Download The Theory of Evolution Teacher

The idea of Ever-changing organisms on the Earth
The Puzzle of Life’s Diversity
 How did all organisms come to exist and rely on one
another for their survival?
 Evolution: The process by which modern organisms
have descended from ancient organisms.
Theory: A well studied idea,
not 100% proof.
Voyage of the Beagle
 This was the ship that carried Charles Darwin
 Darwin is the father of the Theory of Evolution by
Natural Selection
 This ship took him to various places on Earth, many
that were never seen before by humans
 He collected specimens from
the different islands he sailed
to and studied them
Darwin’s journey
Darwin noticed a few things…
 1) Many plants and animals seemed very well suited to
whatever environment they inhabited.
 2) Animals/plants had several ways to reproduce and
survive.
 3) Some organisms that seemed well suited for an
environment on one continent did not live in the same
environment on another continent
 4) Fossils that Darwin found were similar to organisms that
were still alive. Some looked completely different from
anything he had ever seen. Why had species disappeared?
Patterns of Diversity
 Darwin found that organisms were all well suited for
their environments because of the traits that they had
 Example: Animals that lived in the tropics looked
much different than those in the arctic region
 There are patterns to the different forms animals have
The Galapagos Island
 Small chain of Islands in Pacific ocean, each
one is very different
 Darwin found that each island had different
varieties of species
 Tortoises on each island had different shells.
 This occurred because the animals adapted to
the unique climates on each island
Galapagos Tortoises
Ideas That Shaped Darwin’s
thinking
 Most scientists from Darwin’s time believed the earth
to be unchanged from the start of time.
 He found fossils that showed differences over the
years.
 He challenged the ideas that life is created and then
ends, but never changes.
 He provided many samples and specimens to back up
his claims in the book “The Origin of the Species”
An Ancient and Changing Earth
 The earth is over 4 billion years old
 It has gone through dramatic changes: warm periods,
Ice ages, depletion of oxygen
 Organisms must adapt to these changes in order to
survive, a key idea of evolution.
Lamarck’s Ideas
 Along with Darwin, another scientist named Lamarck
also recognized the changing of species over time.
 He felt animals only lived where they could survive,
unless they were forced to adapt.
 Very incomplete ideas
Lamarck’s Theory of Use and
Disuse
 Organisms passed on traits either by using or not
using them.
 The more important a trait was, the more it was used,
this led to that trait getting passed on.
 So, if I lost my left arm in a car accident, then all of my
kids would have 1 arm.
Inheritance of Acquired Traits
 Lamarck thought acquired traits could be inherited
 If an animal changed while alive, this would get passed
on.
 If I gained 200 pounds my children will all be obese
too, we know that’s not true!
Evaluation of Lamarck’s Ideas:
 WRONG!!!!
 We do not inherit acquired traits nor pass traits on by
use and disuse
 Important first step in the ideas of Evolutionary theory
Origin of the Species
 Book Darwin published, although he waited almost 25
years to do it
 1859 published the work, it instantly became one of
the most controversial works ever
 Discussed natural selection, adaptations and
inheritance
Natural Selection
 “Survival of the fittest”
 Animals that are strong and
have good traits will often survive and pass those traits
on to other generations.
 As the world changes, organisms must adapt or they
become extinct.
 Sometimes traits that have allowed animals to thrive
for thousands of years can cause extinction if the
environment changes
 The key to evolution of organisms
Adaptations
 Inherited characteristic that increases an organism’s
chance of survival.
 Examples: Camouflage, webbed feet, wings, etc.
 How did these adaptations show up?
 Genetic Mutations!!! These mutations turned out to be
beneficial and therefore, the organism that had them
survived to reproduce and pass that trait on!
Darwin’s Theory of Evolution By
Natural Selection
 Based on 4 postulates
 1) There is variation in a population (Caused by
mutations)
 2) More organisms are born than survive to reproduce.
 3) Those organisms that survive have an advantage
over those that do not survive.
 4) Some of those advantages (adaptations)are
heritable (can be passed on)
Evolution in Action
 Evolution
Pollinators can cause Flowers to
Evolve
Flower Evolution
 Flower Evolution
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Evidence that Supports Darwin
 1) Age of the Earth – 4.5 billion years old
 2) Fossil Record
 3) Geographic Distribution of Living Species
 4) Homologous Structures
 5) Comparative Embryology
 6) Genetics
 7) Molecular Biology
1) Age of the Earth – Approximately 4.5 billion years old
- That is DEFINITELY enough time for evolution to
occur
2) Fossil Record- although it is incomplete, it still offered
Darwin the opportunity to note that countless species
had come into being, lived for a time, then vanished.
By comparing the rocks and fossils found in them,
scientists could document the fact that life has
changed over time
3) Geographic Distribution of Living
Species
 Land masses such as Hawaii, Australia, and New
Zealand had very distinct plant and animal life
because they were separated by thousands of miles of
ocean from all other land masses
 Australia had 100s of different species of marsupials
(Koalas, Kangaroos, etc.) but very few placental
mammals like dogs, cats, etc.
4) Homologous Structures
 Different animals have similar bone structures in their
bodies.
 They may look totally different, but they are very
similar.
 Is this also proof that many animals evolved from a few
simple animals long ago?
 Look at these examples:
Homologous Arm Bones
5) Comparative Embryology
 All things are extremely similar when they are
embryos
 Could this be a leftover trait because many things
evolved from similar organisms?
 An interesting question theory of evolution brings up.
 Take a look at these examples:
Embryos
Embryos
6) Genetics and 7) Microbiology

