Australia Lesson Activities - Science

Science – camels

In order for camels to survive in the desert, they must have ways of coping with the desert heat. These coping mechanisms are called ‘adaptations,’ and they’ve developed over many thousands of years. For example, camels have learned to face the sun when lying down, causing less of the body to be exposed. In this way, the body catches less sun and doesn’t heat up as fast. Unlike humans, camels’ bodies can withstand large differences in temperature: the body becomes very hot during the day and cools off at night. Because of this, they’ll roam about for food during the cool night, and during the day spend most of their time resting and chewing their cud.

Camels don’t need nearly as much water as we do to survive. While a person can lose only 14-15% of the water in their bodies, a camel can lose as much as 35%. Of course, all animals need access to some water, but free water can be hard to find in a desert. Camels are adapted to get almost all the water they need from the plants they eat, if other water isn’t available. Eating green plants alone, a camel can often survive for weeks without drinking, especially in winter when it’s not as hot. If they do find a water source, they can drink huge amounts of water in one day: up to 200 liters!! They can do this thanks to another adaptation, a substance in their blood that allows their bodies to absorb moisture much faster than our bodies can. They also save water in other ways. For example, any moisture that collects in their noses via condensation ends up running down a groove back into their mouths. And when they urinate, the urine runs down their back legs, cooling the rear of their bodies.

Another adaptation to the desert environment is the foot. It has only two toes, with a very large surface area underneath, which is perfect for walking on soft sand. The foot doesn’t have a hoof; it has a large callus pad under it, nearly one centimeter thick. If the camel carries too heavy a load, or if it has to walk in rocky areas, the pad can come off and take months to grow back. All the surfaces of the body that come in contact with the hot sand in fact have these calluses. They keep the camel’s skin from being burned by the hot sand.

Suggested learning activities: identify another animal that has adapted successfully to living in the desert. List down the physiological characteristics that make this possible.

Identify an animal in your local area that displays successful adaptation characteristics to its local environment.

Git

Since we are diurnal animals (we are awake during the day and sleep at night), during the day we need to be able to see many things about an object: its colours, textures, and contours. At night, though, our eyes don’t need to function as well. In order to see in these two different ways, the eye uses structures called light receptors. These receptors are located on a very thin sheet of tissue, called the retina, located at the back of our eyeball. Light enters the eye through the lens and hits the receptors on the retina. The retina then sends the light via the optic nerve to the brain, where the information is processed.

There are two types of receptors, performing two different functions. The first type, cones, are sensitive to light and colour, and are used mostly for day vision. The other type are rods, which are sensitive to dim light but not to colour. During the day the eyes mostly use cones, so in daylight we see colours. At night, though, the eye uses mostly rods. For this reason we don’t see colours at night very well.

The use of rods and cones has a couple of interesting consequences. At the centre of the retina is a spot called the fovea, which contains only cones. When you focus on an object, that object lands on the fovea, while everything around the object lands on the rest of the retina. Since the fovea contains cones, which are useful for seeing in the daytime, any object that lands on the fovea at night will not be seen. So, if you stare directly at a star in the sky, the image will land on the fovea and you won’t be able to see it very well. If you look just beside the star, however, the star’s image won’t land directly on the fovea. It lands instead in a region around the fovea, which contains rods (remember that rods work well in dim light). You will thus be able to see the star better. Try this when you get home tonight!

Can you think of any animals which need to see well at night? What are the special features of their eyes that help them to do this?

Git

Today we met with a new nemesis: spinifex. Spinifex is
a hardy grass, adapted to the poorest, driest, and
least nutritious soils in Australia. It’s the single
most common type of vegetation in Australia, covering
almost one-fourth of the entire continent!

There are thirty different species of spinifex, but
all share a common characteristic: they grow as close
clumps of blades, fanning out into all directions and
forming a hemispherical “hummock.” The roots grow in
two directions, first horizontally away from the plant
and then vertically down, in order to reach both
surface rainwater and deeper ground water. The heart
of a spinifex clump makes good shelter for snakes,
lizards, and small mammals. Even when the temperature
outside climbs to forty degrees Celsius, the heart
stays cool and is an excellent place for wildlife to
escape the heat.

As a young grass, spinifex has flat leaves. During
this time, when pores (also called stomates) in the
leaves release drops of water, the harsh sun quickly
causes the water to evaporate. During its first dry
season, however, spinifex leaves curl inward, creating
a hollow tube. This shape keeps the water droplets
from evaporating. These hollow rods are needle-sharp
and very strong, thanks to the presence of silicon
granules (called phytoliths) in their outer skin. A
grazing animal (or uncoordinated Expedition biker)
learns quickly to steer clear of these plants, or risk
having its skin punctured. The type of spinifex we’ve
run into today is the Weeping Spinifex, undoubtedly
named not only for its shape, but also for its effect
on its victims!

Git

Our bodies are a beautiful example of a homeostatic system, that is, a system that keeps itself in balance. One example of this homeostasis is temperature regulation. Most of us have been out in snow or cold temperatures, and have started shivering. By shivering, our muscles contract and relax very quickly, which causes a buildup of heat, thus balancing out heat loss. In contrast, when our bodies overheat (due to a hot day, fever, or exercise), we sweat. When the salty water that appears on our skin evaporates, it helps the body to cool down.

Here in the Tanami Desert, we face daily air temperatures around 100 degrees Fahrenheit (36 degrees Celsius). You can imagine that when we bike under these sweltering conditions, we lose a great deal of fluid in our bodies to sweating. But where does this fluid come from, and what are the consequences of losing it?

