Units 7 & 8: Evolution & Ecology

Evolution

• Evolution is defined as the change in a species over time.
• Theory of Evolution:
  • Darwin's voyage to the Galapagos Islands provided key insights.
  • Observed variation in tortoises and finches based on their environments.
  • Proposed the concept of common ancestry.
• Evolutionary Roadblocks (Historical Misconceptions):
  • Belief that Earth was only a few thousand years old.
  • Belief in the immutability of Earth and species.
  • Assumption that geological features were formed infrequently.
• Lamarck's Principle:
  • Based on the idea of "I think I can."
  • Selective use or disuse of traits during an organism's lifetime.
  • Acquired traits could be passed on to offspring.

Evidence of Evolution

• Fossil Record: Demonstrates how living things have evolved over millions of years.
• Homologous Structures:
  • Same underlying structure but different functions.
  • Example: human arm, whale fin, bird wing.
• Analogous Structures:
  • Different underlying structure but same function.
  • Reflects convergent evolution.
  • Example: penguin wing, shark fin, dolphin flipper
• Vestigial Structures:
  • Structures that have lost their original function in a species.
  • Example: human appendix, wisdom teeth.
• Comparative Embryology:
  • Similarities in embryo development across different species.
  • Example: In the embryo stage, humans share characteristics with other species.
• Biochemical Evidence:
  • Similarities in DNA and protein sequences between organisms.

Natural Selection

• Overpopulation: More organisms are born than the environment can support.
• Competition & Struggle:
  • Limited resources lead to competition among organisms.
• Survival of the Fittest:
  • Only the "strong" (best adapted) survive and reproduce.
• Species Change Over Time:
  • Evolution is a slow and gradual process.
• Lamarck vs. Darwin - Giraffes:
  • Lamarck: Giraffes stretched their necks to reach high leaves and passed this trait to offspring.
  • Darwin: Giraffes with longer necks had a survival advantage, leading to gradual increase in neck length in the population.
• Gradualism: Evolutionary change occurs steadily over time.
• Punctuated Equilibrium: Periods of stasis followed by rapid change.

Evolutionary Paths

• Divergent Evolution:
  • Species become more different over time, often due to different environmental pressures.
  • Results in homologous structures.
  • Example: finches with different beak shapes.
• Convergent Evolution:
  • Species become more similar over time due to similar environmental pressures.
  • Results in analogous structures.
  • Example: dolphins and sharks
• Adaptive Radiation:
  • As organisms spread, they acquire new traits that allow them to better survive in their environments.
  • Example: Finches beaks
• Genetic Drift:
  • Change in the frequency of an allele in a population due to random chance.
  • More pronounced in small populations.
• Founder Effect:
  • A few individuals from a population start a new population with a different allele frequency than the original population.
• Bottlenecking:
  • Population size drastically reduced, leading to loss of genetic diversity.

Isolating Mechanisms

• Behavioral Isolation:
  • Differences in courtship or mating habits prevent interbreeding.
  • Example: Blue-footed Boobies with unique mating dances.
• Temporal Isolation:
  • Species have different mating times.
  • Example: Leopard and wood frogs.
• Geographical Isolation:
  • Physical barriers prevent interbreeding.
  • Example: Fruit flies on different banana trees.
• Extinction: 99% of all species have gone extinct.
• Co-evolution: Two separate species evolve together.

Ecology

• Ecology is the study of how species interact with each other and their environment.
• Levels of Organization:
  • Organisms → Populations → Community → Ecosystem → Biomes → Biosphere
• Carrying Capacity: The maximum population size an environment can sustain.
• Keystone Species: Species that has a large impact on ecosystem (ex. beaver).

Energy in Ecosystems

• Trophic Levels:
  • Producers → Primary Consumers → Secondary Consumers → Tertiary Consumers
• Energy Transfer: Only about 10% of energy is passed from one trophic level to the next.
• Food Chain: Linear sequence of energy transfer.
• Food Web: Group of interrelated food chains.
• Arrows indicate the flow of energy in food chains and webs.

Biogeochemical Cycles & Human Impact

• Water Cycle
• Carbon Cycle
• Nitrogen Cycle
• Phosphorous Cycle
• Oxygen Cycle

Symbiosis & Animal Interactions

• Predator vs. Prey
• Three Types of Symbiosis:
  • Mutualism: Both organisms benefit.
    • Example: Clownfish and anemone.
  • Commensalism: One organism benefits, the other is unaffected.
    • Example: Eyelash mites
  • Parasitism: One organism benefits, and the other is harmed.
    • Example: Wasp larvae and caterpillar, tick and cow

Succession

• Primary Succession:
  • Occurs in previously uninhabited environments (e.g., bare rock).
  • Slower process.
• Secondary Succession:
  • Occurs in areas with existing soil.
  • Faster than primary succession.