In 1831 Charles Darwin left on the HMS Beagle on a five-year voyage around the world. He left against his father’s will as the ship’s scientist, and studied the natural world around him on his journey. The ship left Plymouth, England and traveled across the Atlantic Ocean around South America, then across the Pacific to Australia, then to South Africa, and finally back to England.
On his journey, he noticed that there was a large variation in the living things he saw and began to wonder why that was. Darwin reached the Galapagos Islands in 1835. In the Galapagos, he noticed that animals varied from island to island. In particular he noticed a family of birds whose beak was a different shape depending on which island they lived on. Darwin linked the shape of the bird’s beak with the type of food that made up the majority of the birds’ diets. The shape of the birds’ beaks is an example of an adaptation, something that helps a living thing survive or reproduce more easily. This led him to develop the theory of evolution by natural selection, one of the most important theories in biology.
Darwin used these observations and came to the conclusion that the reason the organisms were different was due to gradual changes over time. The organisms which had advantageous adaptations had a high chance of surviving and reproducing, meaning they had a higher chance of passing their genes onto the next generation. Those organisms that did not possess these adaptations had a lower chance of survival and reproduction, therefore having a higher chance of dying before they could pass on their genes. Over many generations, organisms evolved to be better suited to their environment. While still technically a ‘theory’, Darwin’s ideas have been accepted by the scientific community as the reason for varied life on Earth.
In order for organisms to survive, they need to have adaptations which give them an advantage when living in their environment. Every animal, plant, bacterium, fungus, archaeon, and protist has characteristics that allow it to be successful in surviving in its habitat. These adaptations can be categorized into behavioral, structural, or physiological. Behavioral adaptations can be inherited or learnt. Behavioral adaptations include communication and swarming. An example of a physiological adaptation is the ability to make venom. Structural adaptations are ways the organism's body or structure is adapted to help the organism survive or reproduce. An example of a structural adaptation could be the streamlined shape of a dolphin which allows it to move through the water more easily.
Organisms compete with each other for resources. These resources could be water, food, sunlight,
or space. Organisms also compete with each other to reproduce. Organisms which are well adapted will have a higher chance of getting the needed resources. If organisms are unsuccessful and are unable to move to another habitat, they will not survive.
The Polar Bear, Ursus maritimus, is a bear that can be found in the Arctic Circle. It is a mammal and an apex predator that spends a lot of time in and around water hunting for food. Its main source of nutrition is seals. The polar bear is well adapted for its habitat. It has large paws which allows the bear to get a better grip on the ice and not sink into the snow. It is well camouflaged as it has white fur which allows it to hide from its prey on the snow and ice. Thick layers of fat stop the animal getting cold. The bear also has small ears which reduces the heat lost from them.
The Saguaro Cactus, Carnegiea gigantean, is found in many desert habitats, especially in the deserts of North America. It can survive in a hot, dry environment, and has many characteristics that allow it to do this. It is covered in spines which not only stop animals from eating the cactus, but also reduce the amount of water loss due to transpiration. They have a thick epidermis to reduce water loss. The inside of the cactus stem is filled with a spongy tissue that is used to store water.
Essential Questions for Adaptations
- Why are animals different?
- How are animals different?
- How are predators adapted to catch prey?
- How are prey adapted to not be easily caught by predators?