Unit 11: Evolution Flashcards
(20 cards)
What is the definition of evolution?
Change in the heritable characteristics of a population
This definition distinguishes Darwinian evolution from Lamarckism.
Lamarckism: acquired traits can be passed along (falsified)
Acquired changes that are not genetic are not regarded as evolution.
What are the mechanisms that can cause evolution?
Natural selection and other mechanisms
Evidence for evolution?
DNA Sequence data gives powerful evidence of common ancestry.
Evolution is a change in heritable characteristics
**Changes and similarities in DNA ** thorughout time
- New sequences arise (through mutations) and some become more common
- Some genes are common to many species
- Genes in **closely-related species **are more similar
What is selective breeding?
How does selective breeding provide evidence for evolution?
Selective breeding → domestication of plants and animals
Control reproduction, control traits in the offspring
More desirable traits become more common
Variation between domesticated breeds and their wild counterparts shows rapid evolutionary changes.
Define homologous structures.
Examples?
Same structure, same evolutionary origin, different function.
**Pentadactyl limb **and examples of different functions
How are homologous structures evidence for evolution?
What is divergent evolution?
Lots of different species that inherited from a common ancestor
Divergent evolution: The structures came from a common ancestor
What are analogous structures?
Examples?
Convergent evolution?
Analogous structure: Different structure, different origin, same function.
Examples: human & octopus eyes: bee and bird wings (same function flying but different structures)
Convergent evolution: More than one origin that results in structures that perform a similar function (same selective pressures)
What is speciation?
What needs to happen?
Formation of a new species.
- Reproductive isolation
- Differential selection
What role does reproductive isolation play in speciation?
It prevents interbreeding and allows populations to evolve differently.
What is the role of differential selection in speciation?
Differential selection (environment has different selective pressures)
Separated populations evolve in different ways
Climate, predators, competition etc.
What is natural selection?
The mechanism driving evolutionary change.
Continuous and responsible for biodiversity on Earth
What factors contribute to natural selection?
- Overproduction of offspring
- Variation
- Survival of the fittest
How do mutations contribute to evolution?
Variation is required by natural selection
They generate new alleles.
What is the significance of sexual reproduction in evolution?
Variation is required by natural selection
It creates new combinations of alleles.
Through meiosis
Advantage for sexually- reproducing organisms in changing environments
How does Overproduction of offspring promote natural selection
**Carrying capacity for a population: **More offspring are produced that can be supported by the environment
Competition for resources
- Space
- Resources
- Mates
What are abiotic selection pressures?
Non-living factors affecting survival.
Density-independent:
Freezing or hot temperatures
Natural disasters
Salinity of soil
Density-dependent
Soil mineral availability
Access to water
What is intraspecific competition?
What is fitness?
What is the source of competitive advantage in natural selecton? Why?
Intraspecific competition: competition within a species
Fitness : Heritable factors that influence survival or reproduction within an ecological niche
Greater fitness, better adaptation
Longer survival
More reproduction
Greater contribution to the gene pool, more passing along its genes
What is required for evolutionary change to occur?
Traits must be heritable.
Acquired traits can help an individual organism survive/reproduce, but those traits will not be passed down to offspring
Acquired traits do not change base sequences in sex cells
What is sexual selection?
Example?
Sexual selection : identifying and choosing potential mates that are best adapted and likely to produce offspring that are also well adapted
Drives courtship behaviours
Visual or behavioural signs of fitness
Example: birds of paradise
Exaggeration of traits that result in successful courtship
What was the focus of John Endler’s experiments with guppies?
Female preference for bright, spotted males pushes the population toward more vivid colors. (sexual selection)
Predators that detect those colors push the population toward duller, cryptic males. (predator pressure)
His controlled experiments (e.g., using gravel‐bottom tanks with or without efficient predators) demonstrated that when predators are few or ineffective, males evolve to be more colorful; when predators are abundant or efficient, males quickly become drabber.
This shows a a balance-point between sexual and natural selection.
