ADAPTATIONS AND ITS LIMITS

Question 1

What is “adaptive storytelling”?

Answer 1

It’s creating a plausible story for why a trait is adaptive, without actually demonstrating the trait’s adaptive significance.

Peppered Moth (Biston betularia):
Before Industrial Revolution: The light-colored moths were more common because they blended with the lichen-covered tree bark, avoiding predation.
After Industrial Revolution: Pollution darkened the tree bark, making the light-colored moths more visible to predators. The dark-colored moths became more prevalent because they were better camouflaged, an example of adaptive evolution in response to environmental change.

Question 2

What is an exaptation?

Answer 2

A trait that performs a current function different from the one it originally evolved for (e.g., feathers evolved for warmth, now used for flight).

Question 3

Give an example of a trait that is an “unselected result of physics or chemistry.”

Answer 3

Blood is red due to the iron ion in hemoglobin, not because it evolved to signal injury.

Question 4

What is an example of a trait evolving by chance?

Answer 4

The ability of humans to roll their tongues is likely a result of chance, not adaptive selection.

Question 5

What is an example of a trait that is a side effect of another adaptation?

Answer 5

Sneezing in response to the flu virus, which is primarily a reflex to expel irritants, not specifically to spread the virus.

Question 6

What is a historical constraint in evolutionary terms?

Answer 6

A trait shaped by an organism’s ancestry, like humans’ back pain due to vertebrae adapted from quadrupedal ancestors.

Question 7

How does natural selection lead to adaptive evolution?

Answer 7

By favoring traits that increase survival and reproduction, leading to adaptation.

Question 8

What three conditions must be met for natural selection to occur?

Answer 8

Variation, heritability of that variation, and impact on survival and reproduction.

Question 9

: Define “adaptation” in evolutionary biology.

Answer 9

An outcome of the evolutionary process where a trait is shaped and favored by natural selection to enhance fitness.

Question 10

What is an adaptive trait?

Answer 10

A trait that enhances an organism’s fitness, increasing its chances of survival and reproduction.

Question 11

What is a maladaptive trait?

Answer 11

A trait that decreases an organism’s fitness, potentially reducing its chances of survival and reproduction.

Question 12

Why is only natural selection able to lead to adaptation?

Answer 12

Because it specifically favors traits that improve survival and reproductive success in a given environment

Question 13

What is an example of adaptation in Galapagos finches?

Answer 13

Beak depth variation, where deeper-beaked birds had a survival advantage and reproduced more during a food scarcity event.

Question 14

What is the goal of the adaptationist program?

Answer 14

To determine if a trait is an adaptation by asking what it’s for and how it enhances fitness.

Question 15

criteria for a trait to be considered an adaptation

Answer 15

It must increase fitness, have evolved by natural selection, and be heritable.

Question 16

an example of a well-known adaptation.

Answer 16

The thick fur of polar bears, which helps them survive in cold climates

Question 17

If a trait doesn’t meet adaptation criteria, what might it be instead?

Answer 17

It could be a maladaptive trait, result of genetic drift, a neutral trait, or a byproduct.

Question 18

Why are both genetic and phenotypic variations necessary for adaptation by natural selection?

Answer 18

They provide the raw material for selection to act on, allowing traits that enhance fitness to be passed down.

Question 19

What methods can reveal the heritability of a trait?

Answer 19

1) Correlation of traits between parents and offspring,
2) Comparing monozygotic and dizygotic twins, and
3) Associations between phenotypes and genotypes.

Question 20

How can variation affect fitness?

Answer 20

Traits that improve survival or reproduction, such as offspring number, camouflage, or toxins for defense, have clear effects on fitness.

Question 21

Give examples of traits where fitness effects are harder to observe.

Answer 21

Traits like facial coloring, flowering time, and mimicry can influence fitness in subtle or complex ways.

Question 22

What must be confirmed to consider starch digestion an adaptive trait?

Answer 22

1) Variation among individuals exists, 2) The trait is heritable, and 3) The variation affects survival or reproduction.

Question 23

Why is it important to apply the same selection pressure to all genotypes in a fitness experiment?

Answer 23

To ensure that observed fitness differences are due to the genotype, not to varying environmental factors

Question 24

adaptive and non adaptive evolution

Answer 24

Adaptive Evolution:
Involves natural selection, where beneficial traits increase in frequency because they improve survival or reproduction in a specific environment (e.g., the peppered moth example).

Non-Adaptive Evolution:
Genetic Drift: Random changes in allele frequencies, especially in small populations, which can lead to the fixation or loss of traits regardless of their adaptive value.
Gene Flow: Movement of alleles between populations through migration, which may introduce traits that are not necessarily beneficial to the current environment.
Mutation: Random changes in DNA that can introduce new traits, but these traits may or may not be advantageous. Many mutations are neutral, neither helping nor hindering survival.

Question 25

trait might not be considered an adaptation if….

Answer 25

a side effect of another adaption
a consequence of historical constraints
evolved by chance