Seasonality

Question 1

What signals cause the brain to produce hormones?

Answer 1

Environmental

Question 2

What bird has 3 sub species that breed at different latitudes and what are these sub species?

Answer 2

White crowned sparrows

Gambelii: 1 brood, long distance migratory

Pugetensis: 2-3 broods, stay in one place

Oriantha: 1-2 broods, altitudinal migrants

Question 3

What is an annual cycle?

Answer 3

Where the bird optimises it’s body to the different seasons

Question 4

Why do annual cycle events occur in sequence with each at a particular time of year? Include John Bakers explanations

Answer 4

Ultimate factors: evolutionary considerations, e.g. food available for feeding young

Energetic/ temporal constraints: each event is very costly so no overlap is possible

Question 5

How do annual cycle events occur in sequence with each at a particular time of year? Include John bakers explanation

Answer 5

Proximate factors: environmental cues that influence the timing of annual cycle events

Question 6

What are the categories of proximate factors controlling seasonal reproduction that Wingfield, 1980 came up with?

Answer 6

1. Initial predictive information: stimulates the development of the reproductive system e.g. photoperiod
2. Supplementary info: stimulates final reproductive development e.g. temperature and food
3. Synchronising and integrating information: behavioural interactions like cooperating to build a nest
4. Modifying information: tend to disrupt breeding, e.g. storms, human disturbance

Question 7

What is photoperiod?

Answer 7

The annual cycle of day length

Question 8

Describe a study on photoperiodism in birds:

Answer 8

William Rowan, 1920s
Exposed dark eyed juncos to artificial long day lengths in late autumn and winter

This induced the growth of the reproductive system and spring migration

Question 9

Describe the study on photostimulation in quail:

Answer 9

One group was given winter daylight (8hrs) and another group was given summer daylight (18hrs)

The group with the summer daylight had a rapid increase in testes size

Question 10

Who showed that it was the day length that was responsible for the growth in gonads rather than other factors such as feeding time etc.?

Answer 10

Follett and sharp 1969

Question 11

What is a photoinducible phase?

Answer 11

A period when the reproductive system is most sensitive to light

Question 12

What three components in the hypothalamus are required in the processing of photoperiodic cues?

Answer 12

1. Photoreceptor: sensory cells that detect light- birds appear to have light sensitive cells within the brain
2. Clock: they have a circadian rhythm sensitive to light
3. Neural output pathways then lead to the reproductive system