Monocots and Dicots | What They Are and How to Identify Them

In this video I’m going to be talking about plant classification.
If you’ve ever taking a botany or organismal biology class, or if you’re friends with a botanist, you might have heard some of these terms thrown around before.
Some of these terms sound big and intimidating, but hopefully you’ll be able to follow along.
For the purposes of this video, we are mainly going to be focusing on the angiosperms, which are the most common types of land plants.

Monocots and dicots are just two subgroups of the angiosperm taxon.
And the angiosperms are themselves a subgroup of another group of plants called the tracheophytes.
These vascular plants get their name from the vascular tissue they possess - xylem and phloem, or basically plant arteries that conduct water and nutrients internally throughout the plant.
The tracheophytes, or vascular plants, consist of the angiosperms, gymnosperms, and ferns.
For those who don’t know, angiosperms are flowering plants, which develop their seeds inside an ovary, which is protected by a fruit.
Gymnosperms, or conifers, are the cone producing plants. They lack the presence of ovaries, and develop their seeds in woody reproductive organs known as cones. Because they don’t have fruits for protection, the seeds are completely exposed, leading them to be sometimes referred to as naked seed plants.
Ferns lack seeds altogether, instead relying on spores for reproduction.
Non-vascular plants are called Bryophytes.
There are two main groups in the plant kingdom, the bryophytes (nonvascular) and the tracheophytes (vascular).

The bryophytes consist of liverworts, hornworts, and mosses. And they were the first to evolve.

Since they lack vascular tissues, as well as roots, these plants rely on their leaves for water and nutrient uptake and transportation. Water and nutrients diffuse through the leaves and into the plant. It is for this reason that bryophytes must stay in constant contact with water, growing predominantly in moist environments.

Now that we have that down, lets start from the beginning.

Basically, early plants were all aquatic, but things were getting cramped in the oceans, so these early plant pioneers, the bryophytes, needed to figure out a way to support themselves. Since they’re not in water anymore they have to deal with this new thing they discovered called gravity, which is making it difficult for them to stand up straight.

It is for this reason that most bryophytes are small and inconspicuous, never growing to be very tall, like mosses.

So, the other main group are the tracheophytes, the vascular plants.

This group consists of all of the other plants - ferns, gymnosperms, and angiosperms.

And of these sub-divisions or subgroups, the angiosperms are the major players.

They constitute around 80% of all of the world’s land plants, with over 250,000 species.

It was originally thought that these two groups were the only subdivisions of the angiosperm taxon, but we know now, thanks to the advent of phylogenetics and, just, us getting smarter with time, that there are actually 8 groups of angiosperms.

Traditionally, we classified an angiosperm as being either a dicot or a monocot based on the plant’s characteristics.

However, as time went on, we started finding plants that exhibited both monocot and dicot characteristics.

We now know that this is because of shared ancestry between some monocot and dicot species. You see, there wasn’t a clean break in the evolutionary branches of these two groups. The fact of the matter is, the angiosperm taxon simply does not fit neatly into just two clades, or groups.

the first key difference is the number of cotyledons the plant seed possesses.

A cotyledon is kind of like a starter leaf that develops inside of the seed.

Without this cotyledon, or starter leaf, the plant will not be able to photosynthesize and produce enough energy to grow more leafs.
As the name suggests, monocots, or monocotyledons, possess only one cotyledon in its seed phase, while the dicotyledon, or dicot, possess two.

But, this isn’t going to help you very much in classifying fully grown plants.

The best way to tell the difference between a monocot and a dicot is by looking at the vein pattern.
Monocots have parallel veins, while dicots possess reticulate, or webbed veins.

Another key difference is that monocots have a fibrous root system, and dicots possess a taproot.

Furthermore, monocots have scattered vascular bundles, and dicots have a ringed vascular bundle system. However, This is only good if you’re looking at the cross section of a stem,

Lastly, Monocots tend to have flower parts in multiples of 3, while Dicots tend to have flower parts in multiples of 4 or 5.
So there you have it - how to tell the difference between a monocot and a dicot.

Видео Monocots and Dicots | What They Are and How to Identify Them канала 21st Century Nature