworts anchor themselves with one-celled appendages known as rhizoids

Importance of Mosses and Liverworts

• Are often the first plants to grow in new environment, such as a volcanic site or forest fire area• These pioneer plant species grow and die and become food and nutrients for other less hardy plants• They change the conditions in the environment so that

other plants can grow there also

Seedless Vascular Plants • Characteristics:– Produce Spores (not seeds) – Have vascular tissue (unlike the mosses)– The vascular tissue is made up of long, tube like cells– These cells carry water, minerals and nutrients to all the cells throughout the plant– This allows the plants to grow bigger and thicker than the nonvascular plants• Include:– Club mosses and spike mosses– Horsetails– Ferns

Ferns• Largest group of seedless vascular plants in this division.• 12,000 living species• Require very little water to grow• Rhizome is the underground stem system of a fern• The leaf of a fern is called a frond• Reproduce by a spore, a reproductive cell that forms new organisms without fertilization

Rhizome• An underground stem.• Roots grow from the rhizome to root the plant to the soil.

Importance of Seedless Vascular Plants

• Over long periods of time, this plant material built up, became compacted and compressed and eventually became coal• Seedless plants such as bryophytes and ferns make up peat, which in turn becomes fuel• Found in bogs today, a poorly drained area with

spongy, wet ground this is composed mainly of dead plants whose decay has been slowed by lack of oxygen

Peat• Peat – forms in bogs, but after millions of years it becomes coal, natural gas and petroleum.