12.4 Evolution Flashcards
What is natural selection?
It is the theory that certain characteristics or traits possessed by individuals within a species may help those individuals have greater reproductive success, thus passing on those traits to offspring
What are the three tenants of Darwin’s Theory of the Fittest?
- Organisms produce offspring, few of which survive to reproductive maturity.
- Chance variation within individuals in a population may be heritable. If these variations give an organism even a slight survival advantage, the variation is termed favorable
- Individuals with a greater preponderance of these favorable variations are more likely to survive to reproductive age and produce offspring; the overall will be an increase in the traits in future generations. This is termed fitness. An organism’s fitness is directly related to the relative genetic contribution of this individual to the next generation.
Is natural selection evolution?
No, natural selection is simply a mechanism for evolution.
What is inclusive fitness in terms of Darwinism?
This refers to fitness of the population as opposed to the individual.
The early description of evolutionary success were based solely on the number of viable offspring of one organism, however now we look at the survival of the population as a whole.
What is the theory of punctuated equilibrium?
It suggests, that unlike Darwinism, changes in some species occur in rapid bursts rather than evenly over time.
They thought of this when looking at fossils, and noticed that there was not a lot of change, and then suddenly a lot of change.
What are the three modes of natural selection?
- Stabilizing selection
- Phenotype directional selection
- Phenotype disruptive selection
In natural selection, what is stabilizing selection?
It is a type of natural selection that selects against extremes.
E.g. human birth weight (i.e. cannot pass through canal)
- Stabilizing selection
- Phenotype directional selection
- Phenotype disruptive selection
In natural selection, what is directional selection?
The emergence and dominance of an initially extreme phenotype.
An example of this is bacteria that are resistant to antibiotics. Also mosquitos that are resistant to DDT.
In natural selection, what is disruptive selection?
When two extreme phenotypes are selected over the norm.
E.g. bird beak sizes on the Galapagos islands, there were only small or large beaks.
This is facilitated by the existence of polymorphisms.
What is adaptive radiation (genetics)?
Concept that describes the rapid rise of a number of different species from a common ancestor. It allows for various species to occupy different niches.
another definition: Adaptive radiation is a rapid increase in the number of species with a common ancestor, characterized by great ecological and morphological diversity. The driving force behind it is the adaptation of organisms to new ecological contexts.
How do you defined a species?
The largest group of organisms capable of breeding to form fertile offspring.
What is prezygotic reproduction isolation?
Prevent formation of the zygote complete, thereby leading to species isolation.
Examples:
different breeding times (spring vs fall)
Living in different niches.
Behavioral isolation: different pheromones, courtship displays
Reproductive isolation: incompatible reproductive anatomy
Gametic isolation: intercourse can occur, but fertilization cannot.
What is postzygotic mechanisms of reproductive isolation?
Allow for gamete fusion but yield either nonviable or sterile offspring.
Hybrid sterility: like donkey and horse
Hybrid Breakdown: forming first-generation hybrid offspring that are viable and fertile, but second generation are inviable
What are the three patterns of evolution?
- Divergent evolution
- parallel evolution
- Convergent evolution
What is divergent evolution?
Refers to the independent development of dissimilar characteristics in two or more lineages sharing a common ancestor.
Example: seals and cats.
What is parallel evolution?
Process whereby related species evolve in similar ways for a long period of time in response to analogous environmental selection.
What is convergent evolution?
Refers to the independent development of similar characteristics in two or more lineages not sharing recent common ancestor.
An example is that fish and dolphins resemble one and other, although they belong to different classes of vertebrates.
They both adapted similarly to aquatic life.
