Algae - Types & Examples, Defination

What Is Algae?

Algae refers to a vast group of photosynthetic organisms which are aquatic or terrestrial in habitats and they consist of single-celled, tiny forms and giant forms such as seaweed. Being the core producers in aquatic environments, they allow for substantial levels of oxygen generation and nutrient recycling. Thus, in biology, algae play the roles of simple models with which researchers investigate photosynthesis, evolution, and species interactions. Algae are divided into several large groups according to their pigmentation and structure and according to the place they inhabit Green algae (Chlorophyta), red algae (Rhodophyta), brown algae (Phaeophyta), Diatoms (Bacillariophyta).

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This Story also Contains

1. What Is Algae?
2. Characteristics Of Algae
3. Classification Of Algae
4. Algal Life Cycle
5. Habitat And Distribution
6. Algal Blooms And Environmental Impact
7. Economic and Commercial Importance of Algae
8. Recommended Video Of 'Algae'

It is crucial to identify the two classes and their functions in ecosystems to solve environmental issues and examine their possibilities to apply in biotechnology, agriculture, and bioremediation. In this article, the author gives an introduction to algae focusing on the variation of the algae species, their role in the ecosystem and their importance in biological and industrial areas.

Characteristics Of Algae

The characteristics of Algae are described below-

Basic Structure And Morphology

Algae are diverse in structure and size depending on their classification ranging from single-celled microalgae to large and complex multicellular algae like seaweed. They do not possess real roots, stems, and leaves but they possess structures such as hold fast which is used to attach the plant firmly and blades or fronds which are used in carrying out the photosynthesis process.

Cellular Organization

They can be classified as being singular-celled, which is Chlorella and diatoms or many-celled; seaweeds and kelps. Complex forms may contain tissue for performing photosynthesis and other structural tissue.

Photosynthetic Pigments

Chlorophylls (a and b) are photosynthetic pigments found in algae and these help in the absorption of light energy during the formation of algae food. Abundant proteins such as carotenoids and phycobilins are also used to add colours such as green, red and brown to the pigments.

Reproductive Methods

Sexual and asexual reproductive means are possible in algae. Modes of asexual reproduction are binary fission, budding, fragmentation, and spores and/or vegetative structures. The process in which two gametes or sex cells of different organisms or within the same organism are fused so that they form the zygote.

Classification Of Algae

The algal classifications are listed below-

Chlorophyta (Green Algae)

Chlorophyta constitutes the green algae covering the simplest form such as the Chlamydomonas to complex forms resembling the true plants. These include Chlorophyll a and b, carotenin and starchy energy reserve in the Chloroplast. The cell walls are often formed from cellulose even though quite several species do not possess cell walls at all.

Habitat

Green algae are found in aquatic habitats like freshwater bodies of water, and moisture-loving terrestrial habitats, for instance, moist surfaces of soils, rocks etc. Some species also live in aquatic environments, particularly in marine environments.

Examples

• Chlamydomonas: A plant life from freshwater, actinium has a single cell and is capable of moving through flagella.

• Spirogyra: It is the green filamentous alga with spiral chloroplasts mostly found in freshwater.

• Ulva (Sea Lettuce): Large, multichotomously branched marine green alga having thin and transparent flat structures called blades.

• Volvox: Colonial green alga that forms spherical colonies; freshwater habitats; ponds.

Diagram of Chlamydomonas

Phaeophyta (Brown Algae)

Brown algae or Phaeophytes belonging to the kingdom Protista are large multicellular seaweeds that have complicated organization. Being a group of brown or olive appearance, fucoxanthin, the main pigment, overlies green chlorophylls.

Habitat

Brown algae are cool water marine forms which are common on temperate rocky shores and in kelp beds. It generally grows when nutrients are abundant and can endure strong currents and fluctuating water depths.

Examples

Fucus (Rockweed): It is a popular intertidal brown alga that possesses utricles namely air sacs for buoyancy.

Laminaria (Kelp): Massive brown seaweed that creates kelps and other structures responsible for marine communities’ shelter and food.

Sargassum: Sargasso seaweed familiar from films: large floating brown algae that form the basis of one of the tropical ocean’s biomes.

