Curious Kids, is a series for children where kids send in questions and we ask an expert to answer them.

Dear Conversation, I am a curious kid and while I was bush walking I noticed these ferns. I wanted to know why fern leaves are shaped they way they are, and if they don’t have flowers does that mean all ferns are identical? Thank you for your help – Heather, age 8, Brisbane

You’ve asked two great questions, which I’ll answer one by one.

Why are fern leaves shaped the way they are?

Ferns are a very old group of plants that came along more than 200 million years before the dinosaurs walked the Earth. They were food for the plant-eating dinosaurs and they’re really great survivors.

Fern leaves are shaped the way they are because each species has adapted or changed over time to better suit its particular environment. That’s all thanks to evolution.

Some ferns are small and grow on other plants in wet places, while others are tall and tough. There are thousands of types of ferns, which grow in different environments all over the world.

The leaves of ferns are called fronds and they all have different sizes, shapes and textures. There are the tiny, soft fronds of maidenhair ferns.

Then there are the tough, leathery fronds of bracken and the large fronds of tree ferns that may be more than 2 metres long.

The fronds of many ferns begin as small, curled balls. As they grow, they change shape and start to look like the neck of a violin. That’s why they’re called fiddleheads.

Many people think different tree ferns look the same, but if you look closely the various species are very different in size, shape and texture.

If they don’t have flowers does that mean all ferns are identical?

Since ferns are such an old group of plants, they don’t have flowers or cones. Ferns were around for about 200 million years before plants with flowers came along, so they make new ferns in a different way.

Most ferns use things called spores, which are tiny and look like pepper. They can travel long distances on the wind or by getting a lift from a passing animal.

During some times of the year, if you look underneath the fronds, you can see the sporangium (that’s the part of the leaf where the spores are made).

Some look like tiny bunches of grapes, some look like a little brown purse, and others like a dome. Often the sporangium starts out light green and as it ripens, turns dark brown.

Ferns spores develop into what scientists call “gametophytes”, which usually look flat, green and spongy. These gametophytes produce eggs and sperm.

The egg or sperm from one gametophyte can join up with the egg or sperm from a different gametophyte.

When that happens, the baby ferns produced this way are not genetically identical to the parent or to each other. It only works properly if there’s enough water around so that the sperm can swim to the eggs. You can read more about it here.

Some ferns, however, can sprout ferns from their underground stems or from special bulb-shaped bits on their fronts called “bulbils”. When that happens, the baby fern is genetically identical to its parent.

If you want to grow your own ferns, follow the instructions below. It is great fun to watch them grow.

Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. You can:

* Email your question to curiouskids@theconversation.edu.au
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Please tell us your name, age and which city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question but we will do our best.

Gregory Moore, Doctor of Botany, The University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Curious Kids is a series for children. If you have a question you’d like an expert to answer, send it to curiouskids@theconversation.edu.au You might also like the podcast Imagine This, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.

I would like to know how long garden snails would live if they were not eaten by birds (or other predators)? – Alice, age 6, Canberra.

That’s a really good question! There have been reports of at least one snail living as many as 14 years in captivity. His name was George and he lived in Hawaii, in the United States.

Very few people have ever had the patience to study how long garden snails live in the wild. However, it might be longer than we might at first think – studies showed that snails in gardens in California needed to be between two and four years old before they were old enough to have babies. Many of these Californian garden snails, which were studied for almost five years, were therefore over six years old at least – older than you, Alice! It seems that rats and small mammals were the main predators of these snails.

Counting snail shell rings

There is a snail very like the garden snail that is called the Roman or Apple snail – it is the one that some people like to eat.

A study of a population of these snails in England was able to work out how old these snails are. That’s because, as they get older, you can count growth rings at the edge of their shell.

Some of the snails were at least six years old and probably more like eight or nine. The older snails had very thick shells and were often out and about. The scientists thought this might be because as the snails got older and bigger, fewer birds and other predators could crack their thick shells, and so they felt safe enough not hide away all the time.

So, it seems that if you are a snail that can survive long enough to get big then you might stand a good chance of getting even older – maybe 15 years old. It depends on what type of snail you are.

Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to curiouskids@theconversation.edu.au

Please tell us your name, age and which city you live in. We won’t be able to answer every question but we will do our best.

Bill Bateman, Associate professor, Curtin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to curiouskidsus@theconversation.com.

Why do some planets have moons and some don’t? – Siddharth, age 6, Texas

On Earth, you can look up at night and see the Moon shining bright from hundreds of thousands of miles away. But if you went to Venus, that wouldn’t be the case. Not every planet has a moon – so why do some planets have several moons, while others have none?

I’m a physics instructor who has followed the current theories that describe why some planets have moons and some don’t.

First, a moon is called a natural satellite. Astronomers refer to satellites as objects in space that orbit larger bodies. Since a moon isn’t human-made, it’s a natural satellite.

Currently, there are two main theories for why some planets have moons. Moons are either gravitationally captured if they are within what’s called a planet’s Hill sphere radius, or they’re formed along with a solar system.

The Hill sphere radius

Objects exert a gravitational force of attraction on other nearby objects. The larger the object is, the greater the force of attraction.

This gravitational force is the reason we all stay grounded to Earth instead of floating away.

The solar system is dominated by the Sun’s large gravitational force, which keeps all of the planets in orbit. The Sun is the most massive object in our solar system, which means it has the most gravitational influence on objects such as planets.

In order for a satellite to orbit a planet, it has to be close enough for the planet to exert enough force to keep it in orbit. The minimum distance for a planet to keep a satellite in orbit is called the Hill sphere radius.

