Algae are a varied category of all non-plant photosynthetic organisms.
Algae play
a significant role in marine, freshwater, and terrestrial ecosystems.
Seaweeds
are enormous types of marine algae. Phycology is the study of algae.
Algae are
classified as unicellular, colonial, or multicellular. Some algae, such as
diatoms, are extremely tiny. Other algae, such as kelp, can grow to be the size
of trees. Some algae, known as phytoplankton, float in the water. Other algae,
known as epiphytic or benthic algae, attach themselves to rocks, docks, plants,
and other solid things.
Classification
Green algae, diatoms, red algae, brown algae, and dinoflagellates are the five primary groups of eukaryotic algae. They are classified as protozoa. Cyanobacteria are another type of blue-green algae. Some authors do not regard blue-green algae as real algae since they are prokaryotes rather than eukaryotes.
Green algae.
Green algae are the most closely linked to plants. They have the same colors as
plants (chlorophyll a, b, and carotenoids), the same molecules in their cell
walls (cellulose), and the same storage product (starch).
Green
algae can be unicellular or produce filaments, nets, sheets, spheres, or
intricate mosslike formations. There are both freshwater and marine species.
Some green algae species dwell on snow, among lichens, or alongside other
algae.
Green Algae
Green
algae are the most closely related to plants. They have the same colors
(chlorophyll a, b, and carotenoids), cell wall components (cellulose), and
storage product (starch) as plants. Green algae can be unicellular or
multicellular, including filaments, nets, sheets, spheres, or complex mosslike
formations.
There are
freshwater and saltwater species. Some green algae species live on snow, as
lichens, or in symbiotic relationships with sponges or other aquatic creatures.
Chlorella and sea lettuce are examples of edible green algae. There are at
least 17,000 different types of green algae.
Diatoms
Diatoms
are frequently recognized as the most attractive algae.
Each
diatom has a glass cell wall with a species-specific pattern of dots and lines
carved into it. The patterns on diatom cell walls are so accurate that they
have been used to test the optics of new microscopes for years.
Diatoms
are also the most numerous algae in the open ocean, accounting for almost
one-quarter of all oxygen gas generated on Earth each year. In the spring,
diatom populations commonly bloom in lakes, providing a significant food source
for zooplankton and constituting the base of the aquatic food chain. There are
about a hundred thousand diatom species.
Red Algae
Many
edible and commercially significant species of red algae, such as nori and
laver, are virtually entirely marine. Carageenan and agar, which are utilized
as food thickeners and stabilizers, are similarly derived from red algae. The
majority of red algae are big, sophisticated seaweeds.
There are
between 4,000 and 6,000 species.
Brown Algae
Brown
algae, which comprise the biggest and most complex seaweeds, are virtually
entirely marine. Kelp, for example, may grow to be more than 60 meters (200
feet) tall and can create dense underwater forests off the coast of California.
Rockweed and Sargassum, after which the Sargasso Sea is named, are two more
major brown algae. There are around 1500 species of brown algae.
Dinoflagellates
Dinoflagellates
are unicellular algae with cellulose armor and flagella that spin as they swim.
Dinoflagellates live in both freshwater and saltwater habitats. When disturbed,
certain dinoflagellate species create an unusual blue light known as
bioluminescence.
Other
dinoflagellates are poisonous and are to blame for red tides and shellfish
poisoning epidemics. Dinoflagellates range in number from 2,000 to 4,000
species.
Life Cycles
The life cycles of algae are highly diverse. Some algae members exhibit practically any form of life cycle that can be imagined. Individuals reproduce in an asexual life cycle by separating. The asexual division is the primary mode of reproduction for certain dinoflagellates. Three forms of sexual life cycles require the fusing of gametes at some point: gametic meiosis, zygotic meiosis, and sporadic meiosis.
Gametic Meiosis
Meiosis
creates the gametes in the gametic meiosis life cycle (used by humans); hence,
the gametes are the only haploid cells in the life cycle. The person seen is
made up of diploid cells. Gametic meiosis occurs in diatoms.
Zygotic Meiosis
The zygote
undergoes meiosis during zygotic meiosis, making it the sole diploid cell. The
organism's other cells are all haploid. Many green algae, including sea lettuce,
go through zygotic meiosis.
Sporadic Meiosis
Within the
life cycle of sporadic meiosis, there exist both haploid and diploid
individuals. Meiosis generates haploid spores, which split to form a person
composed completely of haploid cells. Mitosis is the process through which this
individual generates gametes. A diploid zygote is formed when two gametes
combine.
The zygote
splits into an individual composed completely of diploid cells. To finish the
cycle, this person generates spores via meiosis. The life cycle is referred to
as the "alternation of generations" because it contains two
generations of humans, a haploid generation and a diploid generation. Sonic
meiosis occurs in plants and many green, red, and brown algae.
The
manufacturing of nori is a billion-dollar-a-year industry in Japan, Korea, and
China, but because the two generations in the nori life cycle look radically
different, the second generation was not identified until the early twentieth
century. This finding significantly enhanced humans' capacity to cultivate
nori, and a memorial park in Japan honors the British scientist who found it,
Kathleen Drew Baker.
Economic and Ecological Importance
Algae are
the foundation of the aquatic food chain. Many forms of algae are also consumed
by humans. For almost two thousand years, the sea algae nori and kelp have been
collected in China. Spirulina, a blue-green algae high in protein and vitamin
B, is gathered in Africa's Lake Chad.
Algae
photosynthesis is critical to the biosphere because it decreases the quantity
of carbon dioxide in the atmosphere while increasing the amount of oxygen.
Some algae
can cause environmental issues, including red tides and fishy-tasting water.
These issues are typically caused by excessive nitrogen discharge from
agriculture, sewage, and other human activities. Overflowing sewage lagoons,
for example, have been connected to an epidemic of the nerve-toxin-producing
Pfiesteria (a dinoflagellate) on the Atlantic coast.
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