PLANTS Chapter 22 p. 550

What Is A Plant? Plants are members of the Kingdom Plantae. Multicellular Eukaryotic (nucleus and membrane bound organelles) Cell Walls made of cellulose Develop from multicellular embryos Carry out photosynthesis using chlorophyll A and B. Autotrophs

Examples Trees Shrubs Moss Grasses Ferns

The Plant Life Cycle Use Alternation of Generation. Alternates between haploid (n) gamete-producing plant called a gametophyte and a diploid (2n) spore-producing plant called a sporophyte. Gametophytes are the haploid (n) generation. Sporophytes (spore-producing plant) are the diploid (2n) generation. Gametes (sperm and egg) are haploid cells that fuse to produce a new diploid individual.

Alternation of Generation

What Plants Need to Survive SUNLIGHT Use the energy from the sun to carry out photosynthesis. Every plant displays adaptations cause by the need to get sunlight. Photosynthetic organs such as leaves are typically broad and flat and arranged on the stem to get as much light as possible.

Water and Minerals All cells require a constant supply of water. Water is one of the raw materials of photosynthesis so it is used up quickly. As plants absorb water, they absorb minerals. Minerals are nutrients in the soil that are needed for plant growth.

Gas Exchange Plants require oxygen for respiration. Plants require carbon dioxide for photosynthesis. They must exchange these gases with the atmosphere without losing water through evaporation.

Movement of Water and Nutrients Plants take up water and minerals in their roots, but make food in their leaves. Most plants have specialized tissue that transports water and nutrients up from the soil and distribute products of nutrients throughout the plant.

Early Plants When plants appeared, much of the existing life on Earth changed. As these new photosynthetic organisms colonized the land, they changed the environment in ways that made it possible for other organisms to develop.

Origins in the Water The first plants likely evolved from an organism much like the multicellular green algae living today. Green algae also have reproductive cycles that are similar to those of plants. Green algae have cell walls and photosynthetic pigments that are identical to those of plants.

Reproduction in Algae

The First Plants The first true plants were still dependent on the water to complete their life cycles. Early plants were similar to today’s mosses in that they were simple in structure and grew close to the ground. Common in damp and swampy regions. From these plants, mosses, ferns, cone-bearing plants and flowering plants evolved.

Overview of the Plant Kingdom Botanists divide the plant kingdom into four groups based on: water-conducting tissue, seeds and flowers. Most scientists now also use DNA. The four groups are: Bryophytes Seedless Vascular Plants Gymnosperms Angiosperms