Bio (Jan 8th)

Natural selection is influenced by the local environment; the same species can evolve differently on different islands due to various environmental factors.
- Environmental factors include:
- Limited food supply
- Different habitats
- Varying predation pressures
- Competition and disease
Misconception: Natural selection has no specific end goal or pattern; it simply responds to environmental changes.

Natural selection operates on individuals but is measured at the population level.
The relationship between heritable traits and their genetic basis is crucial:
- Only traits with a genetic basis can be acted upon by natural selection.
- The speed of trait spread across generations depends on the strength of natural selection and heritability.
Life history traits influence responsiveness to natural selection:
- Organisms with shorter generation times (e.g., insects) adapt more rapidly compared to those with longer generation times (e.g., elephants).

Evolving populations change over generations; individuals do not evolve in their lifetime.
The fitness of a population increases over time as natural selection operates.
Fitness is determined by both survival and reproductive success.

For natural selection to occur, there must be:
- Variation in traits within a population.
- The heritability of that variation is essential for natural selection to influence future generations.

Classic examples studied include:
- Peppered Moth:
- The Industrial Revolution led to the dark coloration becoming favored due to environmental changes.
- Darwin's Finches:
- Variation in beak size based on available food sources on the Galapagos Islands.
Recent studies, such as those by Sarah Leonard, examine sexual selection in salmon, highlighting dual-phenotype fitness under varying environmental circumstances.
**Stickleback Fish:."
- Marine sticklebacks have armor for protection against predators, while freshwater sticklebacks lose armor to allocate energy towards reproduction.

Generation time influences the ability to respond to environmental changes rapidly:
- Organisms with short generation times adapt quickly; organisms with long generation times (e.g., elephants) struggle to adapt and may face extinction under rapid environmental changes.

Long-term studies often focus on organisms with rapid generation cycles to observe evolutionary changes over many generations.
- Example: E. coli bacteria have a generation time of an hour, allowing for extensive generational studies.

Evolutionary thought predates Darwin, with significant contributions from Aristotle, Carl Linnaeus (taxonomy), and Jean-Baptiste Lamarck (acquired characteristics).
Darwin is credited with unifying existing ideas about evolution with the mechanism of natural selection.
Wallace’s Contribution:
- Alfred Russel Wallace proposed similar ideas to Darwin and prompted Darwin to publish his work before Wallace's findings were made public.

Thomas Malthus theorized that population growth would surpass food supply, leading to competition and survival challenges, influencing Darwin's understanding of natural selection.

The modern synthesis combines various fields, including genetics, paleontology, and biogeography, establishing a more comprehensive understanding of evolution and natural selection mechanisms.

Individuals within a population must vary.
Some variations are heritable and can be passed from parents to offspring (genetic basis).
Survival and reproduction are not random; advantageous traits enhance fitness.
Over time, these conditions lead to evolution in populations as they adapt to their environment.