Mulit-cellular Primary Producers - Seaweeds and Plants Part 6

University:
Cameron University
Course:
1004 | General Biology
Academic year:

2021
Views:

259

Pages:

11
Author:

Clint W.

Multicellular Algae ~ The Seaweeds Life History Alternation of Generations (4:00-8:00) Seaweeds ~ Life Cycle Seaweeds reproduces in two ways Asexual (vegetative reproduction) is common and more important than sexual reproduction  Thallus fragments of Sargassum can grow into new individuals  Spores are resistant cells that can disperse to new locations  Zoospores (protected spores) have flagella for movement  Seaweeds ~ Life Cycle Seaweeds reproduces in two ways In Sexual sexual reproduction gametes from different parents fuse to recombine the genetic information  Each generation shows genetic variation  Cells divide and multiply by mitosis; gametes are formed by meiosis  Eggs are non-motile, sperm can swim using flagella (except for red algae)  Seaweeds ~ Life History Four types of Life History 2 generations ~Sporophyte & Gametophyte 1. The most common among all 3 groups of seaweeds  Two types of thalli  2n sporophyte generation that goes through meiosis produces not gametes but haploid (n) spores.  Seaweeds ~ Life History  These divide & develop into the second kind of thallus, a haploid (n) gametophyte  The gametophyte produces haploid gametes  The gametes are release and on fertilization, produce a diploid (2n) zygote that develop into the diploid sporpophyte. Seaweeds ~ Life History Four types of Life History 3 generations ~ Sporophyte & Gametophyte 2. Unique to red algae  More complex  Alternation of 3 generations  3rd generation is a diploid carposprophyte (fused gametes)  Seaweeds ~ Life History Four types of Life History No alternation of generations 3. Easiest to understand  Similar to animals  NO alternation of generation  One thallus which is diploid  Thallus produces haploid gametes by meiosis  Seaweeds ~ Life History Four types of Life History 3. No alternation of generations  After fertilization, the zygote develop into a new diploid thallus  Observed in some brown algae & some green algae Seaweeds ~ Life History Four types of Life History 4. No alternation of Generations ~IN zygote  In green algae  Dominate thallus is haploid & produces haploid gametes.  On fertilization the gametes for a diploid zygote Seaweeds ~ Life History Four types of Life History 4. No alternation of Generations ~IN zygote  IN the zygote meiosis takes place, resulting in haploid spores.  Each of the spores develops into a haploid individual