Download Chapter 4 - Rye High School

There is no grandeur to this view of
life…that, whilst this planet has gone
cycling on…endless forms most beautiful
and most wonderful have been, and are
being, evolved
 Evolution
 Natural
selection
 Adaptations
 Mutations
 Differential reproduction
 Geographic isolation
 Reproductive isolation

Largest reptile in North
America, no natural
predator

1930s: Hunters and
poachers

Importance of gator holes
and nesting mounds

1967: endangered species

1977: comeback, threatened
species
 Concept
4-1 The biodiversity found in
genes, species, ecosystems, and ecosystem
processes is vital to sustaining life on
earth.
 Variety
of species and the genes they contain,
ecosystems they live in and processes that
sustain all life
Do Now:
Take 5 minutes to write
everything you know and think
about the topic of evolution
 Concept
4-2A The scientific theory of
evolution explains how life on earth
changes over time through changes in the
genes of populations.
 Concept
4-2B Populations evolve when
genes mutate and give some individuals
genetic traits that enhance their abilities to
survive and to produce offspring with
these traits (natural selection).
 Evolution
is the change in a population’s
(not individual’s) genetic makeup over
time
 Populations
evolve by becoming
genetically different.
 All species descend from earlier,
ancestral species—theory of evolution.
 Over
time, a population’s gene pool
changes when mutations (beneficial
changes) in DNA molecules are passed
on to offspring
 Mutations are random changes in the
structure/number of DNA molecules in a
cell.
 1)
Gene DNA is exposed to external
agents like X-rays, chemicals (mutagens),
or radioactivity.
 2)
Random mistakes that occur in coded
genetic instructions.
 Occurs
when members of a population
have genetic traits that improve their
ability to survive and produce offspring
with those specific traits.
 1. The
population must have genetic
variability.
 2. The trait must be heritable, capable of
being passed from one generation to
another.
 3. The
trait must enable individuals with
the trait to produce more offspring than
individuals without the trait; this is
differential reproduction.
 Adaptation
or adaptive traits are
heritable traits that help organisms to
survive and reproduce better under
prevailing environmental conditions.
 Natural
selection can only act on existing
genes and is limited by reproductive
capacity.
 Peppered
Moth Online Hunt
Natural Selection
Directional selection favors individuals with traits that are at one
end of a distribution (such as the peppered moth example).
"It pays to be different.“
Ex: Industrial melanism in peppered moths
© Brooks/Cole Publishing Company / ITP
Natural Selection
Stabilizing selection eliminates individuals at both ends in
the spectrum of variation; the average remains the same.
"It pays to be average.“
Ex: Human birth weights
© Brooks/Cole Publishing Company / ITP
Natural Selection
Disruptive (diversifying) selection eliminates average
individuals, but favors individuals at either extreme of the
spectrum of variation.
"It doesn't pay to be normal."
© Brooks/Cole Publishing Company / ITP
 Evidence
of ancient organisms (plants,
animals etc) & internal structure
 Can provide clues as to past climate
 Fossil record incomplete…why?
Do Now:
What are some geologic
processes that may separate
individuals or populations of
organisms?
 Shifting
of tectonic plates
 Volcanic eruptions
 Earthquakes
• All influence earth’s climate and in
turn affect evolution by removing
and/or isolating habitats and
species.
 Volcano, Earthquakes
& Plate
Boundaries
 Types of Plate Boundaries
 Long-term
climate changes relocate
ecosystems, thus determining where
certain species can live.
 Asteroids and meteorites have caused
environmental stress and mass
extinctions.
YouTube - Species Extinction
Video
 The Vanishing
Frogs Part 1
 The Vanishing Frogs Part 2
 The Vanishing Frogs Part 3
 Frogs: The Thin Green Line - Chytrid
Fungus
 Natural
selection can lead to
development of an entirely new species.

In speciation, two species arise from
one when some members of a population
cannot breed with other members to
produce fertile offspring.
• How might this occur??
 1.
Geographic isolation, physical
separation for long time periods.
 2. Reproductive isolation.
 When
population members cannot adapt
to changing environmental conditions,
the species becomes extinct.
 What are some species that have gone
extinct?
 When
local environmental conditions
change, some species will disappear at a
low rate; this is called background
extinction
 “normal extinction”
 Before humans
 Mass
extinction is a significant rise in
extinction rates above the background
extinction level. Usually, 25–70% of
species are lost. Recent evidence
suggests that there have been two mass
extinctions on earth. There appear to
have been five total mass extinctions on
earth.
 Species
diversity is the number of
species (richness) combined with their
relative abundance (evenness).
 Species rich communities tend to be
more stable and more productive.
 Ecological
niche is a species’ way of life
in an ecosystem, everything that affects
its survival and reproduction
 The
niche includes the members’
adaptations; its range of tolerance for
physical and chemical conditions, its
interactions with other components of the
ecosystem, and its role in energy flow
and matter recycling
 The
fundamental niche is the full
potential range of conditions and
resources a species could potentially use.
Its realized niche is the part of the
potential niche that allows a species to
survive and avoid competition with other
species for the same resources.
 Some
species have broad ecological
roles and are termed generalist species.
 Some species have narrow ecological
roles and are termed specialist species.
Number of individuals
Niche
separation
Specialist species
with a narrow niche
Niche
breadth
Region of
niche overlap
Resource use
Generalist species
with a broad niche
 Silence
of the Bees



Keystone species have a large affect on maintaining
balance within an ecosystem.
1. Can be, but are not necessarily, pollinators and
top predators.
2. Foundation species create and enhance
habitats that benefit other species.
 Niches
can be occupied by native or nonnative species.
 Indicator species provide early warning
of ecosystem damage because they have
a narrow range of tolerance.
 Fruit
Fly


Artificial selection has been used to change genetic
characteristics of populations by selecting one or more
desirable genetic traits and selectively breeding them.
Genetic engineering has been used to create
genetically modified organisms (GMO’s) by transplanting
genes from one species to the DNA of another.
• Has great promise
• Unpredictable—trial and error
• Future problems that may results can’t always be
anticipated
 Advantages:
• Can result in:
 Increased nutritional value of food
 Greater crop yield—stop starvation
 Possible medicinal benefits such as addition of
vaccines or removal of allergens from food
 Resistance of plants to pests so decreased used of
pesticides
 Resistance of plants to herbicides so weed tilling can
be decreased resulting in less soil erosion
 Disadvantages:
• Negative effects may be:
 Possible production of new allergens or toxins by GMF’s
due to mutation
 Decrease in genetic diversity by planting only a few
“superfoods.”
 Cost of raising/growing food will increase due to high
costs of creating and patenting GMF’s. This may drive
out some independent farmers
 Pest populations may become resistant to some
pesticides.
 Fruits, veggies, livestock
certified organic.
 How?
and eggs can all be
• Avoidance of most synthetic chemicals:




Antibiotics
Pesticides
Fertilizer
Food additives
• No GMO’s or irradiation
• No use of sewage sludge for fertilization
• Use of farmland that has been free from chemicals
for a # of years