Lecture 11 Algae Bryophytes and Ferns Kingdom Protista Algae Red algae diatoms kelps dinoflagellates green algae Significance of algae to humans Kingdom Plantae moving onto land Features and challenges for living on land Bryophytes Ferns ALGAE Algae belong to the Kingdom Protista Algae are eukaryotes cells have organelles Algae are mostly photosynthetic like plants Have 4 kinds of photosynthetic pigments Many accessory pigments blue red brown gold Require moist environments because they lack a waxy cuticle remember cuticle prevents water loss in terrestrial plants General features of Algae Can be microscopic or macroscopic size ranges from bacteria size to 50 meters long Lack vascular conducting tissues No xylem or phloem No true roots stems or leaves Modes of sexual reproduction Both sexual and asexual Algae illustrate the importance of photosynthesis to the Earth s ecology Diversity of Algae There are millions of algal species but we ll focus in these five groups Diatoms Dinoflagellates Red Algae Kelps or Brown Algae Green algae 1 Diatoms Diatoms Division Bacillariophyta Large group of algae many unidentified Relatively recently evolved group Habitat Diatoms live in cool oceans Structure mostly unicellular have silica in their cell walls Diatoms Very important for aquatic food chains they provide phytoplankton sun Phytoplankton Zooplankton small fish larger fish mollusks whales Can reproduce asexually for many generations then sexually 3 Red Algae Red algae Division Rhodophyta 4000 species Are some of the oldest eukaryotic organisms on earth 2 billion year old fossils Abound in tropical warm waters Act as food and habitat for many marine species Structure from thin films to complex filamentous membranes Why are Red algae red Accessory pigments Phycobilins mask the Chlorophyll a thus they look red Due to these accessory pigments red algae can photosynthesize in deeper waters at different light wavelengths Red algae Commercial uses Carrageenan used for making ice cream jellies syrups breads Also for lotions toothpaste pharmaceutical jellies Agar for growing bacteria and fungi for research purposes As food 4 Kelps or Brown Algae Kelps Division Phaeophyta Closely related to diatoms also a recent group but look very different from diatoms Habitat rocky coasts in temperate zones or open seas cold waters Structure multicellular only Holdfast stipe blade air bladder Up to 50 meters long 5 Green Algae Division Chlorophyta Largest and most diverse group of algae Habitat found mostly in fresh waters and on land Float in rivers lakes reservoirs creeks Can also live on rocks trees soil Green algae Sea lettuce Ulva lives in salt waters along the coast Structure of green algae from Single cells Micrasterias Filaments Colonies Volvox Thalli leaf like shape Green algae Terrestrial plants arose from a green algal ancestor Both have the same photosynthetic pigments Chlorophyll a and b Some green algae have a cell wall made of cellulose Cells divide similarly Benefits of Algae Beneficial algae They are the base of the aquatic food chain photosynthetic organisms Lichens algae and fungi symbiosis Also serve as shelters Kelps form underwater forests red alga form reefs Harmful algae Excessive growth of algae causes Clogging of water ways streams filters makes the water taste bad Can be toxic to animals Red tides caused by dinoflagellates Commercial uses of algae Algin a thickening agent for food processing brown algae Carrageenan foods puddings ice cream toothpaste red algae Iodine brown algae Agar for growth media used in research red algae As food red and brown algae As plant fertilizers Diatomaceous earth used for filtering water insulating soundproofing Kingdom Plantae When moving from water to land both plants and animals faced the same challenges but evolved different ways to deal with them Plants evolved from algae Algae cannot survive on land only in moist environments Plants had to adapt evolve characteristics that would allow them to survive and live on dry land Cooksonia is the earliest known land plant fossil It s non vascular and similar to today s bryophytes Ancestor of plants Green Algae The ancestor of land plants was probably a green alga something like modern Coleochaete 1 They both have same photosynthetic pigments Chlorophyll a b carotenes etc 2 Both use starch to store photosynthetic products 3 Both have cellulose in their wall 4 Both have alternation of generations 5 Both form a cell plate during cell division Kingdom Plantae Evolutionary tree of plants From primitive advanced traits Bryophytes Ferns Gymnosperms Flowers Seeds Green alga ancestor Vascular Terrestrial Angiosperms Living on land Several environmental challenges had to be met by early plants in order to live on land A OBTAINING ENOUGH WATER Plants evolved roots to anchor the plant Roots to absorb water and dissolved minerals B PREVENTING WATER LOSS Plants evolved a cuticle waxy layer Evolution of multicellular gametangia sex organs helped protect gametes from drying out Evolution of a resistant coat on spores that prevents drying out C GETTING ENOUGH ENERGY In land plants obtained enough sunlight for photosynthesis Different strategies for obtaining light Growing taller and above other plants plants began to evolve support cells Others had to adapt to lower light intensities D Photosynthesis water dilemma Problems plants need pores for gas exchange for photosynthesis but open pores stomata allow water to leave 95 water taken is lost Solution stomata open during the day for photosynthesis gas exchange and close during the night to allow plant to recover from water loss E MULTICELLULARITY Evolved in algae Advantages root better protect gametes grow tall to obtain sunshine Disadvantage getting water to all cells Plants evolved vascular tissues xylem and phloem F SEXUAL REPRODUCTION Algae have motile gametes and single sex organs Land plants developed air borne dissemination of desiccation resistant stage Land plants developed multicellular sex organs Sexual reproduction gives plants genetic variability enable them to adapt better to their environments G LIFE CYCLE Algae water dependent life cycle water independent life cycle in land plants Plants developed dryness resistant gametophytes spores or zygotes seeds Smaller size primitive larger size plants Dominant gametophyte stage n dominant sporophyte stage 2n Life cycles animals vs plants Animals like humans live in the 2n stage Dominant 2n stage Single celled gametes