Aquatic habitat explained with its types

len Alfred Ajibola - 17th November, 2023 @ 02:28 PM

Topics in Biology

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Academic Questions in Biology

Please click here to see all Questions and Answers

Male Reproductive System - Len Academy

From the above diagram, which of the organ below isn't a requirement for the male reproductive system?

  • A. Bladder

  • B. Ureter

  • C. Glans Penis

  • D. Testis

  • E. Bulbourethral Gland

  • F. Epididymis

A walnut shaped male accessory sex organ located between the bladder and penis is the _____.

  • A. Ductus Ejaculatorii

  • B. Bulbourethral Gland

  • C. Prostate Gland

  • D. Ductus Deferens

  • E. Seminal Vesicles

  • F. Epididymis

In a food chain, the primary consumers are classified under trophic level  _____.

  • A. Zero

  • B. One

  • C. Two

  • D. Three

  • E. Four

  • F. Five

Cold blooded animals are referred to as _____.

  • A. Homeotherms

  • B. Endotherms

  • C. Poilokitherms

  • D. Ectotherms

  • E. Thermotherms

  • F. None of the above

All reptiles are vertebrates.

  • A. True

  • B. False

_____ cells are responsible for the formation of osteoblasts.

  • A. Osteocytes
  • B. Chondrocytes
  • C. Chondroblasts
  • D. Osteoclasts
  • E. Osteoprogenitor cells
  • F. Osteoblastic

_____ is a bone that constitute the axial skeleton.

  • A. Clavicle
  • B. Scapula
  • C. Patella
  • D. Radius
  • E. Sternum
  • F. Femur

Which of the following is false concerning cartilages and bones?

  • A. Cartilage does not have a direct blood supply while bones have direct blood supply
  • B. The process of ossification replaces a cartilage to bone
  • C. The protein that makes up cartilage is called chondrin while that that makes up bone is called ossein
  • D. Cartilage grows from both ends while bones grow from one of its epiphysis
  • E. They both have living cells within them
  • F. Haversian system is absent in cartilage but present in bones

Aquatic Habitat:

Aquatic habitat may be defined as bodies of water where organisms naturally live in. Simply put, it is a water area serving as home to a variety of organisms. The living creatures dwelling here are generally termed aquatic organisms, and they find their food, shelter and mates within the waterbody. 

Aquatic habitat comprises of the biotic and abiotic components. The biotic component refers to all the living organisms present in an aquatic habitat; and these are adapted to survive within its minimal oxygen environment. Meanwhile, understand that the amounts of available oxygen is lower in aquatic habitat when compared to their terrestrial counterpart.

Please read on terrestrial habitat explained with its types here.


Just as organisms of the terrestrial habitat, aquatic organisms can be classified in three main groups. These are the producers, consumers and decomposers.

The producers in commences the food chain in all habitats. Aquatic organisms that are producers include the hydrophytes that manufacture food through a process termed photosynthesis. Examples are phytoplanktons, algae (sea weed), seagrass, duckweed, eichhornia, vallisneria, kelp, hyacinths, cattails, water lily and so on. However, certain aquatic bacteria may also manufacture food through a process termed chemosynthesis.

Please read on autotrophic nutrition, photosynthesis and chemosynthesis here.


The consumers in aquatic habitat are typically animals. They include the fishes, insects, sharks, dolphins, seals, whales and so on. Some of these feed on the aforementioned producers, while others may feed on other aquatic animals. 

Decomposers in aquatic habitat include the bacteria, fungi, echinoderms, marine worms, trumpet snails, mushrooms, certain crustaceans and molluscs. They bring about the decomposition of dead aquatic organisms.

Please read on food web here.


Abiotic components of an aquatic habitat refers to those non-living components present in the water bodies, and are crucial to the aquatic organisms' survival. They include water pH, light, water temperature, salinity level of water, oxygen concentration, nutrients, velocity of water, substrate, tides and waves.

The biotic and abiotic components of various water bodies give rise to the aquatic ecosystems.

Please read an introduction to ecosystems here.


Aquatic habitat is the largest habitat on earth. The bodies of water comprising this habitat are quite numerous. They include the ocean, sea, river, lake, pond, bay, wetland, lagoon, marshes, bug, swamps and so on. However, these aquatic habitats can be generally categorized into three. They are:

  1. Saltwater

  2. Freshwater

  3. Brackish water

  4. You can read key points on various academic subjects here.


  • Saltwater Habitat

As the name imply, their waters are highly concentrated with dissolved salts, especially sodium chloride (NaCl). For this reason, they are described as saline water. On average, about 35 to 37 gram of salt (NaCl) is present in each kilogram of seawater.

