Evolution Chapter 15 Darwin’s Theory of Evolution

EvolutionChapter 15

Darwin’s Theory of Evolution

HYPHOTHESIS vs. THEORY

Hypothesis:Educated guess that has to be testable by scientific methods.

Theory:Has to be well-supported and has been tested over and over Is an explanation of a phenomena that has occurred in the natural world.

Observation vs. Theory

Observation:An act or instance of noticing or perceivingA remark, comment, or statement based on what one has noticed or observed

Theory:Has to be well-supported and has been tested over and over Is an explanation of a phenomena that has occurred in the natural world.

Father of Evolution: Charles Darwin• Voyage of the Beagle (1831) sailed around the world stopping at the

Galapagos Islands.• He made observations & collected evidence: species, fossils.• He noticed many plants & animals were well suited to their

environment.

15-1 Life’s Diversity

I: Biological Diversity- variety of living things.


II: Evolutionary Theory- a collection of scientific facts, observations & hypotheses; it can explain the diversity of life on Earth.


III: Evolution- change over time; the process by which modern organisms have descended from ancient organisms.


IV: Scientific Theory- a well supported testable explanation of natural events; supported by evidence & can be tested with new evidence.

Galapagos Islands• Each Island has a very unique climate and biotic factors. • Darwin wondered if the animals on all the different islands

once came from the same species or common ancestry.

15-2 Darwin’s Influences

• He felt that many would find his ideas too shocking to accept but he took from the ideas of his day.

1. Hutton and Lyell2. Lamarck3. Malthus

• Hutton and Lyell- stated Earth is many millions years old. Geological processes change the Earth in the past and continue to shape it in the present.


• Lamarck recognize that living things change. He proposed:

1.Tendency toward perfection

2.Use and Disuse3.Inheritance of acquired

traits.


15-2 Darwin’s Influences• Malthus- stated that if human population continued

to grow unchecked, there would be insufficient food and space for everyone.

time

Unfortunately, even with increased agriculture there is only so much land and improvements that can be made.

15-3 Darwin’s Case

• He was reluctant to publish his ideas because they were contrary to the fundamental pillars of Biology at the time.

• He knew it was going to be a difficult task and decided to put his book (Origins of Species) in a drawer for 25 years.

• A scientist named Wallace was getting ready to publish the same findings, it was at this time Darwin decided to publish his work.

15-3 Darwin’s Book

On the Origin of Species was published in 1859.• The book provided evidence that evolution

has been taking place.• He stated that species vary from one another,

in nature and on farm. Artificial selection- “ selective breeding”Natural selection- a mechanism for evolution.

Theory of Natural Selection

1. Genetic Variation2. Overproduction of Offspring3. Struggle for Existence4. Survival of the Fittest5. Descent with Modification


1. Genetic Variation- organisms differ; some variation is heritable.


2. Overproduction of Offspring- organisms produce more offspring that can survive.

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3. Struggle for Existence-members of each species compete to obtain food, living space, etc. Predators that are faster= more foodPrey that are better camouflaged= better protection, not eaten have more babies.


4. Survival of the Fittest- the most fit are able to survive and reproduce.Fitness- the ability to survive & reproduce in a specific environment.Fitness is the result of adaptations ( physical and/or behavioral). Adaptation- an inherited characteristic that increases the organism’s chance for survival. Only the fittest organisms survive, and get to pass on their traits; thus, the species change over time.

Theory of Natural Selection5. Descent with Modification- all species come from common ancestors. • They look different from ancestors because

over long periods of time, natural selection produces organisms that have different structures, niches, or live occupy different habitats- meaning that, they “descended with modification”

• It links all organisms on Earth into a single tree of life. This principle is known as “ common descent”.

Decent with Modification

4 Types of Evidence to Support Evolution

1. Fossil Record2. Geographic distribution of living species.3. Homologous structures of living organisms.4. Similarities in early development, or

embryology

I: Fossil Record

• Comparing fossils from older & younger rock layers documents the fact that evolution has occurred; it is a detailed record of evolution.

II: Geographic Distribution of Living Species

• Species evolve differently in different environments different species evolve similarly in the same type of environment

III: Homologous Structures of Living Organisms

• Similar body structures that do not necessarily have similar functions(Homologous Structures- different mature forms, but develop from same embryonic tissues)

• Similar structures with reduced size and lesser function or no function -Vestigial Structures

IV: Similarities in EarlyDevelopment or Embryology

• Early stages, or embryos, of many animals are very similar- suggesting that organisms share common ancestry.

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Evolution Chapter 15 Darwin’s Theory of Evolution