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From Algae to Terrestrial Plants

From Algae to Terrestrial Plants. By Marie, Rebecca and Filiam. Algae. Algae is a photosynthetic member of the kingdom Protista; it can be either unicellular or multicellular

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From Algae to Terrestrial Plants

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  1. From Algae to Terrestrial Plants By Marie, Rebecca and Filiam

  2. Algae • Algae is a photosynthetic member of the kingdom Protista; it can be either unicellular or multicellular • The multicellular algae (otherwise known as seaweed) are categorized as three phyla based on colour: red, brown and green

  3. Brown Algae (Phylum Phaeophyta) Kelp -largest most complex protist -found in nutrient rich cool waters of west coast -grow up to 60 meters high, underwater forests STRUCTURE HOLD FAST: anchor STIPE: stem like, extends from holdfast, provides support BLADE: leaf like, undergoes photosynthesis

  4. Red Algae (Phylum Rhodophyta) -first multicellular organism on Earth -6000 living species Where: found in warm coastal waters of tropical oceans STRUCTURE -contains chlorophyll and phycoerythrin: additional pigment that makes it more sensitive to light at greater depths COOL FACT: red algae is used for wrapping SUSHI!

  5. Green Algae (Phylum Chlorophyta) -most green algae are aquatic WHERE: most commonly found in fresh water but also in salt water environments STRUCTURE: multicellular or unicellular Example: Chlamydomonas is unicellular, moves with a flagella Ulva is multicellular (sea lettuce) Green Algae are thought to be the closest relative of plants Chlamydomonas ULVA

  6. Some botanists say that green algae are plants while others consider them to be protists

  7. What evidence might lead some scientists to place green algae in the plant kingdom? • land plants and green algae contain chlorophyll • cellulose cell walls  • circular (rosette) shaped arrays of proteins that synthesize the cellulose for the cell wall (compared to linear arrays) • both store food in the form of starch  • peroxisome enzymes: enzymes found in the peroxisomes that help minimize the loss of organic products  • structure of flagellated sperm: structure of flagellated sperm in some land plants resemble that of the charophyte (green algae) sperm   • formation of a phragmoplast: in cell division of land plants and some charophytes, phragomoplast (microtubules) form between daughter nuclei. They serve as the framework for the assembly of the cell plate

  8. Green Algae are the organisms most closely related to plants

  9. Differences between plants and green algae • Plants grow terrestrials environments • Plants reproduce in the process of Alternation of Generation (with an associated trait of multicellular, dependent embryos) • Walled spores producing in sporangia • Plants produce gametes within multicellular organs called gametongia • Plants haveroots and shoots that increase their exposure to environmental resources.

  10. Adaptations to Land -Transition from aquatic to terrestial habitats took place around 460 millions years ago ISSUES: What adaptions kept the algae from drying out on land? How would it transport nutrients from the outside environment to the plant cells? What would be the system support?

  11. First Land Plants • Natural selection favours individual alga that can survive periods without drying out. • The first land plants were small and transferred water and dissolved substances through osmosis and diffusion, but this was inefficient & slow • However they didn’t have necessary tissues to transport different materials over long distances • Eventually vascular tissues evolved into a group called VASCULAR PLANTS

  12. Stages of Evolution: Algae to Land Plants

  13. Vascular Tissue Xylem Phloem Made up of living cells Function: transportation of larger molecules like sugars • Dead, tube like cells containing tough material • Function: transports water and minerals from the roots to the rest of the plant • Importance: permitted the growth of taller plants/trees Note: Vascular Tissue led to the development of roots, and leaves

  14. Plant Reproduction • Plants and certain green algae use sporic reproduction, which is also known as alternation of generations • Sporic reproduction is a type of sexual reproduction that switches back and forth continuously between a haploid stage and diploid stage (this means that there are actually two multicellular stages in their life cycle)

  15. Alternation of Generations

  16. Continuation of reproduction gametophyte Sporophyte The sporophyte, meaning the diploid version of the organism, are created through the fusion of haploid gametes and make spores through meiosis • The gametophyte, meaning the haploid version of the organism, makes haploid gametes through mitosis • Through the gametic fusion of the gametophytes, sporophytes are then created • The spores from the sporophyte then undergo mitotic division and create multicellular gametophytes. Finally, the continuous cycle starts up again.

  17. In Conclusion • …despite the fact that plants live primarily on land and algae in aquatic environments: • BOTH contain chlorophyll, • Photosynthesis occurs in BOTH algae and plants; it is important to keep differences in mind • This makes it tricky to draw a clear line between what is a protist and a plant; therefore where do algae belong?

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