IB 360 Wk 7- Adaptive and Maladaptive Traits

Adaptation Definition

-existence of a trait needed to survive in an environment

-high fitness

Maladaptation

-absences of trait necessary for an environment

-declining fitness

What evolutionary mechanisms result in adaptations?

Natural Selection makes it so alleles of individuals with more fitness prevail, means they’re adapted to their environment.

What evolutionary mechanisms result in maladaptations?

Gene flow- could introduce maladapted gene 

Mutations- may be harmful mutations decreasing fitness to an environment 

Natural selection can act strongly in one instance, environment changes and that allele is no longer favorable. 

Genetic drift- can lose beneficial alleles by chance 

Brady et al Framework for Maladaptation: Biased Arrows 

-trait far from optimum due to individuals “aiming” in the wrong direction due to genetic drift 

-characteristic of population, trait misses optimum

Imprecise Arrows

Excessive trait variability misses the target can be due to mutation rates 

-characteristic of population, excessive trait variance

Moving Target

-environment changes and the optimal value shifts, previously adaptive traits are now maladaptive 

-characteristics of environment, trait misses optimum

Retreating Target 

Evolution doesn’t occur quickly enough to keep up with environment changes

-characteristics of environment, excessive trait variance

Arrow induced target degradation

Traits can negatively impact the environment and cause it to degrade

-eco-evo, poor quality target

Arrow Induced target Shift

-evolutionary changes in part of the ecosystem changes optimal traits for another species

-eco-evo, trait misses optimum

Degrading Target

Environment degrades can reduce the quality pf the trait values and becomes maladaptive. 

-characteristics of environment, poor quality target

Damaged Arrows 

-genetic issues like inbreeding depressing or DNA damage can lead to maladaptation 

-characteristics of population, poor quality target

Arrow Induced Target Contraction

-evolution of traits leads to narrow range of optimal conditions like highly specialized species

-eco-evo, excessive trait variance

Maladaptation: Sickle Cell Disease

-interferes with ability of RBCs to carry oxygen and impedes blood flow

Describe the Conflicting Selective Pressures On the Hemoglobin Gene

-individuals with SCD make it likely to be impacted by malaria as the low oxygen levels in sickle cells impedes parasite growth

-But, sickle cells still carry less oxygen that normal cells 

What is the result of the adaptation and maladaptation of the hemoglobin gene? 

Heterozygotes can provide protection from malaria without causing SCD 

Conflicting Selective Pressure in Melanin

-dark pigmentation provides more UV protection, but harder to synthesize vitamin D

-light pigmentation synthesizes vitamin D better but more susceptible to DNA damage from sun