Tell Me Why?

Dolphins and whales are not fish. Fish is any cold-blooded (poikilothermic) vertebrate animal that lives in water. A fish typically has jaws, fins, scales, a slender body, a two-chambered heart, and gills for providing oxygen to the blood. Fish is capable of breathing under water without making frequent trips to the surface to breathe air like marine mammals. This is due to the fact that fishes have a breathing organ known as gills. This is made up of thin feathery sheets of tissue membrane containing many blood vessels through which oxygen passes allowing fishes to breathe. In other words, fish use their gills to extract oxygen from the surrounding water in which they live.

Dolphins and whales on the other hand, are mammals just like humans and breathe air using lungs, they give birth to live young (rather than laying eggs), and feed their young with their milk. They do not have gills and get the oxygen they need by breathing air, using their lungs. This explains why they come to the surface of the ocean. They have a hole (their nose) in the flat part of the middle of their heads called blow holes. This closes when the whale or dolphin is under water and it opens when they are at the surface and need to breathe.

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Labels: Animals

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When ice covers a pond or lake, it prevents oxygen exchange at the water surface with the atmosphere. However, this is not a problem where oxygen availability is concern as long as light shines through (penetrates) the ice to aquatic plants in the water. Aquatic plants provide oxygen through photosynthesis that is dissolved into the water that fish needs to survive.

If a heavy amount of snow accumulates on the ice, the amount of light penetrating through the ice will be reduced. This will result in less light reaching aquatic plants below the ice which is needed to carry out photosynthesis thus, causing the plant to die and be broken down by bacteria. These bacteria (called aerobic bacteria) will then use up the oxygen and cause a drastic drop in dissolved Oxygen in the water. When this winter oxygen depletion occurs, marine life such as fish that depend on oxygen will die because oxygen concentrations become too low for the fish to survive. That is, the demand for oxygen exceeds the supply. As fish and other marine life die, their bodies decompose and use up even more oxygen, and the depletion of oxygen gets even worse. This is called Winterkill. Winterkill occurs during especially long, harsh winters. Drought also can cause a similar fate by reducing the volume of water in the lake. This means with the less water content present, the less there will be an oxygen rich environment to support life.

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Labels: Animals, Biology, Science

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Water is formed from the combination reaction of hydrogen gas (H2) and oxygen gas (O2) to produce liquid water (H2O). In other words, each molecule of water is made up of two hydrogen atoms and one oxygen atom. Each oxygen atom in a water molecule is bound by a strong covalent bond to each of the two hydrogen atoms in a single water molecule. That is, the oxygen in liquid water is strongly bound to two hydrogen atoms forming water molecules. A fish therefore cannot break water molecules apart to get the oxygen. This simple means that the oxygen that fish breathe is not the oxygen found in water since it is not free to take part in respiration. Thus, since fish cannot breathe the resulting liquid water, the oxygen gas (O2) that the fish breaths comes from that which is dissolved in the water.

Hence, fish "breathe" the dissolved oxygen out of the water using their gills. Fish gills are thin feathery membrane structure that allow water (containing dissolved oxygen) to move between the layers and enable oxygen to diffuse into the fish's bloodstream. A fish's gills take oxygen from the water the same way human lungs extract oxygen from the air. This also means that if there is not enough dissolved oxygen in the water, then the fish can suffocate, just as humans and other animals will if there is not enough oxygen in the air that we breathe.

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Where does the oxygen come from that fish breathes?
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Why dolphins and whales don’t use gills to breathe?

Labels: Animals, Biology, Science

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Most animals including humans have gills in their early fetal stage of development in the womb. However, they lost this organ further into their development since it has no essential function toward sustaining and maintaining live. Therefore mammals which includes humans cannot breathe underwater because our lungs do not have enough surface area, that is necessary to absorb enough oxygen from water. Furthermore, the lining in our lungs is adapted to handle air rather than water. Fish on the other hand, retained these gills, which are necessary for their survival in their environment (water medium). Gills are very efficient at removing oxygen from water due to their feathery structure that greatly increases the surface area for gas exchange. Hence, gills play an important role in the anatomy of fish.

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Why dolphins and whales don’t use gills to breathe?

Labels: Animals, Biology, Science

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Cats and dogs eyes glow at night because of a silver “mirrors” in the back of their eyes called the tapetum lucidum (meaning "bright carpet") which is a thick reflective membrane. This collects and re-emits light back to the retina a second time thus giving the light-sensitive cell (rods) a second opportunity to absorb the image information again. This a adaptation for night vision and makes it easier for them to see at night by maximizing the limited available light. Hence, the reflected light from the tapetum let the animal's eyes appear to glow in the dark.

Labels: Animals, Biology

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The reason why warm-blooded animals like dolphins and whales breath air like humans is due to the fact that it would be hard to extract enough oxygen from their water surroundings using gills. Furthermore, air has approximately 20 times more oxygen in it when compared to the same volume of water. While on the other hand, fish being a cold-blooded animal take on the temperature of their surroundings and uses less energy than that of warm blooded animals which convert the food that they eat into energy to adjust their body temperature. This reduces oxygen demands for fishes thus, gills work best with fishes.

Labels: Animals

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