Evolution: History and Theory

Jean-Baptiste Lamarck ( ) First scientist to propose a mechanism for how organisms change (1809) Theory of change through use and disuse  Through time, a generation would use an organ more than previously, and would pass those traits on to their offspring

Lamarck’s Assumptions 1. Organisms have a desire to change. They have an inborn urge to better themselves for their environment. Ex: Birds tried to fly and eventually grew wings because of their efforts.

Lamarck’s Assumptions 2. Organisms can change shape by using or not using their bodies. Ex: The wings of a bird that does not fly would get smaller from generation to generation and the wings would eventually disappear.

Lamarck’s Assumptions 3. Organisms can pass on acquired traits to their offspring. Ex: If an animal developed muscles from running during its lifetime, it could pass those muscles on to its offspring.

Why was Lamarck wrong? Lamarck did not know about the inheritance of traits through the passing of genes.

Charles Darwin Relied on the Work of Others Thomas Malthus – Populations James Hutton and Charles Lyell – Geological Record Farmers – Breeding

Thomas Malthus Essay on the Principle of Population (1798) He predicts that the human population will grow faster than the space and food supplies needed to sustain it. Stated that the only checks on the human population were war, famine, and disease.

Influence of Malthus Malthus’ theory of population growth was observed by Darwin in other animal populations as well. In nature, Darwin saw many organisms that produced many offspring. Most died. Darwin wondered, what determines which individuals survive and reproduce?

James Hutton and Charles Lyell Hutton is the father of modern geology Based on layers found in rock structures, he proposed the Earth was millions of years old (1785) Lyell proposed that geological features could be built up or torn down over long periods of time (1833) Grand Canyon, Arizona

Influence of Lyell After reading Lyell’s book, Darwin was convinced that the Earth was old. Darwin reasoned that if geological phenomena could change the earth, then life on Earth could change as well.

Influence of Farmers Farmers improved their plants and animals through breeding. Within a population, there are natural variations.

Influence of Farmers Farmers bred the plants or animals with most desired traits. This process of humans allowing only the best organisms to reproduce is called artificial selection.

Who was Charles Darwin? ( ) English naturalist Traveled around the world on the Beagle (1831)—Famous in the Galapagos Islands Observed many species and fossils

Species of Interest Finches Tortoises Blue-footed boobies res/LandBirds/FinchTypes.jpeg

What is Evolution? November 24, 1859 Evolution: the change over time of the genetic composition of populations **Populations evolve, not individuals.

“Survival of the Fittest” Individuals in nature with characteristics best suited to their environment survive the struggle for existence. This principle is called survival of the fittest.

What is Fitness? Fitness is the ability of an organism to survive and reproduce in its environment. Ex: An animal that can easily avoid predators and mates regularly has higher fitness than an individual that does not mate.

Natural Selection The process by which nature allows only the organisms best suited to their environment to reproduce is called natural selection. I have called this principle, by which each slight variation, if useful, is preserved, by the term Natural Selection. —Charles Darwin from "The Origin of Species"

To sum up Darwin’s work…… 1. Species have the potential to increase in numbers exponentially. 2. There is a finite supply of resources. 3. Populations are genetically variable due to mutations and genetic recombinations. 4. Changing environments makes certain phenotypes more favorable. 5. Those organisms with the favorable phenotypes/adaptations will get the resources, survive, reproduce, and pass on their alleles. 6. The accumulation and change in favored alleles leads to changes in species over time, which we call evolution.

Natural Selection Resulting in an increase in brown gene frequency --“Survival of the fittest” --Descent with modification

Evidence from Peppered Moths that populations change in characteristics over time. typicacarbonaria

Peppered Moth There are two variations in color of peppered moths, light and dark. Prior to the industrial revolution, tree trunks were light colored. Predators were more likely to pick the dark moths. As a result, the moth population was primarily light.

Natural Selection: Genetic Variation is Key

Peppered Moth After the industrial revolution, trees were covered in soot making the trees dark. Now, predators were more likely to pick the light moths. As a result, the population shifted from being primarily light to primarily dark.

Natural Selection: Genetic Variation is Key

What is a Niche? A niche is the full range of physical and biological conditions in which an organism lives and also the way in which the organism uses those conditions.

How does a niche affect fitness? An organism’s fitness is higher within its niche than outside of its niche. Ex: A penguin’s fitness is higher in Antarctica than in Union County. Why?

Adaptive Radiation Adaptive radiation is the process by which a single species evolves into several different forms that live in different ways. Different niches for different beaks

Patterns in Evolution Homologous Structures  Indicate that organisms share a recent common ancestor.  The structures are similar and arise from similar stages of embryonic development  The structures have modifications that help the organism be better suited to its environment. (a) – humerus (b) – radius (c) - ulna Example: Human, Cow, Horse, Whale and Bird limbs

Analogous Structures  Do NOT indicate a recent relative.  These structures serve similar purposes for the organisms.  These structures are made very differently and arise from different embryonic parts. Example: Insect wing compared to bat wing

Vestigial Structures  These are structures that seemingly have no function in the modern day organism.  They indicate that perhaps the organism’s ancient ancestors may have used the structure in the past. Example: Wisdom teeth in humans