Chapter 3

• Algae are photosynthetic members of the kingdom Protista, which may be unicellular or multicellular.
• The multicellular algae are commonly called seaweeds, and are classified into three phyla based on their colour: brown, red, or green.
• The only other kingdom that contains multicellular photosynthetic members is the plant kingdom.
• All the unicellular plant-like protists discussed in Chapter 2 can be called algae.
• The phyla of algae include three representative groups of single-celled, plant-like protists: dinoflagellates, diatoms, and euglenoids, as well as three phyla of seaweeds.
• Seaweeds are large, multicellular algae divided into three main groups based on their colour: brown, red, or green.
• Brown algae are the largest and most complex protists, often abundant enough to be key components of marine and tidal environments.
• Nutrient-rich, cool waters, like those off Canada's west coast, can cause brown algae to grow in such density that they form underwater forests.
• These underwater forests provide food and shelter for more than 800 marine species of animals, plants, and protists.
• Red algae can grow to a metre in length and are the most abundant large algae in the warm coastal waters of tropical oceans.
• Red algae have green chlorophyll and an additional pigment, called phycoerythria, that is sensitive to the light waves that reach greater ocean depths.
• This pigment allows red algae to thrive at ocean depths of up to 100 m or more.
• Red algae appear red to the eye because their light-sensitive pigment reflects red wavelengths of light.
• Green algae are mostly aquatic, most commonly found in freshwater, also found in saltwater, sea ice, tree surfaces and fur of sloths.
• Green algae are most plant-like due to the presence of chlorophyll, starch and cellulose.
• One major need of plants is to protect from drying out.
• Vascular tissue allowed the evolution of roots, providing strong anchoring ability and cells specialized in absorbing and transporting water and minerals.
• Plants also need a system to transport water and dissolved gases from the outside environment to cells within the body of the plant, and a system to support the body of the plant, lifting it up into the light and air.
• The adaptations of plants to life on land did not all occur at once.
• The earliest land plants were small, grew in moist places, and transferred water and dissolved substances from cell to cell by osmosis and diffusion.
• These processes are slow and inefficient, and they limited the maximum size of these plants and the types of environments in which they could live.
• One of the major steps in plant evolution was the transition from aquatic to terrestrial habitats about 460 million years ago.
• Plants reproduce using embryos, which are small, simple, multicellular plants that are dependent on the parent plant for a time.
• The first land plants did not have tissues that allowed the transport of different materials over long distances.
• Lignified xylem forms a firm structure that allows water and minerals to be transported throughout the plant.
• Vascular plants have two types of vascular tissue: xylem and phloem.
• More recent developments in plant evolution include vascular tissue for transporting materials, seeds for protecting the embryo, and flowers.
• Xylem carries water and minerals from the roots to the rest of the plant.
• Xylem tissue consists of dead tube-shaped cells that contain a tough material called lignin.
• Vascular tissue eventually evolved in the group known as vascular plants.
• Phloem is made of living cells that are also arranged in tubular form, but it is used for transporting larger molecules, including sugars.
• Non-vascular plants, also referred to as BRYOPHYTES, include three phyla of plant: MOSSES, LIVERWORTS, and HORNWORTS.
• Non-vascular plants do not have vascular tissue, and they are dependent on the processes of osmosis and diffusion to transport nutrients.
• Non-vascular plants provide many important ecosystem services, including nutrient cycling, and are potential sources for pharmaceuticals.
• Non-vascular plants are thought to be the first land plants.
• Non-vascular plants usually grow in mats of low, tangled vegetation that can hold water like a sponge, allowing them to survive cold periods and dry periods.
• Non-vascular plants have no roots, instead, they have small root-like structures called RHIZOIDS, which develop from their lower surfaces.
• Seedless vascular plants provide many important ecosystem services, including nutrient cycling, and are potential sources for food and shelter.
• The seedless vascular plants include whisk ferns, club mosses, horsetails, and ferns.
• Ferns, in particular, are common inhabitants of the floors of temperate forests throughout Canada.