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Did you know an oak tree is way more closely related
to a pumpkin than they are to pine trees?
Look, here are the oaks, next to the pumpkins
and here are the pine trees, all the way over here.
Before I made this map
I thought that all of the trees evolve from each other.
But it turns out the concept of a tree
has evolved throughout history multiple times.
In this map of plants video I'm going to look at
all of the different kinds of plants on Earth
and how they're all related to each other.
And I made this video with the help of the experts
at the Royal Botanic Gardens Kew
here in London.
And like all of my map videos
the poster is available on my website dosmaps.com
as well as all of our Professor Astro Cat books.
If you want to get your hands on it
that's where to go.
In this map I found the most sensible way of organizing all the plants
was by how they've evolved.
So this map is really an evolutionary tree of all plant life,
based on our current understanding.
Let's start at the beginning with the most ancient plants:
algae.
Algae is a name used to describe
a wide range of different unrelated organisms
that have the ability to generate energy through photosynthesis
but not all of these are true plants.
Algae come in many different sizes
from single-celled varieties
to multicellular seaweeds.
In fact, all seaweeds are different kinds of algae,
although algae aren't just found in saltwater,
they can be found in fresh water and on land.
Single-celled algae
known as diatoms,
and the multicellular brown algae
are not considered true plants.
Even so they're very important to life
as three quarters of the oxygen in the atmosphere
is made by tiny single-celled phytoplankton.
Red algae are the first big group of species
considered to be in the plant kingdom
under the current taxonomy,
containing about 6,000 species.
Although there's another small group of around 15 species
called glaucophytes
which may also have evolved first.
But which one came first is still under debate.
So what exactly is a plant?
Technically, it's based on looking at a part of the cells
called chloroplasts, which do the photosynthesis.
In plants these chloroplasts are surrounded by two membranes
which scientists think came from an ancient event
where one cell ate another.
But the cell that got eaten didn't die,
they started working together,
and we define all plants
to have this kind of double-membrane chloroplast.
And red algae and glaucophytes have the double membrane chloroplast
despite not having things we think are more plant-like
like leaves, roots or a stem.
The different colors of algae come from the pigments
they use to convert sunlight into energy.
Green plants all use two types of chlorophyll, known as chlorophyll A and B.
And these are the same pigments used by green algae.
Streptophyte algae are a distinct group of green algae
which are thought to include the closest relatives to the land plants.
The oldest fossil evidence of algae
and possibly all life on Earth,
are found in 3.8 billion year old structures
called stromatolites.
These algae were a kind of photosynthetic bacteria
called cyanobacteria.
So these weren't plants.
But green algae and land plants share a common ancestor
from 1 billion years ago
very early on in the evolution of life on Earth.
Let's move on to the land plants.
Bryophytes contain mosses, hornworts and liverworts,
and are a crucial part of our understanding of the evolution of plants
as they're considered to be very similar
to the earliest land-dwelling organisms on Earth
which started to live on land from around 470 million years ago.
Around 50 million years before animals.
They lack many of the features of more modern plants
like flowers or vascular tissues
which are the parts of plants that transport water and nutrients,
- like sugars - around the plant,
but they do have root-like structures called rizhoids.
Bryophytes typically grow in moist, shady environments
because they can only collect water and nutrients
directly through their cells.
They love soaking up any water around.
Some mosses can absorb 20 times their weight in water.
They also tend to be small, typically around 3 to 6 cm in height,
because they don't have the rigidity and structure
that other plants get from their vascular tissues.
The maximum height they can reach is only 60 cm tall.
Now, every plant we'll meet after this point
has got a vascular structure.
Based on the fossils we've discovered
they first appeared around 420 million years ago.
A vascular plant has specialized tissues called xylem and phloem
which transport water and nutrients throughout its structures.
These tissues are rigid
and enable vascular plants to grow taller and more complex
than the non-vascular plants we've seen so far.
Now we get to club mosses and ferns.
Club mosses aren't true mosses
because they have a vascular structure.
But also club mosses aren't ferns
because they've got a different leaf structure to ferns
and different DNA.
So they're stuck in the middle here on their own.
Ferns include whisk ferns, horsetails
and leptosporangiate ferns, or leptoferns for short.
And these have many of the features we're familiar with from plants:
roots, a vascular structure, and true leaves called fronds.
However, they reproduce through spores and not seeds.
Ferns are a diverse group with over 10,000 known species
inhabiting various habitats worldwide, even underwater.
The fossil record for ferns stretches back to 400 million years ago
and the ancestors of today's ferns were giants
towering up to 40 m in height.
The Earth was covered in forests of tree ferns.
These have mostly died out but some tree ferns are still with us today.
A quick side note:
for this map I can't physically include every plant that exists.
So I've chosen a familiar representative for each major group of plants.
But from here onwards I'm going to include the scientific names that classify each group.
So if you want to find where your favorite plant sits on this map
just look up its scientific classification
and you should be able to place it.
From here on, the plants don't use spores to reproduce,
but seeds.
This was a really important step for the proliferation of plants.
A seed is made of a young embryo,
some nutritive tissue and an outer protective covering.
First let's look at the gymnosperms which today comprise the major groups of cycads,
ginkgo, gnetum and conifers like pines and spruces.
These first appear in the fossil record at around 390 million years ago.
Gymnosperms reproduce through cones which come in male and female forms.
Male cones produce pollen
while female cones contain ovules that develop into seeds upon fertilization.
And these are known as naked seeds
because they're not covered in anything like a fruit or a hard shell.
Gymnosperms have well-developed vascular tissues
enabling them to grow tall and thrive in various environments.
For example, conifers are adapted to cold and dry conditions
with needle-like leaves to reduce water loss
and sturdy cones for seed protection.
I just want to make a little side note on fungi
which naively seem like they're quite like plants,
but actually they're very different:
they don't photosynthesize
and are genetically closer to animals than plants.
But they're very important to this map because most plants
live in a symbiotic relationship with fungi
called micorrhiza.
In this relationship, the plant makes organic molecules by photosynthesis
and gives them to the fungus in the form of sugars and lipids.
While the fungus supplies the plant with water and minerals
like phosphorus from the soil.
Also, when plants die, fungi break them down
and return the nutrients to the soil.
Also, lichens.
They're not plants either: they're a partnership between algae and fungi.
But I'm getting sidetracked now,
I should probably do a map of fungi as well.
Anyway, because of the close relationship between fungi and plants
I've drawn a micorrhizal network as the background
as it seemed fitting.
From now on, we'll be looking at the angiosperms
or flowering plants
which first appeared around 135 million years ago.
They're now the most diverse and dominant group of land plants.
Nine-tenths of the world's plants have flowers
and over 300,000 species of angiosperms
are estimated to live on Earth today.
Around 90% of flowers are adapted to be pollinated by animals
who have also adapted to feed on the nectar or fruit in a symbiotic relationship.
Pollen is the male reproductive cell,
so basically plant sperm
and the female reproductive cell is called an egg.
When they meet they make an embryo
which develops into a seed in the plant ovary.
The ovary then develops into a fruit which encloses the seed.
This was a very successful evolutionary feature
to both help protect seeds
but also to disperse them
when animals ate the fruits and pooed them out.
Although this is just one method:
there are many other dispersal tactics on the outside of seeds, like
hairs or wings to be carried by the wind
or hooks to grab hold of animals.
We also need to talk about fruits because they're a little complicated.
So anything with a seed inside it is a fruit,
which is obvious for things like plums and berries.
People who say tomatoes are fruits are correct
because they have seeds inside them
but then they should also include things like cucumbers or pumpkins.
Basically any fleshy edible thing with seeds in it,
is technically a fruit.
Nuts are also fruits, hard fruits,
containing the seeds in a hard protective shell
which is formed from the ovary wall.
Stone fruits like olives, mangoes and peaches
have got a seed inside the hard pit in the middle.
And beans and peas, they're all seeds
and come in seed pods.
But we also have false fruits
like apples and strawberries, which don't form from the plant ovary
but from the top of the stem of the plant.
So apples and strawberries aren't technically fruits.
In fact, the things that look like seeds on the outside of strawberries
are actually individual fruits.
And the word vegetable is a generic term
because some vegetables are actually fruits, like pumpkins
but other vegetables come from other parts of the plant
like potatoes are an underground stem
and broccoli is actually a flower and kale are leaves.
Okay, back to the map and now let's explore the flowering plants.
We start with the early diverging types of flowering plants -
those that appear early in the fossil record
and which may give hints
as to what the ancestral flowering plants might have looked like.
These include Amborellales
which is a small group as it only contains a single species:
Amborella trichopoda.
Then we have Nymphaeales which includes water lilies
and some other aquatic plants.
Then we get a collection of families which include the peppers
where we get our black pepper.
But this isn't the same as the pepper plant we get chili peppers from;
we'll meet that later.
Then we have magnolias,
and laurels also known as bay trees
where we get bay leaves from.
And it's what they made laurel wreaths out of
in ancient Rome and Greece.
These early diverging angiosperms
are examples of what the very early flowering plants may have been like,
and studying these is valuable for helping to understand
how different features in the flowering plants evolved.
Now we get to a group called the monocots
which developed somewhere between 140 to 125 million years ago.
