Chapter 8: Life History Patterns (Exam 1)

Chapter 8: Life History Patterns (Exam 1)

traits that describe the life cycle of an organism (reproductive rate, maturity rate, lifespan etc.)
asexual reproduction
one parent passes on a complete set of genetic info (binary fission)

less genetic variation-no mate needed

sexual reproduction
2 parent s each pass on 1/2 set of genetic info

reproduction costly but greater variation

development of an individual from an unfertilized egg (lizard)
simultaneous hermaphrodite
has both male and female reproductive structures at the same time
sequential hermaphrodites
spend part of their life cycle as a female and part as male (mollusks, echinoderms)
possessing both male and female reproductive organs
mating systems
1 female/1 male w/long lasting bond (birds)
2 or more mates (cats)
form of polygamy where 1 male pairs w/2 or more females (moose)
form of polygamy which 1 female pairs w/2 or more males (sand pipper)
sexual selection
mate choice and competition for mates among individuals may lead to selection for particular traits
intersexual selection
members of 1 sex consistently choose mates of the opposite sex based on certain traits
intrasexual selection
individuals of one sex compete among themselves for mates
secondary sexual characteristics
not directly involved in reproduction (differences in phenotypes)
runaway selection
members of opposite sex find a trait desirable “runaway” because over time it would facilitate the development of greater preference and more pronounced traits until the cost of trait balances reproductive benefit of possessing it
life-history adaptations
increase of reproductive effort may benefit offspring but can reduce survivorship of the parent
reproductive effort
the amount of energy allocated to reproduction
clutch size
number of offspring per reproductive eent
clutches per year
environmental variation

yearly & seasonal variation

latitudinal and elevational variation (clines)

having only a single reproductive effort in a lifetime over one short period of time
many reproductive events per lifetime
unpredictable environments (lean forage) delay reproduction, survival of parents, abandonment of the eggs or offspring
reproductively active as larvae (tiger salamander)
short incubation times often result in young being born in helpless state, which requires greater parental care
longer incubation periods can produce young which require considerably less parental care
reproductive strategies
placental mammals
The retention in an adult organism of the juvenile features of its evolutionary ancestors.
placental mammals
give birth to live young (r or precocial) who received their nourishment during embryonic development from allartoic placenta
give birth to live young who complete their embryonic development inside a maternal pouch called marsuprum which contains nipples for nursing
lay eggs w/little or no other embryonic development w/in the mother (yolk sac provides nourishment)
young develop w/in eggs or membrane sacs that remain w/in the females body until they hatch (or are able to)
birth to live young (reptiles, fish)
life-history adaptations
characteristics exhibited by a species are the product for evolution and should reflect adaptations to the prevailing environmental conditions under which natural selection occurred
(typical (short lived)), high reproductive rates at low population densities, rapid development, small body size, large # of offspring (but low survival rate), minimal parental care
competitive species with stable populations of long-lived individual can cope w/physical and biotic pressures
opportunistic life-history
low offspring survival, low birth rates, early maturity
periodic life-history
low offspring survival, high birth rates, late maturity
equilibrium life-history
high offspring survival, low birth rates, late maturity
gonadosomatic index (GSI)
index of reproductive effort
synchronous hatching
Hatching that occurs at the same time or nearly the same time, usually within one calendar day (compare to Asynchronous Hatching).
asynchronous hatching
A hatching that does not occur at the same. It may take place over two to three calendar days. Parrots hatch Asynchronously while ducks and chickens hatch Synchronously.