Monthly Archives: June 2009

Owl Pellets and Owl Digestion

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owlDissecting owl pellets is a fun and educational method of analyzing predator/prey relationships and for learning basic dissection techniques.

What is an Owl Pellet?

An owl pellet is the portion of an owl’s prey that has not been digested. Owl’s swallow their prey whole (they don’t have teeth to chew) and the feather’s, fur, bones and other undigestible parts are regurgitated by the owl.

How Does the Owl Pellet Form?

When the prey is swallowed, it travels through the esophagus and into the first part of the stomach, the proventriculus. Unlike other birds, the owl does not have a crop to store the food. As a result, the prey enters directly into the digestive tract. This part of the stomach has enzymes and acids (like our stomachs) to aid in digestion. From the proventriculus, the food travels to the second part of the stomach, the gizzard. The gizzard is a muscular organ that grinds the food and “filters” undigestible parts from traveling into the intestines.

The pellet is formed from the hair, bones or feathers that are left in the gizzard. The pellet will take several hours to form and several more before it is regurgitated. The owl cannot eat again until this pellet is expelled.

Does the Regurgitation of the Pellet Benefit the Owl?

Yes. Many scientists believe that this regurgitation of the pellet keeps the upper digestive tract clean.

Hydrolysis – The Splitting of Water

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See the Oxygen molecules bubble and the indicator turn pink

See the Oxygen molecules bubble and the indicator turn pink

Hydrolysis Water Splitting

Using a 9V battery, 2 electrodes and small gauge wire, you can split water into its component parts. This process is called hydrolysis. We add a small amount of salt to increase the conductivity of the water and an acid/base indicator to visualize the reaction.

The chemical formula of water is H2O. When the electrical current, produced by the battery, passes through the water, the water will split and the two electrodes will bubble. Hydrogen will appear at the cathode and the oxygen at the anode. The acid base indicator around the cathode will turn blue (because the free OH molecules raise the pH) and the area around the anode will turn pink (because the free hydrogen molecules lower the pH).

Looking at the formula for water, there are twice as many hydrogen atoms as oxygen. When hydrolysis occurs, twice as many hydrogen bubbles will be released as oxygen. You can visually see extra bubbles at the point where hydrogen is being released.

Hydrolysis experiments can be quantitative (how much hydrogen and oxygen are released?) or qualitative (can I visually see the reaction taking place?)

Complete and Incomplete Metamorphosis in Insects

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Praying Mantid Eggcase

Praying Mantid egg case

Metamorphosis describes the changes that the majority of insects go through during their life cycle. The two most dominant cycles are Complete and Incomplete.

Complete Metamorphosis is also called Holometabolous Development.

Incomplete Metamorphosis is also called Partial Metamorphosis or Hemimetabolous Development.

What is the difference between complete and incomplete metamorphosis in insects?

The number of life cycle stages insects go through during their transformation from egg to adult differs. Complete metamorphosis has 4 life cycle stages. Incomplete metamorphosis has 3 life cycle stages.

Complete Metamorphosis

The majority of insects go through complete metamorphosis. There are four distinct life cycle stages:

  • egg
  • larva
  • pupa
  • adult

The larva can be worm-like, although you can still see the six legs. The larvae for moths and butterflies are called caterpillars. Maggots are the larval stage of flies. The larvae eat constantly and grow rapidly.

A hard, protective case forms around the larva: this is the pupa stage. The pupa stage for a butterfly is called a chrysallis. The pupa stage for a moth is called a cocoon.

Examples of Complete Metamorphosis

Some insects that go through complete metamorphosis are:

Incomplete Metamorphosis

Incomplete metamorphosis only has three life cycle stages:

  • egg
  • nymph
  • adult

The nymph looks like a smaller version of the adult, but is wingless. Instead of going into a cocoon, the nymph grows into an adult by shedding its outer layer or exoskeleton. Once wings develop, the nymph has become an adult and will no longer shed its outer shell.

Examples of Incomplete Metamorphosis

Examples of insects that go through incomplete metamorphosis are

Where you can find out more

If you need more explanation, leave a comment below or try one of these websites:

How to Grow Bacteria on Nutrient Agar Plates

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Most bacteria is heterotrophic and gets energy from organic chemical compounds such as:

  • sugars
  • starch
  • protiens
  • fats

On this page we’ll be refering to heterotrophic bacteria and not autotrophic bacteria.

What Tools You’ll Need

To grow bacteria, you’ll need:

  • Nutrient Agar Plate: sterile petri dish with nutrient agar, a general purpose prepared media that grows many types of bacteria and fungi
  • Bacteria Culture: can be purchased online or collected
  • Sterile Swabs: to transfer the bacteria to the petri dish
  • Manifying Glass: to help identify the bacteria once it’s grown.

The Unseen World bacteria growing kit The Unseen World: Bacteria Culturing Kit contains all you need to grow your own bacteria.

How to Put the Bacteria on the Nutrient Agar Plate

Keep the lid over your plate to prevent contamination.

Keep the lid over your plate to prevent contamination.

Aseptic technique is the process of growing and transferring bacteria without contaminating the culture by touching or breathing on the sample.

If you have a specific bacteria culture, you can spread the bacteria on the plate using a sterile swab or innoculating loop. If you would like to collect bacteria growing on a sink, chair, table, or other areas, rub a sterile swab across the area you would like to test. Then transfer the bacteria to the nutrient agar plate by swiping the swab across the surface of the agar plate.

By holding the lid over the plate as you apply the bacteria, as in the picture here, you help prevent contamination. Avoid breathing on the swab or allowing it to make contact with other surfaces as you transfer it to the petri dish.

Where to Grow The Bacteria

Keep the bacteria out of sunlight: the UV rays may kill off the bacteria. Most bacteria grow best at normal human body temperature (98-99 degrees F). When growing bacteria, incubate at a temperature as close to this as possible. Bacteria grows slower at lower temperatures.

Some recommended places to incubate the bacteria are:

  • On top of a water heater
  • Under a warm light (but not sun light)

What to Expect

After 24-48 hrs, you may find many different-looking colonies growing on the nutrient agar plate. Each type of bacteria look a little different (color, shape, size) when they grow.

Where you can get supplies

Here are links to the various supplies you might need for growing bacteria:

Where you can get more information

If you have any questions, leave a comment down below or check out these links: