main points of darwin’s theory of natural selection 1.over production. most organisms produce more...
TRANSCRIPT
![Page 1: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/1.jpg)
Main Points of Darwin’s Theory of Natural Selection
1. Over production.Most organisms produce more offspring than can survive.
2. Competition.Organisms compete for food and resources.
3. Variation.There is variation among individuals of a species.
4. Adaptation.Individuals with traits best suited to the environment will survive.
![Page 2: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/2.jpg)
How Gene Frequencies Change
Sources of Variation• Ways that new adaptations and
gene frequencies arise– S – sexual reproduction– C – crossing over during meiosis
(recombination of genes)– A – arrangement of chromosomes
(alleles) during meiosis
– M – mutations of DNA
![Page 3: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/3.jpg)
KEY CONCEPT
• Evolution by Natural Selection, causes changes in POPULATIONS!
![Page 4: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/4.jpg)
Population EvolutionPopulation genetics genetic principles as they apply to entire populations of organismsPopulation group of organisms of the same species living in the same area
Genotype the representation
on the gene of an organism
Phenotype the physical trait
shown by a genotype
Allele different form of a gene
Gene pool combined genetic
info. for all members of a
population
![Page 5: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/5.jpg)
Population Genetics
• Natural selection acts on individual’s phenotypes not genotypes.
• Populations evolve– Individual’s genes
will stay the same– Population’s gene
pool may change over time due to Natural Selection
![Page 6: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/6.jpg)
• Which trait was a better adaptation and selected for?
• How were frequencies of different alleles affected?
Population Genetics
![Page 7: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/7.jpg)
Gene Traits:
A) Single gene trait: controlled by single gene with two alleles
♦ Examples: widow’s peak, hitchhiker’s thumb, tongue rolling
![Page 8: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/8.jpg)
B) Polygenic trait: controlled by 2 or more genes, each with 2 or more alleles
♦ Examples: height, hair color, skin color, eye color
Most human traits are polygenic.
This type of variation can cause different types of selection of one phenotype over others
![Page 9: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/9.jpg)
Directional, Disruptive, and Stabilizing Selection
• Three modes of Natural Selection:– Directional selection favors individuals at one
end of the phenotypic range
– Disruptive selection favors individuals at both extremes of the phenotypic range
– Stabilizing selection favors intermediate variants and acts against extreme phenotypes
© 2011 Pearson Education, Inc.
![Page 10: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/10.jpg)
Three Types of Natural Selection Three Types of Natural Selection
Stabilizing Selection = maintains an already existing system.
> eliminates organisms that deviate from the norm.> environment must remain unchanged.> explains why there are “living fossils.”> as long as environment doesn’t change,
organisms won’t change. Horseshoe CrabGinkgo Tree
![Page 11: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/11.jpg)
Key
Per
cen
tag
e o
f P
op
ula
tio
n
Birth Weight
Selection against both
extremes keep curve narrow and in same
place.
Low mortality, high fitness
High mortality, low fitness
Stabilizing Selection
Stabilizing Selection
![Page 12: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/12.jpg)
Directional Selection = favors one extreme or the other.
> eliminates organisms that are not in that extreme.
> eventually leads to changes in the population.
> occurs when organisms must adapt to a change in their environment.
> may develop into a RESISTANCE (the ability of an organism to withstand a harmful agent).
MALARIA
![Page 13: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/13.jpg)
Directional Selection (page 398)
Food becomes scarce.
Key
Low mortality, high fitness
High mortality, low fitness
Directional Selection
![Page 14: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/14.jpg)
Disruptive Selection = favors two extremes at one time.
> eliminates organisms that are more common.
> eventually leads to changes in the population.
African butterflies can range from red to blue.The red and blues are foul-tasting to predators.
The other colors are eaten more often resulting in a selection in favor of the extreme colors.
![Page 15: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/15.jpg)
Disruptive Selection (pg 399)
Disruptive Selection
Largest and smallest seeds become more common.
Nu
mb
er o
f B
ird
sin
Po
pu
lati
on
Beak Size
Population splits into two subgroups specializing in different seeds.
