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Updated: 1st January 2020 Learning with Prof Bup Oyesiku www.bupoyesiku.net
OLABISI ONABANJO UNIVERSITY | Department of Plant Science
KINGDOM: PROTISTA
PLS201: BIOLOGY OF SEEDLESS PLANTS
(Brown and green algae)
OLABISI ONABANJO UNIVERSITY PLS201: CRYPTOGAMS
Updated: 1st January 2020
Learning with Prof Bup Oyesiku www.bupoyesiku.net Page 1
Contents
Introduction .................................................................................................................................................. 2
Objectives .................................................................................................................................................... 2
Main content ................................................................................................................................................ 2
Background of Algae .................................................................................................................................... 3
Members of Algae ........................................................................................................................................ 3
Characteristics .............................................................................................................................................. 3
Forms/Habits................................................................................................................................................ 4
Habitats of Algae .......................................................................................................................................... 6
Ecology of Algae ............................................................................................................................................ 6
Economic uses of Algae................................................................................................................................ 7
Conclusion .................................................................................................................................................... 7
Summary ...................................................................................................................................................... 8
References/Further readings ....................................................................................................................... 9
Tutorial-marked questions ......................................................................................................................... 10
OLABISI ONABANJO UNIVERSITY PLS201: CRYPTOGAMS
Updated: 1st January 2020
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Introduction
In today’s lecture, we are going to focus our discussion on algae, one of the most natural
photosynthetic aquatic plants. Algae are essential not only to the marine ecosystem but
also for the benefits of their by-products, such as the oxygen that we inhale. From an
ecological standpoint, algae are eco-friendly. For this ecological reason, knowledge of
algae diversity around us makes the environment comfortable for our daily enjoyment.
Furthermore, for those of us that will later specialise in Phycology (algology), this lecture
will provide you with the necessary background to understanding algae.
Objectives
At the end of this lecture, we will be able to:
1. Identify and classify many algae in our immediate surrounding
2. Distinguish between the different types of algae
3. Discover the features that separate algae from other plants (seedless and seed)
4. Know how to collect and preserve algae for future study
5. Appreciate the need to be knowledgeable about the algae
6. Understand how algae act as an indicator of pollution
7. Know the use as biofuel (alga fuel)
Main content
The study of algae is called Phycology or algology. There are two significant habits of
algae, and they include macroalgae and microalgae. Both habits commonly found living in
the sea, rivers, lakes or ponds. All algae are primary producer in an aquatic food web.
They make food (energy) from the sun. We must know that algae contribute about 80% of
the food supply and 50% to 75% of oxygen production in the world. We should note here
that algae alone can produce 50% of what all other plants in the world could produce.
Notably, they are the source of food for many aquatic organisms from the smallest
Daphnia to the mighty Whales. Despite the positive benefits, algal blooms (population
OLABISI ONABANJO UNIVERSITY PLS201: CRYPTOGAMS
Updated: 1st January 2020
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explosion) contribute to mass mortality of other aquatic organisms through suffocation
and competition for limited nutrients.
Background of Algae
Algae (singular=Alga) are eukaryotic plants and closely related to higher photosynthetic
plants in their mode of nutrition. However, algae lack leaves stems, and roots or rhizoids.
Some algae consist of a single cell, whereas other algae are multicellular or occur as
colonies in mucilage or filaments
Members of Algae
There are two different categories of algae. These include macroalgae and microalgae.
The members of macroalgae are commonly known as seaweed (see the cover page).
They are the big plant that lives inside the marine with their roots attached to the seafloor.
They usually are seen with our naked eyes when detached from the seafloor and float on
the sea. On the other hand, the microalgae are microscopic and can be view under a
microscope
Characteristics
Almost all microalgae have either a motile or non-motile spores. Diversity of spores in
algae includes the flagellated motile spores (zoospores), non-motile spores
(aplanospores), thick-walled resting spores with large food reserve (akinetes and
statospores). Almost all the dinoflagellates have two flagella. All pure algae are
eukaryotes having a nucleus enclosed within a membrane and plastids bound in one or
more membranes. Almost all algae have chloroplast (green pigment), absorb CO2 and
photosynthesise and produce energy and oxygen as a by-product. Unlike other algae
species of Chlamydomonas is exceptionally capable of producing oxygen and hydrogen
depending on the current temperature of its habitat.
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Forms/Habits
Microalgae: Unicellular organisms are often
called phytoplankton (Fig 1.) They are floating
(pelagic) organisms. Microalgae are different in
their size, shape and colour. The colour of the
microalgae cell depends on their pigment
(green, blue-green, yellow, brown or orange).
