Water's Role in Life and Its Properties

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Questions and Answers

What is the molecular formula for water?

CO2

H2S

NaCl

H2O (correct)

At what temperature is water densest?

4°C (correct)

100°C

0°C

-61°C

Which property of water is crucial for the mixing in lakes during turnover?

Low molecular weight

Solvent properties

High melting point

Density at varying temperatures (correct)

Which of the following statements about dissolved minerals is correct?

They vary depending on the organism. Signup and view all the answers

What percentage of total water do lakes, rivers, and streams constitute?

0.01% Signup and view all the answers

In aquatic ecosystems, why is maintaining water balance crucial?

It is important for nutrient flow. Signup and view all the answers

What is a solute in the context of water?

A substance dissolved in water Signup and view all the answers

What happens to calcium ions when calcium carbonate dissolves in water?

They dissociate into ions. Signup and view all the answers

What role does water play in photosynthesis?

Water is a reactant needed for photosynthesis. Signup and view all the answers

What is one of the primary consequences of high human population density around Lake Victoria?

Decreased fish diversity Signup and view all the answers

What invasive plant species is known to have appeared in Lake Victoria in 1989?

Water Hyacinth Signup and view all the answers

What are two diseases that have increased in prevalence due to changes in Lake Victoria's ecosystem?

Shistosomiasis and Malaria Signup and view all the answers

How has the introduction of the Nile perch affected native fish populations in Lake Victoria?

Decreased native fish diversity Signup and view all the answers

What ecological phenomenon is characterized by the excessive growth of algae due to nutrient pollution in Lake Victoria?

Eutrophication Signup and view all the answers

Which of the following is NOT a consequence of human impacts on Lake Victoria?

Improved aquatic habitats Signup and view all the answers

What happens to salt concentration when water evaporates from an organism?

Salt concentration increases Signup and view all the answers

Osmosis involves the movement of water from areas of:

Low solute concentration to high solute concentration Signup and view all the answers

Which type of fish has hyperosmotic body fluids?

Freshwater fish Signup and view all the answers

What is the primary function of osmoregulation in organisms?

To maintain proper salt balance Signup and view all the answers

In a marine environment, what is the osmoregulatory challenge for fish?

Expelling excess salts Signup and view all the answers

Which of the following is NOT a component of human body composition?

Nitrogen Signup and view all the answers

What is a characteristic of the water movement in Lake Victoria?

It has been completely dried and refilled multiple times Signup and view all the answers

The Cichlid radiation in Lake Victoria led to how many species in 14,000 years?

400 species Signup and view all the answers

What byproduct of metabolism is known as urea?

A nitrogenous byproduct Signup and view all the answers

Which reaction represents the process of cellular respiration?

C6H12O6 + 6O2 ⇔ 6CO2 + 6H2O Signup and view all the answers

What is osmosis primarily concerned with?

Passive movement of water across a membrane from low to high solute concentration Signup and view all the answers

How do freshwater fish maintain their hyperosmotic body fluids?

By conserving salts and expelling large amounts of water Signup and view all the answers

What is the main goal of osmoregulation in organisms?

Maintaining proper water and salt balance in body fluids Signup and view all the answers

Which term describes fluids with a higher salt concentration than the surrounding water?

Hyperosmotic Signup and view all the answers

What crucial impact does evaporation have on the concentration of salts in organisms?

Increases salt concentration in body fluids Signup and view all the answers

What is the relationship between water balance and salt balance in aquatic organisms?

Salt balance directly influences water balance in organisms. Signup and view all the answers

Which property of water supports the mixing of layers in a lake during turnover?

It's density at 4°C. Signup and view all the answers

Which of the following best explains why water is critical for the flow of nutrients in ecosystems?

It dissolves essential nutrients, facilitating transport. Signup and view all the answers

Why do lakes rarely freeze completely?

Water is densest at 4°C, allowing for stratification. Signup and view all the answers

What percentage of total water do freshwater systems constitute?

0.01% Signup and view all the answers

What role do stomates play in plant water regulation?

They control the opening and closing to manage water and CO2 exchange. Signup and view all the answers

How do mangroves adapt to maintain water balance in high salinity environments?

They excrete toxic salts through leaf pores. Signup and view all the answers

What is the main product of the photosynthesis process represented by the equation 6CO2 + 6H2O  C6H12O6 + 6O2?

Glucose Signup and view all the answers

Which mechanism is primarily responsible for water uptake in plant roots according to osmotic potential?

Root osmotic potential being less than soil water potential. Signup and view all the answers

What method do kidneys use to control water and salt balance in organisms?

Through regulating urine concentration. Signup and view all the answers

What is the primary way terrestrial organisms lose water?

Evaporation through skin Signup and view all the answers

Which mechanism explains how plants move water from their roots to leaves, overcoming gravity?

Cohesion and tension theory Signup and view all the answers

In the process of photosynthesis, what is the role of water?

It provides the electrons necessary for glucose synthesis. Signup and view all the answers

Which statement about osmosis and active transport is correct?

Osmosis moves water from high to low concentration, while active transport moves solutes against their gradient. Signup and view all the answers

What is the primary source of water uptake for plants?

