Lecture 5 - Natural Selection Flashcards
What are the components of natural selection?
Heredity
variation
Competition
What does natural selection lead to?
Impact on the gene pool
Impact on phenotypes and how it leads to optimally designed individuals
What are the three modes of selection?
Purifying
Stabilising
Directional
Explain purifying selection
When an allele is useful - it is fixed at a locus
Explain stabilising selection
Current pop average of the trait is the optimum fitness - any above or below will have reduced fitness
Explain directional selection
Directional selection can build phenotypic adaptations as long as there is a sequence of intermediate phenotypes between the start point and the adaptive end point, and each intermediate tends
to have higher fitness than the last.
How does selection produce design?
Iterations are produced to get an optimal and sufficient design.
Example:
The eye shows that the slow march of natural selection can push phenotypes up the gradient of design quality until optimal design is reached
Outline the 4 examples of how evolution does not always produce optimal design?
Time lags
Inconsistent selection
Genetic correlations
Shape of the adaptive landscape
Explain time lags as an example of non-optimal design
The sperm whale with the femur and pelvis - serves no purpose
Explain the inconsistent selection example of non-optimal design
2 grasshoppers with different phenotypes, green grasshopper camouflages better than a black grasshopper
Explain the genetic correlations example of non-optimal design
Siberian farm fox similar phenotypes to other animals camouflages better than a black grasshopper
What is the adaptationist stance?
a perspective that emphasizes the role of natural selection in shaping the characteristics of organisms, including their behaviors, traits, and physiological features.
This perspective suggests that many aspects of an organism’s biology can be understood as adaptations - traits that have evolved because they conferred some advantage to individuals in their environments, increasing their chances of survival and reproduction.
How can adaptations be studied?
Via experiments
experiments of nature
comparative evidence
As well as motivation, what other ability occurs in sign stimuli?
Learning:
Preferred foods are learnt, spatial learning, emotionally charged places
What is the ESS (evolutionary stable strategy)?
A behaviour that, once common in population, cannot be outcompeted by any alternative behaviour
In the context of selfishness and altruism, what is an ESS?
Selfishness, altruism is not
How can we test hypothesis about evolutionary function?
Using reverse engineering - you see a problem and refer all the way back to its design to find the problem
What is reverse engineering? Human melanin and skin colour example
-Skin colour in humans varies across humans (function is to protect the skin from UV light - melanin)
-Melanin absorbs UV light via the body
-High UV destroy folate, destroying cells
-UV light is needed to synthesize Vitamin D
-Hypothesis of this is the function of melanin is to keep UV in body cells within the critical window
Hypothesis about bio function make predictions which is tested with …
current data
