Hi, I'm tor Hansen author and biologist today.

I'm here to answer your questions on twitter.

This is biology support at jerry.

Peters asks, are viruses alive.

Let me answer that question with another question.

What does it mean to be alive?

Most biologists define life as an organism with cells that respond to their environment and an organism that can reproduce itself.

Viruses don't meet that definition because they do not have cells.

They reproduce only by co opting the reproductive capabilities of a living cell.

Yet we see viruses having a very direct impact on our lives and the lives of other creatures in this world.

So it just goes to show us that the very definition of life is still in some ways open to question at sub nom nom nom asks why are succulents such finicky little bitches, succulent plant lives in the particular condition out in the wild where they have adapted to really dry situations where they need to hold a lot of water in their leaves.

And those are difficult conditions to replicate inside your house, which is part of the reason they can be very difficult to keep as house plants at Hey Adrian asks, seeds are interesting, Who knew that when you eat one you're eating little plant embryos, it's hard to imagine how small a seed can be until you meet the seeds of an orchid.

These come from a small orchid in our flora called the spotted coral root and each seed is like a mote of dust.

only a few cells organized together, there are approximately one million spotted coral root seeds in this vial, which stands in stark contrast to the world's largest seed, the double coconut, which grows on palm trees, found only on two islands in the Seychelles archipelago, isolated out in the middle of the Indian ocean, and a full sized double coconut can weigh £40.11 orders of magnitude larger than an orchid seed.

So ask yourself where else in nature can you find something so different in form that has the same function at our Batra?

No one asks.

Does Darwin's theory of evolution apply to plants also?

Yes, at Hyung lee asks dumb question time, do you think archaeopteryx ricks would have made a good pet?

This replica of an Archaeopteryx fossil hangs on the wall in my office and I look at it every day and biologists have been looking at this fossil for over 100 and 50 years.

Some call it the Rosetta Stone of Biology because it contains so much information about evolution and it reveals a creature that displays characteristics of reptiles and of birds.

This is one of the first fossils that gave people an inkling that in fact the birds are living dinosaurs.

Look at the mouth of it up close, you would see little teeth.

It is what some people at the time it was discovered called?

Evidence of a missing link.

If you will evidence of evolution in progress, we know that it lived in the trees.

If you look at the feathers, they are like modern feathers offset and aerodynamic on the wings, which indicates it was soaring or flapping at the time.

So it would have been a messy pet to have around in the house knocking things over and so forth and it might have given you a nasty bite because it had teeth overall.

It's such an important creature that I think any biologist would love to have one as a pet at john Mace live sent a picture with a question bones found while walking in the woods.

Any idea what it was bigger than my £50 dog.

You are looking at the skeleton of a deer and if you look closely you will see that something is missing from that skeleton.

You have the top of the skull and it so happens that I have the jawbone from a deer skull right here.

This part has teeth in the front.

But if you were to go back in the woods and look at the top of that skull, you would find just a bony plate.

No top teeth on a deer.

They are pinch and tear herbivores meaning they pinch the vegetation with their bottom teeth against that bony plate and then tear it off.

So you can always tell when you're out in your garden whether it's been a deer attacking your favorite shrubbery or whether it's been something like a rabbit That makes a clean cut.

Because deer always leave a rough cut on the end of the vegetation that they've been nibbling at.

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Zenith asks, can dogs and foxes be crossbred or are they two different?

So dogs and foxes are in different what biologists or taxonomists would call genera, They have a different genus.

They're not closely related, they're very very distant cousins.

They cannot interbreed and produce viable offspring.

Whereas dogs and wolves are closely related.

In fact dogs descend from wolves.

They were domesticated from wild wolves only 40,000 years ago, which isn't that long in evolutionary time.

So those two can definitely hybridized and they often do at India at least 16 asks like how the hell did a fish just get up one day and say I want to walk on land and now here we are like.

It just miraculously turns its gills to lungs and can walk, even though we can't say precisely what things were like at that critical moment that there are creatures in the world that still display some of those characteristics.

There are creatures called lungfish which can crawl short distances through the mud to get from one pool to another.

We are all familiar with that cartoon image of evolution with the creature emerging from the water and then progressing through a series of forms until there's a human being at the end.

It's the most destructive cartoon in the history of science because it gives us this false idea that evolution is a linear progression of one form replacing the other along the path when in fact it's much messier, more complex and more wonderful than that.

So yes, there was some creature that first began to emerge from those watery depths onto land, but that led to a great diversity of different pathways.

Once that transition took place at start, soul asks, how will the human species evolve?

The future of our species is a big question and open to question, but we know a lot about human evolution from looking at the past and the story of human evolution is really in many ways the story of brain size and each time we've seen some increase in the capacity are our brains, biologists and anthropologists have associated that With some change in human behavior that allowed us to gain more calories because brain tissue is what physiologists call metabolically expensive.

It takes a lot of fuel to run a brain.

As many as 20% of our daily calories go to fuel something that's only 2% of our body weight.

So if you want a bigger brain, you're going to have to have more calories to run it.

And we've seen that through time as our species has adopted new characteristics, new traits, new habits that have given us more to eat.

Those things include tool use and social behaviors and cooking the food.

So now we are at a period of time where food for many people is plentiful calories are plentiful.

One question for future biologists then will be, how did that change the human brain at fly behavior?

Asks mutant corn for dinner.

Anyone know what mutation would likely cause the double sized kernels?

Well we don't know if it's a mutation at all because sometimes corn or other plants respond in strange ways like that to disease or bacteria or fungi.

So we can't say what's making those kernels large in that situation.

But whoever gets that here for dinner will have a bonus at Cheryl row for asks.

Can crisper save bananas from the fungal threat?

