04/07/06
From Biol301
Contents |
Three (3) conditions necessary and sufficient for any characteristic to evolve by NS
- Variation
- Heritability
- Characteristic must lead to increased fitness
- Struggle for survival is not necessary
Heritability
- 3 ways to study heritability
1. Find the gene
- Try a knockout mutation
- This is difficult as there is seldom one gene controling one trait
2. Common Garden
- Put two organisms in the same environment and note differences
3. Twin Studies Comparisons between relatives
- Using isolated twins to compare differences to infer affect of environment
- Any two relatives can be used for these studies
- Example: Cardinal's song
- Drew graph in class of number of pulses of son's song vs. number of pulses in father's song
- R-value of 0.5 read as "50% of variation in son's song is explained by father's song"
- Remove offspring from environment to control for it learning the song form his father.
- Most behaviors are intermediate: both nature and nurture matter.
- Nothing special about behavior: learning is just one type of environmental influence.
Animal Social Behavior as an Example of Evolved Behavior
- Examples
- Baboons live in groups of 50 - 100.
- White tailed deer and orangutans live almost entirely solitary lives.
- Advantages and disadvantages are balanced by natural selection.
- For the orangutan, the advantages of a solitary lifestyle were greater than the advantages of living in a group (or the disadvantages of a solitary lifestyle were lesser than the disadvantages of living in a group).
Group Living Advantages
- Mate Finding
- Food Finding
- Predator Avoidance
- Group defense; musk ox
- Only have to be faster than the slowest
- More eyes advantage: more sensory detection.
- Predator confusion: school of fish or impalas
- Dilution effect (1/10 vs 1/100 chance of being the victim)
- Learning: not considered much by Dr. Omland
