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Theory of Evolution
WRITE A DEFINITION:
• gradual change over time; the process by which modern organisms have descended from ancient organisms
• a well-supported testable concept that is backed-up by evidence
• Concept has been tested multiple times and is proven
EVOLUTION:
THEORY:
Ideas that shaped Darwin’s thinking:
James Hutton (1795)- the EARTH was shaped by geological forces occurring over very long periods of time, and the Earth ismillions of years old.
Ideas that shaped Darwin’s thinking:
Charles Lyell (1830)-the geological processes still occurring nowhave shaped Earth’s features over long periodsof time
http://www.biologydaily.com/biology/Sir_Charles_Lyell
Formation of Earth
• The Earth is about 4.8 billion years old
• According to science, the Earth was put together piece by piece over the course of about 100 million years
Early Earth Atmosphere
Earths early atmosphere was made up of 6 main things:
• Hydrogen cyanide• Carbon dioxide• Carbon monoxide• Nitrogen• Hydrogen sulfide• water
Could you have lived on early Earth?
Cooling of the Earth
• Not only was the atmosphere not suitable for life the early Earth was VERY hot
• About 4 billion years ago the earth began to cool– Rocks formed on the earths surface
Formation of water
• 3.8 billion years ago the earth cooled even more– Liquid was able to remain on the earths
surface forming the first oceans
video
Free Oxygen
• Fossils of prehistoric bacteria have been found in rocks that are dated to be more the 3.5 billion years old
• 2.2 b.y.a. Photosynthetic bacteria began producing oxygen as a by product of photosynthesis
Free Oxygen• Free oxygen mixed with iron in the ocean
forming iron oxide
• Oxygen gas started accumulating in the atmosphere, forming the ozone layer
• Increased oxygen levels
caused some life forms
to go extinct and allowed
other life forms to evolve
Ideas that shaped Darwin’s thinking:
Theory of Pangaea- All land was at one time connected
Ideas that shaped Darwin’s thinking:
Continental drift- shifting of the earths continent/ crust
convergent
divergent
Transform
Division of Life on Earth• Life on Earth is
divided into Eras and Periods – Eras are bigger than
periods
• Based on fossil evidence– major changes that
occurred in the Earth’s climate and geography affected the living organisms
Darwin’s Theory of EvolutionThe Puzzle of Life’s Diversity
Chapter 15-1
Image from: Biology by Miller and Levine; Prentice Hall Publishing©2006
Charles Darwin-The person who contributed themost to our understanding of evolution
In 1831, he joined the crew of the Beagle as a naturalist for a 5 year voyage around the world.
The Fossil Record
• Fossil record showed 2 types of organisms– Ones that were similar to animals and plants alive
at the time– Ones that were different to animals an plants alive
at the time• Why had these
species disappeared? – 99% of all species that have
ever lived on Earth are extinct
Fossils and Ancient Life
• What is a fossil?– Hardened remains of plant or animal in rock
• Why do scientist use fossils?
• Fossils allow us to infer what past life forms were like
– Structure– Predator/Prey
– Habitat
How Fossils Form
• After the organism dies the remains must be preserved
• The dead organism is buried by sediment– Mud– Sand– dust
How Fossils Form
• Different types of fossils can be formed– Eggs
– Foot prints
– Bones
– Leaves
Relative Dating• Most fossils form in
sedimentary rock– formed by the deposition of
materials at the Earth’s surface
• The age of a fossil is determined by comparing its placement with that of fossils in other layers of rock– Layers of sedimentary rock
are built from oldest to newest
Index Fossil• Fossils used to define and identify
geological time – When the organisms lived
• Species that existed for a short period of time over a wide geographic range
Radioactive/Radiometric Dating
• Uses radioactive elements to determine how old the rock is – Radioactive elements
decay at a steady rate– The use of half-lives to
determine the age of a sample
– Half life: the length of time required for half of the radioactive atoms to decay
To date older rocks you must use elements with longer half-lives
Carbon-14 (5,730 years)Uranium (half-life: 4.47 b.y.)
How the fossil record is used• used to show change in
organisms over time– Evidence of gradual
change
• life on earth is divided based on changes in the fossil record– Transitions marked by
extinction – Extinction makes new
habitats available to species
DARWIN WONDERED?Why do Argentina and Australia have differentAnimals even though they have similargrassland?
Why have so many species disappeared?
How are these extinct species related to living species?
Ideas that shaped Darwin’s thinking:
Jean-Baptiste Lamarck (1830)-• one of first scientists to recognize
living things changed over time and that all species were descended from other species.
Lamarck's Hypothesis:1.Tendency towards perfection2.Use and disuse3.Inheritance of acquired traits
Tendency Towards Perfection
• Innate tendency toward complexity and perfection
• Organisms are continuously changing and acquiring traits that benefit them
The male fiddler crab uses itsfront claw to attract mates and fight off predators.
Through repeated use, the front claw becomes larger.
The fiddler passes on this acquired characteristic to its offspring
Use and Disuse• By selective use or disuse of organs, organisms
acquire or loose traits during their life time• These traits are passed down to offspring
Inheritance of Acquired traits
• Acquired traits could be passed on to offspring– Lamarck didn’t know about
genes and how traits are inherited.
If you lifted weights your
whole young adult life, and
then you had children, would your kids be more muscular?
Inheritance of Acquired traits
What’s wrong with Lamarck’s hypotheses?
• Individuals DO NOT evolve– You cannot change your DNA
• Acquired traits cannot be passed down to offspring
• An organisms behavior has no effect on its heritable characteristics
What’s right with Lamarck’s hypothesis?
Lamarck recognized that organisms are
Adapted to their environment
competition
• Evolution= •Inherited adaption's that accumulate in a population over many generations
What does drive evolution?
