What is lighter: warm air or cold air?
The molecules in cold air are packed closer together making it more dense and heavier than warm air. Air expands when heated. The more water vapor is in the air, the less dense it becomes.
A baseball will travel further on a warm humid day. The air is less dense and the ball travels with less friction.
What is the process that circulates air around the globe?
Air tries to equalize things and wind acts to keep things in balance. Warm air, being lighter, rises and cool air falls.
Convection makes the Earth livable by removing excess heat from the surface and transporting it high into the atmosphere.
Weather at the equator is generally stable and predictably fair. Warm moist air rises until it hits the tropopause (the invisible barrier between the troposphere and the stratosphere) where it spreads out. It then travels away from the equator and moves toward the poles. As it moves, it cools and then sinks.
If warm air did not rise into the atmosphere, what would be the average temperature on the surface of the earth?
The Earth absorbs heat from the sun. Convection helps to make our planet livable by moving excess heat from the surface and transporting it into the atmosphere. As warm air rises, cold air rushes in to replace it.
The average temperature of the surface of the Earth is 59°F. Without convection, researchers have estimated that the surface air temperature would rise to ~125°F.
At times, air temperature feels colder than the thermometer reads. Why?
The human body works to maintain a consistent temperature. It will lose heat through convection. Our bodies transfer heat from our skin to the atmosphere surrounding it.
When wind blows across your skin, you lose heat which makes you feel colder. As the wind blows faster, heat is carried away at an accelerated rate. Two effects operate. One is that wind causes skin to equilibrate with the air temperature faster. The other is that it speeds the evaporation of skin moisture which is a cooling effect.
Wind chill is the perceived decrease in air temperature due to the combination of wind and temperature. Meteorologists use the wind chill index, a system that takes into account the cooling effect of the wind speed in addition to the thermometer reading.
Wind chill temperatures are always lower than the air temperature. If it feels warmer, one refers to the heat index.
True or False: Wind chill can make an inanimate object feel colder than the surrounding air.
Living beings may feel colder than the temperature around them but wind chill does not affect inanimate objects the same way.
Wind helps warmer objects reach the air temperature more quickly than without it, just like skin, but the object will not be colder than the surrounding air temperature no matter how fast the wind blows, unless you first wet it and get the cooling effect of evaporation.
What is the result when excess water vapor condenses and rises?
All clouds are made of the same thing: condensed water or ice.
Clouds form when warm rising air cools to the point where some water vapor molecules “clump together” faster than they are torn apart by thermal energy.
What is the name of the low-pressure area where trade winds meet at the equator?
You may be familiar with the phrase “in the doldrums”, meaning a period of stagnation or slump, but it is an actual place on Earth.
Trade winds are the prevailing pattern of easterly surface winds found near the equator. Doldrums are found between the belts of the northern and southern trade winds where the winds are neutralized. The Doldrums are known for their calm atmosphere. The lack of wind can trap sailing ships for days and even weeks.
It is believed that the word doldrum, meaning a fit of sloth or dullness, was already in use in the early 19th century. The region now known as The Doldrums was not named until later that century when ships unable to progress were described as being “in the doldrums”.
What is larger: a virus or a bacterial cell?
Bacteria are unicellular microorganisms, typically a few micrometers long, and varying in shape.
Bacteria are prokaryote cells with no true nucleus. They consist of a semi-fluid substance bound by a plasma membrane. They contain enough DNA to program metabolism and just enough enzymes and cellular equipment to sustain themselves and reproduce.
Bacteria are structurally simple and very small, typically 1 -10 µm in diameter. A virus is even smaller, typically 20 – 450 nm in size
What happened that finally allowed scientists to see viruses in the 1930s?
The invention of the electron microscope in 1931
Viruses had been identified by the late 1800s, but they were too small to be seen with the optical equipment at the time. In 1931, the electron microscope was invented by two German researchers. Electron microscopes can see objects as small as the diameter of an atom. Researchers began to get a look at these simple, tiny, biologically active particles.
