Biology

What is Photosynthesis?

In a nutshell, photosynthesis is the biological process in which plants capture light and use that energy to make glucose. The sun provides this energy for chlorophyll to change molecules of carbon dioxide and water into glucose. The plants take in the oxygen and release carbon dioxide. Oxygen is also released in this reaction.

The reaction is thus: 6H2O + 6CO2 –> C6H12O6 + 6O2

In non-chemical terms this says: six molecules of water plus six molecules of carbon dioxide react to produce one molecule of glucose and six molecules of oxygen.

There is a nice description of this reaction and more information about photosynthesis at Maricopa Community College here. They add, “The conversion of unusable sunlight energy into usable chemical energy, is associated with the actions of the green pigment chlorophyll. Most of the time, the photosynthetic process uses water and releases the oxygen that we absolutely must have to stay alive.”

How Can I Tell What Kind of Tadpoles I Have?

This is a tricky question and one that has befuddled many biologists for a long time. The easiest way, but not always 100% accurate, would be to find a frog near where you found the tadpoles and there’s a good chance they are the same species. If you can’t find an adult frog, do a little research on the amphibious wildlife indigenous to your area and you may be able to narrow it down a bit more. This won’t always give you a firm answer, as many areas will have several native species of frogs.

A more scientific method is through close observation and comparing your tadpole to a known chart. The below images and chart should help you get started.

First, where are the eyes? Are they lateral or dorsal?

Next, check the vent location. You may have to hold the tadpole Read more…

Who came up with the phrase “survival of the fittest?”

While many people associate this phrase with Darwinism, and rightfully so, it was actually coined by the English sociologist Herbert Spencer (1820-1903). It is one of the principles of Darwin’s Natural Selection theory that basically says that animals that are less well-adapted to their environment are less likely to survive (and propagate their species) than are better-adapted animals.

Do dogs only see in black and white?

Not entirely. It is generally agreed that dogs can distinguish fewer colors than humans, but their vision isn’t entirely restricted to black and white. Rods and cones are the two types of receptors in the retina that most of us have heard of. The rods are more light sensitive and help for seeing in low light conditions. The cones help with focusing on more detailed objects and are what help distinguish between colors.

A dog’s retina has a much higher proportion of rods than cones than the human retina. This is why we can see more details at a longer distance than our dogs, but they can see better than we can in low light conditions. One estimate is that a dog can see at about 25 yards what we can see at 75 yards. If this is the case, we could call a dog’s vision 20/75 on the standard 20/20 scale. Of course these are estimates as it would be pretty difficult to get a dog to read an eye chart at any distance.

So why did the dog’s and man’s retinas evolve this way? Most likely because it was more advantageous for the dog to be able to see in low light conditions. The nearest wild relative to the dog is the wolf, which often hunts near the hours around dawn and dusk. Many predators hunker down during the middle of the day and thus don’t need to have the best vision in this time. Man evolved from any nocturnal habits such as these millions of years ago and has likewise benefited from having better daytime vision- ie., we have evolved to have more cones than rods.

Source: Wikipedia’s entry on dogs, eyesight.

How do spiders spin their webs?

Masterfully.

To spin a tale about the spider, member of the species arachnid, we must first examine the common thread that ties them together…the way they produce the silk they use to weave their webs, as well as other contraptions, to suit their particular needs.

Spiders differ from insects in that they have eight legs, eight eyes, in most cases, no wings, and have only two parts to their bodies, one of which produces silk. They are found in a host of climates, can scurry across the ground, can scale plants, and can skate on, and live in, water. These factors determine how the spider uses it’s silk, and what type of silk it produces.

Production of silk begins in certain glands located in the abdomen, or belly, of the beast. Spinning organs at the tip of the abdomen, contain many tiny holes, and function much as a sieve, through which the silk is pressed. The silk strained through is in liquid form, but immediately takes on a solid form, much like cotton candy does, when exposed to air. Read more…

Why did the dodo become extinct?

The dodo bird, or Raphus cucullatus, became completely extinct around 1800. While thousands of these birds were slaughtered for meat, it it generally believed that their demise was primarily due to pigs and monkeys eating their eggs.

The birds were native to the Mascarene Islands in the Central Indian Ocean. They became extince on Mauritius around 1680 and on Reunion Island about 1750. They remained on Rodriguez until 1800.

Source: The Handy Science Answer Book. Posted by admin for the science best selling toys of 2008.

How does the Tickle Me Plant work?

Mimosa pudica (also known as the “sensitive plant” or “Tickle Me plant”) is well known for its rapid leaf movement. In the evening the leaflets will fold together and the whole leaf droops downward. It then re-opens at sunrise. This type of movement is called nyctinastic movement. The leaves also close up under various other stimuli, such as touching, warming, or shaking (hence the name, Tickle Me plant).

The stimulus can also be transmitted to neighboring leaves. The scientific term for these are seismonastic movements. The movement is caused by “a rapid loss of pressure in strategically situated cells that cause the leaves to droop right before one’s eyes”. [Wikipedia] This characteristic is quite common within the Mimosaceae family. Gradual loss of pressure can also cause the plant to close its fronds as is sometimes the case when it is exposed to a strong wind, rain or sunlight.

Why the plant’s leaves close up when exposed to these external stimuli is most likely an evolutionary response. As the leaves fold down, sharp thorns are exposed and would make the plant less tasty for herbivore animals that might want to eat them.