- Education and Science
Movement a defining Characteristic of Life
Living things move
Movement is one of the 7 defining characteristics of life. The 7 characteristics of life are the 7 things that ALL living things do and they separate living things from non-living things.
I was always taught the acronym MRS GREN to help me remember the 7 essential characteristics of life. There is a little quiz in a minute to see if you know all 7 of them. The acronym mrs gren might give you a few clues.
Here I am going to talk about the M in the acronym, which stands for movement so no excuses for getting the first question wrong now!
Why do living things move?
At some stage in their lives all living things move. This movement can be so subtle you might not notice it or it can be so obvious you might not even think of it. As you read this you are moving in so many ways, some without any conscious effort required.
Living things need to move for the following reasons:
To find nutrition
To excrete waste products
To get a sense of their world
All the other characteristics of living things require the animal or plant to be capable of some form of movement of a greater or lesser extent at some time or all the time.
Movement in Plants
It might seem a bit strange to talk about plants moving, after all when was the last time a Sunflower passed you in the street and said hi?
Plants display radial symmetry, meaning similar parts of the plant like the leaves are arranged around a central part, the stem. This body plan allows plants to face the environment at all angles and also allows some of them to move, following the sunlight, to maximize their growth.
When you talk about plants moving you are talking about growth. Plant a seed and once it has germinated it forces its way out of its seed case and begins to move through the soil until it breaks the surface.
The plant then continues to grow upwards and this is a form of movement. The plant is moving to get as close as it is able to the sunlight that gives it the energy it needs to grow.
The whole reason for a plant to move is so it can grow and develop seeds. It needs to produce viable offspring for the next generation and be in a position to distribute that offspring so it can in turn develop into a new plant, either a genetic copy (clone) of the parent plant or a mixture of the two parent plants that contributed to it.
Some plants don't move very much but others grow rapidly and can be seen to have grown if they are observed on a daily basis. Bamboo is a particularly rapid mover.
Sunflower Following the Sun
This video uses time lapse filming to show how a sunflower moves to face the sun in the course of an afternoon.
Animals that don't move
Some animals are sessile. Sessile animals don't move, they attach themselves to a substrate, for example the ocean floor, and they remain there.
This seems to contradict the 7 defining characteristics of living things but it doesn't. These animals may spend their adult lives attached to the same place but when they were larvae they were motile, meaning they were capable of movement.
One example of a sessile animal is the Hydra. Hydras stay stuck to the spot but as larvae they move freely in water.
Being sessile is a primitive way of living so many sessile animals live in water and their ancestors can be traced back millions of years with very little change in form or function of the animal.
Members of the Phylum Porifera, also known as sponges, are aquatic animals with a simple body plan that has remained unchanged for a long period of time. They haven't evolved because they haven't needed to.
Sessile animals cannot actively seek mates so they have a big problem when it comes to reproducing. They get round this by relying on water currents to carry their eggs and ensure that they get fertilized.
Corals have a syncronized spawning letting all their eggs and sperm go on one special night. This mass spawning is triggered by a full moon the signal they have been waiting for. They spawn in this syncronized way to maximize the chances of the sperm and eggs finding each other and getting fertilized in the huge mass of the ocean.
This need to reproduce has created one of the most beautiful events in the natural world.
Coral Reef Spawning
This video explains the life-cycle of the coral reef and features some beautiful film of corals spawning.
Complexity and Movement
Complexity allows for adaptations that increase movement
The ability to move allows animals to colonize new habitats. Movement is an evolutionary advantage and animals are in an evolutionary arms race to outwit predators so movement became more and more complex over time.
Movement is a real driving force of evolution. If you are giong to move you need to know where you are going so you evolve a more complex body plan. You need a head with some sensory equipment, a body to house your gut and increasingly complex structures required for movement and you need an anus where you can excrete your waste.
Some animals have evolved segmented bodies, each segment having a particular role to play. This allows the body to become more complex and specialized.
Movement also requires structural support. Animals evolved skeletons to support their bodies while they moved. Some animals developed exoskeletons on the outside of the body. These exoskeletons are rigid enough to support movement but too rigid to allow growth. Animals like spiders and insects that have exoskeletons have to shed their skins every time they grow.
As evolution progressed internal skeletons developed so growth wasn't limited. Animals with internal skeletons grew bigger and more sophisticated.
