Biological Benefits of Water
Water in Organisms
- Organisms usually contain 60% to 90% water.
- Lowest- Plant Seed (20%)
- Highest- Jellyfish (99%)
- Water helps all organisms with metabolism, and specifically helps plants with photosynthesis and support.
Water as a Solvent
- Water contains 1 covalently bonded oxygen atom and 2 hydrogen atoms.
- Water molecule is polar, because electrons are not equally shared.
- Due to its polarity water can ionize substances easily, making it a good solvent.
- Water is known as ‘The Universal Solvent’.
Water s a Means of Transport
- Many different substances, such as blood and sap, are transported by water.
- Sap and blood contain high amounts of water making them good solvents.
- Being good solvents allows them to dissolve the substances they are transporting.
Water as a Reactant
- Water, being a good solvent, allows many reactions to occur.
- Water is used in photosynthesis to make NADPH2, and ultimately sugar.
- These reactions release oxygen gas, which is vital to human life.
- Without water in photosynthesis, organisms would not be able to obtain energy, and life as we know it would be impossible.
Water as Means of Support
- When water enters the cell by osmosis, the water fills up the cell so much that the cell prevents another water intake.
- This makes the cell turgid, or stiff.
- The cell must be turgid to support the plant’s leaves.
- Also, organisms that live in the water have weaker skeletons than organisms that live on land because of the water’s buoyancy effect.
Water as a Lubricant
- When bones meet at a joint, they need a fluid between the bones to prevent scraping against each other.
- That fluid is called a synovial fluid, which is made mainly of water.
- Many internal organs have fluid around them to keep them protected. Examples:
Brain: Cerebro-spinal fluid
Lungs: Pleural Fluid
Eyes: Mix of fluids.
Water in Sexual Reproduction
- During fertilization, the sperm, must get to, the ovum in order to make the zygote, which makes a new individual.
- In organisms adapted for internal fertilization, the sperm is transported in semen which contains mostly water.
- In organisms using external sperm can be transported in the water habitat.
Water and Constant Temperature
- Water has a very high specific heat. (4200J/kg0C)
- Much energy is required to change the temperature of water by a single degree.
- That provides a perfect habitat for marine mammals, because of the non-changing temperature.
- Another way water helps mammals maintain their body temperature is by sweating.
- Mammals sweat when their body temperature is too high.
- Sweat is made of mostly water.
- When the water evaporates from the organism it creates a cooling effect, therefore lowering the organisms body temperature.
Water as a Habitat
- Water can provide a good protective layer for organisms in it.
- Water provides buoyancy and support for organisms in the water.
- Dissolved oxygen can be plentiful in water, for use in respiration.
- Fertilization is easier in water.
- Water helps maintain a constant temperature.
- Water keeps out UV rays from the sun.