Lab 8 Algae 2024-2025 PDF

2nd stage Practice Lecture Prepared by: Lanja O. Tahir &Yadi O. AL-Barzinjy Division: Phaeophyta (Brown Algae) Class 1:Isogeneratae Brown algae are practically restricted to sea except a few members of order Ectocarpales....

2nd stage Practice Lecture Prepared by: Lanja O. Tahir &Yadi O. AL-Barzinjy Division: Phaeophyta (Brown Algae) Class 1:Isogeneratae Brown algae are practically restricted to sea except a few members of order Ectocarpales. 1. All the members are multicellular and large in size. Some reach up to 60 meters in length. 2. Have chlorophyll a and c. Due to the presence of fucoxanthin, the members are brown in colour and are commonly called brown algae. 3. Sexual reproduction ranges from simple Isogamy to Oogamy. 4. Various members show different types of Alternation of generations. Division: Phaeophyta (Brown algae) Class:1-Isogenerate Order1: Ectocarpales Family: Ectocarpaceae G.: Ectocarpus (Ecto = external, Carpus = fruit) 1. The genus Ectocarpus is most simple and primitive brown alga. 2. It is abundantly found throughout the world but it is restricted to marine waters. A few species occur in fresh waters. Some species are epiphytes on other algae. Other grows on the fins of certain fish in Sweden. Some are free- floating. Distributed all over the world 3. The plant body is filamentous. 1  2nd stage Practice Lecture Prepared by: Lanja O. Tahir &Yadi O. AL-Barzinjy External feature: 1. Plant body consists of thin, well branched, brown colored filaments. 2. The thallus is differentiated into a prostrate system and an erect system. 3. Erect system arises from prostrate system and consists of many branched filaments. 4. Prostrate system is creeping, septate, profusely branched and attaches the plant with the substratum functioning as holdfast. This system entreats the host tissues in epiphytic conditions. 5. The cells are small. They are cylindrical or rectangular and uninucleate, its remain surrounded by a thick cell wall. 6. The branches terminate into an acute point to form a hair. 7. Chromatophores are discoid, ribbon or band shaped. 2 2nd stage Practice Lecture Prepared by: Lanja O. Tahir &Yadi O. AL-Barzinjy Reproductive Structures: The plant shows isomorphic type of alternation of generation, (sporophytic and gametophytic phases are independent). Sporophytic phase reproduce haploid or diploid spores, while gametophytic phase reproduce gametes. 1. Asexual reproduction: Haploid spores are produced in unilocular sporangia and diploid spores produced in plurilocular sporangia both type of sporangia are developed on the Sporophytic plants. 3 2nd stage Practice Lecture Prepared by: Lanja O. Tahir &Yadi O. AL-Barzinjy A) Uniloclar sporangium: 1. Unilocular sporangium is a structure of asexual reproduction, always present on diploid plants. 2. The sessile or stalked sporangium is situated terminally on lateral branches. 3. The shape varies from round to oval. 4. It is single celled and uni-nucleate when it is young but become multinucleate later 5..Many biflagellate zoospores are produce when unilocular sporangium matures. B) Plurilocular sporangium: 1) It is produced on sporophytic as well as on gametophytic plants, it behaves as sporangium on sporophytic plant and as gametangium on gametophytic plant. 2) Plurilocular sporangium is elongated, sessile or stalked multi-chambered. 3) Each chamber is having a single nucleus. 4 2nd stage Practice Lecture Prepared by: Lanja O. Tahir &Yadi O. AL-Barzinjy 4) At maturity the protoplasm of each chamber metamorphoses into a motile zoospore. Plurilocular gametangium: 1) It is similar to the plurilocular sporangium in shape and structure. 2) Protoplast of each cubical compartment changes into a single uninucleate, biflagellate haploid gamete. 3) Gametes fuse and form the diploid zygote. 4) Diploid zygote germinates directly into a diploid plant which again bears unilocular and plurilocular sporangia. 5 2nd stage Practice Lecture Prepared by: Lanja O. Tahir &Yadi O. AL-Barzinjy 6  2nd stage Practice Lecture Prepared by: Lanja O. Tahir &Yadi O. AL-Barzinjy Class 2: Heterogeneratae Order: Laminariales 1. Member of this order commonly known as kelps like Postelsia, Nereocystis, Egregia and Laminaria 2. The sporophyte of the kelps has the most advanced structure among algae. 3. Construction of the macrothallus is parenchymatous and shows specialized tissues than in other algal groups. 4. The sporophyte differentiated in to three distinct parts: hold fast, stipe and blade. 5. Member of this order show heteromorphic alternation of generation. 7  2nd stage Practice Lecture Prepared by: Lanja O. Tahir &Yadi O. AL-Barzinjy Division: Phaeophyta Class2-: Heterogeneratae Order: Laminariales Family: Laminariaceae Genus Laminaria It’s very common worldwide on temperate and boreal rocky shorelines General characters of Sporophyte 1. The sporophyte is differentiated into three distinct parts: hold fast, stipe and blade. 2. Hold fasts are branched structures, formed of thickened tissues known as Haptera, these are essential for effective anchorage of the thallus. 3. The stipe is always unbranched. 4. The blade of some species is entire but that of others can be split. 5. Within stipes and blades tissues specialization can occur, there is typically an outer layer of pigmented meristimatic cells known as the meristoderm. Internal to the meristoderm are colorless cells of the cortex, within which may occur a central medullary area (medulla) which contains cells specialized for conduction of solutes. 8 2nd stage Practice Lecture Prepared by: Lanja O. Tahir &Yadi O. AL-Barzinjy C.S of blade of Laminaria ((cx) Cortex, (me) medulla; (mr) meristoderm 9  2nd stage Practice Lecture Prepared by: Lanja O. Tahir &Yadi O. AL-Barzinjy Life cycle of Laminaria Laminaria show heteromorphic alternation of generation. 1. A sexual reproduction occurs by means of unilocular sporangia produced on both surfaces of the blade. The zoospores released from unilocular sporangia are haploid and produce filamentous gametophyte, which consist of only a few cells. 2. Sexual reproduction is oogamous. 3. Oogonia of female gametophyte are developed from both intercalary and terminal cells, and its protoplast developed into a single egg, which is extruded and attaches to the outside of the oogonium. 4. Male gametophyte produced antheridia at the tips of 1 or 2 cells lateral branches. Each anthiridium is one celled and form a sperm, which is chemically attracted to an egg. 5. Fertilization and initial development of the young sporophyte occurs while attached to the female gametophyte. As growth continuous the female gametophyte is over grown and disappears. 1 0