L5 Boswell - Seasonality - Season Birds

Question 1

Why is it important for a bird to moult its feathers?

Answer 1

Moults occur just before migration, and change the flight feathers to new ones so they can fly as efficiently as possible, or they will be selected against

Question 2

Why do annual cycle events occur in sequence with each other at a particular time of year

Answer 2

• Ultimate Factors
• Energetic and temporal constraints - each event is very costly so no overlap is possible; some events are temporally incompatible e.g. moult and migration

Question 3

What are ultimate factors?

Answer 3

evolutionary considerations e.g.. food for feeding young e.g. highly productive arctic summer

Question 4

what are proximate factors?

Answer 4

environmental cues that influence timings of annual cycle events

Question 5

What is initial predictive information? Give and example

Answer 5

It stimulates the production of the reproductive system (e.g. photoperiod)

Question 6

What is Supplementary information? Give an example

Answer 6

stimulates final reproductive development ( e.g. food and temperature)

Question 7

What is Synchronizing and integrating information?

Answer 7

Finding a mate and behavioural interactions

Question 8

What is modifying information? Give 3 examples

Answer 8

Tends to disrupt breeding (e.g. storms, humans building, animal disturbances such as magpies, forest fires)

Question 9

Why do bords change the size of their gonads?

Answer 9

It isn’t useful and wastes energy having full sixed gonads all year round. They are increased at the correct time via photoperiod so they are large for breeding season.

Question 10

Name the 3 steps in the Hypothalamus that daylight stimulates to send signals to the reproductive system

Answer 10

DAYLIGHT
        V
Photoreceptor
        V
Body Clock (circadian rhythm)
        V
Neural Output Pathways

Question 11

What is the HPG pathway and what substance is produced at each step

Answer 11

BRAIN
V
Hypothalamus - GnRH (gonadotropin releasing H)
V
Pituitary Gland - FSH and LH via the blood
V
Gonads - steroids - testosterone and oestradiol
V

Question 12

What does the release of steroids from the gonads in the HPG cycle cause?

Answer 12

Causes reproductive behaviour
secondary characteristics
negative feedback to control the hormonal output