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Unit 4: Evolution
Inherited Traits and the Environment Lead to Evolution
CA 7th Grade Science Content Standards
Evolution
3. Biological evolution accounts for the diversity of species
developed through gradual processes over many generations.
As a basis for understanding this concept:
a.
b.
c.
d.
e.
Students know both genetic variation and environmental
factors are causes of evolution and diversity of organisms.
Students know the reasoning used by Charles Darwin in
reaching his conclusion that natural selection is the
mechanism of evolution.
Students know how independent lines of evidence from
geology, fossils, and comparative anatomy provide the bases
for the theory of evolution.
Students know how to construct a simple branching diagram
to classify living groups of organisms by shared derived
characteristics and how to expand the diagram to include
fossil organisms.
Students know that extinction of a species occurs when the
environment changes and the adaptive characteristics of a
species are insufficient for its survival.
The environment, and how it
changes, determines if a mutation is
an advantage or a disadvantage.
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Why do organisms adapt?
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Adaptions affect the
environment
As the environment
changes, organisms
need to change to
survive
Organisms strive for
variety in life
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What is an example of an adaptation
to live in a hot, dry environment?
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Thick, dark fur
Gills and fins
Nocturnalism
and burrowing
Wings
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Evolution begins with…
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An advantage
A random mutation
A decision to adapt
An unchanging
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A.
The Scientific Road to Evolution
Linnaeus (1700s)- Developed a classification system
for organisms. Proposed that an organism’s
characteristics were not fixed, but could change…
 Leclerc de Buffon (1700s)- Based on evidence of
past life on Earth, he proposed that life arose from
common ancestors. Also believed the earth wasn’t
6,000 years old…
 Erasmus Darwin (1700s)- Charles Darwin’s
grandfather. Proposed life arose from simple forms
of life to become complex life forms…
 Lamarck- In 1809 he proposed all organisms evolved
toward perfection and complexity

◦ He believed that a species did not become extinct, but
that environmental changes caused it to change and
adapt into something new and better suited to thrive in
the environment
USING FOSSILS TO
PROVE EVOLUTION
Darwin and The Origin of the Species
Darwin was a scientist in the 1800s who
went to Galapagos Islands to study the
ecology and biodiversity of the Islands
 He noted the variations and attributed these
to adaptation
 He coined the terms natural selection
and survival of the fittest

IT WOULDN’T BE SCIENCE
WITHOUT BILL NYE
New Words! Woo Hoo!
Variation- the difference in physical traits within a species
Adaptation- a feature that allows an organism to better
survive in its environment
Heritability- the ability of a trait to be passed down (or
inherited)
Vestigial Structures- remnants of organs or structures
that once had a function in early ancestors
Homologous Structures- similar structures that appear
different in different organisms
Analogous Structures- similar function, but not similar
in origin
Natural Selection- traits that allow for better adaptation
are passed down
Artificial Selection- breeding. Human intervention in
natural selection
Overproduction- too many offspring to survive in an
area
BILL NYE PART DEUX
In Life After Dinosaurs…
1.
2.
3.
4.
5.
What was the dominant life form on earth
before mammals were dominant?
How big was the earliest known mammal?
What allowed mammals to evolve to become
larger?
What was the first kind of mammal (hint: they’re
still alive on Australia)?
Why are there so many different mammals
when they all started as one kind?
LIFE AFTER DINOSAURS
Wait! Where did Dinosaurs come from?

Before more complex organisms could exist,
there needed to be something smaller and
much less complex…
◦ Unicellular organisms  early Bacteria



These early forms of life changed the earth
by depositing minerals and giving off oxygen
as a by product of photosynthesis
Asexual reproduction (mitosis) allowed for
quick reproduction, which allowed for a
growing population
Changing environment lead to adaptation,
lead to more complex life, lead to sexual
reproduction, lead to… US!
Embryos and Common Ancestors
Homologous Structures
Analogous Structures
Vestigial Structures
Whales have hip bones even though
they lost their legs.
Approximately how long ago did
unicellular life begin on earth?
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100,000 years ago
3.8 million years ago
3.8 billion years ago
3.8 trillion years ago
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A.
What is the biological process by
which species change over time?
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Extinction
Population
Stasis
Evolution
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CAN WE FORCE EVOLUTION?
Yes! It’s called domestication
What is the process by which organisms
best suited for their environments survive
and reproduce at a higher rate than
others?
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Variation
Isolation
Natural Selection
Overpopulation
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Whales have small hipbones even though
they have no rear legs. Structures like
these are "leftovers" from the
evolutionary past of whales. What are
these kinds of structures called?
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Ancestral structures
Vestigial structures
Homologous structures
Orca feet
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PRIMATE EVOLUTION
How we split off
from early apes…
Primate- flexible hands and feet, eyes that face forward, and large brains
Anthropoid- divided into new and old world monkeys and hominoids
Hominid- includes all early humans; walks upright and has an opposable thumb
Prosimian- oldest living primate group; small and active at night
Why are some forms of life still here?

The ability to survive and thrive in an
environment has everything to do with
evolution and existence:
◦ Sharks didn’t need to change  they’re still here
and the same
◦ Primates are still here, but needed to evolve to
survive
◦ The Western Black Rhinoceros could not survive
in its environment or evolve fast enough 
extinct (due to poachers)
Bacteria
THE ULTIMATE SURVIVOR
BACTERIA
Bacteria: The Double-Edged Sword
Not all bacteria is bad or causes infection:
◦ Probiotics [short for prokaryote bacteria] are examples of “good”
bacteria that helps us survive
◦ Certain bacteria produce nitrogen gas, which helps legume plants
◦ Bacteria breaks down organic materials to make them useful 
compost
◦ Bacteria is vital to fermentation. No bacteria no yogurt, cheese,
pickles, soy sauce, beer, wine, or vinegar
 Be careful when taking antibiotics:
◦ Don’t take them more than once every two years*
◦ Some scientists believe that overuse of antibiotics will lead to
resistant strains of bacteria  bacteria will adapt to survive!!!
◦ After a course of antibiotics, load up on the yogurt to replenish your
body’s good bacteria

*According to health experts and published research
Consult your doctor before making healthcare
decisions
Awesome Vocab!
Species: group of organisms so similar to one
another that they can breed and produce fertile
offspring
 Population: all of the individuals of a species that
live in the same area
 Extinction: elimination of species from Earth
 Fitness: measure of an organism’s ability to survive
and produce offspring relative to other members of
a population
 Gene Pool: collection of alleles found in all of the
individuals of a population
 Variation: differences in physical traits of an
individual from the group to which it belongs

Which of the following statements
describes adaptations?
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Adaptations are mutations that help an
organism to survive.
Adaptations are mutations that do not
help an organism to survive.
Adaptations are mutations that cause an
organism to die.
Adaptations are mutations that are not
inherited.
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There are two colors of rabbits that live in mountains, black
and white. Normally there are about equal numbers of each
color of rabbit. The rabbits are hunted and eaten by the
foxes. What would you expect to happen to the rabbit
population if the mountains were covered in snow for
extended periods?
Populations of white rabbits would stay the
same and black rabbits would increase.
B. Populations of white and black rabbits
would stay the same.
C. Populations of white rabbits would increase
and populations of black rabbits would
decrease.
D. Populations of black rabbits would increase
and populations of white rabbits would
decrease.
A.
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