Evolution

Charles Darwin Developed a scientific theory of biological evolution that explained how modern organisms evolved over long periods of time through common ancestors. Evolution- change over time. The most famous of his observations were in the Galapagos islands.

How Darwin made his observations Whilst traveling on the ship the Beagle, Darwin came upon three major conclusions when observing the organisms on his voyage. They were: 1. Species vary globally 2. Species vary locally 3. Species vary over time

Species vary Globally Darwin didn’t just say, “Trust me on this one.” He sailed all over the world including to Australia, South America and Africa. Darwin noticed that different, yet ecologically similar, habitats around the globe.

Species Vary Locally Darwin noticed that although different, yet related, animals species often occupy different habitats within a local area.

Species Vary Over Time Darwin noticed that fossils of extinct animals were similar to living species.

James Hutton and Charles Lyell Many Europeans in Darwin's day believed the Earth was only a few thousand years old. Over the course of time, the science of geology began supporting other theories.

Hutton and Lyell’s contribution to modern day evolutionary theory Hutton and Lyell (geologists) concluded that Earth is extremely old (approximately 4.55 billion years old) and that geological processes that changed earth in the past are the same as processes that operate in the present.

Hutton and geologic change Hutton explained through his research of studying rocks, soil, mountains, and other geologic features that rocks can be built up and squeezed into layers. In turn, mountains can be worn down by rain reducing the sediment on the mountain’s surface.

Hutton’s conclusion was that the earth must be much more than thousands of years old. He introduced the concept of deep time- the idea that earth history stretches so far back that it is hard for humans to conceive- to help explain his postulate.

Lyell’s principle of geology Lyell’s big argument was that laws of nature that shaped the earth in it’s past are constant over time, so scientists must be able to explain what has happened in the past to understand what happens in the present. People called this thinking uniformitarianism.

For example Water erodes surfaces it runs across. It takes a long time for a little erosion to wear away at a rock. If the earth were only a couple thousand years old, then how could water carve out a valley or canyon?

Jean Baptiste Lamarck Darwin was given the credit, but was not the first person with the idea that organisms change over time. Enter Jean Baptiste Lamarck

Theory of Evolution by acquired characteristics Lamarck is famous for the theory of evolution by acquired characteristics. The most famous 'example' of the theory is the giraffe's neck, which supposedly stretched as the creatures reached for higher leaves in trees.

Problem Lamarck? Lamarck had a few major holes in his theory. They are: Organisms don’t have the inborn desire to become perfect. Evolution does not mean a species becomes better in some way. Evolution does not proceed in a predetermined direction. Traits acquired in an organism’s lifetime cannot be passed on to future generations. However, Lamarck was one of the first to try and explain evolution naturally through scientific process.

Population growth Thomas Malthus, an economist, predicted that if left unchecked, a population (in his observation it was human) would not have enough food or space to live in.

Theory behind population growth Darwin noticed that the theory behind population growth really applied more to other animals than humans. One oyster can lay over 1 million eggs in a year. If they all hatched, oysters would destroy the world!

Artificial Selection A.k.a selective breeding, this has allowed for desirable characteristics and even animals to survive over long periods of time.

Evolution through natural selection Combining Lamarck’s, Lyell’s, Hutton’s, and Malthus’s ideas, Darwin attempted to explain a natural process that in itself operated like artificial selection. He named the book On the Origin of Species.

The struggle for existence Darwin realized that if more individuals are produced than those that could survive, then organisms must compete for food, living space, and other limited resources.

Variation and adaptation Darwin understood that there is a variation amongst traits in every individual. Darwin hypothesized that some of these variations allowed for certain individuals to survive better in their environments.

For example If a predator was faster than other individuals in its population, it would be able to catch more prey. If the prey species were to be faster than a predator, then that prey would more likely avoid being caught.

A heritable characteristic that allows for a creature to survive and reproduce in it’s environment is called adaptation.

Examples of Adaptation

Survival of the fittest Different adaptations help an organism’s fitness (an organism’s ability to reproduce and survive) in it’s environment. Survival means more than just living, it means passing on the heritable trait to the next generation.

Natural Selection Natural selection occurs in any situation in which more individuals are born than can survive, there is a heritable variation, and there is a variable fitness among individuals.

Common Descent The principle of common descent states that all species, living and extinct, are descended from common ancestors.

Evidence of Evolution Biogeography- The patterns in the distribution of life. Patterns and distribution of living and fossil species tell us how modern organisms evolved from their ancestors.

Biogeography and the Galapagos: similar, yet different To Darwin, Galapagos species of finch had evolved from mainland species. Due to natural selection on each island produced the variation between species of finch.

Different, yet similar Similar selective pressures can produce the same types of result between continents, resulting in physiologically dissimilar species that are exhibit some of the same properties.

The Age of the Earth, and fossils Evolution is not something that occurs over night, it takes a long time to occur. Half a century after Darwin’s death, physicists discovered radioactivity. Radioactivity can help determine the age of rocks and minerals. Radioactive dating has determined that the earth is 4.5 billion years old.

Recent fossil finds Fossils that have been recently discovered have created links between modern day animals and their extinct ancestors. Other finds in the fossil records have shown links between four legged creatures and bipedal organisms.

Embryology Embryology is the branch of biology that studies the formation and early development of living organisms.

Embryology can be used to show homologous structures amongst varying organisms.

Homologous and analogous structures Homologous structures- Structures that have been shared be related species and have been inherited from a common ancestor.

Analogous structures Structures that are very physiologically different, yet share the same function.

Vestigial Structures Structures that are inherited from our ancestors, but no longer serve a purpose.

Embryology Providing evidence of common descent Similar patterns of embryological development have provided further evidence that organisms have descended from a common ancestor.

On the Genetic Level At the molecular level, the universal genetic code and homologous molecules provide evidence of common descent.

Using Molecular Biology Molecular biologist have discovered almost identical versions of a homologous protein in almost all organisms from yeast to people, called cytochrome c. Cytochrome c is found in almost every organism that undergoes cellular respiration.

Testing Natural Selection One way gather evidence is to see evolution in action. When Darwin figured out that the birds he observed on the galapagos were finches, he figured they must have come from a common ancestor. (Enter Peter and Rosemary Grant)

G-UNIT!! The Grants have spent more than 35 years collecting data and researching the Galapagos finches.

Darwin’s Hypothesis: tested For Darwin to hypothesize that the finches had a common ancestor, and have it be supported, two assumptions must be tested: 1. For beak size to change shape and evolve, there must be the heritable raw genetic material needed for natural selection. 2. Differences in beak sizes must provide differences in fitness.

The Grants did their testing on the medium ground finch The Grants did their testing on the medium ground finch. The island was big enough to sustain the population, and small enough for the Grants to capture and analyze the finches from time to time.

The Grants recorded data like, wing size, beak shape and size, feather color. The Grants noticed individuals of certain beak shape and size could survive longer depending on food availability or prolonged weather conditions.

When food is scarce, birds with larger beaks tend to survive longer When food is scarce, birds with larger beaks tend to survive longer. As a result, the larger beaked finches are more likely to survive and reproduce.

So what does this research show us about natural selection? The Grants have documented that natural selection takes place in wild finch populations frequently, and sometimes rapidly.