Biologist Answers Biology Questions From Twitter

And you're okay with the full frontal on this?

We'll let the Twitter-verse comment on it.

Hi, I'm Thor Hanson, author, and biologist.

Today, I'm here to answer your questions on Twitter.

This is biology support.

[upbeat music]

@Jerre_Peeters 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.

@subnomnomnom asks, Why are succulents

such finicky, little bitches?

A succulent plant lives in a 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 houseplants.

@HeyAdrienne 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 Coralroot, and each seed

is like a mote of dust, only a few cells organized together.

There are approximately 1 million Spotted Coralroot 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 pounds,

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?

@rbatra01 asks, Does Darwin's theory of evolution

apply to plants also?

Yes.

@HungLee asks, Dumb question time:

do you think Archaeopteryx 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 150 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've 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.

@jonmacelive sent a picture with a question.

Bones found while walking in the woods.

Any idea of what it was?

Bigger than my 50 lb 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.

@RJ_Zenith asks, Can dogs and foxes be crossbred

or are they too 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 hybridize,

and they often do.

@ndea_alese16 asks, Like how the hell did a fish

just get up one day and say,

I wanna 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 .

@StartSOLE 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 of 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?

@FlyBehaviour 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 colonels large in that situation,

but whoever gets that ear for dinner,

will have a bonus.

@CherylRofer asks, Can CRISPR save bananas

from the fungal threat?

Serious question for biology tweeps.

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 it 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.

@A_C_Ella 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.

@Kbaumlier 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 and 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.

A 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 hyper competitive environment

for those two species that used to coexist peacefully.

@NekoMiller asks, Blue eyes are weird.

What is AF?

I'm sorry.

How do I?

[Production Crew Member] Uh...

[Production Crew Member Laughs]

[beep]

Oh, as [beep]. Can I say that?

Or what do I say?

@NekoMiller 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 may be.

@TarrahLuzuriaga 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 recreate or bring back some extinct species

like the wooly mammoth from ancient DNA.

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

but some experts are working on that very question.

@LaurenRPeters asks, If we have evolved from monkeys,

why are they not extinct?

Mm.

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.

@karu1402 asks, Is the number of genetically different

human beings that can be formed finite?

People are often curious if there might be a doppelganger,

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,

20,000, 30,000, 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.

@IBIS_journal asks,

What makes #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.

@r_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 DNA,

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 DNA 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.

They're 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.

@michaelmccollor 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,

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.

@lonely_kino asks, What is bioethics?

The ethics of biology?

The answer is yes, and we need to think

about the ethics of biology as our ability to do

more and more develops over time.

Technologically, we have the ability now to change DNA.

We have the ability to combine species in new ways,

so we must constantly ask ourselves,

not only, Can we do these things, but should we?

So those are all the questions for today

and we've covered a lot of ground.

Thank you for watching Biology Support.

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