Unit I: Intro to Evolution Flashcards
What is evolution?
change in allele frequencies of a population across generations
What processes cause evolution?
- Natural selection
- Genetic drift
- Migration
- Mutation
What is Natural Selection?
- reproduction of individuals with favorable genetic traits that survive environmental change because of those traits, leading to evolutionary change
What is Variation?
genetic differences among individuals in a population
What are the 4 Postulated of Natural Selection?
- Variation exists among individual organisms in a population
- Some of that variation is heritable
- Survival and reproduction success is variable
- Individuals best able to survive and reproduce is not a random sample
Explain Postulate 3 of Natural Selection.
- Populations produce more offspring than can survive
- Resource limit populations, lead to struggle for existence
- Some individuals reproduce more than others
What is a Polygenic Trait?
controlled by multiple genes
(ex: expressions of Bmp4 which effects width and depth)
What is Adaptation?
heritable traits or behavior in an organism that aids in its survival and reproduction in its present environment
Note: that environments change, and thus the trait that is adaptive can also change
What is Heredity?
the transmission of genetic characteristics from parents to offspring
What is heritability?
the fraction of population variation that can be attributed to its genetic variance
What did Gregor Mendel discovery?
(1822-1884)
- Each parent passes a combination of discrete ‘factor’ (alleles or genes)
- Each gamete carries only one factor
-Factors segregate independently during gamete formation
- Dominant and recessive factors
Was Gregor Mendel’s work known by Wallace and Darwin?
Yes
What is Evolutionary Fitness?
individual’s ability to survive and reproduce
What is Relative Fitness?
individual’s ability to survive and reproduce relative to the rest of the population
What is Selection Pressure:
environmental factor that causes one phenotype to be better than another (abiotic or biotic)
Name the types of Selections.
- Stabilizing selection
- Directional selection
- Diversifying selection
- Frequency-dependent selection
- Negative free-dependent selection
- Sexual selection
- Artificial selection
In Stabilizing selection, Phenotype higher AND lower than the mean has __________.
low fitness
In Stabilizing selection, mean __________________.
stays the same
In Stabilizing selection, Genetic variation is _______.
reduced
In Directional selection, Phenotype higher OR lower than the mean has _______.
highest fitness
In Directional selection, the mean move in the direction with the ______ fitness.
higher
In Directional selection, Genetic variation is _______.
reduced
In Diversifying selection, Phenotype higher AND lower than the mean has the ____ fitness
high
In Diversifying selection, the mean ___________________.
COULD stay the same
In Diversifying selection, Genetic variation is ________.
increased
Positive frequency-dependent selection is understood to be
stabilizing selection
What is Negative frequency-dependent selection?
is a type of diversifying selection when considered over multiple generations
In Negative frequency-dependent selection the ____ type has a higher fitness.
rare
In populations with sexual dimorphism, the ____ are typically more decorated, larger , or stronger.
males
What is Sexual Selection?
selection that favors phenotypes that increase ability to obtain or choose good mate
Who does Sexual Selection often act on? And Why?
Males, because of fundamental asymmetry of sex
What is Fundamental Asymmetry of Sex?
females invest more in their offspring than do males
What does Sexual Selection predict?
females should be choosy, males compete with each other
What is Artificial Selection?
Deliberate manipulation of fitness by humans through selective breeding
What type of Selection molds domesticated plants and animals?
Artificial Selection
What leads to genetic drift?
sampling error in sexual reproduce
Individuals are ______ & produce gametes that are ______.
diploid (2n), haploid (n)
Gametes contain _________ of an individual’s alleles
random sampling (50/50 probability for each allele)
Allele frequencies therefore ______ across generations.
“drift”
The magnitude of the drift is INVERSELY related to the population size:
large population size = low genetic drift
small population size = high genetic drift
Genetic Drift can lead to _____ or ____ of alleles, which reduces genetic diversity.
loss (freq = 0), fixation (freq = 1)
What causes Genetic Drift?
- Bottleneck effect (sudden reduction in population size)
- Founder Effect (dispersal over a barrier)
Genetic drift affects the whole genome and is random with respect to fitness.
True
Genetic drift will usually result in a _______ in average fitness.
reduction