Charles Darwin spent one month observing life on the Galapagos Islands.
There, he encountered some unique animals, such as finches and tortoises.
http://www.darwinadventure.com/pictures/galapagos_giantortoise.jpghttp://mikebaird.com/ecuador/images/galapagos_off_ecuador_ng_map.jpg
Darwin's greatest influence
A summary of Darwin’s Theory1. Individual organisms differ and some of the
variations are genetic
WHY DOES VARIATION MATTER?
The Galapagos Islands are close together but have very different climates.
• hot and dry, with little vegetation• more rainfall and were rich in vegetation
Each island hadits own uniqueAssortment of plant and animal species.
Biology by Miller and Levine; Prentice Hall Publishing©2006
Inherited Variation
• Inherited variation- passed from parents to offspring
How are traits passed from parents to offspring
hint: think about meiosis• Crossing over• Random lining up of
chromosomes
A summary of Darwin’s Theory
2. Organisms produce more offspring then can survive, and many that do survive do not reproduce.
– High birth rates and a shortage of resources force organisms into competition
Ideas that shaped Darwin’s thinking:
Thomas Malthus (1798)-
• If the human population continued to grow unchecked, there would be insufficient living space and food.
• Individuals adjust
to limited resources
Natural selection• Each individual differs
from other members in its species– Each has unique
advantages and disadvantages
• Natural selection- based on their traits, some individuals are able to survive longer then others– Takes place without human
control or direction
Organisms cannot change their characteristics or force natural selection…
Go to Section:
Pinta IslandIntermediate shell
Pinta
Isabela IslandDome-shaped shell
Hood IslandSaddle-backed shellHoodFloreana
Santa Fe
Santa Cruz
James
Marchena
Fernandina
Isabela
Tower
Giant Tortoises of the Galápagos Islands
Section 15-1
On the desert-like Hood Island,tortoises had long necks…
…while on the lush rainforest of Isabela Island,tortoises had short necks…
and on Pinta Island, tortoise neckswere somewhere in between
Natural Selection doesn’t give organisms what they need to survive
Artificial Selection
• Artificial selection- nature provided the variation and humans selected for the variations they saw useful.– Used to improve crops and livestock
(selective breeding)
A summary of Darwin’s Theory
3. Because more organisms are produced then can survive, they compete for limited recourses.
– Food– Shelter– Space– Mates
The struggle for existence
• Competition what drives evolution
If there is no competition there is no evolution
A summary of Darwin’s Theory
4. Each organism has different advantages and disadvantages in the struggle for existence.
• Survival of the Fittest-
the ability of an organism
to survive and reproduce
in its specific environment
Survival of the Fittest
• Fitness is a result of adaption's– Adaptation= inherited characteristics that
increase an organisms chance of survival
Is the most fit animal always the biggest, strongest and fastest?
Survival of the Fittest?
Adaptation vs. the ability to adapt
• Adaptation- a trait or characteristic that you re born with
• Ability to Adapt- How you use your traits or characteristics to survive
Individuals DO NOT changes
• Individuals are unchanging
• Individuals either live or die based on the traits that they inherited from their parents
A summary of Darwin’s Theory
5. Species alive today are descended with modifications from ancestral species
Review of Darwin’s Theory
• Individual organisms differ and some of the variations are genetic
• Organisms produce more offspring then can survive, and many that do survive do not reproduce.
• Because more organisms are produced then can survive, they compete for limited recourses.
• Each organism has different advantages and disadvantages in the struggle for existence.
• Species alive today are descended with modifications from ancestral species
Review of Darwin’s theory
• Adaptations- an inherited trait or characteristic that is passed down from on generation to the next– NOT something gained during your life time!
• Acquired traits- are not passed down
• The ability to adapt- how an organism is able to use their adaptations to their advantage in order to survive in their environment
Conditions for natural selection
Conditions for natural selection include:• Variations exist among members of a
population• Many more individuals are produced each
generation than will survive• Some individuals are better adapted so they
survive & reproduce• Members of a population compete for food,
space, mates...
Evidence for Evolution
Fossil Record
Geographic Distribution
Homologous Body Structures
Similarities in Embryology
Fossil record
Fossil record
• The fossil record is a history of life on Earth– The earth is millions of
years old• Which scientists
proposed this?
– Fossils that are found in different rock layers show the evolution of living species over millions of years
Fossil Record• Transitional fossils-document various
intermediate stages in the evolution of modern species
Incomplete Fossil Record
• Not all fossils have been found– We are still finding new fossils – The gaps in the fossil record are getting
smaller
• Not all organisms that ever live become fossilized– Soft bodied organisms are not fossilized– Organisms that don’t die in or by the water
are usually not fossilized
Geographic distribution
• when a population gets separated difference selective pressures will work on the populations and cause changes
• Divergent Evolution- populations evolve separately– Formation of new
species
Geographic distribution
• The environment selects for specific adaptations– If the environment is the
same in 2 different locations we see the evolution of similar but unrelated species
– Convergent evolution- evolution of shared traits in unrelated species
• Bats and birds
Homologous body structures
Homologous structures: variations on a body structure that was present in their common ancestor
Vestigial Structures• structures or organs that
seem to serve no useful function– Human tail bone– Whales tiny pelvic and limb
bones– Ostriches wings
• vestigial structures show common ancestry with organisms in which the homologous structure is still functional.
Similarities in Embryology
• The early stages of development are similar in different species– All animals with
backbones
• The same groups of embryonic cells develop in the same order and pattern – Cause for homologous
structures
Descent with modification
• Natural selection produces organisms that have different characteristics – Species today look
different then their ancestors
• Common descent: All living organisms are related to one another– A single tree of life links
all living organisms