Unit 4 – Notes # 1 The Aquatic Plants - ALGAE
A) Introduction:
All plants are multicellular photosynthetic autotrophs and they belong to the
Kingdom: PLANTAE
- One group of primitive plants is classified as being ALGAE.
- ALGAE refers to anything that meets the following two criteria:
1. Photosynthetic
2. Aquatic (but must NOT possesses terrestrial plant-like characteristics. Ex;
true roots, true stems, cuticle and seeds)
- Some Monerans like the photosynthetic cyanobacteria and many Protists
like the phytoplankton phyla we studied, fit into this category. They are the
unicellular algae.
- Kingdom Plantae has a few very primitive members that are considered to
be algae as well, most of these plant-like algae are macroscopic (large) and
multicellular.
- The key differences between these aquatic plants and more familiar
terrestrial (land) plants are as follows:
1. Algae (aquatic plants) lack a system of tubes to move (transport) water
and materials from one part of the plant to another. (Not needed)
2. Algae never develop specialized true roots, stems, or leaf structures,
flowers, and seeds these macroscopic algae use “holdfast” to anchor
themselves.
- Because they lack this transport system they must live in or near a source of
water so that they have water to bathe their cells. This water brings them
CO2 , O2 and nutrients, it also carries away the metabolic waste products.
(Completely dependent on water)
B) Adaptations To Water
1. Lack protective waterproof waxy coverings (cuticle) over exterior, this
allows for direct diffusion of gases, nutrients and waste product with the
water they are in.
2. Lack stem-like rigid tissues for structural support , they are supported by
the buoyancy of water.
3. Do not require specialized reproductive structures to protect and disperse
reproductive cells; instead they rely on currents in the water for dispersal.
4. All algae will contain “chlorophyll a” (suited for absorbing red and violet
wavelengths), and a second chlorophyll, either “b”, “c”, or “d”. This second
chlorophyll is designed to be whichever is best suited to help that algae absorb
whatever sunlight is available to it at a given depth.
5. Many algae have also developed accessory pigments which act to absorb
wavelengths of light that chlorophylls cannot absorb. These give algae some
very unique colours, brown, purple, pinkish and yellow.
C) Grouping Algae
- Algae are primarily classified by their colour, this colour is determined by
the types of chlorophyll and the types of accessory pigments the algae uses.
- Of the three phyla listed below, we only have to study Chlorophyta
i) Chlorophyta ii)Phaeophyta
iii) Rhodophyta
(GREEN)
(BROWN)
1. Phylm: Chlorophyta (Green Algae)
Characteristics:
Pigments: 1) Chlorophyll a
2) Chlorophyll b
Habitat: 1) Fresh water (a few in salt water)
2) Some in moist soil, rocks and tree trunks
(RED)
Morphology: (Form/Shape)
- Small circular balls to large leafy plant-like shapes.
Very Diverse :
Unicellular  ColonialFilamentous Multicellular
(Protista ----------------> Plantae)
Examples: 1) Chlorella (Unicellular)
2) Ulva (Multicellular)
3) Spirogyra (Multicellular Filamentous)
4) Protococcus (Small Colonial)
5) Volvox (Large Colonial)
Chlorella
Protococcus
ULVA
SPIROGYRA
D) Role Of Algae
Food Chains : “Grasses Of The Sea”
-Oxygen producers
-Food : Primary Producers (first link in food chain)
Volvox
Human Uses
-Food : Some ingredients used in a variety of foods
- Medicines, food thickening and some toiletries
-Basic Research (medical, food production, waste treatment)
-Oxygen producers –space exploration
-undersea colony
Man’s Effect Upon Algae
-Pollution –Phosphates, laundry detergents
- Nitrates, Sewer and fertilizers
- These pollutants cause rapid increase in algae (algal bloom)
Top layer of Algae forms a blanket on the surface of a lake or pond. The lower
levels gets no Light, as a result the aquatic plants at those level die off. As they
die they begin to decay. They no longer produce O2 and bacteria begins to
break them down, this decomposition further use up any available oxygen.
- Oxygen is used up and all animal life in the lake soon dies off. Then with no
animals, no Carbon Dioxide produced and therefore all plants die.
***DEAD LAKE*****