The Hill sphere radius is based on the mass of both the larger object and the smaller object. The Moon orbiting Earth is a good example of how the Hill sphere radius works. The Earth orbits around the Sun, but the Moon is close enough to Earth that Earth’s gravitational pull captures it. The moon orbits around the Earth, rather than the Sun, because it is within Earth’s Hill sphere radius.

Smaller planets like Mercury have a tiny Hill sphere radius, since they can’t exert a large gravitational pull. Any potential moons would likely get pulled in by the Sun instead.

Many scientists are still looking to see whether these planets may have had small moons in the past. Back during the formation of the solar system, they may have had moons that got knocked away by collisions with other space objects.

Mars has two moons, Phobos and Deimos. Scientists still debate whether these came from asteroids that passed close into Mars’ Hill sphere radius and got captured by the planet, or if they were formed at the same time as the solar system. More evidence supports the first theory, because Mars is close to the asteroid belt.

Jupiter, Saturn, Uranus and Neptune have larger Hill sphere radii, because they are much larger than Earth, Mars, Mercury and Venus and they’re farther from the Sun. Their gravitational pulls can attract and keep more natural satellites such as moons in orbit. For example, Jupiter has 95 moons, while Saturn has 146.

Moons forming with a solar system

Another theory suggests that some moons formed at the same time as their solar system.

Solar systems start out with a big disk of gas rotating around a sun. As the gas rotates around the sun, it condenses into planets and moons that rotate around them. The planets and moons then all rotate in the same direction.

But only a few moons in our solar system were likely created this way. Scientists predict that Jupiter’s and Saturn’s inner moons formed during the emergence of our solar system because they’re so old. The rest of the moons in our solar system, including Jupiter’s and Saturn’s outer moons, were probably gravitationally captured by their planets.

Earth’s Moon is special because it likely formed in a different way. Scientists believe that long ago, a large, Mars-sized object collided with the Earth. During that collision, a big chunk flew off the Earth and into its orbit and became the Moon.

Scientists guess that the Moon formed this way because they’ve found a type of rock called basalt in soil on the Moon’s surface. The Moon’s basalt looks the same as basalt found inside the Earth.

Ultimately, the question of why some planets have moons is still widely debated, but factors such as a planet’s size, gravitational pull, Hill sphere radius and how its solar system formed may play a role.

Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.

Nicole Granucci, Instructor of Physics, Quinnipiac University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

If you’ve ever visited the fossil gallery of a natural history museum — or its gift shop, for that matter — you’ve probably seen the armoured body remains (or exoskeletons) of an extinct group of animals called trilobites. These ancient marine arthropods lived in the world’s oceans from 521 million to 252 million years ago.

We know a great deal about the diversity, lifestyles and evolution of these iconic invertebrate fossils. More than 22,000 species of trilobite have been named.

This is largely because the trilobite exoskeleton was made of a mineral called calcite, which fossilised very easily. However, fossils showing soft body parts of these creatures, such as the antennae and walking legs, are far rarer. Even when these features have been found, they may be obscured by flattening or partly hidden by sediment.

In a new study, published today in Science, we document a remarkable discovery of Moroccan trilobites preserved in volcanic ash, representing the most anatomically complete examples ever found. These new specimens not only preserve the antennae and walking legs, but also mouth structures and even the entire digestive system in three dimensions.

A palaeontological Pompeii

The new trilobite fossils are Cambrian in age (around 509 million years old) and preserved as undistorted three-dimensional moulds within fine volcanic ash, not unlike the human bodies entombed at Pompeii in Italy by the eruption of Vesuvius in 79 AD.

We scanned the specimens with X-rays to reveal and reconstruct the exquisite anatomy in high resolution, right down to the tiniest bristles (less than a tenth of a millimetre long) on the walking legs.

It may seem highly unlikely to find fossils preserved in volcanic ash, particularly their soft tissues. But ironically, it is the violent nature of eruptions that helps with this style of exceptional preservation.

Explosive eruptions, specifically a type called pyroclastic flows, produce high-speed clouds of ash that can cover vast areas, including marine environments, in a very short amount of time. Such an event would have rapidly buried these trilobites, which were living in shallow waters near the shoreline, with the volcanic ash quickly moulding and cementing the animals in place.

This entombment must have been almost instantaneous, as we also find tiny filter-feeding animals called brachiopods attached to these trilobites in positions they would have been in life, capturing a symbiotic relationship “snap frozen” in time.

Tantalising trilobites

Our discovery has revealed features previously unknown in trilobites.

For example, the new fossils show a sophisticated feeding apparatus. In particular, the first pair of head appendages behind the antennae possess what could be described as “spiny spoons”, used for chewing and scooping food into the mouth. Attached to these “spiny spoons” are antenna-like structures that may have acted as taste receptors or touch sensors.

One specimen (see below) also reveals the entire digestive system, starting with the mouth opening, leading to an oesophagus, which then extends to an enlarged J-shaped stomach connected to a long intestine running the entire length of the body.

There is also a structure called the labrum, a kind of fleshy lip associated with the mouth that forms part of the oral chamber where food is processed.

Interestingly, the labrum has long been hypothesised to exist in trilobites, but never observed in fossils. This discovery now helps us better understand how arthropod mouthparts evolved across living and extinct forms.

These fossils give palaeontologists a new “search image” to look for such anatomical features in newly collected trilobite specimens, or those already sitting in museum drawers. But perhaps more importantly, this discovery highlights volcanic ash deposits as underexplored sources for exceptionally preserved fossils.

John Paterson, Professor of Earth Sciences, University of New England

This article is republished from The Conversation under a Creative Commons license. Read the original article.