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Summary Life History of Aquatic Animals (AFI-31306)
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Summary Life History of Aquatic Animals (AFI-31306)
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Theme 1: introduction to life history theoryLecture 1: Life History Theory Life history theory
predicts how variation
in the (a)biotic
environments
influences natural
selection of
genotypes, concerning
reproduction through
the effects of survival
and fecundity.
Adaptation: phenotypic change in a species, caused by environmental pressure, leading towards better fitness
Constraints: adaptations and patterns of traits on a species are restricted by the phylogeny of the species
Trade-offs: compromise in phenotype when independent optimization of several traits is impossible
Lecture 2: Marine Mammal Life Histories
Most important traits: size at birth, growth pattern, age and size at maturity, number size and sex ratio of
offspring, age- and size-specific reproductive investments, age- and size-specific mortality schedules, longevity.
Success of species is measured as fitness = life
time production of offspring. Determinants are
survival, growth and reproduction.
Allometry: relationships body size to … (character = positive)
Reproductive senescence: menopause (‘(grand)mother’ hypothesis)
,Basic principles of population biology
Marine mammals are slow reproducing (body size and life
history)
Seals: high fecundity and moderate rates of survival, thus relatively high potential rates of increase
Cetaceans (walvisachtigen): low fecundity – annual reproduction rate, high rates of survival, thus relatively low
potential rates of increase
Extinction risk
Population Viability Analysis: Species-specific method of risk assessment that determines the probability that a
population will go extinct within a given number of years → Valuable tool, but requires many input variables
Lecture 3 + 4: Consequences of life history traits in a changing world (vulnerability & food web)
Issues in marine ecosystems: overfishing, seabed destruction, energy transition, marine plastics (and nylon),
climate change, ocean acidification, fishing down the food chain, introduced species, deep sea mining, toxic
pollution / dumping, oil spills / leaking, eutrophication, underwater noise, electromagnetic fields (cables),
blocked estuaries / rivers, lost seagrass / mangroves, ‘blue revolution’
Removing a species or a trophic level means allocation of
the energy and matter to lower levels → total ecological
shift → cascading effect
Different life
stages are often
part of different
trophic levels
, The eel
Tutorial 1: density (in)dependent regulations of populations numbers
Density independent: ‘empty’ environment, no competition → exponential growth: N(t+1) = er N(t)
𝑵(𝒕+𝟏)
Density dependent: per capita population growth = ln (eventually, per capita population growth will drop to zero to prevent indefinity population size)
𝑵(𝒕)
➔ Logistic growth model N(t+1) = er(1-N(t)/K) N(t) r=intrinsic rate of increase, K=carrying capacity
High r → populations perpetual booms and busts → K becomes unstable, but cycle is stable
➔ Include environmental stochasticity: er(1-N(t)/K) N(t) + Ɛ(t)
Tutorial 2: plankton life history
Phytoplankton/algae -> zooplankton -> planktivorous fish -> piscivorous fish
Zooplankton: Protozoa + rotifers + copepods + cladocerans + larvae of fish and insects
r-selected species: many offspring, with low survival till maturity. Found in unstable and unpredictable
environments where rapid reproduction is favourable. (take advantage of short term changes)
K-selected species: fewer offspring, with higher surviving to maturity. Dominate in stable or predictable
environments, where competitive skills are crucial. (conservative)
Knowledge clips:
Requirements natural selection: individuals in a species show a wide range of variation, (at least part of) the
variation should be genetic, individuals with traits more suitable to the environment are more likely to survive
and reproduce (higher fitness)
Theme 2: Nice differentiation and feeding
Lecture 5: Niche adaptation and ecomorphology
Survival of the fittest = reproduction of the fit enough
Natural selection: Individuals in a species show a wide range of variation
This variation is (at least partly) genetic, not just phenotypic plasticity
Individuals with traits most suited to the environment are more likely to survive
and reproduce (= have higher fitness)
The genes that allowed the individuals to be successful are passed to the
offspring in the next generation
Large mutation have a bigger change of being negative
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