Algae (singular alga) constitutes a group of simple non-flowering plants which lack true stems, leaves, roots and vascular bundles. They are mostly aquatic in nature and their typical examples include seaweeds. However, many types of algae exist which are unicellular in nature. Just like other plants, they also contain chlorophyll in their cells.
Fungi (singular fungus) is a group of eukaryotic organisms that have been classified as a separate kingdom ‘fungi’ separate from other forms of life such as plants and animals. Their types range from microscopic forms (such as molds and yeasts) to those visible by the naked eye (such as various types of mushrooms).
Eukaryotic / Prokaryotic
Except for a type of algae which are known as cyanobacteria, all other types are eukaryotic in nature. Eukaryotic organisms are those which contain their genetic material in a nucleus enclosed by membranes. Also other structures of the cell or organelles are also confined within membranes. Moreover, algae also contain phycobilisomes (light harvesting pigments) within their chloroplasts in the form of layers and sometimes circular DNA in the form of nucleoids.
While algae contain both prokaryotic and eukaryotic organisms, fungi contain solely eukaryotic organisms having complex cellular architecture. Fungi contain both unicellular and multicellular organism but some types are also dimorphic which means that it can shuffle between the unicellular and multicellular forms depending on the environmental conditions. This adaptability provides an advantageous edge for the dimorphic forms for survival under harsh conditions.
As algae are placed in the kingdom Protista, the not so formal classification of algae includes three main types of this group named as chlorophyte, rhodophyta and pheophyta depending majorly on the type of pigments present in their cells.
As per their names, they are also called green algae, red algae and brown algae in accordance with the pigments i.e., green, red and brown, respectively. The names of these pigments are chlorophyll, beta-carotenes and xanthophylls (green, red, and brown, respectively).
As fungi constitute a whole separate kingdom, they are further classified into seven distinct phyla. The names of these phyla are Microsporidia, Ascomycota, Glomeromycota, Basidiomycota, Chytridiomycota, Neocallimastigomycota, and Blastocladiomycota.
Of these, microsporidia and Glomeromycota re parasites of animals and plants, respectively, ascomycota and basidiomycete produce spores in specialized sac like structures known as asci and basidia, respectively. The rest of the phyla i.e., chytridiomycota, neocallimastigomycota, and blastocladiomycota are characterized by the production of mobile zoospores.
Algae are mostly aquatic plants, but there are also types being present in various other habitats too. Their presence in a wide range of aquatic and dry habitats leads to a classification of their types according to their habitations too. The algae categorized according to their habitats are named as follows: hydrophytes, edaphophytes, aerophytes, cryophytes, symbionts or endophytes, endozoophytes, parasites, and fluviatile algae.
A brief explanation of these types are along these lines:
- Hydrophyte – more or less submerged in the water, or free floating on the water bodies.
- Edaphophytes – alias terrestrial algae, are present either on the surface of or inside the earth.
- Aerophytes – present in aerial habitats e.g., tree trunks, walls, rocks, fencing wires, animals, and other aerial substrata.
- Cryophytes – exclusively found on ice and snow thus coloring the respective surfaces. Examples include green snow in arctic regions caused by the algae called chlamydomonas species.
- Symbionts / endophytes – grow in association with other plants where both the parties benefit from each other. Typical examples are lichens in the roots of plants.
- Endozoophytes – present inside the bodies of animals.
- Parasites – live on some plants and cause damage to them e.g., red rust of tea.
- Fluviatile – present in flowing waters such as mountain falls and streams.
Just like algae, fungi also acquire a wide variety of habitats ranging from terrestrial and aquatic environments to deserts. The following are the habitats in which fungi can be found.
- Moist and humid forests/woods – by far, the most common habitat of fungi are the woods, meadows, shadowed, moist and humid places. The rotting wood and leaf litter is also the reason for their abundant growth in the forests.
- Grassy places – some are also found in the grassy places of which the best example is the edible mushroom Fairy Ring Toadstool.
- Animal dung – there are specific species of such fungi and some are found growing only on specific kinds of dungs.
- Tree roots – these fungi are found associated with the roots of the trees and both are mutually beneficial to each other. These are also known as mycorrhizae. Among these, some fungi are choosy and will form associations with only a certain type of tree.
- Soil – the most common form in which fungi occur in the soil is in association with bacteria. In this way, they form the primary decomposer of the soil ecosystem along with their partner bacteria.
Autotrophs v/s heterotrophs
Since most of the algae contain chlorophyll – the photosynthetic pigment – they are able to synthesize their own food with the help of sunlight. Such organisms are called autotrophs who can synthesize their own food via the process of photosynthesis.
Contrastingly to algae, fungi are heterotrophic in nature i.e., they cannot synthesize their food via photosynthesis and must obtain it from other sources. The major reason for fungi being heterotrophic is that they do not contain the photosynthetic pigment chlorophyll in their cells.
Light requirements for living
Since algae are mostly autotrophic organisms necessitating the presence of light for the synthesis of their food, therefore they are unable to live in the absence of light.
Since most of the fungi are already decomposers, parasites, or mutually dependent on other organisms for their food and do not require the synthesis of food by their own cells via photosynthesis, thus they are not affected by the presence of light and are able to grow in the dark environments too.
Composition of cell wall
Since algae resemble plants in many of their properties, they also contain cellulose as the major component of their cell walls. Cellulose is also the main component of the cell walls of plants too. It is composed of hundreds to thousands of glucose units.
The cell wall of fungi is composed majorly of chitin. Besides this, some glycans and glycoproteins are also present in their cell walls. Chitin is also a major component of the exoskeleton of many insects. It is a polymer composed of N-acetylglucosamine subunits which is a derivative of glucose.
Key points of difference among algae and fingi
|Basis of Difference||Algae||Fungi|
|Eukaryotic / prokaryotic cells||Eukaryotic except for cyanobacteria||All types are eukaryotic|
|Classification||3 groups||7 phyla|
|Habitats||Aquatic, terrestrial, parasitic||80% humid and damp woods and meadows|
|Mode of food synthesis / nutrition||Autotrophic||Heterotrophic|
|Requirement of light||Yes||No|
|Cell wall composition||Cellulose||Chitin|