Life Histories Flashcards
Life History
The lifetime pattern of growth, development, and reproduction of an organism
Reproductive Strategies
Asexual and sexual reproduction
Asexual Reproduction
Offspring are genetically identical to the parents, an example of this is budding which eventually creates a clone of the body that separates, parthenogenesis is another way (where the unfertilized egg becomes an embryo on its own)
Sexual Reproduction
Offspring are a mix of genetic material from parents, some species that can reproduce sexually can also reproduce asexually such as three species of sharks
Hermaphrodites
Where individuals possess male and female organs, can be simultaneous (the nudibranchs) or sequential (some fish, mollusks, and echinoderms)
Larval Life
Result of sexual production for many aquatic species, can be planktonic or nektonic, before metamorphosing into adult forms
Reproductive Effort
The costs of reproduction per unit of time, includes energy/nutrient requirements, gonad development, mate competition, moving to spawning areas, nesting, parental care // Varies across species, but needs to be balanced to be successful
Maximal Fitness
At intermediate reproductive effort, where the fewer number of offspring means higher chance of survival and where the smaller reproductive effort increases parental survival
Altricial (Parental Care)
Born sooner (lower stage of development), require more parental care
Precocial (Parental Care)
Born later (at a later stage of development), require less parental care
Iteroparous Species
Produce offspring more than once in their lives once they reach sexual maturity (there is a pre-reproductive stage, a reproductive stage, and then a post-reproductive stage)
Semelparous Species
Reproduce once and then die (salmon are an example of this), rely on the survival of the young to continue the species
K Species
Slow and steady, large body size, longer life spans, delayed maturity, low fecundity, few species, constant habitat
r Species
Live fast, die young, small body size, early maturity, high fecundity, numerous offspring, variable habitat, high levels of dispersal
Suite of Traits Related to Life History
Not always accurate anymore, but still useful concepts, r and K species
Dispersal
Movement of organisms between different locations and/or populations, includes migration, colonization, and gene flow // Some organisms can not disperse by themselves and rely on wind, animals, or currents
Passive Dispersal
Rely on something else to move you
Active Dispersal
You move yourself, like crabs in the intertidal areas, or fish
Temporal Dispersal
Dormancy period, did not understand this
Human Dispersal
Invasive species
Lecithotrophic Larvae
Dispersed only to a small degree by short-lived, yolk-dependent larvae
Planktotrophic Larvae
Dispersed great distances by longer-lived plankton-feeding larvae
Viviparity (Sharks)
Gives birth alive
Oviparity (Sharks)
Born in cases that hold the eggs
Ovoviviparity (Sharks)
Eggs hatch inside the mother
Dispersal (specifically)
Undirected movement of an individual to a new place
Migration
Directed movement between specific places
Free spawning
Has a number of costs for planktonic gametes
Marine Parental Care
Could have free-swimming larvae, or guard and brood eggs, or brood young within body cavities, or have live birth like mammals
Modules (Colonial Individuals)
In algae and corals, this is nonsexual reproduction where the clones are connected to each other and exchange nutrients
Why Dispersal
Avoidance of crowding, dispersal to sites that are better trophically, hedging bets over many habitats
Environmental Uncertainty
If uncertainty is high, new young will be less likely to survive, so there is a selective force for repeated reproduction (iteroparity) so that at least one year of offspring will survive
Diadromous Species
Lives divided between residence within the freshwater parts of estuaries and in the open sea
Anadromous Fishes
Spend most of their time in the sea, but breed in freshwater (e.g. salmon, shad, and sea lamprey) // more common in high latitudes
Catadromous Fishes
Usually spend adult lives in fresh water or tidal creeks but move to the sea to breed (e.g. a specific genus of eels) // more common in low latitudes
Philopatry
Species in which individuals tend to show a propensity to return to the general area of their birth
Intrasexual Selection
Males engage in competition with each other for mates
Intersexual Selection
Females look for characteristics in males that are attractive for fitness
Gonochoristic Species
Species that have two separate sexes
Parthenogenesis
The development from unfertilized eggs; it occurs among several disparate phyla of animals
External Fertilization
Aquatic species can take advantage of the buoyancy and mobility of the fluid medium to disperse gametes, so direct contact between male and female is not necessary (e.g. with corals)
Internal Fertilization
A relatively rare strategy among aquatic organisms since the two sexes either need to join together before adulthood or the adults need to be mobile
Univoltine Species
Producing one generation per year, emergence of adults is synchronized to a specific time of year
Semivoltine Species
Life cycle extends over two years, emerge as adults at a specific, predictable time of year
Multivoltine Species
Several life cycles per year, and are more likely to respond to specific water temperature levels as cues
Marine versus Freshwater Strategies
Most marine benthos produce widely dispersing planktonic larvae, yet for river benthos this would be an inappropriate strategy since the offspring would be carried too far downstream
Marine Crabs
Produce many thousands of eggs that are released into the water in a larval stage (zoea)
Freshwater Crabs
Produce relatively few eggs, with each being considerably large than those of marine species, the female continues to carry the eggs in her abdomen
Bivalve Molluscs (Marine)
Practices external fertilization, females release several million eggs that are plankton for 3 weeks to 6 months before settling onto a solid substrate
Bivalve Molluscs (Freshwater)
Some species similar to marine cycle // Others: males release sperm into the water and females retain the eggs in pouches in her gills, larval stages practice parasitism on vertebrate hosts // Others: brood the young in the gill cavity of the females
Intertidal Gastropods
Release pelagic egg masses (that were fertilized internally) that become plankton, although some species are ovoviviparous (keeping the eggs in a brood chamber until born), and others still produce a benthic egg mass (oviparity)
Horsehair Worms
Mainly freshwater as adults, yet the larval stage parasitizes an aquatic host first that then becomes a flying or terrestrial adult (yet the horsehair worm remains as a parasite) // eventually the worm can compel the host to return to the water where the host returns as an adult
Digeneans
Each stage of the life cycle requires a host, yet they are aquatic since there is an active free-living larval stage
