11-Natural Selection & Adaptation

Natural Selection & Adaptation

• Natural Selection: The process through which certain traits become more common in a population due to enhanced survival and reproductive success.

• Adaptation: Characteristics that enhance an organism's survival or reproduction in specific environments.

Mechanisms of Evolution

• Several mechanisms can lead to evolution, but natural selection is the primary one that drives adaptation.

Components of Natural Selection

• Variation: Diverse traits exist within a population.

• Inheritance: Traits must be passed from parents to offspring.

• Differential Reproductive Success: Some individuals reproduce more than others due to advantageous traits.

Examples of Adaptation in Birds:

• Apapane: Feeds on insects and ohia nectar.

• Akiapola'au: Forages for insects under bark.

• Iiwi: Feeds on nectar from ohia flowers.

• Maui Parrotbill: Searches for beetles by tearing back bark.

• Nihoa Finch: Uses a strong bill to crush seeds.

Causes for Adaptation

• Natural Selection: The driving force behind the development of adaptations.

• Examples of Adaptations:

  • Frog Calls: Used to attract females; can be exploited by bats.

  • Philodendron: Young growth moves toward darkness to find support; grows larger leaves that seek light.

Complex Adaptations

Pseudocopulatory Pollination in Orchids

• Flower exudes specific scents to attract wasps, leading to natural pollination.

Adaptations of the American Beaver

• Features:

  • Long incisors that never stop growing.

  • Nostrils and ears that can close underwater.

  • Flaps of skin behind incisors to carry sticks without drowning.

Evolution of Structures

Jaw Evolution

• Movable bones allow venomous snakes to utilize fangs effectively.

Cooperative Behavior

• Weaver Ants: Workers work together to create nests by pulling leaves and using silk from larvae.

Evolution of Complex Structures

• Complexity in biological designs indicates adaptive processes over time, often incorrectly attributed to "intelligent design". For example, the intricate design of the human eye evolved through natural processes.

Evolutionary Considerations

• Evolutionary processes lack an end goal; they adapt based on present conditions.

• Structures may change functions over time, helping explain the transition forms in evolution.

Definitions

• Natural Selection: A consistent difference in fitness among phenotypes.

• Fitness: Measured by reproductive success and survival rates.

Sexual Selection

• Variation in offspring is a byproduct of competition for mates.

• Some organisms develop preferences for specific traits.

Genetic Drift vs. Natural Selection

• Genetic Drift: Evolution can occur without natural selection's influence, impacting future selection processes.

Pleitropy

• Refers to one gene affecting multiple traits, complicating selection since one trait's success may adversely affect others.

Experimental Studies of Natural Selection

• Evidence of evolution can be demonstrated experimentally (e.g., studies on bacteria populations)

Tuberculosis and Natural Selection

• Antibiotic resistance in TB exemplifies swift evolutionary changes driven by selective pressures from antibiotic use.

Widowbird Male Success

• Long tail feathers enhance reproductive success, supported by experimental observations.

Natural Selection's Four Postulates

1. Individuals in a population are variable.

2. Some of that variation is heritable.

3. Some individuals are more successful at surviving and reproducing.

4. Survival and reproduction connect to heritable variation.

Fitness Components

• Survival probabilities, offspring production via female and male functions, contribute to fitness measurement.

Darwin's Finches

• Variation in beak sizes has been tied to food sources; adaptability regarding seed types is crucial.

Adaptation and Feeding Habits of Giraffes

• Long necks may have evolved for either feeding height or for social interactions, impacting mating success.

Understanding Adaptations

• Not all traits are adaptations; some arise as byproducts of other traits.

• Exaptation: Traits that shift to serve new functions.

Recognizing Adaptations

• Analyzing complexity, biological design, and functional alterations hint toward adaptive significance.

Comparative Method in Evolution

• Comparing species for functions and structures to deduce adaptive significance.

Constraints on Evolution

• Physical and biological constraints shape the evolution of traits.

Misconceptions About Natural Selection

• Not driven by necessity, perfection, or progress; does not imply harmony or morality.

Concluding Thoughts

• Natural selection sorts organisms by reproductive success, acting at various biological levels without a conscious "selector".