Internal skeletons, like ours, need to be flexible so joints evolved to allow for that. They also needed to be lubricated so the bones wouldn't grind on each other. Synovial fluid evolved to lubricate joints and keep them moving.
Muscles evolved to help with the movement of the bones. The muscles relax and contract to help animals move. This requires energy so the digestive system needed to get more efficient so it could supply the energy necessary for movement.
Some animals went even further with specializations like swimming or flying. These all required changes in the body plan to allow them to be achieved.
The more you look into the subject of evolution and what caused animals to evolve the more fascinating it gets. There isn't sufficinet space here to talk about it all but hopefully I have given you a taste of this wonderful topic.
4 legged friends
Quadrapeds are animals that get around on 4 legs. There are loads of animals that do this but among these animals there are no insects, arachnids or birds.
Mammals are 4 legged animals that, with the exception of Apes and Humans walk on all four legs. Having 4 legs makes you stable and allows you to spread your weight. Most Amphibians and some reptiles are 4 legged too.
Quadrapeds can walk, run and jump. You might assume that quadrapeds all look quite similar but that isn't really true. Animals also evolve ways to protect themselves and ways to exploit a particular niche. Those that have been successful at doing this have survived to this day.
Quadrapeds built for speed
Some quadrapeds are able to run extremely fast. They can easily outrun us. They need to run fast either to catch prey or to avoid being prey.
Animals that run fast need to be able to use energy very efficiently and they need to have a balanced body plan with plenty of muscles. It helps if they can use oxygen effectively so they don't get cramps from lactic acid like we do when we run for too long.
There are a few examples of fast running quadrapeds below. You can vote for your favourite and comment on why you like that animal best. Watch the videos first to get an idea of which one you like best.
Cheetah running in Slow Motion
Watch and be amazed by how flexible the Cheetah is and how hard the muscles are having to work to propel this animal at such a speed.
Savannah Monitor Running
This video shows a captive Savannah monitor running after a lure. It is important to keep captive lizards like this fit and this is a great way of doing it.
Hippos can run faster than you might think. Their top speed is in the region of 30mph in short bursts, well in excess of how fast people can run.
Your favourite Sprinter
Vote for your favourite 4 legged runner. If you choose other please specify which animal and if it gets enough mentions I will add a video of it running.
Which is your favourite running quadraped?
Quadrapeds that swim
Lots of quadrapeds swim. Some are aquatic, while others swim to get food, cross rivers or escape predators. Lots of sea mammals have 4 legs but they have adapted them for swimming and some have fused their back limbs into flippers that are more useful when swimming long distances than legs.
Some quadrapeds can be remarkably agile in water while others are a little clumsy. There are some you will think of straight away like dogs and otters but how about Marine Iguanas and Crocodiles? They are four legged animals that swim perfectly well.
Now it's your turn to choose your favourite 4 legged swimmer. Watch the videos then cast your vote and see how everyone else voted.
This short clip shows the basic swimming movement of the crocodile
This video shows a really cute otter that is totally at home in the water.
Polar Bear Swimming
Look how graceful this beautiful Polar bear is in the water.
Which is your favourite Swimming Quadraped?
Quadrapeds that Jump
Some Quadrapeds are designed for jumping. They have strong muscular hindlegs and usually their front legs are shortened so they don't add extra weight to the animal.
Animals may travel vast distances by jumping. It can burn less energy than running but get you from A to B a lot faster than walking so it has a real advantage over walking and running.
Some animals only jump when they need to get away from a predator while others jump to get from one place to another. Animals that live in trees are called arboreal animals and they often travel from tree to tree by jumping. It can burn less energy than climbing down one tree and up another or it may just be safer for that animal to stay off the ground.
Below is a selection of videos of jumping quadrapeds for you to enjoy. You can also vote for the one that is your personal favourite.
Frog Jumping Slow Motion
These Kangaroos clearly have the jump start on this guy
Squirrel Jumping Funny Video
This Grey squirrel displays how high it can jump and how accurate it can be. A really funny and delightfully cute clip.
Jumping Quadraped Poll
Which is your favourite jumping quadraped?
Yes there is an animal with 4 legs that can fly perfectly well!
There are quite a few quadrapeds that can glide in a straight or slightly downward motion. Animals like flying squirrels are well known for this. They can't actually fly.
