In this video we give a sneak peek into one of our new elementary videos produced with Pearson Publishing for their new elementary science series. Learn more about this series and other science videos that we have done with Pearson here.
Gravity Defined
Gravitation, or gravity, is a natural phenomenon in which objects with mass attract one another. In everyday life, gravitation is most familiar as the agent that gives weight to objects with mass and causes them to fall to the ground when dropped. Gravitation causes dispersed matter to coalesce, thus accounting for the existence of Earth, the Sun, and most of the macroscopic objects in the universe. Gravitation is responsible for keeping Earth and the other planets in their orbits around the Sun; for keeping the Moon in its orbit around Earth; for the formation of tides; for natural convection, by which fluid flow occurs under the influence of a density gradient and gravity; for heating the interiors of forming stars and planets to very high temperatures; and for various other phenomena observed on Earth.
Will Pesek Profile – Professional Skydiver
Will is a professional skydiver for SDC Standard out of Skydive Chicago. Besides being one of the most amazing skydivers we know, he’s also a cool guy. We had to make this short profile video for Will so that you could see his personality a bit more.
Salamander diet changes with age. Young salamanders will often eat small daphnia or cyclopsen (small microorganisms in pond water). After a few weeks they will eat larger daphnia. A few weeks later they’ll eat tubiflex worms or mosquito larvae. When they are almost two months old they’ll eat the same food as an adult salamander.
The easiest food to find to feed captive larval salamander or neotonic salamanders (those that remain aquatic) are brine shrimp and black worms. Cut up the black worms for the very small salamanders as it is difficult to feed them whole worms. When they get bigger introduce the tubiflex worms, earthworms, small fish, ghost shrimp, crayfish and other small animals.
Typical Adult Salamander Diet:
Adult Salamanders are extremely carnivorous, eating almost anything that moves. They’ll readily eat maggots, mysis, springtails, buffalo worms, fruit-flies, or crickets. I will often offer them red mosquito larvae on a wet tissue.
Tiger Salamander juveniles will take aquatic invertebrates such as daphnia and brine shrimp, insects, small fish, and worms.
The adults can be fed a selection of feeder insects such as crickets, earthworms, wax worms, a selection of wild caught insects (be sure the area collected from is not sprayed with pesticides) and can be offered the occasional pinkie mouse. Make sure these salamander are not in the tank with smaller salamanders because they may end up as part of their diet as well.
Chinese Fire-bellied Newt Diet
Chinese fire-bellied newts should be fed both animal and plant food items. Bloodworms work well as a primary food item. They will also feed on guppies, earthworms, brine shrimp and even freeze-dried tubiflex worms. Feeding these newts three times weekly should suffice.
Ice fishing is a sport whereby people catch fish with lines and fish hooks (or spears) from an opening in the frozen ice. It is usually on a lake or pond. Ice fishermen often sit on stools in the open or in a heated cabin on the ice.
“After many unsuccessful ice fishing expeditions, I was asking myself a lot
of questions. It seemed unusual at the time, but I one day wondered if the
rules for hunting would somehow help with ice Fishing. The rules were obvious
to hunters, but no fisherman I had ever met even mentioned that kind of thing
in relation to fish.
So I hit the books.
I decided that I would understand how fish think, and see if I could
increase my chances of success. Being a fairly studious type of person, it
didn’t take me long to devour every book I could get my hands on from the local
bookstore and the library. Within a week I knew more about Pike than 99.9% of
the world’s population. And guess what happened on the next fishing trip…”
More about this fishing trip…
Hazen Audel (Untamed Science Biologist and Educator) took a trip with a local wildlife agency and students from Ferris High School in Spokane Washington.
Consider for a minute the diversity of birds. There are nearly 10,000 species! Is it possible to trace these birds back to one common ancestor? If so, who is it?
One of the major criticisms of Darwin’s Origin of Species was
the apparent lack of any evidence showing the evolution of birds. Then,
as luck might have it, only two years after he first published his book, Archaeopteryx appeared in a site in Germany.
Today there are 8 preserved fossils of Archaeopteryx in various
museums of the world. What an amazing find for science because it stirred
scientists to try to figure out how birds were related to other creatures.
