Lecture 4 Flashcards
What has natural selection had the influence of?
Wallace and Darwin
What is life history?
description of the traits of an organism, from conception to death
What are the principle life history traits?
size at birth
age at maturity
number, size and sex ratio of offspring
length of life
age and size-specific reproductive investments
age and size-specific mortality schedules
size at maturity
growth pattern
What are the shape of life histories a result of?
natural selection
What are the principle components of fitness?
life history traits
What are some important aspects of adaptation?
- genetic tracking of the environment through natural selection
- phenotypic plasticity to maintain fitness in the new environment
- genotype by environment interactions
What is demography?
age and size-specific reproduction and mortality patterns allow for the calculation of the strength of natural selection on life history traits under many different conditions
What are the considerations of demography?
if age-specific birth and death rates are constant in time and space then the population attains a stable age distribution and the ratios of individuals in different age classes remain constant
What is fitness more sensitive to?
changes in mortality and fecundity in younger age classes than in older ones
What is the connection between fitness and evolution?
the connection between fitness and evolution is direct, individual variation in survival and reproduction causes variation in fitness and natural selection
What is ageing?
ageing is the total effect of those intrinsic changes that accumulate in the course of life that negatively affect the vitality of the organism, and that makes it more susceptible to the factors that can cause death
What is the formula for mortality?
Mortality: mtotal = menvironment + m intrinsic
What is natural selection?
maximal reproductive output within the natural lifespan
Is ageing adaptive or non-adaptive?
non-adpative
What are the two routes that ageing mechanisms have evolved to?
public (shared)
- strong selection for early life fitness at the expensive of late-life health
- late-life consequences
- selection for genes with antagonistic pleiotropic effects
- common principles: public phenotypes and mechanisms
private (unique)
- lack of selection for late-life fitness/health
- no early life consequences
- accumulation of deleterious mutation with late-life effects
- contingency: private phenotypes and mechanisms
What are the three sources of variation?
genetic
environmental
G-by-E
What are some characteristics of quantitative genetics?
- focus on continuous phenotypic variation
- underpinned by multiple loci
- influenced by environmental factors
- the genotypes cannot be directly discerned from the phenotype
What is the formula for phenotype focusing on continuous phenotypic variation?
P = G + E + GxE
What are Q traits?
morphological traits
physiological traits
behavioural traits
life history traits
What is the formula for phenotype to quantify and track genetic variation over time and space?
P = G + E
Vp = Vg + Ve
Vp = Va + Vd + Vi + Ve
P = phenotypic
G = genetic
E = environmental
A = additive
D = dominance (interaction with loci)
I = interaction between loci
What is heritability?
proportion of the phenotypic variance that can be attributed to genetic variance
- measures the phenotypic resemblance between relatives that share alleles
What is the formula for heritability?
H2 = Vg/Vp (broad sense)
or
H2 = Va/Vp (narrow sense - determines evolutionary potential)
What is the difference between parents and offspring and brothers and sisters?
brothers and sisters hsare the alleles and may share the genotype
parents and offspring share the alleles but no their genotypes
How to measure heritability from a parent offspring regression?
if the variation among individuals is due to variation in their genes, the offspring resemble their parents
checking this by plotting the phenotype of the offspring against their parens
the slope of regression line is the heritability
