Title: Chapter 15: Darwin
1Chapter 15 Darwins Theory of Evolution
2Theory of Evolution
- Evolution
- Gradual process (over millions of years!) by
which modern organisms have descended from
ancient ancestors - Evolution is based on scientific facts,
observations and hypotheses - Proposed by Charles Darwin lets examine his
voyage and data.
3Charles Darwin
- English naturalist
- Set sail on a 5 year cruise on the HMS Beagle in
1831
4The Voyage
- At each stop, Darwin
- Made biological and geological observations
- Collect plant and animal specimens
- Collected Fossils
5Darwin Observed
- A great deal of biodiversity!
- Vast number or plants animals
species lived at each location - Each species seemed well adapt to its environment
- An intriguing geographic distribution of species
- Today we know that there are about 1.75 million
species on the planet. - This number only represents 1 of all species
that ever lived on Earth!
6The Galapagos Islands An Important Influence on
Darwin
- Small group of Islands located 1000km west of
South America - The Islands had very different climates
- Darwin noticed that plants and animals varied
noticeably from island to island. - Ex
- Land Tortoises
- 14 different sub-species
- 4- extinct
- 1 almost extinct
- 9- living
7Darwin found the shell shape corresponds to the
habitat
The Giant Tortoise
Lonesome George
8Darwins Thoughts
Has everything always been here?
How old is the earth?
Where did all the animals come from?
Do plants ever change?
Where did humans come from?
What happened to all the dinosaurs?
What about fossils?
9- Darwins ideas were heavily influenced the ideas
of the time
10 Early Explanations of Change
- James Hutton (1726-1797)
- Thought that geological changes were the result
of gradual change over a long period of time - Earth is 4.6 billion years old!
- Significant
- many at and before his time
- believed the earth was only
- a few thousand years old.
11 Early Explanations of Change
- Charles Lyell (1797-1875)
- Developed the theory of
- uniformitarianism
- the present is key to the past
- The current geologic processes have shaped the
earths topography. - Geologic processes take a long time! (millions of
years!)
12 Early Explanations of Change
- Jean Baptiste Lamarck (1744-1829)
- Proposed a theory of evolution based on
selective use or disuse of traits - All organisms have a tendency toward perfection
- Organisms are continually changing and acquiring
features that help them - Use and Disuse
- Organisms can alter the size/shape of a
particular appendage by using it in a new way - Inheritance of Acquired Traits
- modifications could be passed on to offspring
- giraffes who developed longer necks from
stretching could pass these long necks onto their
offspring
13 Early Explanations of Change
- Jean Baptiste Lamarck (1744-1829)
- Lamarck did not know how traits were acquired and
passed on. - His hypothesis had many flaws.
- His ideas helped ideas about adaptation paved the
way for Darwins theory
14 Early Explanations of Change
- Thomas Malthus (1766-1834)
- Was an economist
- Notice babies were being born faster than people
were dying. - Figured, sooner or later living space and food
supplies would be in short supply - Events such as famine, war and disease would
limit population growth - Darwin would later apply this idea to plants and
animals
15 Darwin Presents His Case
- Darwin reflected on his findings for many years
after returning home. - He wrote about his theories in, On the Origin of
Species. - Published in 1859
- 23 years after the voyage of the Beagle
16Inherited Variation vs. Artificial Selection
- Variations
- Different forms of alleles for a trait
- Inherited Variations
- Traits passed on from parent to offspring
- Artificial Selection
- Humans select useful variations from naturally
occurring traits - Selective breeding practices
17Evolution by Natural Selection
- The Struggle for Existence
- Darwin thought nature used an artificial
selection process - Members of each species compete for resources
- Natural Selection
- Processes in nature that over time results in
only the survival of the fittest species - Results in changes of inheritable characteristics
of a population. - Changes increase a species fitness in its
environment
18Survival of the Fittest
- Fitness
- Ability of an individual to survive and
reproduce. - Fitness is a result of adaptations
- Adaptation
- Physical and behavioral traits that allow an
organism to survive in its environment
19Darwin Concluded
- Over long periods of time, natural selection
produces organisms that have different - Structures
- Niches
- Habitats
- Species descended with modifications from a
common ancestor. - Implies all living things are related to one
another - This principle is known as common descent
20Darwins Finches
21Darwins Proof
- Evidence of Evolution
- The Fossil Record
- Geographical Distribution
- Similarities
- Embryology
- Chemical Compounds
- Body Structures
22The Fossil Record
- By comparing older fossils with younger fossils,
evidence of change is clear. - Lets look at Cephalopods
23Geographic Distribution of Living Species
- Darwin discovered the existence of similar but
unrelated species in different locations - Darwin later realized the similar animals were
products of different lines of evolutionary
descent.
24Similarities in Early Development
- Lets examine embryos
- In the late 1900s many thought, embryos looked
the same - While thats not exactly the case
- Similar genes are at work in early development
- As they grow the become more dissimilar
- Differences caused by genes that have changed due
to evolution
25Similarities in Early Development
26Similarities in Body Structure
- Embryos develop limbs that look similar
- Evolutionary changes altered the structure and
appearance - Limbs of different species are adaptations
enabling organisms to survive in their
environment - Structures that develop from the same body part
are called Homologous Structures
27Homologous Structures
28Vestigial Organs
- Organs that have no or little purpose.
- Evolution has lead to adaptations that suit
particular organisms
29Similarities in Chemical Compounds
- All organisms use DNA and/or RNA
- Many organisms have similar proteins
- The more closely related two species are, the
more their chemical properties resemble each
other.
30Similarities can be explained with Darwins
theory
- Living organisms evolved with gradual
modification of earlier forms of an ancestor with
common descent.
31Lets Look at an Example
- In pre-industrial England, there was a species of
moth called the - Peppered Moth (Biston betularia)
- Almost all peppered moths were gray with dark
flecks - Rarely were they black
32The Peppered Moth
- The peppered moth tend to rest on tree trunks
during the day - The gray moth were well camouflaged on the gray
tree trunks - Black moths stand out and are easy targets for
birds.
33The Peppered Moth
- Now, turn to England during Industrial Times
- Pollution from the factories turned tree trunks
black with soot. - Now, the black moths were camouflaged on the
trees.
34The Peppered Moth
- The black moths had a better chance of survival
- They had a higher fitness
- After many moth generations, almost all the
months in industrial areas were black
35The Peppered Moth
- Black coloration is an adaptation to an
environment with black tree trunks - In an industrial environment, black moths survive
to reproduce better than gray moths. - Therefore, their genes are passed on to future
generations
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