Download The Basics of Evolution - Eaton Community Schools

THE BASICS OF
EVOLUTION
Chapter 15
The idea of evolution

Came from observations made by Charles Darwin
when he visited the Galapagos Islands.
 Observed
that organisms differed slightly from one
another in different regions
 Tortoises, finches
Evolution –
Change in a species over time… new types from existing
types OR a hertitable change in a population between
generations
What evolution is


The concept that species change over time
The theory that explains this process is called
natural selection, which includes many variables,
such as “fitness”, environment, population numbers,
predators, genetics, and more
 Organisms
change and adapt based upon biotic and
abiotic factors; this can lead to new species
 Evidenced in antibiotic resistance, new viruses, bird
groups, and many more
What evolution is not: Misconceptions



Humans did not evolve from monkeys; however,
scientists do think that they shared a long-ago
common ancestor
Completely random: evolution can be affected by
many environmental factors
An explanation of how life began; instead, it is an
explanation of how organisms change over time
Lamarck’s incorrect idea
Age of Earth

Until the 1700’s, scientists believed that species
never changed. Then, they saw evidence otherwise:
 Geology:
Rock layers date time much farther back: 4.5
billion years ago, as measured by carbon dating
 Fossils: Fossils found in rock layers are dated back to
early times
 Fossilized organisms resembled today’s organisms, but
with differences
Natural Selection


A way to explain how species change over time
Ways that natural selection might work:
 Overproduction
– environment prevents survival of all
 Genetic variation – different trait in a population
 Struggle to survive – competition in environment
 Differential reproduction – best adapted will
reproduce
Anatomy & Embryology

Homologous structures – most recent common
ancestor shared the same basic structure
 Ex:

human arm, penguin, alligator, bat
Analogous structures – closely related functions
without a shared common ancestor
 Ex:
wings of birds, moths, and bats
Homologous structures
Homologous
Structures
EVOLUTION
Vestigial
Structures
Molecules
Forelimbs
Pelvis
Birds
Whales
Chickens
Mice
Vertebrates
Frogs
Rhesus monkeys Lampreys
Dolphins
Humans
Proteins
Diagramming to show relationships


Phylogenetic tree – diagram showing relationships
of common ancestors, based upon genetics,
anatomy, or other relationship information
Adaptive radiation – a new population colonizes a
new environment by changing to fill many places in
the ecosystem
Cladistics


Using phylogeny (shared ancestry) to show how a
shared characteristics is found within organisms.
A way to show evolutionary relationships around a
specific feature (feathers, arm bones, seeds, etc)
Cladogram
Cladogram – Part 2
Cladogram Analysis




Today, with the advances in genetics and biochemistry, biologists can
look more closely at individuals to discover their pattern of
evolution, and group them accordingly - this strategy is called
EVOLUTIONARY CLASSIFICATION
CLADISTICS is form of analysis that looks at features of organisms
that are considered "innovations", or newer features that serve some
kind of purpose. (Think about what the word "innovation" means in
regular language.) These characteristics appear in later organisms
but not earlier ones and are called DERIVED CHARACTERS.
PART I - Analyze the Cladogram in the previous slide.
In the sample cladogram, each letter on the diagram points to a
derived character, or something different (or newer) than what was
seen in previous groups. Match the letter to its character. Note: this
cladogram was created for simplicity and understanding; it does not
represent the established phylogeny for insects and their relatives.
Write the letter to match the
evolutionary development

1. ______ Wings
2. ______ 6 Legs
3. ______ Segmented Body
4. ______ Double set of wings
5. ______ Jumping Legs
6. ______ Crushing mouthparts
7. ______ Legs
8. ______ Curly Antennae
How species evolve: gradualism vs.
punctuated equilibrium