Mating Systems Monogamy Pair bonds with one male and one female for one or more breeding seasons or for life Estimated that 90% of bird species are monogamous
Emperor Penguins form pair bonds for one breeding season
Where the survival of the young requires the care of both parents for tasks, the species is usually monogamous Defending the nest Incubating eggs Feeding offspring The young of many but not all monogamous bird species are born featherless, blind and helpless.
Polygamy Either one male or one female has multiple partners during a breeding season Often seen in bird species living in habitats with plentiful and reliable food resources; where one parent can ensure survival of the young
Mating Systems - Polygamy Polygyny (poly – many, gunos – woman) When one male has multiple female partners during a breeding season Polyandry (poly – many, andro – male) When one female has multiple male partners during a breeding season
Offspring: How many? How often? Two reproductive strategies commonly identified in animals are; - ‘quick and many’ known as r-selection - ‘slower and fewer’ known as K-selection Many species cannot be pigeon-holed into either category. These two are at either end of the continuum. Plants – generally -shorter-lived plants often produce large numbers of minute seeds - longer-lived plants often produce fewer but larger with food reserves for developing the plant embryo
r-selection Typical of species that reach sexual maturity quickly, produce large numbers of offspring or breed more frequently and may put little or no care into offspring. Fecundity – refers to the number of eggs produced by each female on an annual basis Offspring often have higher mortality rates so few survive to adulthood
r-selection A common female octopus lays from 100,000 to 400,000 eggs in clusters and deposits them in crevices in a coral reef She keeps her eggs supplied with oxygen by squirting them with water and keeps them clean by gently wiping the eggs with her arms.
These species mature slowly, breed later, produce fewer and larger offspring and may care extensively for their offspring Often have a longer lifespan and typically have more than one breeding season during their lifetimes.
Sexual maturity does not occur until whales are about 5 Gestation lasts about 11.5 months Female gives birth to one calf every two years Calf suckles for an average of 10 months Life span is up to 50 years
Eggs or liveborn young? Oviparity – eggs released by the mother so embryos develop outside mother’s body with nutrients for the embryo coming from the egg yolk Viviparity – embryos develop within the mother’s body and are born as miniature copies of the adult. Nutrition of the developing embryo within the mother occurs in different ways.
Oviparous Animals The size of the newly hatched young is determined by the yolk supply in the egg – the larger the yolk, the larger the young. Examples – some sharks, all rays, bony fish, amphibians, monotreme mammals
The eggs of bony fish and amphibians (eg frogs) do not have shells; they dry out if they are not released into water. Embryonic development occurs outside the female body The embryo obtains all its nutrients from the yolk and releases wastes into the water. Egg case of the Port Jackson shark
Instead of laying eggs, some vertebrate animals produce miniature live-born young Examples – most sharks, some snakes, mammals (except monotremes) Viviparity increases the chance of survival by protecting the young within a female’s body rather than leaving them exposed to predators
All mammals (except monotremes) produce tiny eggs with very little yolk. Mammalian embryos are enclosed in fluid filled sacs and develop within the mother’s uterus. Nutrients are delivered from the maternal bloodstream via the placenta to the embryo. The placenta is where the bloodstream of the mother and the embryo come into close contact allowing for nutrient and waste exchange.
Parental Care or Not? Different animal species vary in the energy they put into the care of their eggs or their young. Eg most reef fish, all turtles, most frogs and toads give no care to their eggs or young after laying All mammals and most birds give great care and protection to their young and eggs.
Parental Care or Not? Caring for eggs after laying EEg clownfish guard their eggs EEg seahorse – the female seahorse lays her eggs in a pouch in the male. The male gives birth to live young about 1cm long. EEg Some oviparous snakes. Australian diamond python guards her eggs until they hatch. Children’s python coils around her eggs until they hatch EEg some cephalopods (octopus, squid, etc) attach their eggs to ‘safe’ locations, then cleans and protects them EEg spiders wrapping their eggs in a silken cocoon.
Parental care of young ▫M▫Most bird species, both parents care for the young ▫M▫Mammals care for their young for some period after birth through the young suckling from the mammary glands. ▫P▫Primates care for their young for considerable periods after they are weaned