The monocots contain pond weeds, yams
pandans, lilies,
orchids and irises,
spider lilies, palms,
banana plants, grasses
and bromeliads like pineapples.
I want to highlight grasses
because this group includes all the cereal crops
like corn, wheat, rice, maize, barley
and loads of other cultivated crops
which basically make up around half of human food
and cover a fifth of the Earth's land.
The monocots contain about 85,000 species
but incredibly nearly half of these are different types of orchid
which have got around 30,000 different species.
And one of these gives us vanilla.
Monocots are one of the two major groups of flowering plants.
Everything else we'll meet from now on
are on the other major kind of flowering plant
called eudicots.
The eudicots are the most diverse group of plants today
and appeared around 125 million years ago.
The eudicots are split into three different subsections:
the early diverging eudicots, the rosids, and the asterids.
The name monocot and eudicot
come from how many leaves they sprout out of the ground.
Monocots typically have one seedling leaf when they first grow,
but the eudicots have two.
This seedling leaf is known as a cotyledon.
So monocot is short for monocotyledon -
for single seedling leaf,
and eudicots are short for eudicotyledon -
for two seedling leaves.
Also, all eudicots share a distinctive type of pollen
which is described as tricolpate
because it has got three characteristic grooves.
But a lot of the classification of plants into these different groups
comes from looking at and finely combing through their DNA.
The early diverging eudicots contain buttercups
which are also related to poppies and clematis,
proteas, like lotuses and banksias.
Then we have gunneras
who have some of the biggest plant leaves in the world
which can be as wide as a double bed.
Then there are mistletoes, and then spiky cacti
whose needle-like spines are actually hard pointy leaves.
Cacti are also related to the carnivorous venus flytrap.
But carnivorous plants aren't unique to this group:
there are over 700 species of plant that catch and kill animals.
They typically live in environments with poor, boggy soil.
So, they evolved many strategies to get their minerals from their victims,
by trapping and absorbing them
with fast closing jaws or sticky flowers
or slick drowning pools
that can trap animals as big as mice and small rats.
Then we have the saxifrages,
which contain stonecrops, peonies, witch hazels and gooseberries
which have only recently been recognized as being related, based on DNA evidence.
Although it's still a mystery how the saxifrages
are related to the other groups.
The rosids appeared around 100 million years ago
and their 90,000 species are now found all over the world.
The major groups in the rosids are grape vines, geraniums,
fuchsias which are also related to pomegranates,
then we have passion vines which are also related to poinsettias and violets,
then wood sorrels,
and roses which are also related to figs and cannabis.
Then the legumes which include peas and beans.
Then oaks which are related to walnut trees,
and then all the squash plants like pumpkins.
Then we have the hibiscuses which are also related to the cacao tree
where we get get chocolate from.
Then we have the maples which are also related to horse chestnuts,
and finally, one of the most important groups for our food: the brassicas
which contain mustard
and a single species of plant called Brassica oleracea
which, by artificial selection, humans have turned into
cabbage, broccoli, cauliflower, brussels sprouts, kale,
collard greens, kohlrabi, gai lan,
and many more new ones like purple sprouting broccoli,
all from a single species from within this group.
So the rosids are clearly very important for our food
and interestingly there are more than 80,000 edible plants in the world
but 90% of the food we eat comes from just 30 plants.
The other plants are either inedible or actively toxic.
In fact, there are more toxic plants than non-toxic plants.
Land plants develop toxic chemicals as a defense to protect them from getting eaten,
mainly because they can't run away.
Also some plants use sharp thorns or spiky leaves, like these hollies
and others, like stinging nettles,
use stings which act like hypodermic needles to inject painful chemicals.
With around 100,000 species,
the asterids are as diverse and as widespread as the rosids.
The asterids appeared around 89 million years ago
and contain dogwoods and the related hydrangea,
then we have rhododendrons which is also where we find tea,
and then we have the coffees which are also related to gentians.
Then forget-me-nots, mints,
then potatoes which are also related to aubergine,
morning glories and the chili peppers.
We also have hollies and carrots which used to be white and inedible
before being bred in today's orange ones.
Then we have ivies, honeysuckles and viburnums.
And finally asterales which contain sunflowers and dandelions
and is where the name asterids comes from.
Interestingly, a sunflower is not just one flower
but many hundreds of flowers called florets
which each ripen into an individual seed.
So that's the map of plants video! I hope you found it insightful
and a very special thanks to the people at Kew
for helping me with the research on this video
and also letting me film in their absolutely spectacular gardens.
If you've watched my channel before you know I've delved into many different areas.
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Thanks to you for watching and I'll see you on the next map video:
I've got some really good ones lined up.