Download - 15 Darwin’S Theory Of Evolution (Version 2)
CHAPTER 15
Darwin’s Theory of Evolution
15.1 The Puzzle of Life’s Diversity
Evolution: Change over time, is the process by which modern organisms have descended from ancient organisms.
Scientific Theory: A well supported testable explanation of phenomena that have occurred in the Natural World.
Voyage of the Beagle
Charles Darwin was born in Shrewsbury, England on February 12, 1809
Joined the crew of the H.M.S. Beagle
He set sail in 1831 and his voyage took 5 years!
Voyage of the Beagle
During his travels: Darwin made numerous observations and collected evidence
This led him to propose a revolutionary hypothesis about the way life changes over time
NorthAmerica
Europe
GreatBritain
Africa
Equator
Asia
Australia
TasmaniaNewZealand
PACIFICOCEAN
ATLANTICOCEANPACIFIC
OCEAN
PACIFICOCEAN
TheGalápagosIslands
SouthAmerica
Tierra del Fuego
Cape Horn
Cape ofGood HopeA
ndes
Pinta
MarchenaGenovesa
EquatorSantiago
Isabela
Fernandina
Florenza Española
SanCristobal
SantaCruz
SantaFe
Pinzón
DaphneIslands
40 miles
40 km0
0
Darwin’s Observations
In Brazil, Darwin collected 68 different beetle species.
Patterns of Diversity: Why did some animals grow in some areas and not in others?
Why did the same species of animal look different from one another depending on where they lived?
Living organisms and Fossils: Preserved remains of Ancient organisms.
Darwin’s Observations
The Galápagos Islands: The tortoises varied from Island to Island depending on the vegetation.
He also noticed that the birds on each of the islands had different sizes and beak sizes.
The Tortoises!
http://www.skeptic.com/eskeptic/06-07-28images/TortoiseonPinzon.jpg
http://imagecache01a.allposters.com/images/pic/PTGPOD/OSJOM-00000498-001-FB~Espanola-Saddleback-Tortoise-Adult-Female-Galapagos-Posters.jpg
The Journey Home
Darwin observed that the characteristics of many animals and plants varied noticeably among the different islands of the Galápagos
The Tortoises!
http://research.unc.edu/internal/galapagos/santa_cruz/turtles_feeding.jpg
http://mysite.du.edu/~ttyler/ploughboy/cht102.jpg
15.2 Ideas That Shaped Darwin’s Thinking
We need to learn something about the time and world that Darwin lived in.
Most Europeans believed that the Earth and everything in it was created only a few thousand years ago.
Therefore, all creatures were the same from when they were first created.
Ideas That Shaped Darwin’s Thinking
During the 1800’s explorers were finding many fossil remains of numerous animal types that had no living representatives. This challenged the traditional view point of the time.
After a lot of studying Darwin changed his thinking dramatically.
An Ancient Changing Earth
Hutton and Geological Change In 1795, Hutton published his hypothesis about Geological forces that have shaped the Earth.
He proposed that rock layers form very slowly by up pushed earth or by rock layers forming on top of others
This meant and he proposed the earth was much more than a few thousand years old.
An Ancient Changing Earth
Lyell’s Principles of Geology His first book Principles of Geology He stressed that scientists must explain past events in terms of processes that they can actually observe, since processes that shaped the Earth millions of years earlier.
Erosion continues to carve out canyons, just as it did in the past
Lyell helped Darwin appreciate the significance of geological phenomena that he observed.
The Understanding of Geology Influenced Darwin in 2 Ways
1. If Earth could change over time, might life change as well?
2. He realized that it would have taken a very long time for life to change in the way he suggested.
15.3 Darwin Presents His Case
Publication of On the Origin of Species In 1858, Darwin received a short essay by Alfred Russel Wallace.
Wallace’s paper talked about his thoughts on evolutionary change that Darwin had been mulling over for 25 years!
Evolution by Natural Selection
Nature selects for those traits that will help a species survive.
For example: Certain colors, beak strength, etc.
The Struggle for Existence
Members of each species complete regularly to obtain: Food Living space Other necessities of life
Survival of the Fittest
Darwin observed how well suited an organism is to its environment
Fitness: Ability of an individual to survive and reproduce in its specific environment
Adaptation: Any inherited characteristic that increases an organism’s changes of survival.
Survival of the Fittest
Successful adaptations allow an organism to be better suited to their environment thus increasing their rate of survival and ability to reproduce
Natural Selection
Over time, natural selection results in changes in the inherited characteristics of a population. These changes increase a species’ fitness in its environment.
Descent with Modification
After long periods of time, natural selection produces organisms that have different structures, establish different niches or occupy different habitats. As a result species look different from their ancestors.
Common Descent: According to this principle, all species, living and extinct were derived from common ancestors
Hundreds to thousandsof years of breeding(artificial selection)
Ancestral dog (wolf)
Thousands tomillions of years
of natural selection
Ancestral canine
African wild dog
Coyote
Wolf Fox Jackal
A flower mantidin Malaysia
A leaf mantid in Costa Rica
Evidence of Evolution
Darwin argued that living things have been evolving on Earth for millions of years.
Evidence for this process could be found in: The fossil record The geological distribution of living species
Homologous structures of living organisms Similarities in early development or embryology
The Fossil Record
By comparing fossils from older rock layers with fossils from younger layers.
Scientists can now document the fact that life on Earth has changed over time.
There are gaps in the fossil records but each time a new fossil gets found the gap shrinks.
A Skull of Homoerectus
D Dinosaur tracksC Ammonite castsB Petrified tree
E Fossilized organicmatter of a leaf
G “Ice Man”
F Insect in amber
Geographic Distribution of Living Species
Birds in the Galápagos Islands looked different but where actually finches
They descended from a common ancestor
Animals that live in the same environment, animals will develop similar anatomies and behaviors
Homologous Body Structures
Limbs vary greatly in form and function However they are all constructed from the same basic bones
Homologous Structures: Structures that have different mature forms but develop from the same embryonic tissues
Vestigial Organs: Organs that serves no useful function in an organism
Similarities in Embryology
In early stages, or embryos, with backbones are very similar
Due to the fact that the same groups of embryonic cells develop in the same order and in similar patterns to produce the tissues and organs of all vertebrates.