Chapter 9.2 Evolution Of Populations Flashcards
What is evolution in genetic terms?
A change in the frequency of alleles in a population over time
Define fitness.
How well an organism can survive and reproduce in its environment
What did Darwin believe about fitness?
Only the fittest individuals survive to reproduce and pass on their traits to the next generation
What has to happen to a population for fitness to increase?
Over time, as individual organisms successfully respond to changing conditions in the environment, the population evolves and its fitness increases.
What are four sources of genetic variations that contribute to the evolution of populations?
- Shuffling of alleles during meiosis
- Mutations
- Gene Flow
- Genetic Drift
What is gene flow?
Gene flow occurs when individuals with new alleles physically move from one population to another.
Does gene flow increase or decrease the genetic variation of a population?
Increase
What was one reason for Darwin’s oversimplification of evolution?
He did not know about mutations.
How many new mutations does each human child inherit from their parents on average?
60
Mutations to which type of cell are passed on to offspring and affect their fitness?
sex cells
Do mutations that increase fitness or mutations that decrease fitness become more common in a population?
Mutations that increase fitness become more common
Why do mutations that decrease fitness tend to disappear?
Because the individuals with that mutation die or reproduce less successfully
What creates all the variation among members of a species and accounts for the diversity of organisms on Earth?
Mutations
What is genetic drift?
Random change in a small populations allele frequency.
How are alleles lost to a population?
The only carrier of an allele dies and this is NOT passed to the next generation.
What results from genetic drift?
The genetic variation of the population shrinks over time.
What is reproductive isolation?
Complete separation occurs when some members of a species become cut off from the rest of the species and NO LONGER INTERBREED
What are three causes of reproductive isolation?
- Geographic isolation
- Behavioral isolation
- Temporal isolation
What is an example of behavioral isolation?
Different mating rituals
What is an example of temporal isolation?
Cicadas of a closely related species, some reach adult stage every 13 years, some every 17 years
What is speciation?
A new species can form when a group of individuals remains separated from the rest of its species long enough to evolve different traits.
What are the events in speciation?
- Founding of a new population
- Separation of populations
- Changes in the gene pool
- Reproductive isolation
- Ecological competition
- Continued evolution
Some finches were blown or flew to the Galapagos Islands from South America is an example of which event in speciation?
Founding of a new population
Later, some birds left the group and flew to another island is an example of what event in speciation?
Separation of populations
Over time, populations on each island became adapted to local environment (eating seeds found there - beaks started adapting to new food) is an example of which event in speciation?
Changes in the gene pool
When birds from populations meet again, differences in mating behavior or features prevent reproduction is an example of what event in speciation?
Reproductive isolation
Because there is competiton, species evolve in a way that increases differences in them is an example of what event in speciation?
Ecological competition
Changes have occurred time and again across Galapagos Islands producing 13 finch species is an example of what event in speciation?
Continued evolution
