Transcript Chapter 15 The Theory of Evolution

Chapter 16
Darwin’s Theory of Evolution
Evolution
What is evolution?
• A change in a population over time
• These changes is caused by many
factors and are mapped out through
fossils
Charles Darwin
Darwin on HMS Beagle
• Ships naturalist
A Little Help
Increased food
production leads
to increased
populations!!
Charles Lyell
Geological
changes on Earth
take a long time
and are always
occurring!!
Thomas Malthus
Lamarck’s Malarkey (nonsense)
• Jean-Baptiste Lamarck:
• Acquired characteristics
living things can change to
be the best to survive
• Acquired traits parents
can pass down these traits
to their children
• A giraffe stretches every
day to reach higher and
higher branches; so his
neck gets longer
• He eats better, survives,
and passes his long neck
onto his children
Animals change
themselves to fit their
environments!!
Charles Darwin
Darwin continues his studies
• Many species produce
large numbers of offspring
• Individuals struggle to
compete in changing
environmental conditions
• Only some individuals
survive the competition
and produce offspring
???
Pigeon Breeding
Darwin tests Heredity
Artificial selection:
• breeding organisms with
specific traits in order to
produce offspring with
identical traits
• Controlled by humans;
• Can produce fast changes
Natural Selection
•Organisms with favorable variations
survive, reproduce, and pass their
variations to the next generation.
•Traits are only favorable at that time and
under
specific conditions.
•No giant insects
•No giant lizards
•Humans do not have gills
•Controlled by nature
•Slow process
Adaptations: Evidence for Evolution
Structural adaptations arise over time
• Mimicry a structural adaptation that
enables one species to resemble another
species.
Adaptations: Evidence for Evolution
Camouflage an adaptation that enables
species to blend with their surroundings
Adaptations: Evidence for Evolution
Physiological adaptations
can develop rapidly(Micro-evolution)
Other Evidence for Evolution
Fossils：
• provide a record
of early life and
evolutionary
history.
• Even with holes
in the record,
scientists can fill
in the gaps
Anatomy
• Homologous structures:
• structural features with a common
evolutionary origin
• Homologous structures can be similar in
arrangement, in function, or in both.
Anatomy
Analogous structures:
•the body parts of organisms that do not
have a common evolutionary origin but are
similar in function
Anatomy
Vestigial structure: a
body structure in a
present-day organism
that no longer serves
its original purpose,
but was probably
useful to an ancestor
Biochemistry
• Similar organisms have similar cellular
organelles and/or enzymes
• Living things use DNA as a genetic blueprint
• Species in the 3 Domains use similar sized
ribosomes
Ch. 17
Evolution of Populations
Population Genetics and Evolution
• Population:
– Collection of members in a
species
– DNA explains the variation
among individuals of a
population
• Population genetics(种群遗传学)
– studies of the complex behavior
of genes in populations of plants
and animals
Population Genetics and Evolution
Populations, not individuals, evolve
Gene pool(基因库)
• picture all of the alleles of
the population’s genes as
being together in a large
pool
Allelic frequency(等位基因频率)
• the percentage of any
specific allele in the gene
pool
Calculating Allele Frequency
Hardy-Weingberg Equation: p + q = 1
• p = frequency of Dominate allele
• q = frequency of Recessive allele
A
a
A
AA
Aa
a
Aa
aa
• p2 + 2pq + q2 = 1
100 flowers; 75 are Red, 15 are White, and 10 are Pink.
What are the frequencies for alleles R and R’?
– 75 (RR) = 75 x 2 = 150 R
– 15 (R’R’) = 15 x 2 = 30 R’
AA= p2
2Aa = 2pq
aa= q2
– 10 (RR’) = 10 R and 10 R’
What are the genotype frequencies?
• 160 R and 40 R’
RR= p2 = 0.82 = 0.64
– 200 alleles total
R’R’= q2 = 0.22 = 0.04
2RR’= 2pq = 2(.8)(.2) = 0.32
• R alleles = 160/200 = 0.8 = p
• R’ alleles = 40/200 = 0.2 = q
Population Genetics and Evolution
Genetic equilibrium(遗传平衡)
• The population is in genetic equilibrium when the
frequency of its alleles for specific trait is the same in all
its generations
Changes in Genetic Equilibrium
1) Mutation(突变)
2) Gene flow(基因漂流)
•
The transport of
genes by migrating
individuals
3) Genetic drift(遗传漂变)
•the alteration of allelic
frequencies by chance
events
All three have can huge
effects on small populations
Types of Natural Selection
Natural selection is usually the most significant factor that
causes changes in established gene pools—small or
large
3 Types of Natural Selection:
1) Stabilizing selection
-favors the average
2) Directional selection
-favors one extreme of a trait
3) Disruptive selection
-favors both extremes of a trait
The Evolution of Species
Speciation(物种形成)
• The evolution of new species
• Members of similar populations no longer interbreed to
produce fertile offspring within their natural
environment.
Causes of Speciation
Polyploidy (多倍体)
• any individual or species with a multiple of
the normal set of chromosomes
Causes of Speciation
Reproductive Isolation:
• Species no longer can
physically mate or
offspring are sterile
Behavioral Isolation:
• populations have
different mating
behaviors
Types of Evolution
Gradualism(渐变论)
• species originate through a
gradual change; small
changes over a long time
Punctuated equilibrium(骤变论)
• speciation occurs relatively
quickly, in rapid bursts, with
long periods of genetic
equilibrium
Patterns of Evolution
Divergent evolution(趋异进化)
• species that once were similar to
an ancestral species diverge, or
become increasingly distinct.
Adaptive Radiation(适应辐射)
• Ancestral species evolves into
many species to fit a number of
diverse habitats
Convergent evolution(趋同进化)
•distantly related organisms evolve
similar traits
That’s all !