Diagram of Laminaria

Rhodophyta (Red Algae)

Red algae are members of the phylum Rhodophyta that are multicellular and predominantly of marine habitats; the colour of red algae is red to purplish. This colour is due to the presence of phycoerythrin pigment that hides the green chlorophylls which are present in smaller amounts. They have a relatively large cell size with a complex containing cell walls that are either of agar or carrageenan that is used in the food and drugs industries. They store energy in the form of fluoride starch in their cytoplasm and many of them are also calcified and thus are involved in the framework of the reef.

Habitat

Red algae are mainly marine organisms though they can be found in both the shoreline water and abyssal zones of the seas. Most species are widespread in both warm and cold water regions; they are likely to form large beds or reefs. Some can also occupy the intertidal and substrata of rocks.

Examples

• Porphyra (Nori): Red algae which is consumed in most of its raw forms in sushi, culinary and many other dishes.

• Corallina: This is a picture of the calcareous red algae which forms a part of the coral reef structure.

• Gelidium: The red algae used in harvesting to obtain agar which is used in the food industry and microbiology.

Diagram of Coralina

Other Groups

The other groups of algae include:

Diatoms

Characteristics: Diatoms are a kind of unicellular algae, which is bordered by a complex silica wall named frustule. They come in various shapes that include; cylindrical, triangular and even shapes like stars. They are plant-like cells that contain silica cases perform photosynthesis, and play a critical role in converting carbon dioxide to oxygen.

Habitat: It is a silicon-based algae which are developed in freshwater as well as in seawater but most abundantly in areas which are full of nutrients. They are particularly diverse and numerically dominant mainly in phytoplankton assemblages at the base of the aquatic food chain.

Examples:

• Diatomaceous Earth: Silicon dioxide which belongs to the group of diatoms that are used in different industries.

• Navicula: One type of freshwater diatom that has long cells.

• Like Coscinodiscus, Cyclotella, and Pinnularia; diatom genus.

Dinoflagellates

Characteristics: It is a group of single-celled algae having two flagella organs through which they swim in water. Most of them are of various shapes and sizes and are commonly protected by cellulose plates. Some species are autotrophic as well as photosynthetic, while others are semi-autotrophic called mixotrophic, fully heterotrophic species.

Habitat: These are aquatic algae found in both marine and freshwater environments with populations in both the surface and the midwater and deep-sea water forms. They are capable of developing blooms under some conditions that are a threat to marine life and aquatic water quality.

Examples:

• Gonyaulax: Harmful algal blooms are commonly termed red tides which are caused by a dinoflagellate genus.

• Karenia brevis: Dinoflagellate that is involved in the red tide occurrences near the shores.

• Symbiodinium: Primary dinoflagellate genus which lives in mutualistic association with coral polyps.

Diagram of Gonyaulax

Algal Life Cycle

The algal life cycle is described below:

Haplontic

The haploid life cycle is however characterised by the fact that the algae organism spends most of its life in the haploid form. Haploid means that the cell has an incomplete set of chromosomes, as a result, the cells in this category only have half the set of chromosomes.

The haploid phase is more prominent and this phase carries out mitosis to yield more of the haploid cells. Sexual reproduction occurs when two haploid cells combine to form a diploid zygote. The diploid zygote and then divided by meiosis to form four haploid spores, which then germulate to produce more haploid sporophytes. This life cycle is typical of the green, some red and brown algae like some other protist groups.

Diplontic

In diploid life cycles, algae live mostly their life in the diploid phase much of the time. Diploid cells are the cells containing two sets of chromosomes. The diploid phase is dominant and is followed by mitosis to increase the population of the diploid cells in the factory.

Meiosis happens directly leading to the formation of haploid spores that are formed into the gametophytes that in turn make haploid gametes. The joining of the haploid gametes forms a diploid zygote hence the life cycle is complete. Such a life cycle is found in most animals and many species of brown algae and some red algae.

Haplodiplontic

The two major sections of the plant or algal life cycle, the sexual and asexual phases, are abbreviated as the haplodiplontic cycle or even the alternation of generations. The life cycle of Streptomyces is complex and contains both haploid and diploid steps; nevertheless, the haploid and diploid states are multicellular and separate from one another.

