BIO
201 - Botany
ALGAE
Page references from
Bidlack & Jansky. 2011. Stern's Introductory Plant Biology, Edition 12. McGraw-Hill.
WHAT ARE ALGAE? - Definition
Some
say any photosynthetic organism in the water
would then include organisms from three kingdoms
Plantae, Protista, & Monera
We
will use a more specific definition: aquatic photosynthetic protistans
CHARACTERISTICS OF ALGAE
1)
environment is aquatic
marine or freshwater
only restricted by amount of light
2)
little or no tissue differentiation
mostly in reproductive cells
four general morphological forms:
unicellular, filamentous, colonial, or thallose
3)
diversity of photosynthetic pigments
all have chlorophyll a
other pigments include:
a)
chlorophylls b, c, d
b)
carotenoids (carotene, fucoxanthin, xanthophyll)
c)
biliproteins (phycoerythrin, phycocyanin)
carotinoids & biliproteins restricted to algae at greater depths where mostly blue-green wavelength
light penetrates
chloroplasts: 1-2 large or many small
many have associated pyrenoids for carbon fixation & starch storage
some have means of detecting light = eye spot
4)
many unicellular species have flagella
most unicellular forms have flagella: one or two
big
exception is the red algae (none)
most multicellular forms are attached
5)
diversity of cell wall structures
most have cellulose
common additions into structure: SiO2, CaCO3
many secrete mucilage
some lack cell wall
6)
variation in reproductive methods
asexual of two forms: cell division & fragmentation
sexual with variation in gamete types:
a) isogamous
- male & female sex cells identical
b)
anisogamous - different sizes, male smaller
c)
oogamous - female large & nonmotile = EGG
male small & motile = SPERM
variation in life cycle patterns:
a) diplontic - diploid portion of life cycle largest &
longest
living
haploid
essentially one cell (gamete)
b) haplontic - haploid portion of life cycle largest &
longest
living
diploid
essentially one cell (gamete)
c) alternation of generations - diploid & haploid
about equal
both forms may look alike = ISOMORPHIC
Example: sea
lettuce
the two forms look different = HETEROMORPHIC
Example:
kelp
[to see diagrams of the above life cycles, click here]
GENERALIZED LIFE CYCLE (see handout)
Multicellular
Diploid Sporophyte (2n)
produces a sporangium which will include cells that
divide by meiosis to produce spores
spores germinate and grow into
Multicellular
Haploid Gametophyte (1n)
this produces two types of reproductive structures
Archegonia
("female") which include cells that divide by mitosis to
produce an egg (1n)
Antheridia
("male") which include cells that divide by mitosis to produce sperm
(1n)
Fusion of the egg and sperm (fertilization)
produces the Zygote (2n)
the zygote divides by mitosis to produce the
multicellular diploid sporophyte
GROUPS OF ALGAE
Split
into at least five distinct groups by several characteristics:
1) pigments present
2) cell wall structure
3) carbohydrate storage molecule
Groups
are:
Division Chlorophyta (green algae)
Division Chromophyta (golden-brown, diatoms, and brown algae)
Division Rhodophyta (red algae)
Division Euglenophyta (euglenoids)
Division Dinophyta (dinoflagellates)
Three of the groups
may be considered
plants (not protistans) by some:
green, red & brown algae
Prokaryotes - cyanobacteria (blue-greens)
are not included in our true definition
DIVISION CHLOROPHYTA - Green algae (pp. 321-328)
General Characteristics
Photosynthetic pigments
- Chlorophylls a & b, carotenoids
Cell
Wall - cellulose
Carbohydrate storage molecule
- starch
flagella variable in number
Both freshwater and marine species
Wide
variation in organism size: unicellular, filamentous, colonial, and thallose
Chlamydomonas
- unicellular with 2 flagella (pp. 322-323 + fig 18.3 & 18.4, p. 323)
isogamous, mostly haplontic (fig 18.4, p. 323)
common in ponds & lakes
Volvox
- hollow colonies of many cells, each with 2 flagella (fig. 18.2, p. 322)
oogamous, diplontic
common in small ponds
Ulothrix
- filamentous, no flagella, have holdfast (pp. 323-324 + fig. 18.5, p. 324)
isogamous, haplontic
common to eutrophic lakes
Spirogyra
- filamentous, no flagella (pp. 324-325 + fig. 18.6, p. 325)
slimy texture
spiral chloroplasts
isogamous & haplonitc: sex cells no flagellate, process = Conjugation
common in ponds & pools
(life cycle diagram)
Cladophora - branched filamentous with holdfasts
isomorphic alternation of generations
both marine & freshwater
Ulva - thallose marine with holdfast (fig. 18.11, p. 328)
isogamous alternation of generations
DIVISION RHODOPHYTA - Red Algae (pp. 332-335)
General
Characteristics
Photosynthetic pigments - chlorophylls a & d, phycoerythrin, phycocyanin
Cell
Wall - of cellulose
secrete massive amounts of polysaccharides
agar - microbial culture medium
carrageenan - thickener in dairy products, salad dressings
some have a CaCO3 secretion = Coraline Algae
Carbohydrate storage molecule - floridean starch
Also, no flagella are produced by any cells
Mostly
red algae are marine and of tropical, deep waters (up to 200 m)
many are delicate & small
contrast this with the other large marine algae, the browns
Very complex life cycle with three (3) different forms (see diagram on p. 335)
Gametophyte (1n)
grows and can become quite large
commonly are separate male & female plants
male plants produce spermatangia in which cells
divide by mitosis to produce spermatia (without flagella)
female plants produce archegonia in which eggs are produced by mitosis
after fertilization the zygotes develop ON THE
GAMETOPHYTE
Carposporophyte (2n) grows and eventually produce Carposporangia
as a result of mitosis carpospores are
produced and released
Tetrasporophyte (2n) develop as separate thalli
these produce tetrasporangia in which meiosis
occurs to produce tetraspores (1n)
Life cycle diagram (pdf)
DIVISION CHROMOPHYTA - yellow-green, golden-brown, brown and diatoms (pp. 328-332)
Historically this group was split into several divisions, but recent research has shown that they are very similar, genetically.