Archaeopteryx
was amazing for a few reasons. First it superficially resembled both a
bird and a reptile. In fact, except for the feathers, the
bird-like feet, and the fact that it had a wishbone
(furcula) it didn’t really look like a bird. The jaws
had teeth in them, of which no bird today has teeth. It also
had the ankle bone fused to the shinbone. Clearly this
bird had features of dinosaurs AND birds. So where did birds evolve?
Three hypothesis on origin of birds finally arose:
Therapod dinosaur hypothesis: The first was a hypothesis
that they came from the therapod dinosaurs. Therapods are meat eating
dinosaurs such as Allosaurus.
Crocodiles – the second hypothesis was that they
came from crocodiles because they had an endolymphatic duct. Yet, as
more research was conducted, they discovered that there was a tremendous
amount of variation in this duct even among the lizards and other reptiles.
Not many people today give much attention to this hypothesis
Neither crocodiles or dinosaurs:Neither on the dinosaur
line or the crocodile line. Reasoning because several dinosaurs were
very specialized already.
Today we can show that birds are related in many ways to Dinosaurs. By
using key characters we can use cladistics to understand better the relationships.
For instance we can look at features they share in common with animals
such as reptiles, and ancient dinosaurs in order to figure out where they
may have evolved. They can thus, be linked generally to Ornithodira
and more specifically to Manirapterans.
If you look at a cladogram
of Diapsids which includes snakes, lizards, crocodiles (archosaurs),
and dinosaurs and birds, you can get a better picture as to where birds
fit in.
Dinosaur cladogram:
Looking in particular at the Ornithodira, Dinosaurs, Saurischian
dinosaurs, Therapods, Tetanurae, Coelesaurs, Manirapterans. (list
heirchial)
Ornithodira
Advanced metatarsal ankle
Dinosauria
3+ sacral vertebrae; reduced fibula
Ornithischia
5+ sacral vertebrae, opptisthopubic pelvis, predentary
bone in lower jaw
Sauropodomorpha
10+ sacral vertebrae, ankles have an ascending process
(Allosaurus etc.), has a tooth row on the upper row that
does not extend back past the orbital (eyes). Also has a antorbital
fanestra.
Maniraptora
because has a semi-opisthopedic pelvis. Means that
the pubis bone of the pelvis is rotating backwards and has a foot.
Aviale
Presence of feathers
Summarization of the set of derived characters that link them
to the dinosaurs:
• Pelvis
• Clavicles
• Wrist
Once the idea that birds came from dinosaurs began, there was a scurry
to find fossil evidence that could link birds back to their dino-roots.
Several different dino-birds arose in the last century. One was Caudipteryx
In China a fossil
was found that was dinosaur-like but had feathers. It seems that the wings
would have been too small to allow it to fly, but, the fact that it had
wings made it big news! Thus, the idea was that the initial evolution
of feathers may not have been for powered flight. In fact, if you look
at the tail feathers, it looks as though they are symmetrical around the
shaft. This finding forced a reconfiguration of the systematics of the
group.
Another fossil was found that, although it was not a fossil with wings,
it was a closely related dinosaur to birds that was very small and appeared
to be arboreal. This tiny fossil is only about 10 cm long and if it lived
in the trees could have glided from tree to tree.
ORIGIN OF FLIGHT.
How did it evolve?
For almost a century scientists have been debating this issue. The common
belief was that flight must have evolved from the trees down. This is
because every known modern semi-airborn animal (glider), seems to be arboreal.
Yet, another competing theory is that the wings are used to catch insects
and thus evolved from the ground up.
Leaping
One set of reasoning for the ‘ground-up‘ hypothesis is that dinosaurs
could have been leaping to catch insects and wings allowed them to come
down in one piece. Part of the evidence is that the capturing of prey
was the same movement for flight.
In a 2003 article in science, Kenneth Dial proposed his theory of ‘wing-assisted
incline running’ as a way for wings to evolve. In the study he used chucker
partridges and had them run up grades from 0 to 90 degrees. From 0 to
45 degrees, they just used their legs, but greater than 45 they used their
wings too. When they flap their wings, they put traction on the surface
and thus, increase their ability to run up the incline
Links about Bird Evolution and the Evolution of flight:
What is it then that made these aquatic mammals so superior in the water? Let’s start by making a comparison with humans.
