Humans share the Earth with millions of other kinds of organisms of every imaginable shape, size and habitat

This variety among living things is called Biological Diversity

Biological Diversity leads to many different scientific questions

How did different organisms arise? How are they related?

These questions can be answered using scientific facts, observations and hypothesis

Theory – a well supported testable explanation of phenomena that have occurred in the natural world

Using many different scientific facts, observations and hypothesis, scientists answer the questions of Biological Diversity

Evolution – change over time, the process by which modern organisms have descended from ancient organisms

Contributed most to our understanding of evolution

Was born in England on February 12, 1809

Completed college and joined the crew of a ship called the H.M.S. Beagle

He set sail in 1831 for a 5 year voyage around the world

Although no one knew it at the time, this voyage was one of the most important in the history of science

Darwin made numerous observations and collected evidence that led him to propose a revolutionary hypothesis about the way life changes over time

This hypothesis is known as The Theory of Evolution

Wherever the ship anchored, Darwin collected plant and animal specimens

While at sea, he would study his specimens, record his findings and thoughts, as well as read the latest scientific books

Darwin quickly began to realize that there is an enormous number of species that inhabit the Earth

Darwin was intrigued that so many plants and animals were very well suited to the environment that they lived in

This also included the different ways in which they survived and produced offspring

He became puzzled when considering where animals did and did not live

Even though there were similar living conditions in different parts of the world, why weren’t similar animals found all over the Earth

Ex) there are grasslands in Europe and America, so why did Kangaroos only live on Australian grasslands?

Fossils – preserved remains of ancient organisms

Darwin collected fossils during his travels and noticed that there were some that resembled organisms that are still alive

Other fossils looked unlike any creature he had ever seen

Darwin wondered what happened to these species and if they were related to any species still living

These small islands located off the coast of South America influenced Darwin most

Even though the islands were close together, they had very different climates as well as different types of plants and animals

Land Tortoises

Darwin learned that they varied in predictable ways depending on the island they inhabited

Hood Island Tortoise – had long necks and saddle-backed shells with large openings for the neck and legs

Allowed it to reach sparse vegetation on the island

Isabela Island Tortoise – had dome shaped shell and shorter neck

Vegetation on island is closer to the ground and within easy reach

Birds

Darwin collected several different small brown birds

He noticed that they all had differently shaped beaks, but thought nothing more of it at the time

Darwin spent a great deal of time thinking about his findings

He observed that the characteristics of many animals and plants varied noticeably among the different islands

After returning to England, he wondered if these animals had once been members of the same species and evolved from a common South American Ancestor

Darwin’s journey on the H.M.S. Beagle came during a time of much scientific advancement

There were many scientists that were beginning to challenge common views about the earth

Many people thought that the Earth and all of its inhabitants were no more than a few thousand years old

Also, people thought since its original creation, neither the planet or its living species had changed

New evidence was being discovered that contradicted this “non-changing” view of the world

Fossil evidence was showing that there was not one, but several periods of creation

After each period, there was some type of catastrophe which killed many life forms

Darwin realized that his data contradicted the idea that Earth and its creatures were “non-changing”

During the 18th and 19th centuries, scientists examined the Earth in great detail

Data was gathered which suggested the Earth was very old and changed over time

2 scientists whose data was important in supporting this concept was James Hutton and Charles Lyell

Hutton published a hypothesis which states that geological forces have shaped the Earth and they occur over a long period of time

The resulting structures are exposed to natural forces (such as rain, wind, heat and cold) which give them their final appearance

Since these processes happen very slowly, often over millions of years, Hutton suggestions that the Earth is much older than a few thousand years old

Lyell authored a book called Principals of Geology

he stressed that scientists need to explain past events in terms of processes they can actually see (since they are still happening ~ ex. Volcanoes, Earthquakes, etc.)

When Darwin was on the Beagle, he was given a copy of Lyell’s book and was able to see first hand what he was talking about

Darwin experienced an earthquake which lifted a stretch of shoreline and the animals attached to it 3 meters above its original location

Through Darwin’s understanding of geology, he applied his knowledge and asked 2 questions

1. If the Earth can change, could life not change as well?

2. Since these geological changes, and possibly life changes occur over a long period of time, the Earth must be extremely old!

