kingdom: protista -...

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)

http://www.bupoyesiku.net/

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





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





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.





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)





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





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.





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.





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.





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


http://www.academicjournals.org/AJB




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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