how photoperiod exclusively affects reproduction in seasonal breeders both plants and animals
Answers
Answer:
What is photoperiod:
Seasonality in deer is regulated by daylength, technically known as 'photoperiod'. Photoperiod is the relative amount of light to dark (day to night) in a 24-hour period. The photoperiod observed for a particular place is not constant during the year, but the pattern of change over the year is constant.
Why does photoperiod change:
As the earth orbits the sun on a particular trajectory, it spins daily on its axis. That trajectory and angle of the axis change the amount of exposure a particular place has to the sun throughout the period of orbit (365 ¼ days).
What are the effects:
At the equator, photoperiod changes very little during the year, but with increasing latitude from the equator, photoperiod changes dramatically between seasons. Daylight intervals are longest at the summer solstice and shortest at the winter solstice. The most dramatic differences occur at the poles, where there is virtually no darkness in summer and no daylight in winter.
In New Zealand the amount of daylight in a day changes from 16-18 hours at the summer solstice to 6-8 hours at the winter solstice. However, for any particular place, the photoperiod changes that occur during the year are the same every year. This is a very important factor to bear in mind when considering the seasonal life patterns of all deer located at that place.
Deer synchronise their annual patterns of reproduction, growth, coat moult, antler growth and other aspects of physiology to photoperiod.What is the effect of photoperiod on breeding?
As the day length decreases going from summer into winter, the increase in melatonin production cues the development of reproductive function in both the ovaries of hinds and the testes of stags, leading to the mating season (rut) in autumn. This is why red deer and wapiti are often referred to as ‘short-day breeders’. Thus, photoperiod controls the timing of conceptions in hinds.