Consider the following kinds of organisms:
1. Copepods
2. Cyanobacteria
3. Diatoms
4. Foraminifera
Which of the above are primary producers in the food chains of oceans?
a) 1 and 2
b) 2 and 3
c) 3 and 4
d) 1 and 4
3. Ans: b
Explanation:
The marine biome is the largest worldwide, covering three-quarters of the Earth’s surface. About 15% of all the species living on Earth, containing almost 300,000 species, are marine dwellers. The marine ecosystem consists of a series of interconnected producers and consumers.
Copepods
Copepods feed on microscopic algae and in turn serve as food for millions of other invertebrates and fish. The Copepoda are an incredibly numerous group of crustaceans. There are approximately 9000 species with an average size range of 0.5 to 15 mm. The largest copepods are parasitic ones that can reach as much as 25 cm in length.
There are currently 10 groups of copepods. Most members of seven of those groups are parasites on other invertebrates or fish.
Cyanobacteria: Cyanobacteria are aquatic and photosynthetic, that is, they live in the water, and can manufacture their own food. Because they are bacteria, they are quite small and usually unicellular, though they often grow in colonies large enough to see. They have the distinction of being the oldest known fossils, more than 3.5 billion years old.
They are also important providers of nitrogen fertilizer in the cultivation of rice and beans.
The cyanobacteria have also been tremendously important in shaping the course of evolution and ecological change throughout earth’s history. The oxygen atmosphere that we depend on was generated by numerous cyanobacteria during the Archaean and Proterozoic Eras. Before that time, the atmosphere had a very different chemistry, unsuitable for life as we know it today.
The other great contribution of the cyanobacteria is the origin of plants. The chloroplast with which plants make food for themselves is actually a cyanobacterium living within the plant’s cells. Sometime in the late Proterozoic, or in the early Cambrian, cyanobacteria began to take up residence within certain eukaryote cells, making food for the eukaryote host in return for a home. This event is known as endosymbiosis, and is also the origin of the eukaryotic mitochondrion.
Because they are photosynthetic and aquatic, cyanobacteria are often called “blue-green algae”. This name is convenient for talking about organisms in the water that make their own food, but does not reflect any relationship between the cyanobacteria and other organisms called algae. Cyanobacteria are relatives of the bacteria, not eukaryotes, and it is only the chloroplast in eukaryotic algae to which the cyanobacteria are related.
Diatoms are abundant in both freshwater and marine ecosystems; it is estimated that 20% to 25% of all organic carbon fixation on the planet (transformation of carbon dioxide and water into sugars, using light energy) is carried out by diatoms.
This is possible because they contain chlorophyll. Diatoms are thus a major food resource for marine and freshwater microorganisms and animal larvae, and are a major source of atmospheric oxygen.
Diatoms are a major component of plankton, free-floating microorganisms of marine or freshwater environments. Not all diatoms float freely though; many cling to surfaces such as aquatic plants, molluscs, crustaceans, and even turtles. Whales may carry dense growths of diatoms on their skin. Some may even be found in soils or on moist mosses.
Foraminifera
Foraminifera are single-celled organisms (protists) with shells or tests (a technical term for internal shells). They are abundant as fossils for the last 540 million years. The shells are commonly divided into chambers that are added during growth.
Depending on the species, the shell may be made of organic compounds, sand grains or other particles cemented together, or crystalline CaCO3 (calcite or aragonite).
Fully grown individuals range in size from about 100 micrometers to almost 20 centimeters long. Some have a symbiotic relationship with algae, which they “farm” inside their shells. Other species eat foods ranging from dissolved organic molecules, bacteria, diatoms and other single-celled algae, to small animals such as copepods. They catch their food with a network of thin pseudopodia (called reticulopodia) that extend from one or more apertures in the shell. Benthic (bottom-dwelling) foraminifera also use their pseudopodia for locomotion.
Hence, option b is correct.
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