Transcript Natural Selection

Charles Darwin
The “Origin of Species”
Evolution by natural selection
CHARLES DARWIN
Sailed around the world in the
HMS Beagle
Galapagos Islands
Darwin’s Finches
Natural Selection
Sexual / Asexual Reproduction
Type of Reproduction
Methods
Internal fertilization
Sexual
External fertilization
Conjugation
Budding
Asexual
Advantages
Disadvantages
Diversity in offspring
Better able to survive
environmental
changes
Offspring less likely
to have mutations
show up
Requires a mate to
reproduce
Uses energy to
find/attract a mate
Population increases are
limited
Can increase
populations rapidly
Lack of diversity in
offspring
Lack of resiliency if
conditions change
Because they reproduce
offspring genetically
identical to parents, the
offspring inherit any
mutations of the parent.
Spores
Fission
Does not require a
mate for reproduction
to take place
Energy Spent In Mate Attraction
What qualities do we as
humans seek out in
potential mates? Are they
physical?
Sexual selection
What feature is
giving this bird
an advantage?
Is it a
continuous
or discrete
trait?
Sexual selection
Where do new traits come from?
Basically from mutations, which are oopseys in DNA copying
Mutations happen randomly or are increased by uv light, x rays, gamma
rays, chemicals, viruses, etc
Most mutations are not beneficial
and many times are harmful
But you never know,
perhaps Stumpy’s extra foot could give him a competitive edge some where
and then he and his offspring and their offspring, and so on …
would be “the fittest”
And eventually,
everyone would be used to seeing three legged ducks
So animals such as this
Should not be so unusual after all
Passing the mutations along
Mutations that happen in sex cells (eggs and sperms) during meiosis
will be passed along to offspring (children)
Mutations that happen in somatic or body cells during mitosis will NOT
be passed along to offspring
Recombination of Traits From Parents
Sexual Reproduction
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Some people's hairlines come to a V-shaped
point above their forehead. This is called a
widow's peak. Do you have one or not?
What do your parents have?
Natural Selection
Natural selection –is the engine that drives evolution! The organisms
best suited to survive in their particular circumstances have a greater chance of passing
their traits on to the next generation. Plants and animals interact in complex ways with
other organisms and their environment; like this hummingbird and flower which have
evolved to be perfectly suited to each other for pollination! This is how we get
amazingly diverse range of life forms on Earth!!
Asexual Reproduction
Vegetative
Budding
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the production of offspring that are genetically identical to the parent
organism
only one parent involved
does not provide any genetic variation among individuals of a species
maintains beneficial traits in all offspring
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generally used by less complex organisms
http://www.marietta.edu/~spilatrs/biol202/budding_yeast.mov
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The hydra develops a
"bud".
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The bud develops a
mouth and tentacles
3
When it is fully formed
the daughter hydra
detaches from its
parent.
4
The daughter hydra is
now fully
independent.
Binary Fission a.k.a. Mitosis
Mother Cell splits into Two Daughter Cells
Each daughter cell is identical
Spores
A spore is a structure that is
adapted for dispersal and
surviving for extended periods
of time in unfavorable
conditions. Spores form part
of the life cycles of many
plants, fungi and algae. A
chief difference between
spores and seeds is that
spores have very little stored
food resources.
Survival of The Fittest!
Depends on how successful the organism is when competing for:
mates, food, habitat, RESOURCES
Whose genes will survive to carry on the ‘fittest’ traits?
Who is best adapted to compete for resources?
What does fittest mean?
Is it faster?
Is it stronger?
Is it bigger?
Is it prettier?
Is it smarter
Is it meaner?
Is it nicer?
Is it helpful to others?
Natural Selection
Selection = choosing traits (physical and
behavioural) that give an organism an advantage in a
particular niche
Natural = ????????????????????????
THE ENVIRONMENT!!!!!!!!!!!!!!!!!!!
So what’s doing the selecting or choosing?
THE ENVIRONMENT!!!!!!!!!!!!!!!!!!!
Pneumonia is an infection of your respiratory
tract with bacteria that multiply like crazy and
destroy your ability to breathe
Pneumonia used to kill thousands … before
antibiotics were discovered
HOWEVER
A mutation can occur in bacteria that gives the affected bacteria
Immunity to antibiotics … that’s why sometimes your infections
Do not respond to antibiotic treatment
rapid evolution in bacteria