Chapter 7 Key Concepts

Sex is a nearly universal characteristic, despite the considerable costs to organisms of maintaining it.
Sexual selection increases differences between the sexes and is driven by mate selection and polygynous behavior patterns.
Sexes may be separate (gonochoristic species), simultaneous, or sequential in the same body.
The relative contributions of different sexes to zygotes in the next generation determine the value of hermaphroditism and the relative sizes of males and females.
Dwarf parasitic males are found in some species that live in situations where it is difficult to find mates.
A rare case of eusociality can be found in groups of alpheid shrimp in spaces within large sponges, where one female is served by a large number of males.
Fertilization success is affected by the mode of sperm transfer, the volume of gamete production, the distance between males and females, water turbulence, timing, and behavior.
Free spawning has a number of costs relating to turbulence, polyspermy, timing of spawning, and avoidance of interspecific hybridization.
There are two main phases in small-scale gamete encounter: attraction on small scales of sperm to eggs by means of sperm attractants, followed by surface compatibility of sperm when attempting to fertilize eggs.
In some groups, specialized gamete recognition proteins are employed to avoid interspecies fertilization.
Parental care is nonexistent in many marine animal species, but in some cases, females or males care for eggs, embryos, and young.
Nonsexual reproduction permits the same genetic type to increase rapidly in an open environment.
Age of first reproduction, reproductive effort (resources devoted to reproduction), and longevity may evolve in response to different age-specific patterns of mortality and predictability of reproductive success in the population.
Fishing causes natural selection on life histories.
Fishes, crustaceans, turtles, and marine mammals often migrate between spawning and feeding grounds.
Anadromous fish species are more common in high latitudes, and catadromous species dominate low latitudes. This pattern may be related to the availability of adult food.
Marine invertebrate offspring may be (1) brooded or released as small adults; (2) dispersed usually short distances by means of relatively short-lived, yolk- dependent lecithotrophic larvae; or (3) dispersed great distances by means of longer-lived, plankton-feeding planktotrophic larvae.
Gamete production and larval life must often be timed precisely to allow settlement and promote dispersal, to avoid being swept to inappropriate habitats, and to counter predation.
Variation in egg size is considerable among marine species, and this may relate to different consequences in terms of mortality.
Planktonic larval life is a transition from presettlement morphology and behavior to competence for settlement and metamorphosis.
Planktonic larvae use light and pressure cues to maintain depth for optimal feeding and location of settling sites.
At the scale of meters to centimeters, larvae use chemical and biological cues for a final settlement site.
Ocean acidification and ocean warming may have strong effects on marine populations by affecting larval survival and changes in geographic ranges.
Planktonic dispersal success of marine species is strongly controlled by currents that transport larvae and may have important ecological consequences.
Despite the potential for dispersal, planktonic larvae often come to settle quite near their origin, owing to cyclonic or returning currents.
Many coastal species have evolved mechanisms for retention of larvae near suitable adult sites, take advantage of current systems to return to suitable sites, or even benefit from seasonal reversals of flow that allow them to move out to sea and then return to suitable coastal adult habitats.
Ocean warming should cause the shift of ranges to higher latitudes, but there can be complications from timing of larval release and seasonal current systems.
Planktonic larval populations may fail because of a lack of planktonic larval food or because of concentrations of toxic algae.
Some planktotrophic larvae can increase the chances of survival by cloning or other responses to appropriate environmental conditions.
The geographic range of a species with planktonic dispersal is greater than the range for species without planktonic larvae.
Molecular genetic variation and other markers can be used to identify barriers to coastal zone dispersal.
On the macroscale, isolation between regions may result in a large group of separated populations of a species, which might have only occasional interchange.
Planktonic larval duration is complex. Longer duration of planktonic larvae at high latitudes allows strong dispersal, but fast currents at low latitudes increases dispersal as well.
Why disperse? Dispersal of planktonic larvae ensures that local habitat destruction will not lead to extinction.