Evolution: The Finale!

The last point in our series on evidence for evolution is actually quite simple. It is the age of the Earth. We know, having studied our planet and space, that the Earth is approximately four and a half billion years old. Life has been around for about 3500 million years. This information begs the question – how could life not have changed in that time? There is no way that all life would have remained stagnant and exactly the same for all that time. Having gone from volcanoes and lava covering the Earth, through to forests covering the world to different environments in different places (but at the same time) – how could nothing have changed?

And now I release you, my little scientists, to go and educate the world about the evidence for evolution. And for the little genius out there reading this that finds the evidence to make it a law – you win the Nobel Prize. Congratulations.

Evolution: Comparative Embryology.

So you know by now that when a Mummy and a Daddy love each other very much, they have sex. Well, I’d hope you do by now anyway. And as you (again, hopefully) know, having sex can create a baby. And a baby starts out life as just a few small cells and then grows from there. By the end of about 8 weeks in humans, the child has basic limb shapes and is well on their way to being an incredible annoyance to everyone in the family.

What scientists have observed in a multitude of different animals is that during the early stages of development in the womb, many organisms develop in the same manner before becoming differentiated (fancy word for different).

Again, this points towards the suggestion of a common ancestor.

The next (and final) card in our complex house of cards is: A Surprise! You’ll have to wait and see.

Evolution: The Pentadactyl Limb

Comparison of the anatomy of various plants and animals provide indirect evidence of their evolution from common ancestors. The front flipper of a seal, a cat’s paw, a horse’s front leg, a bat’s wing and your own hand all look different and perform different functions. However, they all consist of the same number of bones, muscles, nerves and blood vessels arranged in a similar basic pattern. The basic pentadactyl limb (a limb with 5 digits) can be traced back to the fins of a certain fish from which the first amphibians are thought to have evolved. These fundamentally similar structures are called homologous structures.

 

 

 

 

 

 

 

 

 

 

 

 

Basically, there are a lot of animals (mostly mammals) that have a very similar arm structure. They have 1 upper bone, 2 lower bones and lots of bones that make up “fingers”. All of this is pointing towards the idea of them having a common ancestor.

Next in our line up: the reclusive Comparative Embryology.

Evolution: Biogeography or Geographical Distribution

Yes, I know I said a dirty word; geography, but believe it or not, geography is actually kind of useful in Science. And all I’m really asking for you guys to know is the name of most of the continents (there are 7) and the general shape.

Biogeography is the study of the distribution of plants and animals, both now and in the past (bio/biology = living things, geography = places). What you start to find (and this is evidence for both the theory of evolution and the theory of plate tectonics) is that along the borders of the continents, you find some very similar, if not the exact same, fossils.

Scientists used these similarities and came up with the idea that at some point in the Earth’s history, all the continents were joined together. Then they started to separate and become the landmasses that we know and love today.

This is all in the lead up to help explain this next idea. Scientists propose that, when the continents started to drift apart, there were living organisms! Shocking, I know. As the continents moved and the environments changed, it is suggested that the organisms adapted to better suit the environment. The example most commonly given is that of the flightless bird. We all know that the emu can’t fly. We all know the ostrich can’t fly. Now, hands up any of you who mixed these two birds up occasionally when you were younger?

Understandable, really. They’re both creepy, angry looking birds. I’m getting a bit paranoid one of them is watching me, just thinking about them.

Anyway, other flightless birds also include cassowaries, kiwis, rhea and penguins. Think about all of the countries that you would find these birds in. You can start to see why we might say that they all evolved  from a common ancestor, right?

In summary, the next point in our evolution theory evidence stack is the similarity between species in vastly different environments.

Next topic up for discussion: The Amazing, Stupendous, PENTADACTYL LIMB!!

Evolution – The Fossil Record

Evolution. Its a controversial topic at best, between the religious groups arguing against it, the hard-core scientists gung-ho for it and the middle men who see the evidence for it but don’t want to let go of their belief in a higher power. Personally, I’m somewhere between the middle and the extremist scientist.

Let’s take a step back though. What is evolution? Simply said; evolution is the process that living organisms go through over time to better fit their environment. Does anyone here watch “The Big Bang Theory”? Remember when Sheldon was talking to his sister about the possibility of her having a baby Sheldon, an improved model, a “Sheldon 2.0” – that’s evolution in a nutshell. A bigger, better,more suited organism.
Most people don’t deny the idea of evolution but what we find hard to believe and endorse is this idea of humans evolving from apes. Yes, there are lots of similarities between us and the chimps, but then again, you could argue that for dolphins as well. Dolphins and humans are the only two species that have sex for fun.

Humans and monkeys, aside; there is an overwhelming pile of evidence supporting the theory of evolution.

The first piece of evidence (and one of the more easy parts to remember) is the FOSSIL RECORD!

The fossil record relies stratigraphic sequence (if you can remember that term and use it then you will sound really, really, really smart). It simply means that the fossil record uses the idea that the layers further down in the Earth are older. Think about it, you finally make the effort to clean your room and all that stuff sitting on the floor under the mountains of everything else has been there the longest. “Hey! I haven’t seen this skirt in ages!” “So that’s where my other iPod cord went”. Its the same principle.
You also find that the fossils further down in the crust are actually a lot simpler than the ones at the top. You get lots of jelly fish, bacteria, single-celled organisms and the occasional shell in the lower layers. These build up and you start finding more complex fossils like fish and then finally, the MIGHTY DINOSAUR! We don’t have all that many fossils of mammals and such but we do have many that have been well-preserved due to the Ice Age. Relax, they’re dead, so even if they thaw out they won’t come back to life.

This progression from simple life forms to more complex organisms is but the first card in our pile of evidence.

Next up: Geographic Distribution.