marine life histories and life cycles Flashcards
general stages of a life cycle in the ocean
- spawn eggs + sperm (fertilisation)
- larval stage
- juvenile
- adult
what are larvae
distinct form that many organisms go through before metamorphosing into adults – dispersal
what is metamorphosis
conspicuous change in body structure
what is a juvenile
organism that has not reached its adult form before it reaches sexual maturity – here we get settlement + recruitment
what is Recruitment/settlement
metamorphosise into adult at a site where they can survive as an adult
what kind of different habitats do organisms use during their reproductive stages
Benthic
Pelagic
Land
Sea ice
4 steps of an organisms life cycle in the ocean
- reproduction
- fertilisation
- larval phase
- Recruitment/settlement
what is reproductive success
number of offspring produced that contribute to the next generation of reproducing adults
what is fecundity
number of gametes
how does fecundity vary
with species
- low fecundity = larger offspring + brooded of direct development
- high fecundity = smaller larvae, feeding larvae, usually planktonic
3 Modes of fertilization
- Spawning / external – eggs + sperm released into water column
- Internal – sperm released into water + captured by female
- Direct internal – sperm placed directly into female e.g. mammals, sea turtles
challenges for each mode of fertilisation
- Spawning – have to have close distance + close timing + rough water can reduce success
- Internal – lower density of species - store sperm for delayed fert
- Direct internal – finding mates
how does larval survival vary
- with space and time - “sweep stakes”
- larval mortality = high overall
- planktonic larvae has higher mortality than non planktonic larvae
what is Effective population size
way to measure genetically how many individuals are contributing to the reproductive output of a population
3 factors that determine dispersal distance from parents
- Pelagic larval duration (PLD) - amount of time a larvae spends in the water column as a plankton
- Currents - move gametes + larvae
- Larvae behaviour - Can move up and down / side to side to control their position in the water column + can detect odour plumes + sound
3 Larval types
- Planktotrophic larvae = feed while in plankton - long PLD
- Lecithotrophic larvae = require no food – use reserves
- Direct development – fert egg is brooded – live birth – little or no PLD
what is recruitment
arrival of new individuals to a population
factors that determines settlement and recruitment of individuals
- Supply of recruits – depends on overall larval supply
- Settlement process – look for a cue e.g. sediment grain size, food availability, presence/absence of conspecifics, bacteria, algae - “competent” to settle?
- Recruit survival to adulthood – environmental, biotic interactions, predation, competition, food, parasites, disturbance
2 ways recruitment varies
- with time: climatic factors, current changes, changes in other oceanographic factors
- spatially: gyres, frontal zones, larval behaviour
Sources and sink populations
how does importance of recruitment vary between species
long-lived adults is not a big deal – is for short-lived species
what are source and sink populations
- Source Populations → Produce excess recruits that disperse to other populations
- Sink Populations → Do not sustain themselves and rely on recruits from other populations
what is genetic structure and how does it vary
GENETIC DIFFERENCES within and between populations
- Low Genetic Structure → Found in well-connected populations with high gene flow
- Moderate to High Genetic Structure → Found in populations with barriers limiting gene flow e.g. geological history changes, changes in sea level, divergent currents, fronts, distances between habitats
what are otoliths used for
Record an organism’s environmental history and help track population connectivity
