Kingdom Animalia. Animals have several characteristics that set them apart from other living things. Animals are eukaryotic and multicellular, so where other kingdoms can have creatures that are comprised of just one cell, animals are going to have more than one cell.
They are also heterotrophic, this means they cannot create their own food and must rely on other sources of nourishments. They’re going to eat other plants or animals, they’re not going to be able to create their own food with sunlight, like plants can.
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Animals do not have cell walls, but they may have an exoskeleton, which is like a hard skeleton they secrete onto the outside of their body or a shell. Now they don’t have to have that, obviously we don’t have a hard exoskeleton or a shell, but some animals like your crawfish or lobsters would have an exoskeleton or things like snails have a shell. All animals are motile. This means they can move even if only during certain stages of life.
Some animals may only move a little bit or very slowly, but all animals are motile, even if it’s just for a short period of time or during one stage of their life. Nearly all animals undergo some form of sexual reproduction, but some animals are also capable of asexual reproduction and this is possibly and a lot of times through parthenogenesis, which is when a fertilized egg is produced without any mating, budding or fragmentation.
It is possible, but most of the time animals are going to undergo sexual reproduction to produce offspring. Animalia is also known as Metazoa as far as a kingdom name goes and it is divided into the subkingdoms, parazoa, which consists of sponges and trichoplax, as sponges I’m sure you can think of, but trichoplax, kind of looks like a puddle you spilled on the floor. It’s very flat, but is still an animal. It doesn’t have differentiated cells, it even has some eye cells on it.
Parazoa such as the sponges and trichoplax, have differentiated cells, but no distinct tissue or tissues or body symmetry. They’re kind of oddly shape, where most animals you would be able to see some symmetry, there is no symmetry as far as parazoa are concerned. Now, all other animals are put into the subkingdom eumetazoa and these have two or three distinct layers of cells with differentiated tissues and either radial or bilateral symmetry. What that means is that you can divide them a certain way, if they have radial symmetry, you would be able to divide them any way going in a circle and the halves would match up.
A jellyfish would be an example of that, if you divide the jellyfish here, if you could divide it across here, if you could divide it across here going any way in a circle around the top of the jellyfish, down across the top and down through all the tentacles. If you cut it, it would be more of a circular shape and anywhere you cut it, it would be the same on either side, so it’s symmetrical. Which means it would have radial symmetry, because there isn’t just one symmetrical line you can cut along. There’s not just one line of symmetry there are several.
The same goes with a starfish. You could cut it along a line going this way, a line going this way, a line going this way, a line going this way or a line going this way. If you go along that circle, it can have symmetry, it can have all these different lines of symmetry and what’s on the other side of the line of symmetry is going to match what’s on the first side of the line of symmetry. Bilateral symmetry, you can only divide the body in half one way, so people have bilateral symmetry.
You can divide straight down from the top of your head to between your two feet and these two halves should match up pretty well, at least as far as body type and tissues are concerned. People have bilateral symmetry, you can divide straight down in the middle and the half should match up pretty well. Butterflies or moths are another example that should match up, cats, dogs, a lot of animals displays bilateral body’s symmetry. But there are some that have radial symmetry, but these are all eumetazoa, remember the parazoa is not going to have any kind of body symmetry, because it doesn’t have distinctive tissues, and it is not going to have a distinct body shape every time, it’s going to be different.
Whenever you are thinking about Kingdom Animalia, remember these certain characteristics that set them apart. They’re eukaryotic and multicellular, made of more than one cell, they’re heterotrophic, they cannot make their own food and must receive nourishments from other sources. They do not have cell walls but they have an exoskeleton or a shell and animals are motile, they are able to move at least at some stage in their life.