reproduction definition
a biological process during which a living organism produces offspring
reproductive strategies
structural, functional and behavioral adaptations that increase the chances of fertilization and survival of offspring
r-strategy
- when some animals use more energy in producing many offspring, but spend little time in parental care
- many offspring die before adulthood
K-strategy
- animals which produce fewer offspring, use enormous amounts of energy for parental care
- offspring have better chance at survival
external fertilization
- outside the female’s body
- courtship and specific mating behavior ensure eggs and sperm are released at the same time and place to inc
- pheromones are sometimes released by females
how ext fert works
- gametes are released into water where fert takes place, water prevents drying out
- lots of gametes produced to inc the chances of fert
- eggs secrete chemicals to attract the sperm
what happens after ext fert
- zygote develops into a larva that lives on a yolk or plankton = parents do not need to expend any energy into feeding the young
- env factors such as predators reduce the probability of offspring survival
- offspring are dispersed by currents, settle in diff areas, minimize competition
internal fertilization
- inside female’s body
- does not require water, fewer gametes produced as poss of fert is much higher
- during mating the sperm is released directly into the female’s body and the sperm swims to egg for fert
inc chances of survival in int fert
- in reptiles & birds, the embryo is nourished by yolk and protected by shell
- in mammals the developing embryo remains inside the female where it receives protection & nutrition
ovipary
embryo develops in an egg outside the female’s body and is surrounded by a jelly like layer
oviparous aquatic animals
- fish and amphibians
- fert takes place ext in water
- lots of gametes prod
- egg has v little yolk, less energy
oviparous terrestrial animals
- mammals, birds
- int fert
- developing embryo is surrounded by a shell that protects it from dehydration
- large yolk, more energy
ovovivipary
- sharks, lizards, snakes
- int fert, embryo surrounded by thin membranous shell inside female body, rec nutrition from yolk
- embryo hatches inside body and the young are born live
- in some species, eggs laid and embryos hatch almost immediately
- protected inside female
vivipary
- int fert, fert egg develops into embryo w out the shell
- embryo/foetus directly connected to mother and receives nutrients through the placenta
- parental care requires lots of energy
amniotic eggs
- prevents dehydration of the embryo and provides it with nutrients water and oxygen
- adapted for terrestrial life
structure of amniotic egg
- developing embryo
- three extra-embryonic membranes
- yolk sac filled with energy rich yolk
- albumen (reserve food)
- shell
three extra-embryonic membranes
- amnion - surrounds embryo, protects it from shocks
- allantois - sac that grows from the embryo’s intestines, collects waste
- chorion - forms part of the placenta in mammals, gas exchange in birds & reptiles
precocial development
- species where the young are practically fully developed and mobile when born
- fewer offspring produced, mothers less involved after birth
precocial development in birds
- long incubation time so that the young can develop fully before hatching
- large amount of yolk for sufficient food
- open eyes, still dependent on rents body heat, immediately active
precocial development in mammals
- long gestation time so that the young can develop fully
- receives food from placenta
- open eyes, covered in hair, immediately active
altricial development
species where the young are not fully developed and cannot move around immediately after being born/hatched
- more offspring prod
- spend most of their energy on postnatal dev
altricial development in birds
shorter incubation period, hatching asap
smaller eggs, less yolk
opp of precocial basically
altricial development in mammlas
young are born asap
opp of precocial
parental care
any behavioral pattern where parents spend time/energy on the feeding and protection of offspring
