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Campbell Biology: Concepts & Connections with MasteringBiology® (7th Edition)
Chemistry: The Central Science with MasteringChemistry® (12th Edition) (MasteringChemistry Series)
Key Observations by Darwin
1) Species tend to: over-reproduced, but don't all survive
2) Individuals in a population vary extensively
3) These varying traits are inherited
Differential reproductive success. Individuals whose characteristics best adapt them to their current environment are most likely to survive and reproduce.
Well adapted to environment, more likely to pass along genes
3 Key Points on NS
1. NS is an editing process, not a creative process
2. NS is contingent on time and place
3. Significant evolutionary change can occur in a short time
The ideas of Darwin and Mendel put together
4 Processes of Evolution
1. Natural Selection
2. Genetic Drift
3. Gene Flow
NS acts on _______________ but the effect is a change in the _____________
Group of organisms of the same species living in the same time/place
Allele frequencies in a population, change over time.
Hardy-Weinberg Model (non-evolution): 5 conditions
1. No mutations
2. Infinitely large
3. Complete Isolation (no immigration/emigration)
4. Random mating
5. Equal reproductive success (survive equally and have same number of offspring)
Do non-evolving populations exist?
Nope, only theoretical
Gene pool remains constant if these 5 conditions are met
p + q = 1
p^2 + 2pq + q^2 = 1
Evidence that species had not been created "perfect"?
Sequence of complexity in species, Simple to complex
Anatomist, make sense of evolutions. Compared fossils with living organisms. Abrupt changes in fossil record=mass extinction (Catastrophism)
Hypothesized that offspring inherited traits from parents developed during lifetime. This is not true.
Ex. Stretched giraffe neck
Wrote "Principles of Geology". Strange catastrophes not explained by earth's surface.
"Father of Biology" - outlined Darwin's theory pre-Darwin.
"Variations in traits can influence and individual's ability to secure limited resources and thus to survive and reproduce". Came up with idea of natural selection.
Correlated populations size with famine, disease and war. Compete for resources.
_____________ do not evolve, _____________ do.
What created new alleles in a population?
What shuffles alleles already existing in population?
Mutations are not necessarily bad because...
They give rise to structural, functional, and behavioral alterations that increase changes of survival and reproduction.
Micro-evolution is when there are small changes in a population's...
Five Types of Natural Selection
1. Directional Selection
2. Stabilizing Selection
3. Disruptive Selection
4. Sexual Selection
5. Balancing selection
Environmental conditions can cause a shift in allele frequencies in a consistent direction.
Ex. White moths blend in to lichen
Intermediate traits favored, not extremes.
Ex. Over and underweight babies.
Forms at both ends of a range of variation are favored, intermediate forms are selected against.
Ex. two typed of bills in species, for different plants.
Distinct male or female phenotype, sexual dimorphism.
Ex. Male more larger and more colorful, because genetic "winners" reproduce more.
Two or more alleles of gene persist at high frequencies. Heterozygotes are favored.
Ex. Sickle cell anemia, Heterozygote less likely to get malaria.
Differential survival and reproduction among individuals of a population that vary in details of shared traits.
Original Source of new Allele
Random change in allele frequencies brought about by chance.
Individual (and allele) movement in between populations.
When all individuals have become homozygous for some allele?
Fixation - Genetic drift. Magnitude in genetic drift is larger for smaller populations.
Origin of Species
Ernst Mayr's Biological Species Concept
A group of populations whose individuals have the potential to interbreed and produce fertile offspring.
5 Pre-zygotic Barriers
1. Temporal isolation
2. Behavioral Isolation
4. Mechanical Isolation
5. Gamete Isolation
Different reproduction times
Different mating rituals
Physical barrier, based on habitats.
Sexual parts don't fit together.
Ex. Pollination by different birds.
Sperm and Egg incompatible.
2 Post-Zygotic Barriers
1. Hybrid inviability
2. Hybrid Sterility
Zygote starts to divide and fails and dies.
Horse and donkey = Sterile mule
How do reproductive barriers form?
Two species from one ancestral species
A burst of divergences from a single ancestor that leads to many new species each adapted to a new habitat.
(Honey Creepers in Hawaii)
"Other homeland", there is a geographical barrier causing speciation.
No geographic barrier.
Plants: can become reproductively isolated in one generation due to polyploidy.
Polyploidy in Plants
Creates a tetraploid, a 4n cell, then to a triploid
D. Parapatric Speciation
One population that extends across a large diverse region. Populations at the edge of this region become different species.
Speciation occurs when...
Gene flow ends between populations
Occurs over brief time span followed by a long periods of no change.
Slight changes over long periods of time.
Changes in gene pool population over time - relatively small, not result in newer organisms being considered as a different species.
Changes in organisms that are significant enough that new species arise.
Process occurs when close ecological interactions among species cause them to evolve jointly. They can't survive without each other.
2 hypotheses on how life on earth began
2. Formed in outer space (presence of amino acids in interstellar clouds)
Which came first, DNA or RNA? And proof?
RNA came first we think, RNA store genetic information and functioned like an enzyme in protein synthesis.
Prokaryotes gave rise to...
Advantage of nuclear envelope? How did it evolve?
Keep genes safe from foreign DNA ,and evolved keep genomes separate when two prokaryotes fused.
Hypothesis of Lynn Margulis?
Endosymbiosis; symbiont lives life inside host. Mitochondria is a symbiont of cell, was once separate. Also chloroplasts evolved in this way.
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