The article title is Features of Organisms : Groups within the plant kingdom | Cambridge IGCSE Biology [Please watch the video attached at the end of this blog for a visual explanation of this topic]
In the previous two lessons, we studied the 5 Kingdoms of Living Things and Features of the Animal Kingdom. In this article, we will focus on plant classification and the groups within the Plant Kingdom.
There are thousands of plant species on Earth, and one common feature shown by almost every plant is that they have some part that is green in colour. This green colour is caused by a pigment known as “chlorophyll".
What is chlorophyll?
This is a green pigment that is present in all green plants and cyanobacteria. The function of chlorophyll is to absorb light energy which is needed for the process of photosynthesis. All green plants carry out photosynthesis, and for photosynthesis, light energy or sunlight is required, and therefore chlorophyll performs the function of absorbing this necessary sunlight.
Note how it mentions that “green” plants have chlorophyll and therefore photosynthesise? That is because there are some extremely rare plants that do not have chlorophyll in them. They lack the characteristic green colour. Monotropa uniflora , also known as the ghost plant, does not have chlorophyll and gets its nutrients from other plants with the help of fungi.
Since the Plant Kingdom is a huge kingdom, things are made more convenient when they are divided further into smaller groups. The Plant Kingdom is divided into two main groups:
Ferns
Flowering Plants
Ferns
Ferns are a simple type of a plant which contains leaves, an underground stem, and roots of its own. The leaves of a fern are called fronds. Ferns do not produce flowers as they are non-flowering plants.
(Image by Leonhard_Niederwimmer)
This begs us to ask the question, if ferns do not produce flowers, how do they reproduce and produce new plants?
Ferns have little structures on the underside of their leaves called spores and this is how they reproduce.These spores are gathered in groups called sori on the underside of the fronds. Once these spores are ripened and dispersed, they give rise to new ferns.
(Picture from Wikimedia Commons )
Flowering Plants
Flowering plants are also another huge group of plants. Since they all have flowers, they are able to reproduce sexually as the flowers are the sexual reproductive structures of these plants. After fertilisation occurs within the ovary of the flower, a seed which can give rise to a new plant is produced.
Flowering plants are further divided into two groups:
Monocotyledons/ Monocots
Dicotyledons/ Dicots
The term “mono” usually refers to having one of something, and the term “di” usually refers to having two of something.
Monocotyledons are, therefore, flowering plants that have only one cotyledon (a seed leaf within the embryo of a seed) within their seeds. Dicotyledons on the other hand, are so called because there are exactly two cotyledons within their seeds.
Look at the diagram below and see if you have understood what you have read so far :)
Differences between Monocots and Dicots
Monocots have one cotyledon, Dicots have two cotyledons within their seeds
Monocots have parallel veined leaves, dicots have net-like veined leaves
The monocots happen to have leaves with parallel veins running through it, meaning that the veins within these leaves run parallel to each other. This is referred to as “parallel venation”.
In a dicot leaf however, the veins within these leaves are net-like. This type of venation is known as “reticulate venation”.
The vascular bundles monocots are complex, those of dicots are arranged orderly, in the form of a ring
Monocots have a fibrous root system, Dicots have a tap root system
The monocot root system is called the fibrous root system, which is usually formed by thin, averagely branching roots growing away from the stem of the plant. The dicot root system is the tap root system, which is where there is a main root running down and many side branches arise from this main root.
A. Fibrous Root, B. Tap Root.
Monocot flowers have petals in multiples of three, whereas dicot petals are found in multiples of four or five.
This might sound a bit complex, but if you look at the picture below, there is a monocot flower and a dictionary flower given. The monocot flower has six petals ( a multiple of 3), whereas a dicot flower would have petals in multiples of five.
(Monocot Flower).
(Dicot Flower)
A diagram entailing all the differences between monocots and dicots:
These differences are frequently questioned at the exam, so make sure you read through them carefully and watch the video below for a detailed explanation of the lesson!
Revising Plants
Since this is a subtopic under Characteristics and Classification of Living Organisms, make sure that you know your basics regarding Characteristics of Living Organisms and Classification.
This lesson is quite interesting and questions are of various types. Some questions can be found here as well, and you can time your answers to see if you can stick to the time limit given.
If you are struggling with IGCSE revision or Biology in particular, you can reach out to us at Tutopiya to join revision sessions or find yourself the right tutor for you.
Attempt the quiz to know where you stand!
[embed]https://youtu.be/uLx4z0Lt6oE[/embed]
