Darwin's theory: those that adapt survive

Tuesday, 28 March 2017
The Galapagos are connected to Darwin because he began to develop his theory of Natural Selection after visiting the islands. On the ship, during our vacation there, we were treated to lectures on wildlife and other topics relevant to the Galapagos. Martin, one of the trained naturalists talked about evolution one afternoon.

Sally Lightfoot Crab hunts on the rocks.

He explained Darwinian Theory. The basic concept is that animals produce more offspring than can survive due to natural circumstances or happenings in nature. The stronger, most adaptable live. "Strongest" means that the animal survives, perhaps gets lucky, and he is the “strongest.” This was not what I thought the "Natural Selection" theory was based on. I thought that literally the "strongest" animal is the one to live. Not necessarily so.

Nazca Boobie chick waits to be fed.

Surprise - but Darwin was not a scientist. (Notes based on information from a Silversea publication:) He was born in Shrewsbury, Shropshire, showing an early fascination with the natural world. As a medical student at Edinburgh, he found that he just couldn't handle the trauma of surgery traumatic and decided to get his Bachelor's degree at Cambridge with the goal of serving the Church of England.

In 1831, Darwin joined the voyage of The Beagle as an unpaid companion and Geologist. This experience and more than 20 years of study led to his theory of evolution. He went to the Galapagos, visited 4 islands, and stayed on shore for 19 days.

Sea Lions lounge on the beach after going out to sea to feed.


Ultimately, Darwin's theory acknowledged: “The one most adaptable to change survives.” To expand with an example, it is interesting to note that the Galapagos Tortoises changed the shape of their shells over time to adapt to the landscape of the different islands. Read more about that here. 

Evolution is not directional. When do creatures change and adapt? They evolve when they struggle and suffer then, adaptation occurs. Changes in populations = evolution. Darwin's theory wasn't so much about man evolving from apes but instead he focused on slight CHANGES to the animal. Another example is how, over time, finches beaks changed to accommodate the food supply in the Galapagos islands. Their beaks have evolved so they can eat off the ground, in the trees, from cactus, seeds, etc.

Night gull sits on its nest during the day, preparing to hunt at night.

If an animal doesn’t adapt it is because it doesn’t have a need to change. Species are limited in the Galapagos because food is scarce. The islands are isolated, fragile ecosystems.

14 species of finches in Galapagos derived from a single species

Sunday, 26 March 2017
(Notes come from Silversea's publication.) The nickname “Darwin’s Finches” was attributed to these finches because they played such an important role in Darwin’s thoughts that eventually led to his development of the theory of evolution by means of natural selection. 



Darwin was interested in the diversity of the species and how quickly they seemed to have evolved from a common ancestor and adapted to different food types on each island. These adaptations are mainly manifested in the shape and size of their beaks.

Despite all their fame, these birds are not particularly beautiful or striking, although they do have a melodious lilting song. They all look pretty much alike (size, plumage, behavior). They are small, sparrow-sized land birds with drab black and brown or olive feathers. They have short round wings and short tails which are cocked to one side.


Although commonly seen, they are hard to tell apart without close observation. The major difference remains with size and shape of their beaks. It is believed that all 14 species derived from a single species similar to the Blue-back Grassquit commonly found along the Pacific Coast of South America.

Galapagos Prickly Pear Cactus

Friday, 24 March 2017


(Notes about the Galapagos Cactus come from Silversea Excursion publications): Arid conditions prevail in the Galapagos archipelago. Due to the geography, there are many drought resistant plants that can live with very little water. Much of the landscape is harsh and dominated by this type of vegetation.

The most common plant in the dry inland portions of the Galapagos is the cactus. These succulent plants are able to store water in their stems and leaves, allowing them to thrive in hostile climates and during times of drought.


Most cacti have spines, which have evolved from leaves. Spines serve several purposes. They guard against predation, provide shade to keep the internal temperature of the plant lower, and the spines channel rainwater towards the base of the plant.

Another important adaption of the cactus is the waxy coating that covers the skin. This is called the “glaucus bloom” and it reduces evaporation as the plant seals in moisture. Leaf-like stems, known as "pads" store and conserve moisture and work as photosynthetic organs for the cacti.


Endemic cacti in the Galapagos Islands include the Lava Cactus, Candelabra Cactus, and the species of Prickly Pear.

We watched a Land Iguana climb a Prickly Pear and strip a portion of its spines so that it could take a bite! Check it out here: 

Land Iguanas on the Galapagos - yellow, brown and pink

Tuesday, 21 March 2017
Land Iguana shows off his yellow colors. The males iguanas are larger than the females.

(Information and description from Silversea Expeditions publication): There are three endemic species of Land Iguanas in the Galapagos archipelago. One has a yellow/orange color. One is brown and whitish, and the other was identified in 2009 and has a distinctive pink coloration with some black stripes along their back. The late discovery was because of how remote the land is where they are found. Approximately 450 pink iguanas are found in the world!
This photo shows the pink coloration of one species of the Land Iguana.


Land Iguanas are much larger and more colorful than Marine Iguanas. They can grow to more than three feet in length and are stocky with a wide girth. They live in dry, arid portions of the islands. They are diurnal – that means they move, and eat during the day and sleep during the night.


Our guide today told us that the male iguanas are easy to spot because they are much larger than the females and that the males have spikes on their back and on the top of their heads. After those clues, I was able to pick out a huge male iguana.
Just look at those claws! We watched one climb a cactus and break off pieces to eat.

Iguanas are not lazy, they conserve energy in the heat by moving slowly. Although in our experience, we noticed that they are able to run at top speeds. They burrow into the ground, creating tunnels, which give them a bit of a respite from the sun during the day and a place for their nests.