L10: Microevolution Part II

T/F Natural Selection has little effect on the traits that show up after post-reproductive. Name an example that proves this.

True; Example: Huntington’s disease → neurodegenerative disorder, progressive breakdown of nerve cells in the brain and this happens during a person’s 30s-40s, long after reproductive life)

Three Modes of Natural Selection (name what is favored & animal examples)

1. directional selection (one extreme, increased frequency of favored alleles

• Galapagos birds
  
  

2. stabilizing selection (intermediate allele is favored, leading to a more stable population but less genetic variation)

• human birth weight, intermediate
  
  

3. disruptive selection (two extremes, leading to increased genetic variation. this can occur when environmental changes or enough resources create two species)

• black peppered moths, favored extreme traits

Three Conditions of Natural Selection

1. variation

2. heritability (to pass down the genetic trait to offspring)

3. fitness differences

Difference between polymorphism vs monomorphism

polymorphism = genetic variation of the alleles
monomorphism = no variation (only one allele remains

Balanced Polymorphism (Name the two examples)

Heterozygote Advantage → two or more versions of alleles (homozygous and heterozygous) are in a population. Heterozygotes have a survival advantage over individuals with homozygote alleles because it has certain advantages within the trait

Environment → genetic variability of both alleles but each depend on where a population is favored in different places or times. Shell color in European garden snails is an example: traits help change color to camouflage to avoid predation

Name all the constraints of Natural Selection

1. not every trait is an adaptation (advantageous for survival)

2. some traits are byproducts (doesn’t have a specific function accidental side effect)

3. evolution works with what’s available → it cannot “invent” new solutions

4. structures are often repurposed for new functions (exaptation)

5. developmental constraints matter (a trait is impacted by how an organism grows up)

6. historical constraints shape what’s posible

7. adaptations involve tradeoffs

Byproduct traits. Give at least four examples of a byproduct trait.

characteristics that don’t solve a specific problem/function, accidental side effect of another trait that was selected for by evolution

Example: Wisdom teeth, tonsils, goosebumps, tailbone, infants when they are born with the grip of toddler strength

Define Exaptation. What does that connect to?

structures inherited during natural selection are repurposed for new functions.

it connects to one of the constraints for natural selection, suggesting that it isn’t perfect and has its limitations

Define Tradeoff in Natural Selection. Give at least two examples of this word.

a trait being favored in one context but harmful in another

Examples:

• large antlers help in mating but are heavy and take more every

• Ostrich v. owl (360 view or binocular vision) in terms of hunting and surviving

What does the Scaling Law say in Biology?

when an organism grows in size, its volume (weight/mass) increases by cubic factor (x³) while its strength of bones/legs only increase by squared factor (x²)

Why are there no organisms with small bodies and big legs?

Thicker legs would be unneeded strength while adding dead weight, which can be disadvantageous for the organism if they want to run away from predators

Coevolutionary Struggle

the prey are not always able to escape and the predators are not always able to capture the prey because both of them are being selected effectively to survive from each other → locked into the cycle of coevolutionary struggle

What was the evolutionary arms race?

a form of coevolution that is the result of competition for better adaptations and counter adaptations between a pair of species

Define reciprocal selection and give an example of an organism that demonstrates this.

a process where two or more species influence mutual evolutionary and selectively pressures on each other

Example: a predator is developing faster speed, prey evolves better escape tactics

plant produces a stronger toxin while an insect develops toxin resistance (two species influence mutual evolution)

What is an example of selective pressure that individuals experience?

Lactose intolerance: the ability to digest lactose depends on where you live in areas. if you live in areas with more lactase production, you are more able to digest lactose but if not, you are likely intolerant.