Are you a living thing? If you are we should totally talk because we have a lot in common
In fact you and I both have a lot in common with all living things
Your teacher trees your pet parakeet bumblebees
Everything and one of the most important things is we all eat everyone needs food
which is why one of the best ways to learn about life on Earth is to
Follow the food see where it comes from and where it goes while living things are eating and being eaten
So here are the basics about the flow of food and the energy it contains making life possible. Let's start with a simple question
Why do we have to eat in the first place?
We all eat right but have you ever wondered why we eat I
Mean some animals only eat plants others. Just eat other animals
And some creatures eat both plants and meat but the thing is all
Animals, including humans eat and we don't just eat because we're hungry or bored or tired or it tastes good
Although I could really go for a slice of pizza right now. We eat because we need food to live more exactly
We need the energy that food gives our bodies to grow move and stay warm
You've probably figured this out already
from the things you've heard about how and when we eat like you've probably heard that breakfast is the most
Important meal of the day or you might know that runners will carb load before a big race
But food is necessary for all living things all the time
You may have noticed that your collection of cool rocks that you have under your bed never needs a lunch of club sandwiches and baby
Carrots, that's because they're nonliving things. But food is most definitely a necessity for animals and plants, too
Even though we don't think of plants as eating because they don't have mouths
They still need food to grow and repair themselves. Just like we do in fact
Plants make a nifty model that can help us understand how the energy from food affects living things
to see how food affects plants we can test what happens when they get more or less food plants get most of their food from
The Sun water and carbon dioxide in the air
More on that another time but to test how food affects plants for yourself. You can use liquid plant food
That way you can control how much food or nutrients of plant gets so consider this little investigation
Say you have two little plastic cups filled with potting soil and you planted a lima bean seed in each one
Then you give each plant a different amount of food plant. Number one would be your control
That means you don't give it any additional food at all
just a little water and sunlight and it'll do what plants do all on its own then you can make plant to your
extra food plant ask your parents for some liquid plant fertilizer and add the recommended amount to plant two now if you kept watering and
Feeding your plants the same amount for say four weeks. What do you think would happen?
Would you expect both of the plants to grow the same amount or would one grow more than the other if so, which ones?
Well what you'd find is that plant two grew bigger than plant one because living things need food to give them energy so they can
Repair themselves and stay healthy and in this case grow
So with more food plant two got more energy and that allowed it to grow bigger now go eat your vegetables, okay
So food is energy plants can make their own food while many animals swipe the energy from plants by eating them
But what happens to that energy once it gets eaten up well
You might say that it gets all tangled up in a food chain, and you are part of it
Not everybody likes the same kind of food right? That's probably a good thing
I mean all the more pizza for me
But whether we eat milk shakes or mangoes pizzas or pears
Tacos or toast we use the energy that's in our food to stay alive
But how did that energy get into our food in the first place? The answer is that energy flows between living things?
