chapter 15 the theory of evolution section 15.1 natural selection and the evidence for evolution
TRANSCRIPT
Chapter 15The Theory of Evolution
Chapter 15The Theory of Evolution
Section 15.1 Natural Selection and the Evidence for Evolution
Section 15.1 Natural Selection and the Evidence for Evolution
EvolutionWhat is evolution?• A change in a population over time• These changes is caused by many factors and are mapped out through fossils
Charles DarwinDarwin on HMS Beagle• Ships naturalist
A Little Help
Charles Lyell
Thomas Malthus
Increased food production leads
to increased populations!!
Geological changes on Earth take a long time and are always
occurring!!
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
Charles Darwin???
Darwin tests Heredity
Artificial selection( 人工选择 ) :
• breeding organisms with
specific traits in order to
produce offspring with
identical traits
• Controlled by humans;
• Can produce fast changes
Pigeon Breeding
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
Structural adaptations arise over time
• Mimicry( 拟态 ):a structural adaptation
that enables one species to resemble
another species.
Adaptations: Evidence for Evolution
– Camouflage( 伪装 ) : an adaptation
that enables species to blend with
their surroundings
Adaptations: Evidence for Evolution
Physiological adaptations( 生理性适应 )can develop rapidly; “Micro-evolution”
Adaptations: 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
Other Evidence for Evolution
• Homologous structures( 同源器官 ):
•structural features with a common
evolutionary origin
• Homologous structures can be
similar in arrangement, in
function, or in both.
Anatomy
Analogous structures( 同功器官 ):
•the body parts of organisms that
do not have a common evolutionary
origin but are similar in function
Anatomy
Vestigial structure
( 遗迹结构 ) :
•a body structure in
a present-day
organism that no
longer serves its
original purpose,
but was probably
useful to an
ancestor
Anatomy
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
Section 15.2 Mechanisms of EvolutionSection 15.2 Mechanisms of 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
Population Genetics and Evolution
Hardy-Weingberg Equation: p + q = 1
• p = frequency of Dominate allele
• q = frequency of Recessive allele
• p2 + 2pq + q2 = 1
– 75 (RR) = 75 x 2 = 150 R
– 15 (R’R’) = 15 x 2 = 30 R’
– 10 (RR’) = 10 R and 10 R’
• 160 R and 40 R’
– 200 alleles total
• R alleles = 160/200 = 0.8 = p
• R’ alleles = 40/200 = 0.2 = q
Calculating Allele Frequency
AA= p2
2Aa = 2pqaa= q2
A a
A AA Aa
a Aa aa
100 flowers; 75 are Red, 15 are White, and 10 are Pink. What are the frequencies for alleles R and R’?
What are the genotype frequencies?RR= p2 = 0.82 = 0.64R’R’= q2 = 0.22 = 0.042RR’= 2pq = 2(.8)(.2) = 0.32
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
Population Genetics and Evolution
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
Changes in Genetic Equilibrium
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
Types of Natural Selection
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.
The Evolution of Species
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
Causes of Speciation
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
Types 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
Patterns of Evolution
That’s all !