BIO1042 Lecture Notes - Lecture 10: Rhynchocephalia, Environmental Science, Thermoregulation
24 Aug 2018
School
Department
Course
Professor
BIO1042 Lecture 10 –Life and Diversity
Environmental Biology and Evolution
The old view of the environment
• Genotype + environment = Phenotype
The link between the genotype and phenotype is often complex
• The effect that a genotype has on the phenotype is often contingent on the environment that
the indivuals lives in
• The genotype interacts with the environmental to form the phenotype
• Effects of genotypes are not usually additive across environments
• Instead "Genotype x Environment interactions (G X E) prevail
• Using an additive model, genotype 1 would always be taller than genotype 2, within a given
environment
o As nutrient availability increases in an environment, fitness levels of genotypes will
increase
o However no matter the increasing levels of nutrients and fitness, genotype 1 will
always be more fitter for an environment that genotype 2.
• Using the G X E model, the effect of a given phenotype can be ‘specific’ to a particular
environment.
o As nutrient availability increases in an environment, genotype fitness can fluctuate
o So genotype 1 at a low nutrients availability may be weaker than genotype 2, but at
a high nutrients availability genotype 1 becomes for fitter than genotype 2.
• Key terms in relation to genotype/phenotype fitness
o Reactive norm = the environmental sensitivity of a genotype/gene
o Phenotype plasticity = enable indivuals to make short term responses to
environmental change.
Phenotypic Plasticity
• Ability of an organism to modify its phenotype in response to a change in the environment
• Response can be to physiology, morphology, behaviour development etc.
• Behavioural (Thermoregulation)
o Ability of individuals to make short term responses to changing environments is crucial
for their survival
Reptile Sex Determination
• Temperature that eggs are exposed to determines the sex of the offspring
• Different species change their ratio of male and female offspring in response to temperature
increase or decrease
o One species of turtles = offspring percentage that are male decrease with increasing
temperature
o One species of lizards = offspring percentage that are male, increases with increasing
temperature
Tuatara
• Order: Rhynchoephalia
• Family: Sphenodontia
• Living fossils - only living member of order
• Average life span 60 years
• Take 10 - 20 years to reach sexual maturity
