Biology Chapter on Evolution

Study Notes

Descent with modification

Evolution is a gradual process of change in the genetic makeup of a population over time.
This change can occur through natural selection, where individuals with advantageous traits are more likely to survive and reproduce, or through genetic drift, where random fluctuations in allele frequencies can occur.
Macroevolution refers to the formation of new species, which can take thousands of years.
Evidence of evolutionary change:
- Soapberry bugs: these bugs have evolved to have different beak lengths depending on the size of the fruit seeds they feed on.
- Finches on the Galapagos Islands: these birds have evolved different beak sizes and shapes depending on the type of food available.
Vestigial structures: these are functionless or rudimentary body parts that were once useful in ancestral species. Examples include the pelvis of whales and the arrector pili muscle in humans.
Extinction: this is a natural process of evolution where species disappear due to environmental changes or competition.
- Fossil records provide evidence of extinct species and their relationships to modern species.
Law of succession: fossils found in a particular area often resemble the species that currently live there. This suggests that modern species are descended from the extinct species that lived in the same area.
Transitional forms: these are fossils that exhibit characteristics of both ancestral and descendant groups. They provide evidence of evolutionary transitions between species.
Homology: similar structures in different species that have evolved from a common ancestor. Examples include the metacarpals in humans, bats, whales, and horses.
Analogy: structures in different species that have similar functions but have evolved independently. Examples include the wings of insects, birds, and bats.
Reverse transcription: the process of converting RNA back into DNA. This can lead to the insertion of new DNA sequences into the genome.
Retrotransposons: these are DNA sequences that can move around the genome. They are thought to be "junk DNA" but may play a role in regulation of gene expression.
Introns: non-coding sections of DNA that are removed before translation.
Exons: coding sections of DNA that are translated into proteins.
Pseudogenes: non-functional duplicates of genes that are created by reverse transcription. They are often used to study gene evolution and gene regulation.
Radiometric dating: a method used to determine the age of rocks and fossils based on the decay of radioactive isotopes.

Darwin’s postulates:

Variation: Individuals within a population vary in their traits.
Inheritance: Some of this variation is heritable, meaning that it can be passed down from parents to offspring.
Overproduction: Organisms produce more offspring than can survive.
Non-random survival and reproduction: Individuals with traits that make them better adapted to their environment are more likely to survive and reproduce, passing their traits on to their offspring.

Darwinian fitness

This is a measure of an individual's reproductive success.
It can be measured by the number of surviving offspring, number of offspring, and number of gametes produced.
Surrogates for fitness: physical size, energy reserves, number of flowers per plant, etc.

Adaptation

This is a trait that increases an organism's fitness relative to other organisms.
Example: Panda thumb. This is an adaptation that allows pandas to hold and shred bamboo more effectively.

Homoplasy

This is a shared characteristic that is not due to a common ancestor.
Convergent evolution: This is when two species evolve similar traits independently.
Example: The wings of insects, birds, and bats are all used for flying, but they are structurally different.