General
Characteristics
Photosynthetic Pigments
- chlorophylls a & c, fucoxanthin (type of xanthophyll)
give them a yellowish to brown color
Cell
Wall - cellulose
variation in additional components
some with no cell wall
Carbohydrate storage molecule - laminarin
Four distinct groups (recognized at level of class - as it is in the text book)
1. Xanthophyceae
- yellow-green algae
have cholorphylls a & c, but lack fucoxanthin
some lack cell wall
carbohytrade with chrysolaminarin + lipids
mostly nonmotile (lack flagella)
most species are freshwater
2. Chrysophaceae
- golden-brown algae or chrysophytes
chlorophylls a & c, fucoxanthin
some lack a distinct cell wall (but may have silica plates), have two flagella of unequal lengths
important part of freshwater and marine plankton
3. Bacillariophyceae
- diatoms
Most important groups of this division, especially in cooler oceans
also become important organisms on surfaces of soil, trees, and buildings
cell walls impregnated with SiO2
made of two half shells fit over each other (petri plates)
- see fig 18.14 (p. 329) + 18.15, (p. 330)
with cell
division progressive decrease in size
regenerate
size through sexual reproduction
shells resistant to decomposition = DIATOMATOUS EARTH
nonflagellate except gametes
4. Phaeophyceae - brown algae
Produce the largest of the algae - kelp can be over 100 meters long
most are marine in cooler climates, typically shallow waters, especially high energy environments (low/high tide zone)
Most
are thallose with holdfasts - but variation
produce a flattened portion (blade) and gas-filled chambers (floats)
The cell
wall is composed of cellulose + alginic acid (gelatinous polysaccharide)
extracted for food products: food thickeners & stabilizers,
ice cream, chocolate milk - note comment
on algin (pp. 338-340)
Most
are isogamous with alternation of generations
anywhere from isomorphic to heteromorphic
The most
common & studied genus is Fucus, the rockweed (fig. 18.19, p. 333)
unusual - heterogamic, diplontic
tips of thalli with reproductive Receptacles
each with many Conceptacles = reproductive cup or cavity
reproductive cells surrounded by sterile Paraphyses
64 small
motile sperm in each antheridium
1-4 large
nonmotile eggs in each archegonium
DIVISION EUGLENOPHYTA - euglenoids (pp. 334-336)
General
Characteristics
Photosynthetic pigments
- chlorophyll a & b, carotenoids (some forms without chloroplasts)
Cell
Wall - none, flexible structure of a protein = Pellicle
Carbohydrate storage molecule
- paramylon
Have
two flagella
Common freshwater algae that can produce dense colonies (blooms) in high nutrient areas (barnyard ponds, sewage treatment lagoons)
Numerous species have a gullet, which allows for
ingestion of food - hence there are heterotrophic
only about a third have the ability for photosynthesis
DIVISION DINOPHYTA - dinoflagellates (pp. 335-337)
General Characteristics
Photosynthetic pigments
- chlorophylls a & c, peridinum (a carotenoid)
gives them a brownish color
Cell
Wall - cellulose plates;
contains two grooves or furrows: transverse & longitudinal
some also contains spines
Carbohydrate storage molecule
- starch + lipids
Two flagella within the grooves
Are
mostly marine
Many
species are BIOLUMINESCENT produce light when disturbed
Very
important part of the phytoplankton (photosynthetic organisms in water column)
can give water a yellow to red coloration if concentrated
= RED TIDE
(with up to 150 million cells/liter)
production
of toxins can result in death of many fish
one of the most toxic organisms is Pfiesteria
piscicida (see handout)
commonly associated with
eutrophic (nutrient polluted) waters along coast