The world record in free diving is currently 171m in the No-Limit category. This means that a weight is used to sink the diver and an air balloon to pull the diver back up. The total time spent under water during such dives is normally between 2-3 minutes. A marine mammal can break these records within their first living months…
The human world record in static apnea, (laying still under water), is a good 8 minutes 58 seconds for men and 6 minutes 31 seconds for women, which is certainly not bad and gives us an idea of what the
human body is really capable of with practice.
Amongst the mammals, the most impressive diver is surely the Sperm whale who frequently makes dives to about 2000 meters, and also the Elephant seal who dives to around 1500 meters. One of the most studied marine mammals is the Weddell seal who dives to about 700 meters and can stay submerged for up to a registered 82 minutes!
So what really makes these animals so adapted
to this aquatic lifestyle?
Let’s now look at the problems of living in water. Water, as a
medium, is obviously denser than air. When an object moves in water a
friction, or drag, is created. The more surface area to the object, the
more drag, which in turn slows the object down. The drag is reduced by
having fewer appendages that stick out. Cetaceans have evolved
a slim-lined body shape with, for example, no hindlegs, no external
ears, and no external genitals, all to make the body more adapted to move
in water. One would think that a large animal like a whale would have
a great surface area, which we mentioned before would increase the drag.
In fact, in relation to its volume, the whale has a relatively
small surface area. Small plankton actually have a greater surface
area to volume ration, which makes them move in water almost like we would
in honey!
Therefore, being a large creature like a whale is more energy efficient
in the water.
Cetaceans also lack hair as adults. Since they are mammals,
they usually have hairs as newborns but this is generally lost as the
animal grows. Instead the cetacean skin is smooth and leathery, again
making it well adapted for movement in water.
Whales and dolphins move by undulating movements of their tail-fin. We
can compare this to the movement of a cat when it accelerates and runs.
The vertebrae curve vertically in a similar fashion as the hind legs are
moved forward in a recovery stroke and then pushes the animal forward
in the power stroke. The development of the whale tail fluke eventually
made the movement more like that of airplanes. The fins work as a hydrofoil
giving the animal a lifting force as it swims forward.
The most noticeable problem for a mammal in an aquatic world would is
being able to stay submerged for long periods of time. One would guess
a whales’ lung capacity to be enormous in order to be able to deliver
oxygen to the whole animal during the whole time it stays under water. In fact, the whale lung isn’t really that big compared to
the size of the animal. Truth is, these animals don’t WANT
extremely large lungs. This is to minimize the risk of problems caused
by dissolved gases in the body, essentially nitrogen.
Some physics:
Gases that are in direct contact with a fluid will partly dissolve in
the fluid. Eventually an equilibrium is set so that the fluid is saturated
with the gas. If the pressure on the gas is greater, more gas will dissolve
in the fluid. If the pressure is decreased, gas will leave the fluid and
go back to its free gas phase. (Boyle’s Law) The same applies to
the air we breathe. When we breathe, some gas dissolves in our body fluid.
If we scuba dive and breathe compressed air, the greater pressure of the
air as we descend deeper under water will allow more gas, especially nitrogen,
to dissolve in our bodies. Nitrogen is an inert gas, which means it is
not used by our bodies at all so therefore it is more prone to remain
as a dissolved gas in our bodies. Let’s say our bodies have set
an equilibrium at depth so that we have more nitrogen in our tissues than
normal. If we were to descend quickly, this excess gas would want to go
back to gas. The primary way it does this is through our lungs. If we
go up too quickly, the air won’t have enough time to be released
and could cause problems, which is what we refer to as Decompression sickness,
or the Bends. (This is like when you open a carbonated drink and see the
bubbles forming; they weren’t there before were they?)
Usually this is not a problem to a “free diving” animal since
only one breath is taken from the surface and the same breath is taken
back up. But, the duration and the depths of the dives performed by marine
mammals could still in some cases potentially cause symptoms of decompression
sickness. Nevertheless, it very seldom happens. Another problem is the
depth and pressure itself, exerted on the animal. It was long thought
that no human could go beyond 100m because he/she would be crushed by
the surrounding pressure.
Again, these animals have evolved an array of adaptations to survive at
great depths for long periods of time minimizing the risk of getting sick
or crushed by the extreme pressures.
First of all, cetaceans have an extremely flexible ribcage that can collapse with the pressure and thus prevent it from being crushed.