It's almost like each form of food is a link in a chain a food chain
You might have heard that humans are on the top of the food chain
Because we eat pretty much everything and except for the occasional video game monster and maybe the odd bear
Nothing tries to eat us. But what is a food chain exactly a
Food chain is a model that shows how energy flows between living things
You can think of animals and plants in the same food chain as all living in the same neighborhood
Which scientists call a habitat and they all have a job to do
Interacting with each other day in and day out together
they form a kind of system a
self-contained collection of different things that all work together as a whole and they also interact with the
Nonliving stuff around them like the water the air the ground and the Sun put it all together
and what do you get a special system called an
Ecosystem and food chains show us what eats what in an ecosystem now everything that's alive is in a food chain
Including you my friends and actually most living things are in more than one food chain
Depending on what or who they're munching on at the moment. I mean you don't eat the same thing for dinner every night
Do you didn't think so now? Let's see how a food chain works by making a diagram of how these interactions happen in nature
First all of the energy that's in a food chain starts with the Sun. I can't stress that enough people
Plants take the energy from the sun's rays and change it into chemical energy
So when a nice patch of lush green grass
Starts to grow it's capturing some of the energy from the Sun to do it
Then when an animal like a rabbit
Wanders by and nibbles on that grass the energy from the plant is transferred into the rabbits body
now if a hungry hawk decides that the rabbit would make a yummy supper then the energy from the rabbit is
Transferred to the hawk and in this ecosystem
Nothing is large or brave enough to take on the hawk. I mean just look at her
So we've hit the top of the food chain, and we've just made a nifty model of it
So a food chain is a model that shows how energy flows between living things in an ecosystem
Energy in a food chain starts with the Sun
which is turned into chemical energy by plants and this energy moves up the food chain as animals eat the plants and then other
animals, eat those animals and
Speaking of energy I'm starving. So I'm off to take my place in the food chain. See you next time
So a food chain is really a model of how energy flows among living things in an ecosystem
But in the real world things are a little more complicated than just rabbit eats grass and hawk eats rabbit
So, let's see how the flow of food and therefore energy works within a habitat where many different plants and animals live
Picture of polar bear in the desert know what you're imagining is way too cute take off the sunglasses and the swim trunks there
He's hot. He's hungry. He's downright miserable. Why is he such a grumpy bear? Well, it's because he's not where he belongs
There aren't any tasty seals to eat
No cold water to enjoy and no snow to sleep in the desert isn't his habitat
You know that a habitat is the area where something lives
But from polar bears the porcupines animals don't just need a place to live
They also rely on the other living and nonliving things around them to survive and life looks different in different places around the world
So what makes a habitat a home?
Well, what do you need I need
Sandwiches pancakes carrots, maybe some nice peaches, so I need food and I need water
I need a place to live and I need a place to film crash course videos
You could say this is my habitat animals need these things to food water shelter
And space to live for animals their food comes from their neighbors the other living things in their habitat
You know that plants and animals all fall somewhere along the food chain
Which is a model we use to describe the flow of energy between living things
But the real world is made up of lots and lots of food chains and those chains can get kind of messy
I mean look at our polar bear sure, his favorite food is seal but in a pinch he'll eat. Walrus dead
whales birds eggs and if he has absolutely no other choice
Plants the polar bear is at the top of multiple food chains, and that's not unusual most animals
Don't just eat one thing and neither do I
I'm at the top of the pancake food chain and the carrot food chain. It just so happens
I prefer pancakes so you can see how food chains are actually all tangled around with each other with many different ones
Overlapping kind of like a web
so we call this a food web food webs are big tangled systems that include every plant and animal in a habitat and as you
Might guess all food webs are different. Let's compare two different habitats to see how the food webs play out
First we'll go back to our old stomping ground the forest
Let's begin with you know, this people the plants trees grass and other plants that change energy from the Sun into sugar
But then you have some animals that eat other animals
This is where things get a little more complicated today an owl makes a mouse his lunch
but tomorrow it may be a rabbit today a snake snacks on a squirrel but a few days later our our friend might make a
Meal of another meat-eater like the snake finally the decomposers
insects fungi and bacteria are breaking down whatever is left over from
Uneaten rotten fruit - leftover animal carcasses as they break down matter. They provide more nutrients for the plants
It's a bit of a different story up in the Arctic. I mean look at all that ice. I know what you're thinking
Where are the plants?
How do we have a food web without plants zoom in on the seawater zoom way in further further stop?