Beak Size
Nu
mb
er o
f B
ird
sin
Po
pu
lati
onKey
Low mortality, high fitness
High mortality, low fitness
![Page 16: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/16.jpg)
![Page 17: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/17.jpg)
![Page 18: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/18.jpg)
ORGIN OF SPECIES
What is a Species? A Group of interbreeding organisms that can produce fertile offspring.
![Page 19: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/19.jpg)
The Origin of Species The Origin of Species (Macroevolution)(Macroevolution)
Macroevolution
• the formation of new species between organisms (speciation) and accompanying events
Microevolution • refers to changes in allele frequencies in a
gene pool from generation to generation. Represents a gradual change in a population.
![Page 20: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/20.jpg)
• Macroevolution Microevolution
![Page 21: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/21.jpg)
How Do New Species Form? Speciation- formation of a new species
Causes of Speciation:
1. Geographic Isolation2. Temporal Isolation3. Behavioral Isolation4. Ecological Isolation
![Page 22: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/22.jpg)
Geographic Isolation
• Physical separation of members of a population
(by formation of a canyon, mountain, river, etc.)– Leads to different adaptations on
each side of barrier, and eventually new species (allopatric speciation)
![Page 23: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/23.jpg)
Geographic Isolation = New Species: An Example
![Page 24: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/24.jpg)
Temporal Isolation
• Species isolated because they reproduce in different seasons or times of day
• Prevents species from ever breeding together – keeps two species separate but usually arises after species have formed.
![Page 25: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/25.jpg)
Behavioral Isolation
• Species Differ In Their Mating Rituals (e.g. different bird songs, mating colors, dances, pheromones, etc.)
![Page 26: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/26.jpg)
Ecological Isolation
– Species inhabit the same area, but different habitats, so they don’t encounter each other
![Page 27: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/27.jpg)
Other Factors Can Affect Genetic Variation In A Population
• Other factors that increase variation in the genetic material (gene pool) of a population on which natural selection acts:– Random/nonrandom mating =
sexual selection– Gene traits-single/polygenic– Isolation– Genetic Drift– Fitness is the relative ability
of genotypes to survive and reproduce
![Page 28: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/28.jpg)
Microevolution refers to changes in allele frequencies in a gene pool from
generation to generation. Represents a gradual change in a population.
Causes of microevolution: 1) Genetic drift
2) Natural selection
3) Gene flow (migration of genes from one population to another)
2) Mutation
![Page 29: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/29.jpg)
GENETIC DRIFTDNA frequency in a population
changes simply by CHANCE not fitness
![Page 30: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/30.jpg)
![Page 31: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/31.jpg)
FOUNDER'S EFFECT:
some individuals of a population colonize a new habitat
ex: Columbus bringing organisms to USA
Spain: DNA Frequency66% pink33% red
S. America: DNA Frequency25% pink75% red
![Page 32: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/32.jpg)
Bottleneck Bottleneck Effect:Effect:
Small representation of the original population after a catastrophic event. Alleles in gene pool are not equally represented and species may evolve.
![Page 33: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/33.jpg)
HOW DOES GENETIC DRIFT AFFECT THE DIVERSITY OF A
POPULATION OVER TIME?
![Page 34: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/34.jpg)
Genetic drift decreases diversity. In this case yellow and pink DNA are gone, and red DNA is now the majority.
Genetic drift = decrease in DNA diversity
![Page 35: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/35.jpg)
Patterns of Evolution
• Convergent Evolution
• Divergent Evolution
• Coevolution
![Page 36: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/36.jpg)
Convergent Evolution• Organisms appear similar, because of similar habitat and
selection pressure. These organisms aren’t closely related
• Why?– Similar environments select for similar traits
![Page 37: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/37.jpg)
Divergent Evolution• accumulation of differences between
groups which can lead to the formation of new species; evolving from a common ancestor
• Related populations or species become less and less alike
![Page 38: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/38.jpg)
A Second Type Of Divergent Evolution
• Artificial Selection– Humans, rather than
nature, select traits
![Page 39: Main Points of Darwin’s Theory of Natural Selection 1.Over production. Most organisms produce more offspring than can survive. 2.Competition. Organisms](https://reader031.vdocuments.mx/reader031/viewer/2022013004/56649e495503460f94b3c0ca/html5/thumbnails/39.jpg)
Coevolution
• Two or more species in close association w/one another change together– Predator/Prey– Parasite/Host– Plant/Pollinator