The two common types of microalgae are
diatoms and dinoflagellates. Diatoms have
different shapes (spheres, elliptical, triangles or
stars). Diatoms contain tiny oil bodies within
Figure 1. Phytoplankton foam
their cell. Also, the cell protoplasts enclosed by a pair of overlapping, glassy box-like cell
walls. Other forms of microalgae include
1. Capsoid (individuals of non-motile cells in mucilage envelope)
2. Palmelloid (palm-like non-motile cells in mucilage envelope)
3. Dendroid (cell with basal mucilage stalk)
4. Motile colony (many small spherical groups of motile cells)
5. Coccoid (many small spherical non-motile cells with cell walls)
6. Filamentous (a string of non-motile cells connected straight or branch in one
plane) Heterotrichous (a branch string of non-motile cells )
7. Siphonaceous (plant body lack cross-walls)
8. Parenchymatous (cells forming thallus with simple differentiation)
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Macroalgae:
Multicellular (more than two cells layers) organisms often called seaweed. The main parts
of macroalgae are the holdfast, the blade, the frond, the stipe, the thallus, the midrib and
the air bladders. Examples are red and brown, and
green algae are growing under the sea attached to the seafloor by the holdfast part. In
most cases, the growing length extends between 25 and 50 m except for few species that
could exceed 50 m in length. We must know that there are exceptional macroalgae. The
brown algae have two types, the benthic (sea floor-dwellers) and pelagic (sea surface
dwellers). An example of pelagic macroalgae includes a mixture of genus Sargassum
natans and S. fluitans (Fig 2) floating massively off the Atlantic coast near Ajegunle-Erun-
Ama (Lat. 06o 19′ 32″ N, Long. 04o 30′ 32″E, alt 5 m) in Ondo State, Southwestern Nigeria
(Egunyomi and Oyesiku (2014).
Figure 2. Pelagic macroalgae.
A mixture of Sargassum natans and S. fluitans
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Habitats of Algae
Marine Habitat
1. Salty lagoon
2. Salty lakes and marshes
3. Ocean
Brackish water
1. Lagoon: having an abundance of microalgae, e.g. Desmids
2. Marshes, swamps, mud, and sand
Freshwater
1. Rivers, stream, springs, brook, stagnant pond water
2. Roots of aquatic plants: Lotus, lettuce and other submerged water plants
3. Bryophytes and ferns infusion (prepared in the Lab)
Animal waste: Fecal of snails, worms, and crustacean
Trees: shady side of trunks, and branches, on both surfaces of leaves
Rock surfaces: In a wet or moist situation
Artificial materials: water reservoirs, water filters, woods, old fences, abandoned
vehicle windscreen, and metal container
Ecology of Algae
Algae are essential plants. They form the broad base of the ecological food chain (web)
with many living plants and animals depending upon them. Algae are distributed
worldwide in marine, freshwater, wastewater and moist terrestrial habitats. Most abundant
are microalgae while a few macroalgae found growing on the ocean floor.
From the ecological standpoint, algae members can be distinguished based on their
mode of nutrition. Such mode includes, phototrophic (using light energy only),
chemotrophic (use organic carbon only) and mixotrophic (use both light energy and
organic carbon). However, algae are carbon fixing and oxygenating organisms.
OLABISI ONABANJO UNIVERSITY PLS201: CRYPTOGAMS
Updated: 1st January 2020
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Algae can be grown under conditions, which are unsuitable for other plants to reproduce.
Microalgae are capable of fixing atmospheric CO2, thus aiding the reduction of increasing
atmospheric CO2 levels (a global warming problem). Diatoms and dinoflagellates
proliferate and form algal bloom on the surface of the water. Few dinoflagellates glow in
the dark when disturbed
The oil body within the cell of few algae (diatoms and dinoflagellates) helps them to sink
or float and move within the water toward their food. Flagellum helps many motile algae
spores to move towards their food in the water.
Economic uses of Algae
With the current trend in research, the use of algae as a source of fuel and heat
generation is gaining ground. Algae are now a promising source of biodiesel, because of
their non-toxic, no sulphur, and the high biodegradable tendency. Besides, they could
provide biomass and fuels, 10-100 times higher than comparable higher plants. Positive
benefits include the removal of toxic substances by treating sewage and wastewater with
algae. Algae trap fertiliser run-off from farms for seed plants to reuse. Negative benefits
include food poisoning by toxic algal blooms
Conclusion
This lecture is an eye-opener to the potential that is locked up in the algae; We must have
learnt how to recognise, and where to find the algae. Futuristic use of algae as a biofuel
contribute to no small extent in solving the problem of electrical energy in Nigeria.
OLABISI ONABANJO UNIVERSITY PLS201: CRYPTOGAMS
Updated: 1st January 2020
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Summary
Having studied this lecture note, we should have:
gained understanding of the characters that separate algae from other groups of
plants
gained understanding of the types of algae in our environment
getting ready to look around our environment for the common types of algae
been better knowledgeable about the generation of biofuel from microalgae.
OLABISI ONABANJO UNIVERSITY PLS201: CRYPTOGAMS
Updated: 1st January 2020
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References/Further readings
Egunyomi, A. and Oyesiku O.O. (2014). Identification and chemical studies of pelagic
masses of Sargassum natans (Linnaeus) Gaillon and S. fluitans (Borgessen)
Borgesen (brown algae), found offshore in Ondo State, Nigeria. African Journal
of Biotechnology 13(10): 1188-1193, DOI:10.5897/AJB2013.12335
http://www.academicjournals.org/AJB
OLABISI ONABANJO UNIVERSITY PLS201: CRYPTOGAMS
Updated: 1st January 2020
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Tutorial-marked questions
1. Algae are eco-friendly. Briefly discuss
They produce a higher yield of food and oxygen
They help remove excess CO2 from the atmosphere
They help remove toxins from wastewater/sewage
They produce non-toxic biofuel
2. List the two members of algae
Macroalgae
Microalgae
3. State the three modes of nutrition in algae
Phototrophic mode of nutrition
Chemotrophic mode of nutrition
Mixotrophic mode of nutrition
CLASS CODE: MATRIC NO.: DEPT.:
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