Can you see those tiny plants? They're called phytoplankton and just like plants on land
They convert energy from the Sun really small creatures called ZOA plankton eat the phytoplankton
In all kinds of small fish dine on the ZOA plankton larger fish eat the smaller fish
There are big marine mammals - beluga whales eat fish while humpback whales eat the tiny plankton and krill and what else eats fish
Seals that's our polar bears favorite food. But up here. You can't afford to be picky
So we may have to nibble on some whale carcass if necessary as for decomposers
There aren't many bugs or earthworms in this cold climate. There are bacteria
But since it's so cold the decomposers break down matter much more slowly than in the forest
So you can see food webs and the ecosystems that support them look different in different parts of the world
Depending on the habitat conditions flat or mountainous land more or less water
These seemingly small changes in habitats
affect what kind of plants and animals
Live there up in the Arctic a polar bear has the right conditions to keep him happy first
He fits into his food web perfectly the food that's available to him has enough fat and protein to keep his energy up second
He fits into his habitat perfectly
He has the body
adaptations to not just survive
But feel really comfortable in the super cold a polar bear isn't built to survive in the desert or the forest
So let's put our poor polar bear back where he belongs. I was starting to feel bad for the guy now
we're getting somewhere an owl might eat a rabbit one day and a mouse the next just like I might have
Pasta for dinner one night and the next night. Have a nice Caesar salad
So the flow of energy among living things doesn't just go in a straight line
Every living thing in a food chain might eat or be eaten by someone else in another chain
So when you look across a whole ecosystem, the flow of energy is not so much a chain as it is a web
So last time we put a polar bear in the desert and I still feel bad about that the good news
is that in real life a polar bear probably won't just wander into the Sahara but not everything stays in the same habitat all the
Time a new species might come into a habitat a species might die off
even the habitats themselves can change as a result of things like floods and droughts point is
habitats and the food webs they support can get out of whack and sometimes
It's not pretty let's look at what happens when an ecosystem gets out of balance
Last week we learned that a habitat is home to a tangle of food chains called food webs
The animals depend on each other for food, but they don't just need each other
They rely on the nonliving things in the habitat, too
This interaction of living and nonliving things in a habitat is called an ecosystem
The things in an ecosystem are all connected
Just like when you touch one part of a spiderweb and the whole thing vibrates when one linked in the food web is threatened it
Can shake up the whole ecosystem. Let's see what might happen. For example, if an ecosystem loses a species
Since we're talking about food webs, I think we should look at spider monkeys
They're called spider monkeys because they hang upside down from their tails with their arms and legs dangling
This is somehow completely adorable these primates live in a tropical rainforest habitat
Which is just bursting with some of the coolest creatures out there
Toucans Jaguars sloths as we learned last time these animals need each other to survive
And spider monkeys happen to play a particularly important role in the rainforest food web
They eat mostly fruit which contains seeds and we know that seeds are how plants make more plants
when a spider monkey snacks on a berry he gets to enjoy the tasty fruit while also doing the plant a solid favor when the
monkey moves on to another part of the forest and um
Passes the fruit. He leaves the seeds behind wait a while and then voila you have a new plant
Imagine thousands of monkeys eating thousands of fruits every day
more monkeys equals more plants and trees
Those trees support lots of other animals insects and sloths eat those plants too and more spider monkeys
Insects and sloths mean more food for carnivores leopards dine on the sloth sand spider monkeys while frogs eat the insects
And of course our decomposers like fungi and bacteria break down leftover plant and animal matter
So we're talking around 50,000 plant and animal species that rely on these plants now imagine the SpiderMonkey population starts to decline
maybe they're hit with a strange new disease or maybe humans over hunt them if the monkeys aren't around to eat the fruit then the
Seeds aren't scattered around in the forest stops growing leaving fewer fruits for fewer monkeys
Not only that fewer plants means less food for other animals, like insects and our sloth friends
That means the insect and sloth numbers start to decline and that
Means less food for the animals that eat them all of a sudden
None of the animals in our ecosystem have enough to eat all because of the loss of one species
Do you see how this could get really bad remove one piece of the food web and you might knock down the whole thing
That's bad news for us, too
The good news is that ecosystems want to be in balance?
After a natural disaster like a forest fire or a flood things might be wacky for a while
But habitats can usually get back to normal, but if things get really bad the habitats might change forever
The old species will leave searching for a better place to live new species will come in life will keep going but it won't look
the same
In every ecosystem the plants in animals are connected
You can't mess with one species without affecting all the others food webs are delicate like spiderwebs
We don't want to be all crazy pants and just go knocking them down now
You have the whole picture all living things need food for energy if they can't make it like plants
Do they have to get it by eating other living things on a small scale?
You can think of this flow of energy as a food chain, but on the broader scale
It's more like a food web
No matter how you look at it food is energy and energy is life
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