The Kingdoms of Life
Life on Earth can be found in forests, deserts, the ocean and even places it seems impossible for life to exist!
Organisms can be grouped by the things they have in common into Six Kingdoms:
- Plantae (Plants) and
- Animalia (Animals).
The Six Kingdoms of Life, and some of their branches
But even with this system some organisms are difficult to classify as they have characteristics of more than one kingdom, and scientists are currently debating these six kingdoms. Some want eight kingdoms! Stay tuned for more developments in the future.
An organism (a living thing) can be:
- single-celled: just one cell that carries out all life processes itself
- multicellular: made of various cells that are organized and complex (like us!).
Prokaryotes and Eukaryotes
Each Kingdom is either:
Prokaryote comes from Greek "pro" meaning before and "karyon" meaning nut or kernel
And Eukaryote has the Greek "eu" meaning good
So Prokaryote loosely means "before the nucleus" and Eukaryote means "good nucleus".
This kingdom holds the most ancient bacteria on Earth. They are found in some of the most harsh places on Earth.
They are prokaryotes and reproduce in a simple way through asexual reproduction. They simply split into two in a process called "binary fission".
The picture shows thermophiles ("heat loving" organisms) that can live in some of the hottest places on Earth!
Archaebacteria can be found in places as different as the Great Salt Lake and the Hot Springs of Yosemite.
These are the "bacteria" that we all hear about. You may think that you only encounter this kingdom when you get sick. But they are everywhere!
Like Archaebacteria, they are prokaryotes.
They divide very quickly and are able to adapt to changes in their environment.
Bacteria must get their nutrition by consuming others ... they are heterotrophs.
Heterotrophs must consume other organisms in order to get energy.
Autotrophs can get energy from sunlight (like plants do), or in other ways.
Bacteria also play a vital role in ecosystems. They are responsible for decomposing dead organisms and help to return nutrients back to the environment.
Protists are considered one of the most diverse kingdoms on Earth.
Protists are divided into three groups:
- animal-like protists,
- plant-like protists,
- fungus-like protists.
Protists are eukaryotes. There are a few protists that have the potential to be harmful.
Animal-like protists are simple. They are usually found in freshwater environments and are mostly harmless. They are heterotrophs and can engulf other organisms to consume them. An example of an animal like protist is an amoeba.
Plant-like protists are organisms that share some characteristics of plants. They usually have the ability to perform photosynthesis. A euglena is an example of a plant-like protist.
Fungus-like protists are usually heterotrophic. They include slime molds. They can reproduce asexually and sexually.
Fungi play an important role in ecosystems - they are great recycling organisms.
As heterotrophs they take nutrients from dead or decaying organisms and help to return nutrients to the soil.
Fungi can reproduce asexually with spores (tiny light-weight seed-like particles), they can also reproduce sexually.
The vast majority of plants on Earth are autotrophs and contain a pigment called chlorophyll that helps them take the sun's energy and convert it into food.
Plants can be vascular or non-vascular.
Vascular plants have special tissue (xylem and phloem) that give the plant the ability to transport nutrients and water.
Non-vascular plants cannot grow very tall (because they have trouble moving water and food around), for example mosses, hornworts and liverworts.
Vascular plants include ferns, angiosperms (flowering plants) and gymnosperms (cone bearing plants like pine trees that do not lose their leaves in winter).
The animal kingdom is also a very diverse group of organisms. They include worms, sponges, insects, amphibians and mammals ... which includes us!
Animals have a great ability to adapt to their surroundings. They have many specialized characteristics such as nerves, spines, external exoskeletons and segmentation.
Some animals have the ability to regenerate body parts. Animals typically reproduce through sexual reproduction. Animals are heterotrophs that can be broken into herbivores (plant eating), omnivores (plant and animal eating) and carnivores (animal only/meat).
|Archaebacteria||Prokaryote, one-celled, live in harsh places on Earth||Thermophiles, Halophiles, Methanogens|
|Eubacteria||Prokaryote, common bacteria, found everywhere, one-celled||E.coli, staphylococcus|
|Protista||Eukaryote, some one-celled, some multi-celled, diverse||Euglena, Paramecium, Slime Mold|
|Fungi||Eukaryote, multi-celled, heterotrophic||Mushrooms, Morels|
|Plantae||Eukaryote, multi-celled, autotrophic||angiosperms (flowers), gymnosperms, mosses, ferns|
|Animalia||Eukaryote, multi-celled, heterotrophic||worms, sponges, insects, amphibians, birds, mammals|