The other one is the haploid phase also known as the gametophyte where structures which are created through mitosis are the haploid gametes. This is accomplished by the fusion of haploid gametes, which produces a diploid zygote with a sporophyte which is diploid and results through mitosis. Through meiosis the mature sporophyte forms haploid spores that in turn grow into new haploid gametophytes thus completing the cycle. This life cycle is typical for most of the green and red algae and some of the brown algae and plants.

Habitat And Distribution

The details are given below:

Aquatic Ecosystems

Algae can be found in inland water bodies like freshwater lakes, ponds and rivers through producers like diatom and green algae respectively. In the marine ecosystems of the world, some of the important phytoplanktons include brown algae (kelps), red algae and diatoms that feed on nutrients present in the ocean waters.

Terrestrial Algae

Terrestrial algae can be found in soil, rocks, and trees. Aerobic and anaerobic soil algae are directly involved in the improvement of soil fertility as well as the management of soil stability while the rock-inhabitant species prove useful in the formation of biological soil crusts in arid zones. Certain algae are mutualistic with fungi wherein they make up part of lichens which means that algae can colonize a variety of terrestrial environments.

Extreme Environments

Some of the algae are adapted to high-stress environments including, hot springs and the Arctic region. These thermophilic and psychrophilic algae can be found in hot springs with high acidic concentrations in extensive areas which have high temperatures or in the polar region with extremely low temperatures and scarce light.

Algal Blooms And Environmental Impact

The environmental impact on algal blooms includes:

Causes Of Algal Blooms

Algal bloom characteristics include nutrient pollution which commonly includes nitrogen and phosphorus, warm water temperatures, and calm and sunny conditions that encourage growth.

Consequences On Aquatic Life And Human Health

Blooms can suffocate fish, alter the food chain, and even release toxic substances lethal to marine organisms and humans (e. g shellfish poisoning and respiratory problems). It influences tourism as well as recreation.

Measures To Control Algal Blooms

Some of the promising measures which can be applied are such tactics as improving the quality of water and nutrients through better agriculture and wastewater treatment, barrier zones, integrated approach to land use, water quality controlling, aeration and biological controlling using zooplankton. Usually, the general population doesn’t seem to care about nutrient pollution, and this often has to do with sheer ignorance.

Economic and Commercial Importance of Algae

The economic importance of algae is:

• Algae carry out photosynthesis and are major producers of bodies of water, oceans, and lakes.

• Algae absorb 50% of the total CO2 fixation on Earth. They provide food and oxygen to aquatic animals. It also increases the amount of dissolved oxygen in the water.

• Chlorella, single-celled green algae, is rich in B vitamins and protein and is also used in space exploration. Acetabularia, Chlorella, etc. are used in biological research programs. Laminaria, Fucus, Sargassum, etc. are used as food and fodder.

• The antibiotic chlorelin is isolated from chlorella.

• Algae are rich in minerals. Iodine and bromine are extracted from seaweed.

• Algae such as focus, macrocysts, and sargassum are used as fertilizers.

• Have high water-holding capacity, high organic matter, and mineral content.

• Microcysts produce toxins that are harmful to various microbes.

• Carrageenans from red algae are used as emulsifiers and stabilizers in ice cream, chocolate, cosmetics, toothpaste, etc., as well as emulsifiers in pharmaceuticals, the textile, leather, and brewing industries.

• Algin is extracted from the cell walls of brown algae. Algin is used to prevent crystals from forming in ice cream. Also used to stop bleeding. Suitable for preparing soups, creams, sauces, etc. Algin is also useful in the processing of paints, pigments, rubber, the pharmaceutical automotive polish industry, and dentistry for making impressions of teeth.

• Agar is extracted from representatives of red algae such as Agaricus and gracilaria. Agar is used as a base for bacterial, algal, fungal cultures, and tissue cultures in laboratories. It is also used as an emulsifier in the food, cosmetics, textile, leather, paper, and pharmaceutical industries, as well as in the bakery and confectionery industries.

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