Algae (Chapter 20) Aquatic plants

Ecological Role Habitat marine or fresh water, possibly in very moist soil, tree trunks, snow and on rocks They have to live in moisture due to the lack of internal transport tubes called “vascular tissue” to transport water and nutrients chlorophyll containing organisms, with no true roots or leaves

Ecological Role Chlamydomonas nivalis phenomenon commonly known as watermelon snow, red snow or blood snow

Ecological Role Major roles as phytoplankton (unicellular forms) number one food producers (act as a food source for many organisms) supply 70%+ of global oxygen supply as seaweed (multicellular forms) provide food source and habitat for marine organisms source of agar, among other things

Taxonomy 3 main phyla (green, brown and red algae) algal classification is very unstable, some biologists are not convinced that all algae are plants and prefer algae to be placed in Kingdom Protista, with only some multicellular phyla (seaweed) remaining as plants, so there is a bit of confusion with classification to the present day

Taxonomy Phylum chlorophyta (Green Algae) marine and freshwater habitats contain chlorophylls a and b store food in form of starch reproduction is quite complex! Undergo alteration of generations, which means they shift back and forth between haploid(n)and diploid (2n) generations asexual reproduction involves haploid sporophytes sexual reproduction involves gametes

Taxonomy Phylum chlorophyta (Green Algae) have evolved into many forms such as : a) Single-celled Green Algae (e.g. Chlamydomonas) grows in ponds, ditches and wet soil small, egg-shaped cell with two flagella light sensitive eyespot that can sense bright light or darkness large, cup-shaped chloroplast that photosynthesizes to produce starches two contractile vacuoles no cellulose in cell wall characteristics of both Protists and Plants

a) Single-celled Green Algae (e.g. Chlamydomonas)

Taxonomy Phylum chlorophyta (Green Algae) have evolved into many forms such as : b) Colonial Green Algae (e.g. Volvox) many identical cells living together each cell functions independently colonies can have anywhere from 500 to 50,000 cells individual cells are connected by strands of cytoplasm that allow them to communicate when colony needs to swim a few cells are specialized for reproduction saytoplsm

b) Colonial Green Algae (e.g. Volvox)

Taxonomy Phylum chlorophyta(Green Algae) have evolved into many forms such as : c) Threadlike Green Algae (e.g.Spyrogyra and Oedogonium) create long, threadlike colonies called filaments grow and reproduce asexually if filaments are broken, the cells continue to divide and grow can reproduce sexually by gamete production attach to the bottom of a lake or pond by a specialized holdfast cell Spirogyra has spiral-shaped chloroplasts!! filament

Spyrogyra

Oedogonium

Taxonomy Phylum chlorophyta (Green Algae) have evolved into many forms such as : d) Multicellular Green Algae (e.g. Ulva or ‘sea lettuce’) live in marine environments are only 2 cells thick, so easy diffusion of gases holdfasts attach Ulva to rocks A holdfast is a root-like structure that anchors aquatic sessile organisms, such as seaweed, other sessile algae, 

Taxonomy Phylum Rhodophyta (red Algae) almost exclusively marine habitats red because of the presence of pigment phycoetrythrin, an accessory pigment that reflects redlight and absorbs blue light contains chlorophyll only since blue light penetrates water to a greater depth than light of longer wavelengths, these algae can live a somewhat greater depths than other algae, up to 170 m. rhodophytes are important sources of food, such as nori (Poryphyra) and dulse (Palmaria)- an Icelandic snack! also used as fertilizers on coastal agricultural land some rhodophytes are important in the formation of coral reef. rhodofaites

dulse (Palmaria)- Nori Poryphyra Nongeniculate corallines are of particular significance in the ecology of coral reefs, where they provide calcareous material to the structure of the reef, help cement the reef together, and are important sources of primary production.

Taxonomy Phylum Phaeophyta(brown Algae) mostly marine habitats brown colour results from the dominance of the xanthophyll pigment contains chlorophyll a and c brown algae generally larger and more species found in colder waters than other seaweeds common forms include kelps (Sargassum) and wracks (Fucus) chlorofil

Taxonomy Phylum Phaeophyta (brown Algae) Kelp forest Sargassum wracks (Fucus)

Taxonomy Phylum Phaeophyta(brown Algae) also some forms use for food such as Japanese kombu (Laminaria japonica) kelps grow in underwater forests, some grow to more than 60 m. long and are secured to rocks with holdfasts structures Fucus keep upright with help of air bladders chlorofil

Reproduction Quick review: Meiosis vs. Mitosis chlorofil

Reproduction chlorofil

Reproduction in Ulva chlorofil

Reproduction in Fucus Alteration of generation = alters between gametophyte (n) and sporophyte (2n) Female gamete = egg (n) is large and cannot swim Male gamete=sperm(n) is small and swims with help of flagella Diploid sporophyte plant (large seaweed structure) is the only multicellular part of the life cycle chlorofil

conceptacles receptacles

Reproduction in Fucus The blades (leaves) of the sporophyte plant contain specialized reproductive structures (receptacles, in openings called conceptacles), one produces eggs (oogonia) and one produces sperm (antheridia) The eggs and sperm are released into the water and if sperm find some of the floating eggs, fertilization occurs and a zygote(2n) is formed The zygote sinks to the ocean bottom and, with luck attaches to an object such as a rock where the zygote will grow by mitotic division into a new diploid (2n) sporophyte riceptical