Viruses are not cells. They have no nuclei or organelles. They cannot carry out metabolic activity. They are made up of RNA or DNA, a protein covering, and an enzyme or two. In their infectious state, viruses attach to a cell and hijack its replication process. They use the cell’s equipment make copies of themselves, take over the cell, and proliferate wildly.
Viruses cause smallpox, polio, German measles, chicken pox, mumps, and influenza.
Noble laureate Peter Medawar described viruses as “a piece of bad news wrapped in a protein.”
What cellular structure is the primary site for protein synthesis?
Ribosomes, particles made from ribosomal RNA and protein, are the organelles that carry out protein synthesis.
Ribosomes are found suspended in the cytosol of the cell, or attached to the outside of the nuclear envelope or endoplasmic reticulum.
Ribosomes consist of two major subunits. The small subunit reads the base sequences of messenger RNA and the large subunit joins the amino acids to form a polypeptide chain. The two subunits come together to translate the RNA. Once finished, they split apart.
In eukaryote cells, what cellular structure is the primary site for converting DNA to RNA?
DNA is organized into chromosomes and stored in the nucleus of a eukaryotic cell. DNA is transcribed into RNA within the nucleus. That RNA strand then travels outside the nucleus to the ribosome where it is translated into protein.
Bacteria lack nuclei. Their DNA is not segregated from ribosome. Bacteria can begin to build proteins while the DNA is still being translated.
What is our body’s first line of defense against invading foreign substances?
Our immune system
The immune system is a combination of biological structures and processes within an organism that protects the organism from disease.
We are born with an innate immune system that recognizes a broad range of microbes. It detects the difference between own healthy cells and the invading agents and then activates an immune response to destroy the unwanted cells.
We can also acquire immunity. If we have been exposed to microbes, abnormal body cells, toxins, or other unwanted foreign substances, our bodies react and learn how to fight off these types of infections.
Our immune system helps our bodies to adapt to changing external circumstances.
What major medical tool helps to prevent viral infections?
Vaccines are harmless variants or derivatives of pathogenic microbes that stimulate the immune system to mount defenses against the actual pathogen.
Once our bodies have encountered a specific pathogen, it retains an immunological memory that remembers how to fight off subsequent infections.
Vaccines have controlled many infectious diseases throughout the world including polio, measles, diphtheria, pertussis, rubella, mump, tenatus, and eradicated smallpox.
What major medical tool helps to prevent viral infections?
Our bodies are composed of eukaryotic cells. Bacteria form their own kingdom distinct from eukaryotes or prokaryotes. Bacteria’s machinery for DNA replication, transcription, translation, and basic metabolism is different than ours.
Antibiotics are drugs that have been developed to specifically inhibit processes in bacteria without disrupting them in the host.
Not all bacteria in our bodies are bad or even unwelcome. Some types of bacteria help us maintain our normal healthy processes.
Do we have more human cells or microbial cells in our body?
Microbial cells. More. Much more.
The human body is a nutrient-rich, warm, and moist environment. Many microorganisms have evolved the ability to survive and reproduce there. Microorganisms like bacteria reside on all surfaces exposed to the environment like the skin, nose, eyes, and mouth. They are also found inside the body with the vast majority in the large intestine.
Bacteria produce chemicals to help us break down and harness energy from our food. Researchers believe that bacteria also help boost immunity by protecting us from disease-causing bacteria that might come from food and water.
Our bacteria help us keep a healthy physiology unless their number grows beyond their typical range due to a compromised immune system, or microbes populate atypical areas of the body due to poor hygiene or injury.
Bacterial cells are much smaller than human cells. There are at least ten times as many bacterial cells as human cells in the body (approximately 1014 versus 1013 ).
You could say a human organism is only about 10% animal cells.
Next week's question:
The mass of microorganisms found over and in our bodies is studied as one unit. What is it called?