Transcript Unit 10 – Part 2 Evolution

Chapter 15 – Evolution:
Theory & Evidence
Theories of Evolution
 Jean Baptiste Lamarck
Proposed that similar species
descended from a common
ancestor
Acquired Traits –
Hypothesized that organisms
“picked up” traits during
their lifetime
I really
want some
leaves!
Lamarck’s
theory
At first, there are only short-necked giraffes.
They try harder to reach the leaves.
I really
want some
leaves!
Lamarck’s
theory
So their necks get longer because they use
them more.
Lamarck’s
theory
Lamarck’s
theory
Lamarck’s
theory
And then their babies have long necks, too!
Darwin’s
theory
At first, there are some long-necked giraffes and
some short-necked giraffes. Only the long
necked can reach the leaves.
Darwin’s
theory
The short-necked giraffes are more likely to die
of hunger.
Darwin’s
theory
The long necked giraffes have babies that will
also have long necks when they grow up.
Write/Pair/Share
What is another possible reason
for giraffe necks to have evolved
for length? Write at least 2 lines!
 Natural Selection
Charles Darwin & Alfred Wallace both suggested
the theory of natural selection
Natural Selection – organisms best suited for the
environment reproduce more successfully than
others
The favorable trait increases in a population
Making a population the smallest unit able to evolve
 Charles Darwin
H.M.S. Beagle
Read books by Charles Lyell (geologist) placing an
emphasis on uniformitarianism
Darwin observed various habitats and considered that
these changes of earth played a part in the adaptation
of organisms
 Darwin’s Data
Traveled all over the world
Collected species of all
types of animals
Compared animals from
each destination
Galapagos Islands
Collected beetles and
finches
13 species of finches
Observed tortoises
 Darwin’s Finches
Based theories on the 13 species of finches collected in
the Galapagos
Hypothesized that the finches all evolved from a
common ancestor (originating in South America)
The environments of each island produced different
challenges
The finches would have to overcome these different
environments to survive.
Darwin’s Theories
Descent with Modification
Newer forms in the fossil record are modified
descendants of older species
Reproduction allows species to change over time
Proposed that ALL organisms descended from a few
ancestors with changes
Natural Selection
HOW descent with
modification occurs
Influenced by Thomas Malthus
Populations can double and
redouble
Human population is limited
by adverse conditions
Theorized that the environment was the limiting
factor for populations
Some organisms have traits that make them better fit to
respond to certain environmental pressures
Organisms better fit reproduce more and pass on the
favorable traits
 REMEMBER
Natural selection is not an ACTIVE process
Meaning that you can’t MAKE yourself change
Traits (ALLELES) MUST be present in a population
for evolution to occur
1. Variation exists among individuals in a species.
2. Individuals of species will compete for resources
3. Some competition would lead to the death of some
individuals while others would survive
4. Individuals that had advantageous variations are more
likely to survive and reproduce.
Evidence of Evolution
The Fossil Record
 What is a fossil?
A fossil is the remnants of an organism
Found in sedimentary rock
Types of fossils:
1. Mold – imprint in rock in the shape of the organism
2. Cast – a rock-like model of the organism
Distribution of Fossils
Nicholas Steno – Law of Superposition
Successive layers of rock or soil were
deposited on top of one another
Lowest strata (stratum) is the oldest
Observing these strata allows them to
determine the relative age of a fossil
and the absolute age
 Studying Fossils
The fossil record tells us that
organisms appeared for
awhile and then died off
Mass Extinctions
Evidence in fossils shows
us that there are periods
where large numbers of
species disappeared
Caused by environmental
changes
Transitional Species
Organisms that have
features that are
intermediate between
hypothesized ancestors
and current species.
Hypothesis that whales
descended from land
mammals based on a
sequence of transitional
forms.
Don’t believe me???
Whale Evolution
Biogeography
Scientists study the distribution of fossils and
living relatives to help determine how organisms
have changed
Similarities between fossils and living organisms
allows us to make connections with our ancestors
This is what
Darwin did
with the
finches,
turtles and
beetles!!!
Comparative Anatomy & Physiology
 Examining the structure & function of organisms
 Homologous Structures
Same structure but has a different function
Evolved from a common ancestor
 Analogous Structure
Same function but different structure
Evolved from a different ancestor but faced similar
pressures
 Vestigial Structures
Organ or structure that
was useful to an
ancestor but now has
no use to the current
organism
Examples
Appendix in humans
Pelvic and limb
bones in snakes
Leg bones in whales
Macromolecules
Examination of major macromolecules in organisms
(specifically proteins)
Genetic Evidence
DNA and RNA - Similarities in these molecules are
evidence that organisms evolve from common
ancestors
Embryology
Early stages of development are strikingly similar in
organisms
The more closely the development, the more closely
they are related
Evolution in Action
Interactions between species and
environmental pressures continue to drive
evolution
 Types of Evolution
Co evolution – Change of two or more species in
close association with each other
Predators and prey, parasites and hosts
Flowers and pollinators
Darwin’s Orchid
Darwin’s Moth
Convergent Evolution– unrelated species evolve
due to similar environmental pressures
Shark and porpoise, bird and bee
Divergent Evolution – two or more related species evolve
from a common ancestor
Species DIVERGE (separate)
Adaptive radiation – many species evolve from a common
ancestor
Artificial selection – divergence is sped up by choosing the
parents of offspring (found in dogs)
Parallel Evolution
Similar to convergent but this happens in
SAME environment
When two different species in the same type
of environment develop the same adaptations
for survival, it is considered parallel evolution