Major groups of algae

Transcription

1 Algae general features. All are protists They require moist environments because they lack a cuticle They lack vascular tissues Algae are photosynthetic and reproduce both sexually and asexually Major groups of algae Alveolates: dinoflagellates Heterokonts: Brown algae, diatoms Excavates: Euglenoids Plantae: red algae, green, algae, glaucophytes 1

2 Lecture 17 Algae Heterokonts: Brown algae, diatoms Plantae: red algae, green, algae Unicellular algal life cycle Fusion of two gametes = plasmogamy+karyogamy 2

3 Unicellular algal life cycle n 2n Unicellular algal life cycle 3

4 Unicellular algal life cycle n 2n 2n n Muticellular Unicellular Specialization in Haploid Phase Specialization in Diploid Phase 4

5 Monobiontic life cycle: only one generation (haploid or diploid) can undergo mitosis. Unicellular n 2n 2n n Muticellular 2n n n 2n Specialization in Haploid Phase Specialization in Diploid Phase Dibiontic life cycle: Both haploid and diploid generations can undergo mitosis With alternation of generation The two generations can be either isomorphic (appear the same) or heteromorphic (different appearance) 5

6 Plantae Plantae 6

7 Red algae Marine algae, abundant in warm water Can grow in shallow or deep water Diverse body forms: o Few species are simple, unicellular o Majority of species are multicellular. The simple ones are filamentous and branched. Some complex red algae have a holdfast, a stipe, and leaf-like blade. They never have gas bladders. The red algae use a light harvesting complex called a phycobilisome that efficiently absorbs blue-green light and channels it to chlorophyll a. Phycobilisome is a also found in cyanobacteria. Red algae are red due to phycoerythrin. Red algae store fixed carbon as floridean starch, a branched glucose polymer Phycoerythrin (red protein-pigment complex) Phycoerythrin in red Phycobilisome Chlorophyll a Photosystem Red algae thylakoid with regularly arranged phycobilisomes 7

8 Relative photosynthesis (%) red alga growing at some depth Longer wavelength light is absorbed in the surface layer of the ocean. This antenna allows red algae to grow at greater depth in the ocean to the record of 268 m. green surface-growing alga Wavelength (nm) Red algae life cycle: Very complex, diverse, and poorly known. Completely lack swimming cells 3 multi-cellular phases: two diploid and one haploid. 8

9 Which of the following on this red algae life cycle is FALSE: a. Is dibiontic b. Has two sporophyte phases c. Haploid vs. diploid generations are heteromorphic d. Produces swimming gametes Seaweeds are an important part of the human diet in several parts of the world. Nori - The red alga Porphyra is used in Japanese cuisine. Agar - polysaccharide from red algae (agarose is purified from agar). Carrageenan - polysaccharide from red algae (Irish moss). It is added to most foods including ice cream, bread, toothpaste etc. Harvested off the coast of Maine. 9

10 Plantae Chlamydomonas: Unicellular green algae 10

11 Which stage of the Clamydomonas life cycle is diploid? A B D C Gonium - colony of 16 cells arranged in a flat plate (4 inside 12 outside). Can have 4, 8, 16 or 32 cells/colony. No cell specialization. 11

12 Volvox - colony of flagellate cells connected by plasmdesmata. They coordinate flagellar beating to move the colony in one direction. Differentiation of vegetative vs. reproductive cells. Ulva: sea lettuces, generally small green seaweeds growing as thalli attached to a substrate in shallow water. Thalli (singular thallus) undifferentiated vegetative tissue. 12

13 Life cycle of Ulva is a. isomorphic and dibiontic b. isomorphic and monobiontic c. heteromorphic and dibiontic d. heteromorphic and monobiontic Acetabularia, called The Mermaid s Wineglass Each wineglass is a single cell with a single nucleus (many chloroplasts). 13

14 Ulvophyceae: sea lettuces Caulerpa - root-like, stem-like and leaf-like tissues. It is an exotic species in the Mediteranean Sea. It out-competes native algae and produces toxins that kill fish. Chara, common name is stonewort, displaying nodes and internodes. sex organs branch 14

15 Chara is sister to land plants according to DNA evidence Reproductive character in common with land plants with layer of sterile cells Most algae Chara and land plants The stem-like structure is actually single large multinucleate cells. Fun fact: cytoplasmic streaming in Chara is faster than in any other cell. 15

16 Heterokonts: Brown algae, diatoms Plantae: red algae, green, algae Diatom: Unicellular, dominant generation is diploid Repeated mitotic divisions of the 2n cells result in smaller and smaller cells 16

17 2n cells go through meiosis to produce gametes that fuse and produce a new 2n generation that makes a new wall. Meiosis cell wall forms zygote fusion of gametes to produce a diploid zygote gametes Brown algae Closely related to diatoms. They are all multicellular and almost all marine algae. They have holdfast, stipe, blade and air bladder, are up to 50 meters long. The brown alga Fucus. 17

18 Kelps forests of the ocean Life cycle of the brown alga Fucus. This is dibiontic, heteromorphic and the gametes are not similar, it is oogamous. Antheridia - male gametangia (structure of the gametophyte that makes gametes) Oogonia - female gametangia 18

19 Lecture 17 Study Guide Algal life cycle: Define monobiontic and dibiontic. Dibiontic algae can be either isomorphic or heteromorphic. What does that mean? Define the term oogamous Red algae: What is a phycobilisome? Why is it important for red algae to be very efficient at absorbing blue light? Name one red algae that is important in human cuisine, such as Nori. Describe the difference in form of starch stored by red algae and flowering plants. Green algae: Wat is the difference between Chlamydomonas and Gonium? What is the difference between Gonium and Volvox? Chara is a particular type of green algae that is sister to land plants. Name one key character that is present in both Chara and plants. Brown algae Name an example of human use of brown algae Diatoms In diatoms, which generation has asexual reproduction? Would you say diatoms are monobiontic or dibiontic? 19