Migration Flashcards
What reasons do species have for undergoing migration?
Breeding in warmer areas (e.g. Humpback whales) or avoid intolerably cool winters (e.g. Monarch butterflies) or search for food sources.
Suggest a theory for the evolution of migratory behaviour.
Sedentary ancestors gained reproductive success from partial migration which may have then repeatedly been lost and resurfaced in different avian lineages.
Explain the interaction between migration and natural selection.
Migration probably has a large genetic component meaning natural selection can quickly pressure partial-migration into full migration or back into sedentary lifestyle through breeding success/food abundance etc.
Explain homeostasis.
The ability of an organism to regulate their internal environment. Including temperature, concentrations of dissolved oxygen, carbon dioxide & sugar, osmotic pressure, redox potentials and pH.
Compare the basal metabolic rates of mammals and birds.
Birds are higher. They use energy at a higher rate and have higher body temperatures.
What does BMR stand for?
Basal metabolic rate
Comment on the differences between BMR of different bird species in relation to their body mass.
Very large, flightless birds, such as ostriches, have lower BMR. Body temperatures are closer to that of mammals, around 38 degrees c. Very small, active birds have higher BMR. Hummingbird body temp is 43.5 degrees c.
How do birds prepare for long distance migration? How do these preparations help with homeostasis?
They consume greater amounts of food, sometimes doubling in mass. This energy is stored as lipids which produces energy as well as carbon dioxide and water when metabolised. This helps with osmoregulation.
How do birds cope with migrations across desserts?
Many birds pant or fly at higher altitudes to reach cooler temperatures.
Suggest some navigational techniques which help migrating birds.
Celestial cues from the sun, moon & stars. Cues from the earth’s magnetic field. The plane of polarisation of light. Chemical signals detectable as smells. Visual landmarks.
List the three internal compasses which allow birds to sense which direction they are going.
The sun compass, the star compass and the magnetic compass.
Define migration
Regular movement of animals each year between separate breeding and wintering grounds
Define directional selection.
Occurs when conditions favour individuals expressing one extreme of a phenotype range, thereby shifting a population’s frequency curve for the phenotypic character in one direction.
Define stabilising selection
Occurs where there is an optimal value for the trait of interest. This means that selection acts against both extreme phenotypes and favours intermediate variants which have the highest fitness.
Define disruptive selection
Selection that favours individuals with the smallest and largest values of a trait. These individuals have the highest fitness and individuals with intermediate values are at a fitness disadvantage.