Serious question for biology tweets.

It's a serious question for anyone who loves bananas.

The common banana that we buy in the grocery store is called the cavendish banana.

And unlike many other fruits in the store, the cavendish bananas are not produced from seeds and traditional crop breeding, a banana plant produces offshoots that are easy to separate from that plant that are clones of the banana plant itself.

So if you find a banana that has the characteristics that will be successful commercially, it lasts a long time.

It has good flavor.

You can ship it around the world to grocery stores.

That is a truly valuable fruit and that's why the cavendish banana is so popular and why it's produced via cloning.

So when there is a threat like this fungus that lives in the soil and destroys the cavendish banana plant, they're all susceptible to that fungus in the same way CRISPR is a tool in molecular biology that's used for turning on or turning off particular genes within the genome of a species.

So if there is a gene currently turned off in the cavendish banana that could be turned on again to provide resistance, that is a possible solution to this problem.

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Asks friday debate in the office.

Do plants grow from the bottom or the top?

Well typically plants grow from the top but there are situations that we're very familiar with where that growing part of the plant is lowered down and we see that in our own lawns, grasses have evolved to grow from the bottom in response to grazing by animals.

And more recently by the cutting of lawnmowers so that that leaf that you see when we cut it off will be replaced from below.

But most plants like a fir tree or an apple tree are growing from the tips of their shoots.

At K.

Baum wire asks, how does climate change affect wildlife.

We often summarize the impacts of climate change on plants and animals with the acronym Mad short for move, adapt or die.

And we see examples of all three of those playing out in nature all around us between 25 85% of species on this planet are now moving, shifting their ranges in response to climate change, looking for the temperatures and conditions that they're used to.

Many other species are adapting by changing diets or behaviors to try to cope with this crisis.

And yes, some species are dying and going extinct and we also see species struggling to adapt and adjust their relationships to one another.

Fascinating example.

Recently out of Gabon in Africa, where for the first time scientists observed chimpanzees attacking a group of gorillas and in fact, even killing one of the gorillas, One of the reasons this may be happening.

One of the theories is that there is now a shortage of fruit and other foods for those creatures in that forest because of climate change, creating a new hypercompetitive environment for those two species that used to coexist peacefully at Nico Miller asks, blue eyes are weird.

What is a f I'm sorry, Oh, can I say that?

Or what do I say at Nico Miller asks, blue eyes are weird af like honestly, how does a mutation like that even happen, mutations in biology occur in the DNA when it's being copied.

It's not a perfect process, mistakes are made.

Oftentimes those mistakes lead to new features in the organism.

Usually they're not very useful and they disappear over time, but sometimes they can impart a benefit and they persist.

This is one of the fundamental ways that new traits are introduced into the evolutionary process.

Blue eyes were introduced in that way fairly recently in human evolution.

They have persisted, but no one's quite sure yet what the advantage of blue eyes maybe at terra Luzuriaga asks, how do extinct species come back to the world short answer?

They don't, they're extinct.

But there are efforts underway now to try to re create or bring back some extinct species, like the wooly mammoth from ancient D.

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It's still a work in progress a long way off.

But some experts are working on that very question at Lauren are Peters asks if we have evolved from monkeys, why are they not extinct when new species evolve?

It's not necessary for them to replace the species they evolved from.

In fact, it's more common for new species to exist side by side with many closely related species.

At Karu 14 02 asks, is the number of genetically different human beings that can be formed finite.

People are often curious if there might be a doppelganger or someone almost exactly like them out there in the world today or at some point in history.

And the fact is we can be pretty close genetically, but every individual is indeed unique.

When you consider the number of genes in the human genome 50,000.

But also considering the number of base pairs in those DNA molecules, you're talking about billions of different combinations on top of that.

It's not just the genes themselves that are crucial, but how those genes are expressed, all of those things can be different among individuals.

We're not going to run out of unique individuals anytime soon.

At Ibis journal asks what makes hashtag penguin feathers ice proof?

They're not just ice proof.

They are waterproof, structurally waterproof.

And biologists still aren't sure exactly how that works.

But if you look microscopically at the veins of those feathers, you see that they trap all sorts of small air pockets and it may be that air preventing water moving through the feather.

That intricate feather vein has thousands and thousands of individual places where the feather surface is pushing against the natural surface tension of the water.

Either way, you don't have to worry about penguins getting wet on their skin.

At our Heisman asks, what are some of your favorite unsolved mysteries in biology interpret.

However you like one of the great mysteries that we've really only discovered somewhat recently is just how mysterious our own genome is.

When the human genome project sequenced our D.

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I think many people thought we would have the recipe book for how to make a human being.

But it turned out to be far more complicated than anyone thought because it's not just the sequence of the genome but it's the shape of the molecule.

It's the genes, it's the patches of D.

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Around the genes that control them.

It's all sorts of things that combine to see how those genes are expressed and what makes us human.

But you don't even have to go into molecular genetics to find mysteries there all around us.

A constant reminder that there's so much to learn about ourselves and about nature.

Consider something as familiar to all of us as yawning.

We still don't understand why people yawn at Michael McCaul er asks how did Darwin know all that evolution stuff?

He didn't know he learned it As he traveled and explored his world.

Because in the 19th century it was still widely assumed that everything was created very recently if you will um by the hand of God.

And so Darwin was fascinated by geology and how there were species in the rocks in fossils that were no longer present in the modern world.

He came up with the idea of evolution by natural selection.

Would help explain how things changed through time and how you had this great diversity of life on the planet.

And it was a radical idea at the time.

He sat on it for years and years before finally publishing his theories because he knew they would be controversial at lonely kino asks what is bioethics?

The ethics of biology.