A French naturalist who was among one of the first scientists to recognize the following

that living things have changed over time

Also realized that all species were descended from other species

Organisms are somehow adapted to their environment

He stated that by selective use or disuse of organs, an organism could acquire or lose certain traits during their lifetime

These traits could then be passed to their offspring and cause a change in the species

Tendency Towards Perfection

Organisms are continually changing and acquiring features to help them be more successful in their environment

Ex. Birds kept trying to fly, so they developed larger/stronger wings so they could be better fliers

Use and Disuse

Organisms could alter their bodies by using something more or less

Ex. If the bird kept trying to use its wings, they would get larger

Inheritance of Acquired Traits

If you used a particular structure often and were able to enhance it, that trait would be passed to the offspring

Ex. The offspring of the bird with large wings would then get large wings (muscle example)

Unlike Darwin, Lamarck did not know how traits were inherited

He didn’t know that an organisms behavior (how much it does or does not use something) has no effect on its heritable characteristics

Lamarck was the first to hypothesize that organisms are adapted to their environments and that they can change overtime

English economist who published a book in 1798 noting that babies were being born faster than people were dying

He stated that if this trend continued, there would eventually be insufficient food and space for everyone

The only forces that worked against this trend were war, famine and disease

Darwin applied this to plants and animals

Humans reproduce less frequently than other animals and plants

ex. A maple tree can produce thousands of seeds; an oyster can produce millions of eggs

Darwin suggested that more offspring must die rather than survive and applies this information to the question of how evolution occurs

When Darwin returned from his voyage, his specimen collection caused a stir in the scientific community

The bird specimens which he thought were different species were actually found to all be finches

All of the Galápagos Island species also looked similar to many animal species found on the South American mainland

Darwin continued to study his specimens and record his findings of what might have caused such changes and diversity

In 1858, Darwin received an essay from a fellow naturalist Alfred Russel Wallace

In it Wallace summarized the same thoughts on evolutionary change that Darwin had been recording

In 1859 Darwin published his findings in The Origin of Species

He proposed a mechanism for evolution which he called natural selection and how this process had been taking place for millions of years and continues today

Darwin stated that members of each species vary from one another in very important ways

This variation can occur as a result of humans as well as in nature

Plant and animal breeders use heritable variation (also referred to as genetic variation) and select organisms which are the best producers

The offspring would inherit the trait which makes them best producers as well

Artificial Selection – nature provides the variation and humans select those variations which are found most useful

Darwin compared processes in nature to artificial selection

By doing this he suggests how evolution occurs

Darwin suggests that the best suited organisms are the ones which will survive as a species

Struggle for existence – members of a species need to compete regularly for life necessities (space, food)

Survival of the Fittest – organisms that are better suited for their environment survive

Fitness – the ability of an individual to survive and reproduce in its specific environment

Adaptation – any inherited characteristic that increases an organism’s chance of survival

Because of its similarities to artificial selection, Darwin called survival of the fittest natural selection

In both instances, only certain individuals in a population reproduce

Causes an increase of the fittest organisms

Can occur with or without human involvement

Over time, natural selection results in changes in the inherited characteristics of a population

This isn’t seen directly, but over many generations

Darwin proposed that over long periods of time, natural selection produces changes in organisms which can lead to:

Different body structures

Different niches in a population

Cause them to inhabit different locations

These changes can cause organisms to be different than their ancestors

Descent with Modification - the principle which states that each living species had descended, with changes, from other species over time

This principal suggests that all living organisms are related to one another

Common Descent – the principal which suggests that all species – living and extinct – were derived from a common ancestor

Fruit Fly example

Cats > Mammals > Non-Mammals > Common Ancestor ex.

Darwin’s argument suggests that the Earth was millions of years old and that over that time it was continually evolving

We can see evidence to support this idea in multiple ways

1. Fossil Records

2. Geographic Distribution of Living Species

3. Homologous Body Structures

4. Similarities in Embryology (early organism development)

Fossils – preserved remains of ancient organisms

By comparing the age and structures of different fossils, Darwin could document that life on Earth changed over time

After comparing the finches Darwin saw on The Galápagos Islands, he wondered how they came to be similar but yet very different from each other

His idea was that each group changed over time as they adapted to their environment

In addition, when there were similar ecosystems which contained similar but different organisms

Darwin suggests that they would be exposed to similar ecological conditions, causing them to evolve in a similar manner

Darwin noticed that there were many different body structures among animals with a backbone that were similar to one another

Limbs of reptiles, birds and mammals (arms wings and flippers) vary in function, but all had the same basic bone structure

Homologous Structures – structures that have different mature forms, but develop from the same embryonic tissues

This idea provides strong evidence that all four-limbed vertebrates (organisms with a backbone) descended, with modifications, from common ancestors

Vestigial Organs – structures that may resemble small legs, tail or other organs which do not serve a direct purpose

Embryology – branch of biology that studies the formation and early development of organisms

During the early stages of development in vertebrates are very similar in appearance and structure

The same groups of cells develop in the same order and in similar patterns to produce the tissues and organs of all vertebrates

These common cells and tissues create homologous structures

1. Individual organisms differ, and some of this variation is heritable

2. Organisms produce more offspring than can survive, and many that do not survive do not reproduce

3. Each organism has different advantages and disadvantages in the struggle for existence. The best suited survive

4. Species alive today descended with modification from ancestral species that lived in the distant past. This process unites all organisms to a common ancestor.

New scientific advances have both supported and expanded Darwin’s theories

His ideas today start new research into exactly how new species arise and why species become extinct