Download File

 Genetic
Toolkit Video
 Read “Animal Body Plans: Homeobox Genes”






What are homeobox genes?
What did Walter Gehring show with his experiment with the eyeless gene?
How do homeobox genes provide evidence that all living things are
descended from a common ancestor?
Why are homeotic (aka "homeobox", or Hox) genes considered "master
switches?"
How many Hox genes are there in fruit flies, mice and humans? How do
scientists know all these carriers of Hox genes arose from a common
ancestor?
The fruit fly (Drosophila) and mouse homeobox gene sequences do not look
exactly alike. Can you guess why?
 Molecular
Connections WS- groups of two
 All In The Family
 Molecular Clocks WS
 Common Genetic Code Video
Natural selection- the main
mechanism by which
evolution occurs
• Change over time in
the heritable (genetic)
traits of a population
• Process by which
modern organisms have
descended from ancient
organisms
What is the difference between a hypothesis and a
theory?
What do most people think a theory is?
What does science say a theory is?
What is a law?
How does science scaffold the importance of all of
these?
A theory is a well-supported testable explanation of
phenomena observed in the natural world
 Born
1809 in England
 Studied medicine and
theology
 Joined HMS Beagle crew in
1831
 Ship naturalist
Collected specimens
 Made observations
 Recorded thoughts

Darwin Movie- PBS “Evolution”

Patterns of Diversity


Plants & animals well suited
to environments
Similar ecosystems had
different animals present
Fossils – preserved
remains of ancient
organisms
 Some resembled living
organisms
 Some had no living
counterpart

 Small
group of islands
west of South America
 Observed many
different organisms
on the islands


Tortoises
Finches
 Islands
had different
climates and different
species
Darwin observed that
the characteristics of
many animals and
plants varied
noticeably among the
different islands of
the Galapagos
What would cause such variation to occur?
 Common



ideas around his time:
Earth was only a few thousand years old
Neither the planet nor its species had changed
Geological features had been produeced by
SUDDEN catastrophic events that humans rarely
witnessed



Scientists that helped others
recognize that Earth is many
millions of years old (Hutton),
processes that change Earth in
the past are the same
processes operating in present
(Lyell).
James Hutton- proposed
geological forces acted
extremely slowly, Earth
millions (instead of thosands)
of years old
Charles Lyell- processes that
shaped Earth a long time ago
still continue today, over long
periods of time geological
changes occur
One of the first scientists
to recognize that living
things changed over time
 Use-Disuse Argument:




Organisms have a tendency
toward perfection
Orgas can alter the
size/shape of their organs by
using bodies in new ways
These new altered
characteristics could be
inherited
 Inheritance
of
Acquired Traits
Thought acquired traits
could be inherited
 We now know how
traits are inherited (not
by behavior but by
________?)

English economist, late
1700s
 Noted babies being born
faster than people were
dying
 Human population
growing – sooner or later
not enough living space
and food
 War, famine, and disease
slowed down growth

 If
human population
continues to grow
unchecked, sooner or
later there won’t be
enough resources
(living space, food)
for everyone!
http://www.fordham.edu/halsall/mod/lect/malthus.gif
 Darwin
realized the
same theory could be
applied to plants and
animals
 Many plants and
animals produce lots
of offspring and most
do not survive or
reproduce
 1836
– returns from Beagle
voyage
 1859 – publishes ‘On the Origin
of Species’


Proposed natural selection is how
evolution occurs
Evolution has worked over
millions of years and continues
today

process of how evolution takes place in
nature
1.
2.
3.
Struggle for Existence
Survival of the Fittest
Descent with Modification (variation)
 Malthus
 High
birth rates, shortage
of basic needs =
competition for resources
 Environmental limiting
factors (food, living space)
prevent all individuals
from surviving to
reproduce.


