How often do matings occur? Matings often occur just before each fertilisation event because sperm cells typically do not live long after being released by the male – either into the environment (external fertilisation) or into the female’s reproductive tract (internal fertilisation).

Patterns and times of breeding Breeding season – period when mature members of the population have sperm and eggs ready for release and fertilisation Spawning season – (external fertilisation) same as breeding season but for aquatic environment Mating season – for animals with internal fertilisation

How often do matings occur? In some animals sperm from one mating remains viable for a long period and can be stored by the female Eg. honeybees

Patterns and times of breeding Sexual reproduction Eggs and sperm must be available at the same time in members of the population

Patterns and times of breeding Producing sperm and eggs (gametogenesis) is influenced by internal factors such as hormone levels also by external factors such as temperature and day length

Patterns and times of breeding Most animal populations have distinct and regular breeding seasons. Single annual breeding season Biennial pattern of breeding (2 years required for individuals to mature and to spawn)

Patterns and times of breeding Female mammals produce eggs during a oestrous cycle that varies in length for different species Eg wolves, foxes and bears – one oestrous cycle per year Eg deer, sheep and goats – several oestrous cycles in a short period when hormonal changes are triggered by shorter day length How would the influence of day length on breeding improve survival for offspring?

Patterns and times of breeding Females of most mammalian species will accept males for mating only at limited times of the year At these times the females of non-human mammals are said to be in oestrus (heat)

Patterns and times of breeding Mate then die Eg short-finned eel – mates once then die. Eg Chinook salmon – female lays eggs for the male to fertilise, covers the eggs, then lays more eggs in another location. The adults die after breeding. The young make their way out to sea, eventually return to the same spawning grounds to breed and die.