The saltwater habitat is often termed as a marine habitat. On average, they have a salinity of 35ppt to 37ppt (ppt means parts per thousand). In simple terms, salinity refers to the amount of dissolved salt within a body of water. You can think of it as the concentration of salt in water.

Marine organisms can easily float in saline waters since they have a high density of about 1.03g/cm3 at its surface. This density reduces as one goes deeper into the ocean. Similarly, the oxygen concentration is highest at its surface, and reduces beneath the waters. Tides and waves are often observed in the marine habitat.

You can read interesting facts in biology here.


The oceans and seas are examples of a saltwater habitat. They are the largest habitat on earth. In fact, it covers about 70% of the earth's surface, and account for 97% of earth's water supply.

With regards to the ocean, organisms that live on its surface area termed neuston. Examples are the golden seaweed, barnacles and marine snails. They act often as producers and primary consumers in the marine food chain.

Please read on food chain in ecosystems here.


The marine habitat can be grouped into zones with regards to its varying water depths and shoreline features. These zones include:

  • Oceanic zone: It comprises the vast ocean space (or the sea). They include the atlantic ocean, pacific ocean, indian ocean, antarctic ocean and arctic ocean respectively. Animals present here include sharks, orca, dolphins, starfish, sea lion, seahorses and whales.

  • Benthic zone: They contain the lowest level of water. Beneath the water lies a good amount of substrate upon which organisms thrive upon. The organisms in the benthic zone are termed as benthos. Examples are crustaceans, molluscs, worms, sponges, sea anemone, bivalves and bacteria.

  • Intertidal zone: You can think of this zone as the foreshore, seashore or littoral zone. Several invertebrates of different phyla are present here. The include the annelids (segmented worms), coelenterates, molluscs, and anthropods.

  • Neritic zone: These zone are present in mangrove swamps, lagoons, mudflats, marshes and meadows. The waters here aren't deep. Animals seen here are lobsters, clams, oysters, scallops, crab and shrimp.

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The community of plants present in the saltwater habitat are termed as halophytes. Simply put, a halophyte is a salt-tolerant plant that thrives in saline soil (or waters). They include seaweeds, algae, planktons, seagrass, mangrove trees, kelp and sargassum.

Animal community of the saltwater include shrimps, periwinkles, barnacles, sharks, orca (killer whale), dolphins, turtle, eel, jellyfish, octopus, water striders, tuna, starfish and so on. These organisms may become adapted to living under harsh temperature and pressure.

Please read more on the characteristics of saltwater habitat here.


  • Freshwater Habitat

Although the freshwater habitat account for just about 3% of earth's water, it still represent a home to a large variety of living organisms. In addition, freshwaters like rivers and streams have served as a source of drinkable water in many rural communities. The people of these communities may also wash their clothes, carry out fishing activities, and even bath in these freshwaters.

In biology, the term limnology refers to a study regarding the freshwater ecosystems. Therefore, scientist that study freshwaters are termed limnologists.


Freshwater habitat (or ecosystems) include the rivers, lakes ponds, creeks, streams, bugs, springs, swamps and wetlands. They have very low or insignificant salinity, and are much smaller in size when compared to the salt water habitat. Also, they are less deep than their saltwater counterpart. However, freshwater is more easily penetrated by sunlight, and will also contain more oxygen than marine water.

You can read on swamp forest ecosystem here.


The concept of freshwater ecosystem refers to the interaction of living (biotic) factors, and non-living factors (abiotic) within the freshwater. Freshwater ecosystems are of different types. They include the following:

  • Lotic Ecosystem: Their waters are fast moving. They include the rivers, streams and springs.

  • Lentic Ecosystem: The waters are slow moving. Examples are the lakes and ponds.

  • Wetland Ecosystem: The waters are present on the soil and will often saturate it, either seasonally or permanently.

  • You can read interesting facts for students in biology here.


With regards to surface area, the largest freshwater lake in the world is Lake Superior in North America (USA and Canada). It reaches a size of over 31,000 square miles and depth of about 1,300 feet.