Bats can fly though and they have changed their body plan a lot to enable them to do so. Bats are capable of rapid flight and they have all sorts of other adaptations like echolocation to enable them to work out where they are going as they fly.
Two legged wonders
Birds have two legs. I'm not really counting humans because we sort of have 4 legs but we walk upright on only two of them. This type of walking is called Bipedal literally meaning two feet.
Most birds can fly but some are flightless and they have evolved in a different way. Lots of the worlds flightless birds are listed as threatened or endangered. It seems that for birds being flightless these days is a disadvantage.
The main problem for flightless birds is ground predators. A lot of flightless birds live on islands that were free of significant predators to the birds or their eggs. Since Humans spread around the planet this has changed.
The change may have been slow to us but in evolutionary terms it has been very rapid. Introduced predators like cats, dogs and rats have led to a drastic decline in flightless birds.
The flightless birds that have coped best with introduced species are the ones that are able to run at high speeds.
Birds that run
Running fast means you can get away from predators. The problem with running fast is that you need to be big and have a heavy build. You need to carry lots of muscle and be well adapted to energy conservation.
Most of the birds that run really fast are flightless. They have sacrificed their ability to fly in order to stay quick. In general the most successful birds are the ones that can fly.
Below are a few videos of birds running and after that a poll so you can vote for your favourite runner.
These ancient looking birds can run faster than you'd expect.
Kiwi on a treadmill
Kiwis are adorable and after breaking both legs this one was nursed back to health. Part of the recovery process involved using a treadmill as shown in this lovely video. Ok so it isn't really running but still a good example of how they move.
Ostrich Educational Video
This video talks about how fast the Ostrich can run and how it uses its wings when it runs. This is a really great educational video.
Running Birds Poll
Which running bird is your favourite?
Birds that Swim
Plenty of birds have some swimming ability, some are better at it than others.
Birds can swim on the surface of the water and some can dive down underwater to catch fish or other aquatic prey.
Some of the swimmers have webbed feet enabling them to use their feet as paddles. Birds like ducks spend the majority of their time on the water and are clumsy when they walk around on land.
Penguins have to swim long distances to catch enough food to survive and to feed their young. They have waterproof fathers like other birds that spend lots of time on the water.
Most of the birds that swim can also fly but they need to take a long run on the water before they can get airborne. Penguins can't fly and look a lot more at home on the water than they do on land.
Time for some swimming birds and the inevitable pick your favourite poll, enjoy.
Some beautiful footage of a penguin swimming underwater.
This video of a swan swimming around as her Cygnets climb on her back is so adorable. Look at how serene the swan looks as it swims.
Cormorants Swimming Educational Video
You'd never expect a bird to be this graceful underwater.
Swimming Bird Superstar
Which is your favourite bird that swims?
Birds that Fly
Most birds can fly but the way they fly can be dramatically different.
All birds that fly have evolved hollow bones to make them as light as possible so they can get into the air and stay airborne. Feathers are also crucial allowing birds to glide and protecting them from the weather as they fly.
Birds are aerodynamic and we have studied how they fly when developing aeroplanes, our own flying machines.
Flight is used to catch prey, avoid predators, migrate, travel from place to place and even in courtship displays. Birds are totally amazing. They are so varied it isn't possible to include them all but here are a few videos of flying birds for your enjoyment.
Hummingbird Flight in Slow Motion
This beautiful slow motion footage shows how the Hummingbird hovers. This takes a lot of energy and the Hummingbird feeds on sugar rich nectar to get the energy it needs.
Eagle Flying in Slow Motion
Beautiful video taken in slow motion showing an eagle fishing.
Barn Owl Flying in Slow Motion
Which is your favourite flying Bird?
Getting yourself moving
Now you've taken a look at how animals move why not try doing some movement yourself.
Get all those bones jiggling, muscles twitching and work up a bit of a sweat. Exercise is great for us and we will be healthier if we do some exercise every day.
I've found a nice fitness video for you to have a go at but running, cycling, swimming, and my favourite dancing, are all great forms of exercise. Get active and get your kids active too. They will thank you for it someday.
A short exercise video for all the family
Get moving with gifts from Amazon
Time to get those fingers moving on the keyboard and let me know what you think of all those moving animals.