Predators that are faster get
more food
Prey that are faster or
camouflaged avoid being
caught
For all species, if every individual born
into a population were to reproduce,
the population would grow
exponentially
Population
A.
Time
Population
Environmental factors (limiting factors)
prevent the majority of individuals from
surviving to reproduce- organisms
“struggle for existence
What are possible limiting factors for a
population?
Time
 Fitness
= how well
suited an organism is to
its environment

Ability to survive AND
reproduce
 Adaptation
= inherited
characteristic that
increases an organisms
chance of survival
Orangutan’s long arms
 Harmless flies that mimic
the sound of an angry
bee/wasp
 Butterflies of one species
that resemble other
poisonous butterflies
 An insect that looks like a
leaf or a stickcamouflage
 An opossum playing dead

http://animals.nationalgeographic.com/staticfiles/NGS/Shared/St
aticFiles/animals/images/800/orangutan-traveling-forest.jpg
• Tundra
• Boreal forest
• Temperate
broadleaf
forest
• Temperate
grasslands
• Tropical
savannas
• Deserts

For each of the biomes, list ONE adaptation that an
organism in that biome has developed to make it “fit”
in its environment

Individuals in the
population with more
favorable (advantageous)
traits survive and
reproduce more
successfully (high fitness)

Traits not suited to
environment die or have
few offspring (low fitness)
Evolution clip
 Only
certain individuals
produce offspring for
next generation
 Over
time, natural
selection changes the
inherited
characteristics of a
population

Individuals without
advantageous traits die before
reproducing.
Individuals with advantageous
traits survive to reproduce.
Frequency

These individuals
survive to reproduce
Characteristic
 The
environment determines what
characteristics are “favorable”
 Because the environment changes over time,
the characteristic that is more favorable for
a population changes
 Therefore, characteristics of the population
change, or evolution occurs
 Modeling
Camouflage and Natural Selection
 Each
living species as descended – with
changes – from other species over time
 All
living organisms related to one
another
 Individuals
in a population are not
identical to each other. Traits are passed
to offspring; traits have a genetic basis:


With different structures
Occupy different habitats
“average” characteristic or other
measure of the population changes over
generations
Frequency
 The
These individuals
survive to reproduce
Characteristic

Members of a population have traits similar to
the average trait of the entire population, but
they are not identical.
Polygenic trait- controlled by at least 2 genes; can
have many possible genotypes and even more
phenotypes
Mean (average) height
YOUR TURN:
Using height as
an example,
sketch a graph to
represent the
statement above.
Frequency

Height (cm)
 Variation





exists in nature (some examples)
Fruit size
Milk production
Speed
Height
Coloration
 DNA
determines the traits of individuals
DNA
 Individuals
 This
mRNA
protein
trait
inherit DNA from their parents
causes the traits of the offspring to resemble the
traits of the parents
Take out your notes sheet from last class
Take out your Peppered Moth Homework
On your warm-up paper:
1.
What role do you think mutation plays in
evolution?
2.
Where does mutation fit in with the 4
factors for Natural Selection?
http://en.wikipedia.org/wiki/File:Biston.betularia.7200.jpg
Before we learn about how mutation influences
evolution, let’s discuss the evolution of peppered
moths…
Dark form
Peppered form
1.
2.
Describe what trait evolved.
Describe how each of the 4 conditions for natural
selection exists in the moth example:
1.
2.
3.
4.
Variation
Inheritance
Population limits
Selection
 The
population of peppered moths became
darker in color near industrial areas.
 Originally, some moths were dark, some moths
were peppered (light).
 Color is determined by genes inherited from
parents.
 Not all moths survive to reproduce- some are
eaten by birds.
 Pollution killed lichen and made the
environment darker, so darker moths were
better camouflaged and not eaten as much as
peppered (light) moths.
 This caused the average color of the moth
population to become darker
Remember that evolution means change in a
population’s traits. Scientists agree that evidence
shows evolution of the moths has occurred.
Natural selection is the mechanism for the change,
and recent evidence suggests that camouflage
might not be the sole reason for the environmental
selection.
?- Sunlight absorption and heat
Evidence of
Evolution
includes
The fossil record
Geographic
distribution of
living species
Homologous
body structures
Similarities
in early
development
which is composed of
which indicates
which implies
which implies
Physical
remains of
organisms
Common
ancestral
species
Similar genes
Similar genes