The longest freshwater river is the Nile River, with a length of about 6650 kilometers. It is present in Africa and flows through Egypt, Uganda, Ethiopia, Kenya, Tanzania, Rwanda, the Democratic Republic of the Congo, Eritrea, Burundi, Sudan, and South Sudan. Lake Victoria is considered to be the source of river nile.


Examples of freshwater plants include spirogyra, water lettuce, algae, water lily, cattails, water weed, aspen, and willow trees. The animal community present in freshwater include alligators, snakes, frogs, lake trout, mayfly, hippopotamus, crocodiles, herons, kingfisher, crayfish, catfish, freshwater crab, and a variety of fishes and insects.

You can read interesting facts on various academic subjects here.

The world's largest freshwater habitat is the 1.5 million acre water body named Everglades in southern Florida.


  • Brackish Water Habitat

The brackish water (or brack water) is formed at estuaries where freshwater and saltwater mixes together. You can think of estuaries as the point (or region) where a river meets the sea.

All rivers drain into a larger body of water, typically the ocean. However, a few rivers may drain into lakes. Recall that the ocean is a saltwater, while a river is considered freshwater. Consequently, the region of meeting between the river and sea creates a unique type of aquatic habitat whose water can become somewhat salty. In fact, the term brackish means 'somewhat salty'. A brackish water is therefore more salty than freshwater but less salty than the ocean (or sea).

You can read explanations on various ecological concepts here.


Brackish water are generally grouped into delta, bay and lagoons. Their waters are quite shallow with high level of nutrients. It often has a varying amount of salinity with low amounts of oxygen. Brackish water contain more salt (more salinity) than freshwater, but are less saline than saltwater. Their salinity is between 0.5g - 30g of salt per liter (0.5ppt - 30ppt).

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Examples of brackish water include river Thames in London, Baltic sea, Hudson bay, lake Texoma and various mangrove swamps (or mangal).

Examples of plants found in the brackish water habitat include coontail, waterweeds, water hyssop, marimo and anubias. Animal community present in brackish water are catfish, fiddler crab, catfish, lamprey, pufferfish, herring, salmon, mudskipper, hippopotamus, dragonfly, bull sharks, and various aquatic insects.

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Pufferfish contain a toxin called tetrodotoxin. This makes them foul tasting and poisonous to predators. Tetrodotoxin is about 1,200 times more poisonous than cyanide, and there is enough toxin in one pufferfish to kill 30 adult humans. Unfortunately, there isn't any known antidote to this poison.

Interestingly, a delicacy in Japan (called fugu) is made from pufferfish. This meal is very expensive, and must be prepared by trained and licensed chefs. An improper preparation of fugu may lead to the customer's death. Sadly, such deaths are recorded annually

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An artery is composed of three layers:

  • The outermost layer is termed tunica adventitia (or tunica external). It consist mainly of collagen fibres and connective tissues that anchors the arteries to other nearby tissues.

  • The middle layer is named tunica media. It is made up of smooth muscles and elastic fibres that supports the artery in conveying blood at high pressures.

  • The inner layer is called tunica intima (or tunica internal). It is lined by a smooth tissue called endothelium, and is made up of a fine network of connective tissues.

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All living organisms possess various features in order to survive in their environment. This is the concept of adaptation. As an instance, a fish is able to live in water because it has gills and fins.

Also, a camel is able to survive in the desert because it has large feet to aid walking on sand without sinking. It also has long eyelashes to help protect it from the blowing sand and wind.

Plants are also able to live in different habitats because they have the required adaptive features towards that habitat. For instance:

  • Plants that live in/on water are termed hydrophytes.

  • Plants that live on land with moderate amount of water are termed mesophytes.

  • Plants that live on deserts or arid lands are termed xerophytes.

The point is:

All organisms have various features on them that enables them adapt in their habitat

For a thing to be considered living, it must possess all the basic characteristics of life. These include:

  1. Movement

  2. Respiration

  3. Nutrition

  4. Irritability or Sensitivity

  5. Growth

  6. Excretion

  7. Reproduction

  8. Death

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This is the concept of anaerobic respiration

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A food chain is a diagram that shows the relationship between plants and animals within a habitat on the basis of how they rely on each other for food.

Note: Habitat is a place where an organism live. It is of three types:

  • Terrestrial (Land)
  • Aquatic (Water)
  • Arboreal (Treetops)

You can read on food chain here