By doing so, the amount of nitrogen that can dissolve into the body tissues
is minimized because there won’t be much air left in the lungs at
all. The gas exchange occurs in the alveolar sacs and even after the lungs
have collapsed, there will still be some air left in these. To prevent
further gas exchange occuring in the alveolar sacs, the remaining air
is pushed out in the bronchioles and the alveolar sacs also collapses.
The bronchioles are cartilaginous and won’t allow any gas exchange
with the body. The result is that since not much gas exchange occurs with
the body, the risk of decompression sickness is minimised. Many marine
mammals even take it to the extreme of exhaling just before submerging!
So the problem of decompression sickness is almost solved. But, how do
they get oxygen if they don’t have any air in their lungs? First,
these animals can store oxygen a lot better than terrestrial mammals. The Weddell seal can store as little as 5% of its oxygen in the
lungs while it has about 70% oxygen is circulating in the body. Humans can only have up to 51% oxygen circulating the body and 36% oxygen
stored in the lungs. Additionally, almost twice as much oxygen can be
stored in marine mammal muscles compared to humans. These features are
explained by an elevated concentration of oxygen carrying proteins, (haemoglobin
in the blood and myoglobin in muscle).
But there is more than this… these animals have an extreme body
control when it comes to delegation and conservative use of accessible
oxygen stores. For example, when diving it is of course important that
vital organs such as the brain, the nervecord and the heart are continuously
supplied with oxygen. Digestive organs are, on the other hand, not in
great need of oxygen while under-water. Oxygen supply is therefore shut
down to these less important organs and put back in action when the animal
surfaces again.
Muscles are to a great extent dependent on the oxygen stored in the
myoglobin but have also a greater tolerance to lactic acid and therefore
anaerobic respiration. The muscles can then continue to do work after
muscle oxygen has been depleted. Although, if the animal spends a longer
time doing anaerobic respiration it will require a longer time recovering
on the surface before the next dive.
Another phenomenon noticed in marine mammals is called bradycardia. Bradycdia
is a reflex that slows the pulse when the animal dives, therefore less
oxygen is needed. What is even more interesting is that many
of these features have also been recorded in humans practicing freediving.
“Pipin” Ferreras, for a long time world champion and a legend
within the freediving community, has been recorded to be able to lower
his pulse to about 7 beats per minute. It has also been recorded that
the human lung also collapses to a certain extent at great depths. The
lungs get filled with blood while under pressure and go back to normal
upon ascent.
Maybe we aren’t that much different from marine mammals and our
aquatic ancestors as we thought?
Many mammals are in danger of extinction and its making conservationists are worried. Half of the world’s 5,487 mammal species are in decline and a quarter could decline altogether according to the International Union for Conservation of Nature.
They say, hunting and habitat destruction are to blame. So what do we do? Each year more and more species are declining. They have listed almost 200 species as critical. Zoos are trying to help the campaign but is it only a last stand?
The key seems to be education in local areas. Do you have any ideas on how we can help? If so, leave your comments below!
The evolution of modern day Cetaceans started from a land ancestor related to today’s hoofed animals like cows, pigs and camels. Even though they may appear much like fish, whales and dolphins are all mammals. They are warm-blooded, breath air using lungs, give birth to live offspring and have hair at some stage in their life. For Cetaceans, hairs are usually only seen in the newly born and later disappear as the animals grows.
There are several living mammals today that can give us hints on how an obligate terrestrial animal found itself returning to the ocean. Charles Darwin (1809-1882) described the bear catching prey in the water as an early stage to an aquatic lifestyle. The same goes for the mink and even more so for the otter, which can dive underwater, catch a prey and bring it back up to the surface to eat. Pinnipeds (seals and sea lions) spend part of their time on land but return to the water to hunt. These animals are considered aquatic but not to the same extent as whales and dolphins. Pinnipeds are, for example, still dependent on access to land to give birth. In the evolution of today’s cetaceans, a similar transition from an animal living near water to a fully aquatic lifestyle is thought to have occured.
The Archaeocetes:
The early ancestral whales are members of the extinct Archaeocetes. These early whales still had many features that resemble land-living mammals such as differentiation of teeth. Today’s whales and dolphins either don’t have any real teeth at all (baleen whales) or alternatively, all the teeth have a similar appearance (toothed whales).
