Topic 2 Flashcards
Navigation in migrating birds.
magnetoreception through cryptochromes
What other cues might be available to birds to help them navigate?
Possible navigation cues:
celestial cues derived from the Sun, Moon and stars
magnetic cues from the Earth’s magnetic field
the plane of polarisation of light
chemical signals detectable as smells.
6.1
The star compass in birds
Birds do not learn the star patterns themselves but learn to respond to a star pattern that rotates about a single conspicuous star.
6.2
The Sun compass in birds
The use of the Sun for orientation by birds was first demonstrated in the 1950s with European starlings (Sternus vulgaris). Mirrors were used to alter the apparent position of the Sun and the birds then orientated to the apparent position rather than orienting in the correct compass direction.
The Sun on its own is not sufficient, because it moves across the sky during the day; so to maintain a constant direction using the Sun as a guide, a bird needs an internal clock.
Describe some of the migratory journeys made by birds and other animals?
To do
Explain the process of adaptation by natural selection and how this results in evolution?
To do
Describe the possible selective advantages that accrue to birds that migrate and the costs of migration compared with the benefits.
Apply the conclusions from breeding experiments to a description of the control of migration and the role of the environment in its evolution.
Describe what is meant by homeostasis, with particular reference to how migratory birds regulate body temperature in order to conserve energy.
Provide examples of the use of celestial and magnetic cues for navigation by migratory birds?
To do
Semelparous reproduction is:
is one reproductive episode before death (during the lifetime),
Iteroparous reproduction is:
is more than one reproductive episode.
What are the three requirements of evolution by natural selection?
The three requirements are:
- variation in the trait
- heritability of the trait
- differential reproduction or survival as a consequence of having the trait.
An example of coevolution from Topic 1
The evolution of toxin tolerance in cinnabar moths (Tyria jacobaeae) in response to the evolution of toxins by its host plant, ragwort (Senecio jacobaea), is one example, but several others were also given in the topic.
The two species of plant both require the same resources, particularly light for photosynthesis. When growing side by side, they will shade one another, negatively affecting the other’s performance. Either species would survive and reproduce more effectively if the other species were absent.
This interaction is called competition and in shorthand it is denoted as (−,−). It occurs wherever more than one species requires a limited resource. It often leads to the loss of one or other of the species from the community, a process referred to as competitive exclusion.
Originally the eukaryotes were free-floating planktonic organisms in the oceans and it is thought to have been a billion years before a major evolutionary development occurred producing two new branches on the evolutionary tree. One branch has been labelled the unikonts
which were cells characterised by one flagellum (a whip-like tail that helps the cell swim) that over time gave rise to slime moulds, animals and fungi;
The other branch called the bikonts
had two flagella and gave rise to algae, mosses and flowering plants
three characteristics shared by animals and fungi that demonstrate their common evolutionary history and which set them apart from plants and algae.
Points of similarity between animals and fungi that have already been mentioned include:
Animals and fungi use the polymer chitin to give them rigidity; plants and algae do not.
Animals and fungi have only a single flagellum on motile cells; plants and algae tend to have two.
Animals and fungi lack chloroplasts and therefore have to rely on ingesting other organisms (or products of other organisms) for their energy requirements; most plants and algae are able to capture their own energy.
