Chapter 7 - The Theory Of Evolution Flashcards
What was the 100 year experiment?
Since 1896, corn plants were selected based on whether they had high or low oil content. Initially, corn was ~4.7% oil content, but after 100 years/80 generations, one group had 19% oil and the other had
Define evolution.
The process in which significant changes in the inheritable traits of a species/population occur over time
5 areas of evidence for evolution
- The Fossil Record
- The Geographical Distribution
- Homologous Structures
- Similarities in Embryonic/Early Development
- Biochemical Similarities
What are vestigial features and an example
Homologous features that no longer hold any function (e.g, cave-dwelling fish have eyes but do not see
What are analogous features and an example
Structures similar in function but not in origin of anatomical structure (e.g, butterfly wings/bird wings, fly eyes/human eyes, spider legs/dog legs)
What is The Theory of Evolution?
The idea that species acquire traits as they interact with their environment and then pass these on to their offspring
What were some problems of Lamark’s principles?
- many features do not change in response to use
- features that do change do not change on a DNA level, they are not passed down
Who was the first to propose a mechanism for evolution?
Lamark
Lamark’s principle of use & disuse
- structures that were used became larger and stronger
- structures not used became smaller and weaker
Lamark’s principle of inheritance of acquired traits
- individuals could pass on traits to offspring that they had acquired during their lifetime
Problems with Lamark’s principles
- many features do not change in response to use
- features that do change do NOT change at a DNA level and therefore cannot be passed on to the next generation
Define gene flow, list an example and a benefit.
any movement of individuals from one population to another (AKA migration); e.g. pollen being blown; may be an important source of genetic variation
The Hardy-Weinburg Principle states that…
the frequency of an allele in a population will remain constant over time, as long as:
- pop. is very large
- mating opportunities are equal
- no mutations
- no migration
- no natural selection
Define genetic drift
changes to allele frequency as a result of chance; the smaller the # individuals, the greater the influence of genetic drift
Genetic bottlenecks
a loss of genetic diversity following an extreme reduction in population size (usually results in genetic drift)
Founder effect
genetic drift resulting from when a small # individuals establish a new population
What is adaptive radiation?
when a single species evolves into a # of distinct but closely related species
Difference between divergent evolution and convergent evolution and an example of each
divergent evolution: similar species begin to evolve to look extremely different from one another (large scale; e.g. deer mouse, flying squirrel, porcupine, beaver)
convergent evolution: distantly related species evolve to look similar (e.g. dolphins & sharks)
Coevolution
one species evolves in response to the evolution of another species
Darwin’s 5 key observations that led to his theory of evolution by natural selection
1) Individuals within a species vary
2) Some of this variability can be inherited
3) Every generation produces more offspring that can survive
4) Populations of species tend to remain stable in size
5) Result of natural selection is a pop. adapted to it
Darwin’s inferences (3)
1) Members of the same species compete w/ each other for survival
2) Individuals w/ more favorable variations are more likely to survive (survival is not random)
3) As surviving individuals produce more offspring, favourable conditions become more common
Convergent evolution
The evolution of similar traits in distantly related species
Coevolution
One species evolves in response to the evolution of another species
Divergent evolution
Similar species evolve to look very different (large scale)
What makes a cladogram different from a phylogenetic tree?
Cladograms do not indicate the amount of time in between, and is based upon ancestry and synapomorphies, while phylogenetic trees are more based on physical similarities between species.
Synapomorphy
A characteristic shared by two or more groups, first appearing in their most recent shared ancestor
Adaptive radiation
single species evolves into a number of distinct but closely related species (e.g. Darwin’s finches)
Genetic drift
changes to allele frequency as a result of chance (smaller population = greater influence of genetic drift)
Genetic bottlenecks
an extreme reduction in population size results in a loss of genetic diversity, usually resulting in genetic drift
Founder effect
genetic drift resulting from when a small # of individuals establish a new population
Hardy-Weinburg principle
frequency of alleles will remain constant as long as:
- pop. is very large
- no migration/mutations/natural selection
- equal chance of reproductive success
- mating opportunities equal
Gene flow
(AKA migration) any movement of individuals from one pop. to another; may result in increase of genetic variation
Cladistics
Determining evolutionary relationships based on presence or absence of recently evolved traits
Synapomorphy
A shared derived trait