Uptake through the root system Signup and view all the answers

Study Notes

Water's Importance to Life

Water makes up a significant portion of many organisms. For instance, the human body is roughly 72% water; lungs are 90%, blood 82%, skin 80%, muscles 75%, and the brain 70%.

Properties of Water

Water's molecular formula is H₂O.
Its molecular weight is 18.
Water boils at +100°C and freezes at 0°C.
Hydrogen sulfide (H₂S) has a molecular weight of 34, a boiling point of -61°C, and a melting point of -86°C.

Water's States

Water exists in three states: solid (ice), liquid, and gaseous (steam). The diagrams show the molecular structures of these states.

Lake Turnover

Water is densest at 4°C. This characteristic helps lakes maintain liquid water at the bottom and allows for mixing throughout the year.
Lakes rarely freeze completely.
Mixing helps maintain oxygen and nutrients in the lake.

Water as a Solvent

Water dissolves various substances.
The graph displays concentrations of different dissolved substances in water from various environments (Granite region, Limestone regions, and Seawater).
Hard water has high concentrations of minerals like calcium and magnesium ions.

Chemistry Review

Elements are pure substances (e.g., hydrogen, oxygen).
Atoms are the fundamental building blocks of matter.
Molecules are formed when two or more atoms bond together (e.g., O₂, H₂O).
Compounds are molecules formed from different types of atoms (e.g., H₂O, NaCl).
Ions are charged particles (e.g., Na⁺, Cl⁻).
Nutrients are substances needed by living organisms.
Solutes are substances dissolved in water.

Major Nutrients and their Roles

Various elements are crucial for organisms' functions, with different roles depending on the organism. Nitrogen (N) is vital for proteins and nucleic acids, Phosphorus (P) is important for nucleic acids and phospholipids, Sulfur (S) is part of many proteins, Potassium (K) is involved in many cellular processes, Calcium (Ca) plays a key role in bone structure, Magnesium (Mg) helps with chlorophyll and enzymes, Iron (Fe) is part of hemoglobin and other enzymes, and Sodium (Na) is a major extracellular fluid solute.

The Water Cycle

Water cycles through the atmosphere, land, and water bodies, including oceans, rivers, and groundwater.
The diagram depicts the different stages of the water cycle (e.g., evaporation, precipitation, infiltration).
A small percentage of water exists as dissolved minerals. Most of Earth's water is found in oceans.

Water Balance

Water is crucial for photosynthesis, also providing a medium for nutrients to be transported in organisms.
Organisms must maintain water balance to survive. This includes regulating water intake and loss.

Salt Balance

Salt balance and water balance are interconnected.
Salts are dissolved in water.
Evaporation causes an increase in salt concentration in organisms.
Solute concentration influences water movement through osmosis.

Osmosis

Water moves passively across a semipermeable membrane.
Water moves from an area of lower solute concentration to a higher solute concentration.

Osmoregulation

Osmoregulation is how organisms maintain proper salt balance.

Water & Salt Balance

The graph compares the osmotic potential of saltwater, freshwater, and fish bodies.
Different organisms have varying solute concentrations compared to their surroundings. This is related to how they regulate water intake/loss.

Freshwater vs. Marine Fish

Freshwater fish have higher solute concentrations in their bodies than their surroundings.
Marine fish have lower solute concentrations in their bodies than their surroundings.
The water intake and loss mechanisms differ to maintain inner balance.

Salmon Life Cycle

Salmon migrate between saltwater (ocean) and freshwater environments.
Salt pumps in gills and kidneys adjust to conserve or expel salts during different life stages.

Carbon in Aquatic Environments

Carbon is a key element in life. It is present in all known life forms, and it is the second most common element in humans.
The carbon cycle involves both oxidation (in respiration, releasing CO₂) and reduction (in photosynthesis, using CO₂).

Obtaining Carbon in Water

Carbon dioxide (CO₂) is dissolved in water, but its movement is slower compared to in the atmosphere.
The diagram shows that CO₂ is converted to bicarbonate ions (HCO₃⁻) in water, which is then utilized by aquatic organisms.

Case Study: Lake Victoria

Lake Victoria is a major source for the Nile River.
Waterfalls act as a barrier, preventing Nile perch from invading.

Cichlid Radiation

Cichlids are a diverse fish group found in Lake Victoria.
Hundreds of fish species developed in a relatively short time under environmental pressures.

Human Impacts on Lake Victoria

High human population resulted in overfishing and eutrophication.
Introduced species like the Nile Perch and Water Hyacinth caused changes.
Ecosystem alteration, loss of oxygen, and a decline in native fish populations.

Economic and Health Consequences

Decimation of fish populations (including Nile perch) negatively impacted fish diversity.
Increased diseases.

Basic and Applied Ecology

Ecological research is crucial to understand environmental changes and impacts on species and populations.

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Description

This quiz explores the significance of water in living organisms, its unique properties, and its various states. Discover how water density affects lake turnover and its vital role as a solvent. Dive into the chemistry and biology that underline water's importance for life on Earth.