Special Sub-Topic: The Way We Were
|DNA, the molecule that sparked life, had been around for billions of years, but life remained quite dull for most of this. Around 630 million years ago (mya), however, the first complex animals emerged, and life would never look back. Which of these is LEAST like the first complex animals on earth? |
A stingray. Fossilised evidence of stingrays shows that they evolved several hundreds of millions of years after animals such as jellies and sponges.
Jellyfish, polyps and sponges are so different to what many would think of when asked to imagine an animal - they are largely stationary, have no eyes or complex organs, and sometimes resemble plants.
Still, the arrangement of cells (which are complex in themselves*) which make up these animals is an incredible solution to life, and provides the blueprints on which we are all based.
*The cells referred to here are eukaryotic (with membrane bound organelles), which are larger and more complex than the bacterial cells which existed before them.
|Around 90 million years after the first complex animals emerged, there was a major change. A feature was developed which allowed these ancient animals' bodies to be preserved in the rocks when they died. This feature is still possessed by crabs, snails, and lobsters. What is this feature? |
A shell. Around 540 mya, what became known as the Cambrian "explosion" occurred. Here, lots of new species evolved, and many possessed the first shells, and were therefore called hard-bodied organisms. In contrast to the soft-bodied organisms which already existed, these shelled animals could be partially preserved in the rocks as fossils, and so made it much easier for geologists and natural historians to determine the age of ancient rocks and animals.
Another important feature developed in this Cambrian explosion was the backbone. This was of vital importance to the progression of life. It meant that animals could grow bigger and more complex.
|Some animals grew gills, which meant they could take in more oxygen and so could move faster. Thousands of these animals still exist today - big, small, beautiful and dangerous. What animals are these? |
Fish. Shortly after the Cambrian explosion, jawless fish evolved. These fish have no backbones and so are called invertebrates. Few species of jawless fish still exist, but one which does is the rather nasty looking hagfish.
Around 450 mya, bony fish evolved from jawless fish. These animals were very successful and are still found all over the world.
Another type of fish is the shark, which has a skeleton made from cartilage instead of bone. The largest fish in the world is a type of shark - the whale shark.
|Although most life was still in the water, one fish developed a simple organ around 400 mya which allowed it to breathe air and so live on land. What type of organ was this? |
A lung. Fish get most of their oxygen from water, which passes over their gills. Some, however, evolved a type of lung which allowed them to absorb oxygen from air. Some types of fish also left the water and grew four legs, allowing them to walk on the land. This gave rise to a new type of animal - the amphibian.
|Amphibians evolved around 370 mya, and spent part of their lives on land and part in water. Next were the reptiles, which evolved from amphibians 340 mya and which lived almost entirely on land. Which of these is a reptile, not an amphibian? |
A turtle. An amphibian's skin easily dehydrates and so they must return to the water regularly. Reptiles solved this problem by evolving a cover of waterproof scales. Reptiles also lay hard eggs as opposed to the soft eggs of amphibians.
Amphibians were not the first animals to take to the land, but were beaten by the invertebrates, which made the move some 80 million years earlier.
|Shortly after the rise of the dinosaurs (230 mya), the first mammals emerged. These evolved from a type of reptile, but developed several characteristics of their own. Which of these is not a quality of a typical mammal? |
They are cold-blooded. Mammals were around for most of time when dinosaurs were, but were small, burrowing creatures. They were prevented from becoming large due to the dominance of the reptiles. However, after the extinction of the dinosaurs (around 65 mya), mammals were able to become the dominant animals on earth.
Though most mammals give birth to live young, some (monotremes) lay eggs, and though most mammals have hair/fur, some marine mammals (e.g. dolphins) have gotten rid of their fur so as to become more streamlined. All mammals, however, suckle their young with milk.
|Another type of animal which evolved from reptiles were the birds. This happened around 155 mya. TRUE or FALSE, the scales of reptiles evolved into the feathers of birds.|
t. Birds, like reptiles, lay hard-shelled eggs. Their feathers and hollow bones meant that they could develop flight. Also, they evolved a lightweight beak in place of a bony jaw, reducing their overall weight. These adaptations meant that they could fly more gracefully than the winged reptiles which evolved before them. Flying reptiles were totally wiped out in the mass extinction 65 mya.
|As mammals evolved, they achieved new standards of intelligence. But as well as brains, they had brawn. TRUE or FALSE, the largest animal to have ever lived is/was a mammal.|
t. The title goes to the blue whale. Larger than even the largest dinosaurs, the whale belongs to a group of mammals which returned to the water around 55 mya. The blue whale was only able to grow to the size it is (90 ft long and 150 tonnes) because of the buoyancy of the water, as an animal that size, if living on land, would suffocate from its own weight.
As well as mastering the land and the water, mammals also took to the sky, as the bat evolved special adaptations for flight. This happened around 40 mya.
|The order which we humans are part of first appeared around 60 mya. This order also includes gorillas, orang-utans, tarsiers and lemurs. What is the name of this order? |
Primates. Primates are able to grasp things with their hands, meaning they could move around easily in the trees. Their eyes face forwards, meaning that they can accurately tell how far away things are - another important adaptation.
Many, such as the orang-utans, lemurs and aye-ayes have remained in the trees, but some grew larger and came down to live most of their lives on the ground.
The largest of the primates is the gorilla, which can weigh up to 400 pounds. They live in small social groups and now only exist in a few small areas in Africa.
|150,000 years ago, after all the fish, lizards, llamas, dolphins and snow leopards had evolved, along came the humans. What is the fancy scientific name for human beings? |
Homo sapiens. These scientific names are usually Latin words which describe the animal or its habitat. Occasionally scientists will joke around with animal names. If you'd like to learn more, please play my quiz, "Taxonomy Is Not For Wimps."
The appearance of Homo sapiens 150,000 years ago signalled the rise of the most successful animal to ever live on planet earth. Humans have made huge advances in technology and depend on it for many things in their every day lives, yet it is easy to see many of our own qualities in the animals that still swim in the seas, or swing through the trees.
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