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scientist, Charles Darwin?
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their nests. Look at a close up photo of wren eggs. Look at
collections. Why was this introduced? Crack open a chicken's
egg and discuss the various parts and purposes of the egg. Talk
egg contain? Explain that this is an unfertilised egg. Ask pupils what they'd
find if it was a fertilised egg. Watch a video of a fertilised egg developing to an embryo and chick, then hatching. Explain that a similar process is undertaken in wren eggs. Incubation is by the female only. Wren parents spend time raising their chicks. The young are fed by both parents. Do pupils think this is a large
investment of time and energy? How does this compare to other species? (eg. Frogs and tadpoles, humans).
Breeding Data for Wrens:
Breeding Starts: Late April
Number of Clutches: 2
Number of Eggs: 5-8
Incubation (days): 13-18
Fledge (days): 15-20
2) Ask children to collect different natural materials from a grassland and woodland. Back in the classroom glue the various parts together to create a nest; let it dry. Think of a made-up species name for the bird of your nest. On another day, ask pupils to hide their nests in bushes etc. Ask other children to search for them. Can they find them? What are the consequences of having a nest found or not to the make-believe bird? They are unable to reproduce and spread their traits (genes) to offspring. If those who made the badly camouflaged nests continue to produce badly camouflaged eggs, what will happen to that species? It will become extinct. Those that survive are best 'fitted' to their environment (by producing better camouflaged nests) and can pass on their traits (genes) to subsequent generations.
3) Look are various videos on the evolution of birds (eg. No. 1, No.2, No.3).Look at a diagram showing the external anatomy of a house sparrow. What colours are the equivalent parts of the body of a wren - brown! Discuss the roles/benefits of feathers, including their role in camouflage.
SUMMARY OF LEARNING POINTS IN THE STORY
*Plants are often adapted to live in specific environmental conditions. In the case of the Wood sorrel, in diffuse light.
* Appropriate camouflage, such as that in the wren, is one way in which a species comes to survive and go on to breed. Through evolution, the 'successful' trait of 'good camouflage' would become more prevalent in the population and come to form a key feature of the species.
* Some species produce a small number of individuals and invest a significant amount of parental time in upbringing their offspring, when reproducing (such as in the Wren), whilst other species produce lots of offspring and invest less time. These different strategies (K and R respectively) are different approaches to trying to maximise the transfer of genes to the next population.