Lecture 11: Algae Flashcards
Algae
Photosynthetic protists who
gained oxygenic
photosynthesis via primary
or secondary endosymbiosis
How much of Earth’s oxygen does algae produce?
- 30% by algae
- 20% by prokaryotes such as
cyanobacteria - 50% by land plants
Algal Blooms
Rapid growth of ‘algae’ due to increase in nutrients from fertilized agriculture lands, untreated factory waste water, etc.
Which two organisms cause algal blooms
Caused by both algae and cyanobacteria
how do algal blooms affect the environment?
- Water hypoxia through bacterial decomposition
of dead algae - Mechanically damaging gills
- Production of algal toxins
Concerns for environmental conservation and economic damage by affecting aquacultures and tourism.
what is increasing algal blooms
climate change
Alveolate in the SAR supergroup
- Unicellular algae
- About half are chemoheterotrophs, others are
photoautotrophs/mixotrophs
Algal bloom of dinoflagellates causes
red tide
Photoautotrophic dinoflagellates contain ___ as one of their photosynthetic pigments
carotenoids
what group do Haptophytes belong to?
‘Unresolved’ group in the eukaryotic
phylogenetic tree. Compromises of mostly marine, unicellular photoautotrophs and mixotrophs
morphology of Haptophytes
- Two flagella for motility plus a haptonema for surface attachment and/or predation
- Surface of haptophytes are covered with small scales made of polysaccharides
some Haptophytes have ___ scales
- Some haptophytes like Emiliana hyxleyi have hard, calcified scales
Stramenopiles, of SAR supergroup morphology
- Straw-hair (Latin, Stramen-pilos), as
many members have flagellum with fine, hairlike projections - Diatoms, a unicellular, photoautotrophic Stramenopile
- One of the most abundant photosynthetic organisms in oceans and lakes
- Diatoms have glass-like cell wall made of silicon dioxide for mechanical protection vs. predation
Diatoms of various shapes are distributed in
aquatic systems such as oceans, rivers and lakes
Diatoms are well preserved due to their
silica shell
Forensic limnology isolates diatoms from crime scenes to better understand the case. However why isn’t it useful as legal evidence?
Not as useful as legal evidences due to the amount of variation in samples
Brown algae (seaweeds)
Multicellular photoautotrophic
Stramenopile, and the largest, most
complex algae
Brown algae (seaweeds) morphology
Have organ-like structures which are analogous to plants:
* Blades: increase surface area (leaf-like)
* Stipe: support the blades (stem-like)
* Holdfast: anchor the alga (root-like)
* Can get up to 60 m tall
* Some have gas-filled floats to help the blades get closer to the water surface
* Plant-like reproduction cycle
Diploid
Cell with a pair of chromosomes (2n)
* n=23 for human, 46 chromosome total
Haploid
Cell with a single set of chromosome (n)
Human example for sexual reproduction
- Diploid adult (n=46) produces haploid, unicellular gametes (sperm/egg, n=23) via meiosis
- Haploid sperm (n=23) fuses with haploid egg (n=23), producing a diploid, unicellular zygote (n=46)
- Diploid zygote divides by mitosis to grow into diploid adult (n=46)
For reproductive cycle of animals,
multicellularity only occurs
during the diploid stage
Alternation of generation
Plants and some algae produce multicellular bodies in both diploid and haploid stages
Sporophyte
Spore-producing, diploid
multicellular form
Gametophyte
Gamete-producing, haploid
multicellular form
Alteration of Generation process
- Diploid sporophyte produces haploid spores by meiosis
- Haploid spores divide by mitosis to become the haploid gametophyte
- Haploid gametophyte produces haploid gametes by mitosis
- Two haploid gametes fuses, producing a diploid, unicellular zygote
- Diploid zygote grows by mitosis to become the diploid sporophyte
Brown algae spores are called
zoospores since they can move with
flagella
About half of zoospores develop into
haploid multicellular female
gametophyte, the other half develop
into male gametophyte
Female and male gametophytes
produce
gametes (egg and sperm),
which meet and fertilize into the
diploid zygote
Archaeplastida
- Direct ancestors of primary endosymbiosis
- The ‘source organisms’ of secondary
endosymbiosis
‘Green algae’ is a ___ group which is missing the Embryophytes (___)
paraphyletic
(plants)
Two main groups of green algae:
- Chlorophytes: the sister group to the clade Streptophyta (Charophytes + plants)
- Charophytes: the closest relative to land plant
Charophytes, Green algae
- Closest relative to plants
- Determined by molecular phylogeny of nuclear,
mitochondrial and plastid DNA, as well as morphological features
Charophytes and plants:
- Both synthesize cell wall using ring-like protein structure, embedded in plasma membrane
- Both have flagellated sperm
- Both have similar nuclear, mitochondrial and chloroplast DNA
- Both have sporopollenin
Sporopollenin
tough layer which surrounds
charophytes zygotes to prevent it from drying out
Sporopollenin eventually enabled ___
ancestral charophytes to live permanently on land, above
water surface
Plants have sporopollenin walls which encase
plant spores
Note the difference: Charophyte sporopollenin encases their zygotes, plant sporopollenin encases their spores.
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