Genetics – what we know about how traits are inherited supports Darwin’s ideas.
Molecular Biology- looking at amino acid sequences of proteins or DNA sequences show that closely
related species have almost identical DNA.

What percent of their genes match yours?

Another human?

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A chimpanzee?
A mouse?
A fruit fly?

Yeast?

A weed (thale grass)?
100% - all humans have the same genes, but some of these genes
contain sequence differences that make each person unique
98% - chimpanzees are the closest living species to humans
92% - all mammals are quite similar genetically
44% - studies of fruit flies have shown how shared genes govern the
growth and structure of both insects and mammals.
26% - Yeasts are single-celled organisms, but they have many
housekeeping genes that are the same as the genes in humans,
such as those that enable energy to be derived from the
breakdown of sugars.
18% - Plants have many metabolic differences from humans. For
example, the use sunlight to convert carbon dioxide gas to
sugars. But they also have similarities in their housekeeping
genes.
Phylogenetic Trees
Phylogenetic
Trees show how
animals have
evolved over a long
period of time. The
further away a
branch is, the less
similar their
genetics are.
Population Growth
 In 1798 Thomas Malthus said “the world is heading for
a population crisis”
 Darwin believed there is a reason for death and
imperfections: to keep population numbers in check
 If not, he believes that any species, especially humans,
can take up too much food, space and other resources.
 The human population of the world has doubled in
the last 20 years.
Evolution
 To sum up the theory of evolution:
 The world is a constantly changing place
 All organisms must adapt to change or become extinct
 Natural selection or “survival of the fittest” is the
mechanism for change in evolution.
 We are still seeing examples of evolutionary change
today: resistant bacteria
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Population Genetics
 Genetic variation is studied in populations
 A gene pool refers to all of the genes, including the
different alleles, that exist in a population.
 The frequency of an allele is the number of times that
the allele occurs in a gene pool, compared with the
number of times other alleles for the same gene occur.
Usually shown as a percentage.
Frequency
Genetic Drift
 Natural selection has its effect on the frequency of alleles in
a population. Some of these changes in allele frequency,
however, can happen randomly. This kind of random
change in allele frequency is called, genetic drift.
 Example: A small group of beetles may colonize a new
habitat. This group of beetles may carry alleles in a
different relative frequency than the one they came from.
Therefore, the new population will be genetically different
from the original. This is known as the founder effect.
Are there any conditions where
evolution would not occur?
 Hardy Weinberg Principle – states that allele
frequencies in a population will remain constant
unless one or more factors cause those frequencies to
change.
 Situation in which allele frequencies remain the same
is called genetic equilibrium.
FIVE CONDITIONS ARE REQUIRED TO MAINTAIN
GENETIC EQUILIBRIUM FROM GENERATION TO
GENERATION:
 Random Mating-must have equal opportunity to reproduce
 Large Population – less chance of genetic drift to affect a
population
 No movement into or out of the population – no new genes
can be added or taken away
 No mutations - genes mutate from one form into another,
new alleles may be introduced into a population
 No natural selection – all genotypes have an equal chance
to survive and reproduce
How do changes in allele
frequencies lead to new species?
 Species- group of organisms that breed with one
another and produce fertile offspring
 In order for a new species to arise (speciation),
something needs to happen…
 They have to be reproductively isolated…
 1) Behaviorally
 2) Geographically
 3) Temporally
Behavioral Isolation
 Two populations are capable of interbreeding but have
differences in courtship rituals or reproductive
strategies that involve behavior
 Ex: Different mating calls between the eastern and
western meadowlark
Eastern
Western
Geographic Isolation
 Populations are separated by geographic barriers such
as rivers, mountains, or bodies of water
 Example: Abert and Kaibab Squirrels
Temporal Isolation
 Occurs when two or more species reproduce at
different times.
 For example, three similar species of orchid all live in
the same rainforest, but they release their pollen at
different times. Because they release their pollen on
different days, they cannot pollinate one another.
Speciation in Darwin’s Finches
 Founder’s arrived
 Geographic isolation – on different islands
 Changes in the gene pool – depended on the food
source
 Reproductive isolation- Mates choose specific traits so
the different birds would not reproduce with each
other
 Ecological competition-Competed for resources
 Continued evolution- over a long time this process
kept occuring (14 species of Galapagos Finches exist)