lecture 1- descent with modifications I

Evolution: Defined as "descent with modification."
Key theme: Evolution implies that species change over time (the concept of change through time).

Various levels of organization within biological studies include:
- Individual: A single organism.
- Population (popn): A group of individuals of the same species living in the same area.
- Species: A group of organisms that can interbreed and produce fertile offspring.
Question posed: "What is the process that leads to evolutionary change?"

Natural Selection: A mechanism of evolution that describes the process by which certain traits become more common in a population due to their advantageous effects on survival and reproduction.
- Selection Pressure: An environmental factor that influences the survival of organisms, leading to a change in populations over generations.
- Example: In a population of beetles, if brown color provides camouflage from predators, those beetles are more likely to survive and reproduce.
- Adaptation: Traits that enhance survival or reproduction; brown coloration is an example of an adaptation in beetles, which may lead to an increase in the proportion of brown beetles in the next generation.

Title: "On the Origin of Species by Means of Natural Selection Or The Preservation of Favored Races in the Struggle for Life"
Author: Charles Darwin, published in 1859.
Focus: The book presents Darwin's theory of evolution by natural selection.
Key question: "What is our evidence for evolution, over both short and long timescales?"

Short Time Scale: Evidence for evolution on short timescales can be gathered from:
- Observations of Artificial Selection: The human-driven process where traits are selected based on desired characteristics.
- Example: Breeding of plants or animals by humans, which can dramatically affect traits in subsequent generations.
- Observations of Natural Selection: The natural process in which certain traits enhance survival and reproduction in the wild.

Darwin's studies in the Galapagos Islands provided critical evidence for his theories.
Notable observations include adaptive radiation in species such as finches:
- Adaptive Radiation: The diversification of a group of organisms into forms filling different ecological niches.
Example species of finches observed by Darwin include:
- Medium Tree Finch (Camarhynchus pauper)
- Small Tree Finch (Camarhynchus parvulus)
- Large Tree Finch (Camarhynchus psittacula)
- Mangrove Finch (Camarhynchus heliobates)
- Vegetarian Finch (Camarhynchus crassirostris)
- Large Cactus Finch (Geospiza conirostris)
- Cactus Finch (Geospiza scandens)
- Sharp-beaked Ground Finch (Geospiza difficilis)
- Large Ground Finch (Geospiza magnirostris)
- Small Ground Finch (Geospiza fuliginosa)
- Medium Ground Finch (Geospiza fortis)
Geographic context: These finches were studied among the Galápagos Islands, highlighting their adaptation to different environments.

Descent with Modification: Refers to how species evolve over time through natural selection.
Evolution by Natural Selection: Causes populations to modify and adapt to their environment over time.
Evidence: Short-term evidence for evolutionary change arises from direct observation of both artificial and natural selection.
Darwin's approach to developing his theory involved recognizing similarities (descent) and differences (modification) between living species and fossils, as well as among living species occupying different ecological roles.