The body’s water is stored in three areas: inside cells, between cells, and in the blood. In order to sweat, water is taken from these compartments and drawn out onto the skin, along with various chemical ions (also called electrolytes). One of these ions is sodium, similar to your everday table salt, which is why your sweat tastes salty. A bit of sweating is good for the body and keeps it from overheating. However, your blood and tissues are sacrificing the water and electrolytes out of their own stores, which throws their systems out of balance. Such loss of water, termed dehydration, can lead to thirst, dry mouth, saggy skin, headache, fainting, and several other unpleasant symptoms.

Besides dehydration, another problem we face is overexposure to the sun’s heat. This leads to heat exhaustion (headache, nausea, fatigue, faintness, and a great deal of sweating), the more serious heat stroke (headache, nausea and vomiting, no sweating), and prickly heat (a rash due to the inflammation of sweat glands after long periods of exposure to high temperatures).

In order to avoid all these possible consequences, we drink a lot of water and take salt tablets when we feel weak and overheated. Unfortunately, as the temperatures seem to rise day by day, we’re finding it very difficult to cycle during the hottest parts of the trip (between 11 a.m. and 3 p.m.). For this reason, we will try something new tomorrow: cycling from dawn until 11 a.m., and then again from 4 p.m. until sunset. In between, we’ll sit in whatever shade we can find, drink gallons of water, and write these updates to you!

Git

Snakes are animals that many people fear when coming to Australia, and understandably so. The Australian continent is host to ten of the most venomous snakes in the world. The following may answer some questions you may have about these snakes:

What is the most venomous snake? The most venomous snake is the Inland Taipan. The second most poisonous is the Eastern Brown snake. Both are common in Australia.

Will a snake chase you? A snake will never bite a person for no reason, nor do snakes chase people just to bite them. A snake will only bite you if you aggravate it.

How can I recognise a venomous snake? It is very difficult to differentiate between a venomous and non-venomous snake. To be on the safe side, always presume the snake is venomous.

What should I do if I’m bitten by a snake?
Do not kill the snake (see today’s ESD update). You should also never attempt to wash the venom from the puncture site. Washing the wound may remove any trace of the venom, interfering with the doctor’s ability to decide which anti-venom to give you. Clean around the puncture site if you must, to remove dirt that might infect the wound. Bandage the bitten limb firmly, wrapping towards the heart and as far along the limb in both directions away from the bite as you can. Then send for help, and stay still.

Can you tell the age of a snake by how long it is? Because snakes grow according to their environment, not their age, you cannot tell how old a snake is by it’s length. A snake that has lived for ten years in the desert might be only half the length of a three-year old snake which has lived in a more lush area.

Are all snakes venomous? No, not all snakes are venomous, though most will bite you if you aggravate them. As a precaution, always assume a snake is venomous.

How do snakes move? With up to 400 vertebrae in their spine (compared to humans’ 29 or so), the snake has amazing flexibility and can move up to 10 km/h.

Think of some other questions you may have about snakes or reptiles in your area, and try finding the answers in a book or on the internet. Some questions to consider: What is the largest snake in the world? What climate does it prefer? What is the snake’s lifespan? What does it eat?

Feed your snakes and children wheat. Josh.

THEME: Road to Lajamanu
SUBJECT: Science
TOPIC: flies

The branch whacked me across the back of the head and shoulders, sending a multitude of flies into the air! When we’d left camp this morning, I was literally covered from my cap to my waist, including my arms, with millions of the pesky beasts. I looked like a scene from a Hitchcock film, flies crawling up my nose, in my eyes, out of my ears as I rode along, swatting furiously while trying not to fall off my bike on the sandy track. It was actually a relief to have Jason swat at them with the tree branch, even though most of them came back at me with a vengeance! They’d been an extreme nuisance to us all in camp the past couple of days and moving air, either from a breeze or from the back of a bike seemed the only relief.

So what is this phenomenon here in the Bush? The common fly occurs everywhere on the continent, but seems to prefer the wide open spaces. It roosts at night, but returns with first light of day. It begins its life in a dung heap, where creamy white eggs are deposited. The larvae hatch and, after eating its way through the dung, leave to pupate in the soil. The longer the larvae have to feed, the bigger the fly.

The adult fly needs a diet of protein; blood, pus, milk, tears, and saliva. That’s why their voracious appetites lead them to wherever we’ve scratched ourselves, sweated heavily, or near our dinner table at tea! And, the smaller the fly, the more starved it is for protein. Females in search of protein for their developing eggs seem to be the most tenacious of all, outnumbering their brothers three to one in search of essential juices.

The nuisance value of these flies has been measured. If we put our hand into a cage filled with them, ten blood-fed flies will be attracted to your hand per minute. However, if they are protein starved, the figure increases to 48 per minute. Flies with an underprivileged upbringing in a low protein dung heap, once adult and continuing to be undernourished, are up to 70 times a nuisance factor. These must have been the ones we’ve lived with the past couple of days!

Suggested activities: Investigate what attracts flies in your area. Compare the attraction value of table scraps, animal dung, sweat, to name a few, creating a graph of fly attractors. Which seems the most palatable to flies? Why do you think that is? What time of day are they the most annoying? Are there certain weather patterns that make them more of a nuisance? What is the role of the common fly in our ecosystem? Why is it important for them to be a part of the food chain?

April