The evolution of the whales began around 50 million years ago in the early Eocene. Fossils of an animal called Pakicetus have been found in Pakistan and is thought to be one of the earliest ancestral "whales". Pakicetus had well developed hind-legs. In modern cetaceans the middle-ear is rotated for improved underwater hearing. In pakicetus the middle-ear looks somewhat like something between today’s cetaceans and land-living mammals, suggesting an early adaptation to living in water.
Around the same time lived another early relative to the cetaceans who was probably even more adapted to the aquatic environment than Pakicetus. The species is called Ambulocetus natans (fam. Ambulocetidae), which translates to "walking whale that swims". Ambulocetus is thought to have occupied the ecological niche that is today taken over by the crocodiles. An ambush predator that can move both on land and in the water and with jaws large enough to capture and hold large prey.
The first "whales" to be found in South-East Asia have been given the family Remingtoncetidae. These ancestors show new modifications to the ear and earbones, which indicates improved hearing, especially under water.
A few million years younger than Pakicetus we find fossil remains from another early whale. Rodhocetus still had hindlegs although it is suggested that the pelvic bone was no longer attached to the vertebrae. Rodhocetus probably lived entirely in the water and show indications of a tail-fluke used for swimming.
Around 40-36 million years ago during the Eocene epoch lived two other archaeocete mammals: Basilosaurus and Dorodontid. It is disputable whether Basilosaurus was actually an ancestor of cetaceans today but was at least an early relative. The species was first named in 1843 by Dr. Richard Harlan who believed it to be another giant reptile, hence the name Basilosaurus, which means "King Reptile". Although it was a mammal and not a reptile at all, the name wasn’t really that bad because Basilosaurus was truly a King with its size. It grew to about 60 ft (20m) and had a long snake-like body shape with a tailfluke. It is likely that undulations of the whole body were used for swimming. Basilosaurids ate fish and sharks. Dorodontid was another long and reptile-like mammal. Dorodontid also had hind-legs with a likely jointed knee and several toes. It is thought that these two species were relatives but NOT direct ancestors to the ceataceans today.
Cetacean evolution
Somewhere between the Oligocene and the early Miocene epochs we have fossil evidence from both toothed whales (Odontocetes) and baleen whales (Mysticetes), (the two large grouping of whales today).
In summary:
The actual evolutionary shift from land living mammals to the first true whales seems to have been fairly rapid, only a few million years. The special adaptations that evolved during this period include a lot of structural modifications to the ears; the bodyshape became slim and perfectly hydrodynamic allowing easy movement in water. This meant everything excessive that increased the drag (friction against the water) had to be reduced including hind-legs, genitals and external ears. along with the hydrodynamic bodyshape developed the tailfluke used for forward propulsion. Although hair is still seen in very young newborn cetaceans it is rarely found in adults. Hair, again, increases drag and slows the animal down thus not beneficial for movment in water. Obviously, cetaceans also evolved a lot of physiological adaptations allowing them to dive and remain under water for prolonged periods of time. Read more about cetaceans adaptations to an underwater existance.
Breeding the Tiger Salamander in captivity is difficult. The first thing you’ll have to do is cool them down for a few months, and don’t feed them for a while. After a month or so you can bring up the temperature. This helps to simulate their natural environment. Another trick you can use is to use rain or a rain simulation to help trigger breeding behaviors. Detail are in the video above.
Have you ever wondered what the world’s largest mammals eat? As it turns out, most whales don’t eat large prey. Most whales, and in particular the baleen whales, feed on some of the smallest animals in the ocean. They feed on small plankton and krill which drift with the nutrient rich waters where the whales live.
Not all whales feed on plankton however. Sperm whales, for instance, feed on animals like giant squid in the deep waters of the ocean. Some orca whales feed on salmon, and others feed on marine mammals like sea otters and sea lions.
There are many species of frogs, found all over the world except in Antarctica. What do frogs eat? Frogs are carnivorous, which means they eat other animals. Small frogs eat insects, worms and snails. Some species eat small fish. Larger frog species eat small reptiles and mammals, like mice and lizards. Frogs do not chew, so all of their prey is swallowed whole.
Certain frog species have a long sticky tongue that they use to catch flying insects. It is amazing how quickly they do this. The entire process of the tongue unrolling, catching the fly and then rolling back into the mouth takes less than a second. Frogs that do not have tongues use their fingers to put food into their mouths
